Thinking about ditching the tunnel ram...

[Bryan Rose]

Well here goes , again with the boat , I have it running great but am thinking the tunnel ram may be history.... The engine is running great but I know it is not at it's full potential I have a Wiand high rise tunnel ram for rectangle port heads 2 fresh 660's on it, geez this thing is a pain in the arse to tune, nice new Mr.Gasket scoop etc thinking about going to a single carb for ease of tuning...with the 660's it is all or nothing, no middle ground. My engine builder says ditch it, you will make more power with a single carb, easy to tune etc...... what's the real story? Also thinking about covering my motor with a hatch (insurance Letter) to make it look more like a sleeper. easier to do with a single carb on a lower intake.
Help me figure this one out, What's the real deal?
http://www.***boat.com/image_center/data/520/766DSC01691-med.JPG
Bryan

[MudPumper]

I'm running a single carb on my BBC with 500hp and the boat runs mid to upper 70's. I do like the look of the twins on a high rise though.

[HotHallet]

Bryan-All I can say is tunnel rams look bad ass. I rebuilt my motor this year and am running one. However I am running two 4150 style 600 cfm Holley double pumpers. I had a friend who had the 660 center squirters and he had to do a lot of tuning as well. I would say try some other carburetors. I know it gets expensive to "try" things but before you go buying another manifold and throwing a dominator up there I would say try these carbs or something comparable. As for the insurance thing and the engine hatch all I can say is don't be gay dude. You have a low profile jet boat and they look lame with engine hatches. If it was a 20 foot Spectra or a crusier of some sort I would say go the sleeper route but with a low profile jet you gotta let it all hang out! Have some sort of rinky dink engine hatch built for the insyrance inspection and then yank that sucker off and use it as wall art. If I were you I would plug the transom holes and put some frikkin pipes on that thing. Little jet boats should have OT's. Just my $.02.

[FoMoCo]

I say ditch the 660's. Always a pain to get those set up right. I run 2 750dp Holleys on my BBf and it runs perfect, no miss no stumble. I even Wake Board with it! all I had to do was change the power Valves to 4.5's and up the jetting a bit, and that was it! They are turn key!

[QuickJet]

Tunnel rams look great but if they hurt your mph I'd say ditch it. I have a single carbed BBC that has run it's best of 87 mph with a passenger. Some tunnel ram jets won't do that. Try a single carb before you sell your setup.

[HBjet]

I've ran dual 450's on a Weiand, and now dual 750DP's on an Edlebrock tunnel ram, never had a problem with them once they were tuned correctly. I would maybe get a second person to check them out and tune them for you on the water. Someone who has a lot of experience with them. Does your current builder have experience with them, or do you notice he doesn't really do anything with tunnel rams. If tunning is the only issue, you can sell those carbs on ebay and get some 6109's (750's) which are designed to run on a tunnel ram. As for covering the motor... why not cut up the bow and make it an open bow? Get a ski tower, speakers, lights, etc....:D
I remember AAA insurance covered boats with exposed motors, but if they had headers, then they only allowed singled carb. Dual carb was ok, but no headers.
Good Luck
HBjet

[shaun]

I have always liked the way dual carbs with a hi-rise looked!
Looking at it from a performance aspect i cant really say. Both hi and sort style intakes have there advantages over one another i'm sure but for saying that single carb will give you more power over dual carbs just doesnt make sense in my mind. As long as both are tuned/setup properly i dont see why one should preform better than the other. But hey, what do i know, i'm no pro.
And for enclosing the motor, just covor it with a cardboard box thats painted to match when they look at the boat :p

[flat broke]

without any spec on the motor it would be hard for anyone to say which intake/carb choice would work best. Plenty of mid HP motors running well with duals though, so don't dispair.
Like Randy said, get someone who KNOWs how to set up a pair of carbs and the difference will be night and day. If they guy you are using prefer's singles without regard for your application or motor, it might be time to look elsewhere for tunning assistance.
I'd say work more with a knowledgable individual that can make what you have work. It will cost less in the end to have a pro go through your 660s than a swap to a single plane with bigger carb and then setup time on the new induction.
As for the headers... Disregard the earlier statement about loosing the through the transoms. The lightnings will keep your valves a lot happier than injected rewarders/bassetts, and you wont ever have to worry about some stupid ass $.05 spring breaking and subsequently hydraulicing your motor.
BTW, the increases you've made to date are nice, keep up the good work.
Chris

