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dyam
10-03-2001, 04:05 PM
Can anyone get me up to speed on boost referencing holley carbs on a blower moter?!
I have a 1998 21' eliminator daytona with a 502, superchiller, b&m 250 and dual holleys with no power valves. It runs a max of 6lbs of boost.
It's jetted very fat.
I want to add the power valves so I can idle through marinas and not load up or have black smoke all over!
HELP!
Do I need to boost reference the carbs with this amount of boost?
Can I do this myself or should it be done at a shop?
Next question-where should the ride plate be installed in relationship to the bottom? I know it's not supposed to be level with the bottom but at what degree should it angle upward?
Last question-does anyone have any experience with the dual impellers on the jets?
I am running a setback Legend with an A impeller(I think)-85mph @ 5500rpm.
I would like to get that awsome holeshot everyone says a jet should have and I would also like to get just a little more speed at 4000rpm. Currently I'm running about 40mph @4000rpm.
Any help would be appreciated!!!

Unchained
10-04-2001, 04:12 AM
I know everyone says that you need to boost reference the power valves but that is only needed if the vaccuum draw at WOT is enough to close the power valve. Example, 1 in. vaccuum at WOT, no problem, 6 in. vaccuum at WOT, boost referencing required. The power valve will be open when the vaccuum drops below the power valve rating. I use 4.5 power valves and they are in the primarys and secondarys. In my blown 540 Arias engine I don't have boost referencing and my vaccuum at the carb base at WOT is 1 lb. I am running 14lbs. boost. When you put in the power valves you will have to jet way leaner because they account for about 6 to 8 jet sizes. Check the vaccuum right at the base of the carbs at WOT. Your carbs need at least primary power valves or the engine would have a major flat spot.
The ride plate wants to be about 2 degrees up from the keel line. This can vary from boat to boat.
I put in a cavitation reducer impeller and it helped slightly, Now when I floor it from a dead stop the RPM will overrev by about 800 rpm and then the pump loads and away you go. Before the engine would overrev wildly and could not be floored from a dead stop. If you want to go real fast shim the ride plate down until the pump intake pressure gets up to 30 or 40 lbs. You will be amazed at how much the hull will lift at high speed. You should be running faster than 40 at 4000 rpm.
The 21' daytona is a great boat. I am going to buy one soon. Post a pic of your boat. My 19' Cheyenne is a fun drag boat but too small to carry back seat passengers, They get scared riding next to the monster.

dyam
10-04-2001, 06:19 PM
Thanks for the info.
I'm going out next Sunday so I'll get some vacuum readings then.
When you installed the cavitation reducing impeller did you increase the size of the main impeller? Who installed it?
I don't understand how shimming the ride plate down will increase the pump intake pressure but I am going to shim it down.
I think I'm at about 5 degrees now.
It tends to porpose slightly at part throttle, 35-45mph. Will shimming the ride plate help with this problem? I'm hoping it does. It's not a big problem but it's kind of irritating.
I've got a droop snoot, with a 4 degree(down) wedge added and a place diverter.
Everyone has told me the diverter should take care of the porposing and it does under hard acceleration but not at part throttle.
I have a handheld GPS unit and it's supposed to be pretty accurate. 40mph @ 4000rpm really sucks.
I'll post a pic when i figure out how.
THANKS again.

DEL51
10-05-2001, 12:30 AM
Hello unchained, I am putting together a 486 chev 871 blower motor and I am curious about carb size. If the carbs are not large enough would this increase the vaccuum reading below the carb.What size carbs do you run and what would you reccomend for an engine of 468 cubic inches. I was also wondering about what suction piece pressure is considered optimum.Thanks for your time.DEL51

Unchained
10-05-2001, 05:14 AM
Sorry, I mis,spoke that one part, I meant shim the shoe down to increase pump intake pressure.
No, I didn't increase the main impeller size. I'm running a AA now. The cavitation reducer just brings the water to the main impeller so it does'nt have to draw it in. As Don says, the cavitation reducer is unschrouded so it will flow more water than the main impeller can use. I pulled the shaft and machined the step and the keyway in it for the Cav. reducer myself. It is easy if you have access to some machine tools.
Anyway try to have the ride plate about 2 degrees up from the keel and experiment from there. Maybe that will help with the porpoise problem.
So you have a 2 degree down wedge. I had to put in an up wedge so my diverter wouldn't drag in the water because I have a Place droop and a 5 degree intake.
Del51, I questioned about the carb size that I am using because the guy at Fowler Engine told me two 850s were way too small for my 540 engine. He told me I would pick up 200hp by going up to two 1050 dominators and had run the dyno tests on other engines to prove it. So I took a carb base vaccuum reading and got about 1 in. at WOT so I concluded that the carbs can't be restricting that much. You know how with boats and engines you ask ten different people and get ten different ideas.
For your 468 I would run two 850s better too much than not enough. I know everyone says you need blower carbs. I just bought two off the shelf Holley 850DP and they have run fine. We even water ski with my boat. I did rejet smaller than what came in the carbs because the plugs were reading a little rich.
Pump intake pressure wants to be 30 to 40 lbs. at high speed but any pressure is better than the pump sucking the boat down to the water at high speed.
I am by no means a jet boat guru so don't take my opinions too seriously but I hope I can give some ideas that you guys can use.

DetroitJim
10-05-2001, 11:20 AM
Hey Unchained, saw you at Brower Park. I had the blown Sanger flat. You have a wild ride there. Anyway, del51, for what it's worth I am running an oval port 454 with a Mike Kuhl 8-71 at about 7