[Bryan Rose]

HB Jet
you said it right , he does not do much with tunnel rams and I don't really think he wants to, however ,He is not the only person I have spoken with on this issue, Also spoke by phone with an Ex- jet boat racer and he advised me to get back to basics , all the boats he ever ran were singles and he was pretty good at what he did. wish I could find someone in my area that is well versed with the tuning of dual carbs...likeyou guys in the west.... Don't get me wrong I like the tunnel ram and it runs stout but it is a pain in the ass.... I know this motor has more in it and want to get the maximun performance out of it like all of us do....Just don't really see the bennifit of a tunnel ram turning under 6000RPM's, over that and it becomes more clear...
Thanks for the reply's so far ... food for thought.
Bryan

[flat broke]

Brian,
Comming from a max mph mentality on my current engine build, I can tell you all the advice I got was "go tunnel ram". I orriginally was gonna run an 850 demon and a single plane deal, but I would have been leaving HP on the table, so I bought a 2nd 850 and a tunnel ram, and we'll see how I fare on 7/29
BTW, good to see ya back on the boards Randy
Chris

[Squirtcha?]

I made the switch from an 850 dp and Weiand Stealth to a tunnelram and a pair of 660's. I'll toss up what mine did and maybe it'll help you decide.
I bought the TR and carbs used. Rebuilt the carbs myself and installed everything. Carbs came with secondary blocks (not installed) so I removed and replaced the stock metering blocks allowing me to jet all four corners.
First time out I jetted with 76's all the way around. It ran great but I thought it was a little too lean. Jetted with 78's and headed for the river and freeboard challenged the next day. Ran the dog crap out of it and had no problems whatsoever. No stumble at all and awesome off idle performance.
I was reving 5300 prior to the change, and 5300 after. No RPM or speed increases at all. Needless to say I was bummed. I agree that you'd need to be running higher RPM to get any kind of gain from the thing.
Here's a DD sheet clearly showing that my horsepower is sitting there (unused) at about 5500 to 6000 RPM.
http://www.homestead.com/jetboat/TR.jpg
The only thing that irked me, was absolutely terrible fuel mileage/hourage. This thing sucks gas like there's no tomorrow. If you look at the linkage, the secondaries are kicking in at anything above an idle (practically). I'm going to modify the bellcrank and have them come in around half throttle. Hopefully it'll help with the fuel economy some.
I'm also going to get my impeller cut down to a B in an effort to get my rpm up where my horsepower lives.

[565edge]

Im switching from a dart tunnel-ram and 2 -1150 dominators to a single brodix (hv2001) and a king demon 1195 carb.I think it changes with everybodies set-up.Put a victor jr on it and a 850 double pumper.

[Squirtcha?]

I think if I were going to do mine again, I'd run a single 1050 dominator and a victor.
I was going to sell my stealth and 850, but I couldn't even sell it for half what the new ones go for. I'm gonna keep it and may even change back at some point. (especially if reworking the secondaries on the 660's doesn't help with the fuel useage). I'm using damn'd near twice the fuel I used to, and it's no faster. Frustrating to say the least.

[TIMINATOR]

The problem as I see it is that the engine guys and pump guys never get together on the combination,and most engine guys don't know JACK about boats, jet or otherwise, AND the Desk Top Dyno assumes a perfectly machined and blueprinted engine, perfect jetting,mixture distribution and timing. Things that you probably don't have all of...... My 21 Daytona runs mid 90s on regular gas(before the latest pump work), with a single 1050 Holley on a single plane intake, atop a CUSTOM BUILT 572 BBChevy. The gas mileage IS AWSOME! But so is the combination, it pulls between 7 and 12" vacuum at cruise(30 to 60 mph) and runs 63+ mph on the primarys! Get a new engine and carb guy! If I don't need a t-ram, you probably don't either. The best thing of all is beating blower and T-ram guys with a single carb! The only problem is that every squirrel with a T-ram and Bassetts thinks he has a race boat and I get tired of showing them that they don't! My new EFI Crower stack injection will take care of the sleeper problem and keep the mileage too! Moral of the story: dump the T-ram or get someone GOOD to help you! TIMINATOR :D

[Infomaniac]

Tunnel rams are harder to tune.
You have to jet up because of the POOR vac signal that the carbs get. They are too far away from the engine. Squeezing the main air bleeds down some will let the main metering system come in a bit sooner. More accel pump etc are all part of it.
It does not like the part throttle driving because of the poor vac signal. The bigger the carbs, the worse it is.
You wiill be happier with a good intake and single carb. Will loose some bling factor.

[berk]

do you live in a furniture store?

[Jet Hydro]

I have an intake I`d sale ya SQ port that a dominator bolts on.
http://www.***boat.com/image_center/data/520/208P1010883-med.JPG
http://www.***boat.com/image_center/data/520/208P1010885-med.JPG

[Hotcrusader76]

Come on Bryan....leave the boat alone, excercise some patience, grab a beer, and get to tuning that beast. She looks awesome and once it's dialed in you'll be stoked that you didn't go to a single set-up.
If ya go to a single, run a Dominator 750:D:D:D...Oh yeah.
~Ty

[LVjetboy]

Squirtcha, you mention using twice the fuel, what's your gas mileage? Timinator, you mention your gas mileage is awesome, what is it with your single 1050?
My experience with gas mileage: I upgraded from a 340 hp 454 with dual Holley 715's to a 650 hp 540 with dual Demon 850's and gained gas mileage. In fact, I get better gas mileage now than many low power prop jobs. Why? The engine flows better, the carbs are tuned better, the pump flows better...efficiency. While I think a single carb can be more efficient and still deliver nearly the same performance in the power levels most of us run, I also think some true life stories about poor dual carb gas mileage are skewed by poorly tuned carbs and/or poorly matched carb-to-engine combinations.
I have my numbers just wondering what Squirtcha and Timinator measured for gas mileage?
jer

[Bryan Rose]

Originally posted by berk
do you live in a furniture store?
No that is in my warehouse... I like old stuff. plus it is my business...
Bryan

[OMEGA_BUBBLE_JET]

tunnel rams are not designed to work well under 6000rpm:p they look cool but do not yield any performance gains in the range you are in. if you were spinning say 7-8000 rpm it would be noticeable. with gas prices get cheaper than ever it makes sense to consume as much fuel as possible:rolleyes:. I know the trend is to use huge carbs because they make huge power :rolleyes:but a 750 holley double pumper with mechanical secondaries would probably perform beautifully in your application and increase your fuel mileage and throttle response.
sell the blingtastic tunnel ram and carb setup and get a single carb intake and a 750dp holley. you will not regret it. Listen to your engine builder, he might know a few things;)
Omega

[BrendellaJet]

Originally posted by TIMINATOR
The problem as I see it is that the engine guys and pump guys never get together on the combination,and most engine guys don't know JACK about boats, jet or otherwise,
Maybe not in Arizona they dont. The premier pump guy in CA and one of the more popular motor builders in Ca work two doors down from each other. They both do builds for the same people on many race boats as well as pleasure boats, and there shit flat gets with the program.
If your talking to the wrong people, dont be surprised if your shit aint workin.

[MAXIMUS]

Ok here is my 02. I just set up a tunnel ram with 2 660's for a friends 71 ranchero with a 460. This is a driver not a racer! The motor is a 9.5 comp deal with a hydraulic flat tappet & very little head work done. 2200 stall converter & 3:50 gears in the ass. When we first started testing it on the street, it was a very responsive & unforgiving piece of sh*t. It hauled the mail but was not driver friendly. I sh*t canned the 660's & went to a couple of 600 vacum secondaries. With a few adjustments (increasing the squirt for the long draw, softer vacum springs for the secondaries, and completely shutting down the air on the secondary barrels during ideling for a better signal to the idle circut) This car runs clean, idles clean & excellerates perfect etc... I get tired of hearing how tunnel rams don't work!!! If you don't want to put the effort in then follow the sheep!;) I have a corvair with a really long home made tubler tunnel ram set up that I was told would not work nor would the hp 650 that I wanted to put on it. Wrong again! Good torq & driveability & very duner friendly!:)

[Squirtcha?]

Originally posted by LVjetboy
Squirtcha, you mention using twice the fuel, what's your gas mileage? Timinator, you mention your gas mileage is awesome, what is it with your single 1050?
My experience with gas mileage: I upgraded from a 340 hp 454 with dual Holley 715's to a 650 hp 540 with dual Demon 850's and gained gas mileage. In fact, I get better gas mileage now than many low power prop jobs. Why? The engine flows better, the carbs are tuned better, the pump flows better...efficiency. While I think a single carb can be more efficient and still deliver nearly the same performance in the power levels most of us run, I also think some true life stories about poor dual carb gas mileage are skewed by poorly tuned carbs and/or poorly matched carb-to-engine combinations.
I have my numbers just wondering what Squirtcha and Timinator measured for gas mileage?
jer
I think we're talking apples and oranges to some degree here Jer. I looked at my Holley 850 dp and the secondaries don't open/actuate until the primaries are at the halfway point. The 660's are mechanical linkage and the secondaries are literally opening just off idle. I'm running on 8 barrels at everything except an idle.
If you look at the picture you can see where the eccentric starts to accuate the secondaries. Just barely touch the peddle and they're starting to open, and it happens fast.....
Apparently these things were designed for an all or nothing situation. Works fine for dragging, but not so hot for cruising around etc. When my boat's on plane at about 2300 rpm, it's already starting to open the secondaries.
I don't think it's a tuning issue as it starts great, idles perfectly and doesn't bog, or hesitate. My plug color is right on and if I were out of tune somehow, I'd think there would be some kinda problem with the way the thing runs.
http://www.jetheaven.us/photopost/data/500/19secondaries.jpg
As for my mileage, I'm not sure. How do you check yours? Use a gps with each outing and take down your mileage? I'll try it this weekend and let you know.

[Blown 472]

Originally posted by Squirtcha?
I think we're talking apples and oranges to some degree here Jer. I looked at my Holley 850 dp and the secondaries don't open/actuate until the primaries are at the halfway point. The 660's are mechanical linkage and the secondaries are literally opening just off idle. I'm running on 8 barrels at everything except an idle.
If you look at the picture you can see where the eccentric starts to accuate the secondaries. Just barely touch the peddle and they're starting to open, and it happens fast.....
Apparently these things were designed for an all or nothing situation. Works fine for dragging, but not so hot for cruising around etc. When my boat's on plane at about 2300 rpm, it's already starting to open the secondaries.
I don't think it's a tuning issue as it starts great, idles perfectly and doesn't bog, or hesitate. My plug color is right on and if I were out of tune somehow, I'd think there would be some kinda problem with the way the thing runs.
http://www.jetheaven.us/photopost/data/500/19secondaries.jpg
As for my mileage, I'm not sure. How do you check yours? Use a gps with each outing and take down your mileage? I'll try it this weekend and let you know.
Do yall wonder why there is a single accel pump that feeds all four barrels? the true 660 is a drag race carb built to idle or go wot! no cruising, it is a tunnel ram carb for drag racing plain and simple.

[mrgoslow]

the best $$ ever spent on my motor was on a dyno after i couldnt tune the sob. my carbs sit sideways which basically gives each cylinder a jet. the jets are all over the place, ive go a 58 next to a 72. but it starts at the bump of the key, economy has been greatly increased, responsiveness is outstanding, plusa are uniform unless you idle excessively (R side takes on a darker shade) but quickly clean up after running. do i need a T/R @ 5400 probably not but it looks nice.
btw, brian i think you should cover the motor. it adds to the sleeper effect. 80.1 on gps w/482 hp @ 5400.http://www.***boat.com/image_center/data/521/87ToTheWood_engine_cover2-med.jpg

[Squirtcha?]

Originally posted by Blown 472
Do yall wonder why there is a single accel pump that feeds all four barrels? the true 660 is a drag race carb built to idle or go wot! no cruising, it is a tunnel ram carb for drag racing plain and simple.
That has become abundantly clear, as you can see from my previous post. I have a buddy that ran a set of them on a BBC and he reshaped the eccentric so that the secondaries came in at half throttle and less abruptly. It worked out o.k. for him and I'm gonna try it too. I'll make a template of his and copy it. If it doesn't work out, I'll be selling these and picking up a different set of carbs for it. I have two buddies that run BBF's with TR's and vacuum secondaries and suffered no loss of mileage (or if there was............... it was imperceptible).
Incidently mrgoslo..............that's a coolass'd looking engine cover you have there.

[mrgoslow]

thanks. Squirtcha. i walk around the edges when we ski, my wife like to get in and out of the boat back there, it cuts down on the noise and heat has never become an issue w/the lightnings.

[Bryan Rose]

What kind of boat you got there? any more pictures of it....
Bryan

[LakesOnly]

Originally posted by Bryan Rose
...I have a Wiand high rise tunnel ram...geez this thing is a pain in the arse to tune...thinking about going to a single carb for ease of tuning...with the 660's it is all or nothing, no middle ground. My engine builder says ditch it, you will make more power with a single carb, easy to tune etc...... what's the real story?
Bryan
Uh, I think your just need to dial in your tunnel ram set-up.
My T/R and 660's works fine at 1000, 2000, 3000, 4000, 5000 rpm. Starts easily and idles fine.
A properly set-up tunnel ram has damn-near no headaches whatsoever, except maybe gas consumption. :D
A tunnel ram set-up will not make night and day horsepower over a sigle carb set-up, but can make 30-40 HP more. How much this will help your top speed is negligible in a jet.
LO

[Squirtcha?]

Originally posted by LakesOnly
A properly set-up tunnel ram has damn-near no headaches whatsoever, except maybe gas consumption. :D
LO
This is the key for me. I don't mind spending the extra money I did, however I don't like the fact that I'm using lots more gas to go the same speed as with a single carb.
A couple weekends ago I went to a remote lake and burned 12 five gallon jugs of gas in 2 1/2 days. That's a bit much........
I even had to go out and buy more jugs. The fuel useage is significantly more than before the TR.

[LakesOnly]

Originally posted by Squirtcha?
I have a buddy that ran a set of them on a BBC and he reshaped the eccentric so that the secondaries came in at half throttle and less abruptly. It worked out o.k. for him and I'm gonna try it too.
This is an archaic street racer trick that is a BIG no-no. The 4-point accelerator pump nozzle will still discharge fuel into the secondary side and puddle-up over the closed throttle plates.
The right thing to do is simply set up your fuel metering to discharge fuel efficiently at all throttle positions.
If you want graduated primary/secondary throttle openings, then buy a pair of double-pumpers that were engineered to function in this way.
LO

[LakesOnly]

Originally posted by Squirtcha?
The fuel useage is significantly more than before the TR.
No doubt! I think I can dust a 55-gal drum in a day if I wanted...
LO

[mrgoslow]

bryan, its a 19' 75 anthony which im told is a splash of a rogers. jacuzzi suction piece dom bowl, berk "b"
http://www.***boat.com/image_center/data/521/87ToTheWood_Interior2-med.jpg
http://www.***boat.com/image_center/data/521/87ToTheWood1-med.jpg

[Snowboat]

I might have missed it.........but, what color are your plugs?

[Squirtcha?]

Originally posted by LakesOnly
This is an archaic street racer trick that is a BIG no-no. The 4-point accelerator pump nozzle will still discharge fuel into the secondary side and puddle-up over the closed throttle plates.
The right thing to do is simply set up your fuel metering to discharge fuel efficiently at all throttle positions.
If you want graduated primary/secondary throttle openings, then buy a pair of double-pumpers that were engineered to function in this way.
LO
I'm completely understanding what you're talking about here. When this modification is done, the accelerator pump is still shooting fuel even though the secondary plates are closed. That much makes sense.
I am kind of an archaic dude though.
I could use some clarification on this part.
simply set up your fuel metering to discharge fuel efficiently at all throttle positions.
How exactly is this accomplished. Please excuse my ignorance.

[LakesOnly]

Squirtcha,
I just checked the PM you sent me awhile back...you already have the secondary metering block that allows for jet changes. Don't know your cam's lobe separation etc, but it's otherwise a lot like mine. I'm also running 10.5:1 c/r. Currently, I'm jetted 78/82 & 40 BTDC, and need AvGas to stay alive (or it's bye-bye pistons).
2x4 tunnel rams provide far better air/fuel distribution than a single four ever will; you will just have to adjust twice as many components/circuits half as much as you would a single four (general rule of thumb). Get it?
I re-read your PM and conrary to what you state above, you're not ignorant or stupid... Do timing/jetting/plug readings.
The more adjustable componentry on an engine, the more of a balancing act fine tuning becomes. Start by changing one thing at a time and seeing how it affects your rpm's, plug readings etc. This will not be a day at the lake with beer and family, it's a day with one friend assisting you while you are working.
The results will be more than favorable.
Can't help ya with your fuel consumption, though. :D
LO

[LakesOnly]

http://www.culverbrothersracing.com/Tech/sparkplug101.html]
LO

[Hotcrusader76]

There is a successfull modification that makes the 660 combo very streetable or as I say, perfect for the TR lakeboat. This is basically similiar to the procedure mentioned above. Template the linkage on the 1:1 primary peice so that you have 20-25 degrees of "tip-in" prior to the secondaries opening.
To minimize fuel pool up, drill the primary side of the center squirter from 0.025" to 0.031". This will minimize the amount of shot being delivered to the secondary side. Also drill a 0.089" hole
in each butterfly to assist in the over-rich condition at idle, which is inherent to big motors with small carburetors.
I personally built the carburetors Lakesonly has on his boat and the build process was very similar to the above mentioned, but since we were after idle to WOT it wasn't necessary to grind out the shafts. Matter of fact I believe I built his with conventional links...guess I'll have to double check his build specs again.
Nonetheless the 660 when tuned right is workable from all angles and as LakesOnly mentioned, it provides for infinite amount of tuning to each cylinder....very nice assest for the BBF:D
~Ty

[LakesOnly]

Originally posted by Hotcrusader76
....very nice asses for the BBF:D
~Ty
Is your BBF attracting very nice asses too, Hotcrusader? Guess it goes with the territory. Gotta loved those BBF's! :D
LO

[HBjet]

Originally posted by OMEGA_BUBBLE_JET
Listen to your engine builder, he might know a few things
Except tuning carbs on a tunnel ram :D
HBjet

[TIMINATOR]

Everybody doesn't live in LA and have experts on all street corners. Squirt,get 600 DPs and be happy. Gas mileage- better than my 205 Carrera w/330 HP. I get to the lake at 7:00 AM and run pretty much continously 35-60 MPH on the primarys (except for an hour swimming and munching) till I leave at 12:00(noon)or so and usually don't switch tanks (24 gal each). It runs regular gas and in the mid 90s on the motor. To me thats good mileage, I'm happy. I run it usually twice a week. Life is good. TIMINATOR

[LVjetboy]

Dan, comparing Demon 850's to 660's apples to oranges, but my post was directed at comments about ditching tunnel rams and dual carbs in favor of a single carb...the implied cause of poor gas mileage.
"As for my mileage, I'm not sure. How do you check yours? Use a gps with each outing and take down your mileage? I'll try it this weekend and let you know."
I've used both GPS and a measured course, one was 40 miles at an average speed of 60 mph with light ripple to smooth (Lake Mead), the other was 25 miles at an average speed of 45 mph, rough to light chop (Havasu). So I have more than on data points, and more than one test condition. Recording test conditions and average speed are important when you measure mpg.
That said I'm averaging between 3.1 to 3.2 mpg so my range (26 gal) is just over 80 miles.
With a total of 1700 cfms mounted on a dreaded gas-guzzling tunnel ram and cruising at 4,500 rpm you'd think gas mileage would su*k? But my mpg compares with say, the Bullet 20XD low profile fishing boat equipt with a Mercury Racing 2.5L 280 EFI and capable of 100 mph. Fishing hole-to-hole no doubt. And way more insurable than mine...
http://members.cox.net/lvjetboy/BulletFish.jpg
After all, they're only fishing. Note the EFI...and the prop job. Most would consider this hull with outboard EFI on a prop a model of fuel efficiency at my performance level. Apples to apples. Here's a review...
Prop job fuel economy (http://www.bulletowners.com/NEWS/BWB2.htm)
The speed at 4500 rpm? Very close to mine. Fuel economy at 4500? 3.3 mpg just a tad higher than mine if you believe their review. Length and top speed...very close.
Timinator...others? Have you really measured your gas mileage? Getting to the lake 7am or leaving at noon during a typical outing plus swimming and munchies and what you drink doesn't tell me (or anyone else) sh*t. Accurately measure distance, fuel, speed, and water conditions over several runs then you have a valid data point. I wouldn't be surprised if fuel economy has more to do with tune and matched components than single carb versus dual carb or tunnel ram. My cruise rpm's way lower than accepted tunnel ram operation and my carb total cfm's way bigger. I don't live in LA, although my carbs were tuned and my components matched by someone who does.
jer

[Squirtcha?]

Originally posted by Squirtcha?
I have two buddies that run BBF's with TR's and vacuum secondaries and suffered no loss of mileage (or if there was............... it was imperceptible).
Hey Jer. I realize you can get good mileage with the TR when properly tuned, I was eluding to my particular carbs as being the culprits.
That's some great stuff there Lakes and Crusader. I'm gonna try the mod after the holiday. Thanks for putting that up.
If it doesn't work I'll go the route Timinator suggested and find some vac sec carbs.

[LVjetboy]

My old 715's vacuum secondaries. The Demons mechanical...opening about 1/2 throttle or maybe a bit less? At cruise they may not open...but then neither did my vacuums.
Anyone with single carb jets out there have accurately measured gas mileage? Just curious.
jer

[TIMINATOR]

Actually 600 DPs or 750 Vacs will work better on your boat than the 660s Squirt..... 660s were originally designed to work in a drag racing idle/WFO /idle scenario, not part throttle. You can improve them, but the 600 DPs or the 750 Vacs will work much better out of the box. I prefer to get the closest thing right out of the box, then modify it only if it becomes nesessary. I have enough challenges in my life! As far as my mileage is concerned, take what I said with a grain of salt if you wish... My Eliminator absolutely uses less fuel and gives greater speed than my Carrera. I choose to not analyze it any further. AS I SAID "I AM HAPPY AND LIFE IS GOOD". Happily TIMINATING! :D

[Floored]

Jer closest I have for mileage is Avi to sandbar and back on 18 gallons of gas. how do i know, paddled last 50 yards. 455 with single carb, jacuzzi in my Beisemeyer. that was cruisin, trying to roost bridges,and general fartin around in heat of day. tossed tunnel ram 3 years ago, when you get your olds into a TR powerband range the internal engine parts have left the building like Elvis, never to be seen again. plus I picked up 200 rpm. It was more than my combo could work with

[shaun]

By all means i'm not expert at this stuff but one thing i dont understand is that you guys keep saying dual carbs use more fuel that a large single carb and this just doesnt make sense to me. The idea is fairly simple, you need the ratio right for Air and fuel. If you ran one single carb and the boat was running great and wasnt too lean/rich and then swaped to a dual carb setup that was tuned why would the boat be using more fuel? In my head if the boat was using more fuel than with a single carb than wouldnt it be running too rich now? It seams like the same amount of fuel should be used.
Only thing that i can think of that would change this would be the fact that maybe the single carb was restricting the flow on the motor and now dual carbs have opened it up a bit.
Just my food for thought. I'm sure there is alot more variations/calculations to make this more complicated/complex.

[LVjetboy]

Floored, that's one hard way to test...:D If you knew the total miles traveled you could figure mpg. I'm still curious if anyone with a single carb's tested their mpg at cruise over a measured distance and can post it so we can compare?
Shaun, I'm no expert either, but I think it's a matter of both fuel-to-air ratio and how well fuel is mixed or atomized within that air. Two carbs and a ram make it harder for that perfect mixture or fuel distribution at low to mid rpms...compared to a single carb. This because airflow thru the venturi's slower than optimum. And dual carbs are more likely to run off-design at cruise.
BUT...
As you posted, I think carb tuning makes a big difference. Bad carbs or tuning and the resulting poor fuel distribution at cruise speed may be the difference between a gas guzzler or decent mileage no matter single or duals, ram or no ram. But without an accurate measure of mpg, what have we? Just guesses.
jer

[sanger rat]

If anybody has a Weiand oval port TR they don't want anymore please let me know.

[396_WAYS_TO_SPIT]

I run dual holley 600's vac secondaries on my 455 olds .30 over at 10-1 comp. I only run 14 gallons a day at the lake. I switch to my other tank at the very end of the day. I gained 400r's switching to a tr on my olds. I was spinning 4300 now i spin 4700r's! I am also spinning a A inpeller to keep the r's down on the olds.
396

[LVjetboy]

That's all cool, but running 14 gallons a day w/o miles run (ave. speed, conditions) means nothing to mpg.
jer

[Hotcrusader76]

On a properly tuned engine, it doesn't matter whether you have a single or dual carburetor set-up, fuel mileage is the same. This means both systems are calibrated for a set A/F ratio...
If the motor gains more HP from the tunnel ram, thanks to straight runner designs and more CFM, then yes your mileage is going to be less.
But my next question is....Who freaking cares about mileage on a big block powered jetboat doing 4500-5500RPM as an average? That's like counting the carbs in your beer, after a case who cares?:idea2: :D
~Ty

[LVjetboy]

"my next question is....Who freaking cares about mileage on a big block powered jetboat doing 4500-5500RPM as an average? That's like counting the carbs in your beer..."
I care. On a race boat I'd agree... You get humiliated at least they tow you in. Mis-judging gas on the 1/4 mile? How often? Maybe no big deal.
For a true LAKE boat...paddling 150 feet or towed that last 1/4 mile by a jet ski 'cause you ran out of gas? Not good. Besides humiliation (minor), you may risk sinking for dead-in-the-water depending on weather conditions and who happens to come along willing to help. A major risk, for me at least. I boat big lakes. And if you restrict you "lake boat" usage to short jaunts from the marina because of mileage or octane then do you truly have a lake boat?
Running out of gas not good for a low freeboard jet. Lake or on the track. But for a lake jet, certainly important and all about mileage. So ya, I care.
jer

[OMEGA_BUBBLE_JET]

the only thing I would put under 2 carbs is a blower:D
Omega

[shaun]

I can understand the need to know how much fuel to run on the track but on the lake most people dont know how long or how far they have been running that motor on there current tanks anyway so really gas mileage doesnt matter that much. My boat never even had a gas guage, we just poped the top and looked in the tank.
I dont agree with the the quote on who cares about gas milage... why waste fuel, expecially with how expensive it's getting and expecially when your running race fuel!

[Hotcrusader76]

Just to clarify a little on the gas mileage dealio...hahaa...
For the average lakeboat running the typical 400-500HP on a used/worn Jetpump which is inherently very inefficient...with a driver whom normally can't remember how many beers were packed in the ice-chest let alone where the gas level is at, despite the fact he doesn't even know how old is gas sender is, let alone it's existance or operational condition...Who really cares?
Now on the flip side....when I used to run missions in the Middle East with military gunboats (KaMeWa jet propulsion) then yes!!... fuel consumption was critical and our operational range was critical not to mention life saving at times. So sure it can matter, specially when you're running off-shore powerboats where the tides are turned, for a lack of better words. But for the average lakeboater running Parker, Blythe, or even Yuma....don't really think it's in the equation.
But then again this is just my opinion and I respect the fact that some of you disagree with me...;)
~Ty

[LVjetboy]

You should see the mileage course line I ploted on the Lake Powell map last trip. I figured I could make Warm Creek Bay easy with reserve and loiter, but Padre a bit of a stretch depending on water conditions...run out of gas in the channel on the way back and my jet could sink easy with that water. No place to beach, big water, and VERY deep. So I guess it's how and where you boat...and how risky to loose power. Some CA lakes no big deal compared to Mead or Powell.
Normally, I don't run long distances so don't care either. But sometimes I do and plan ahead. Like Temple Bar to Iceburg or Havasu Springs to the sand bar and back. And I can't plan without a clue to mpg, be it good or bad.
But my question on mpg was related to single vs dual carbs and jet boat efficiency. Just curious, trying to learn more, not saying everyone needs or even cares to know this. Has anyone else checked or just me? :confused:
jer

[Hotcrusader76]

Leaving hull drag out of the equation, I believe you could get an accurate measurement on the Dyno with the brake specifics. This would be the only other way beside measuring fuel flow with an inline meter. Just depends on how far you want to take it.
The SPECWAR Mk.V boats we ran in Kuwait had fuel flow meters on them which allowed me to figure out consumption. Being that we ran dual V-12 Detroit/MTUs with Twin Turbos each...fuel consumption was out rageous....5000lbs of Fuel/Oil at 50+knots in less than 6 hours....
http://www.tpcracing.com/images/MKVCOLLAGE.jpg

[LVjetboy]

5000 lbs...whoa!
But lake jets? I don't think you need a dyno or inline fuel flow measure. At least for ballpark. I top-off at the dock, then run measured or gps mileage. Return and top-off. Given top-off error, measured or gps error, my mpgs have been close both times.
jer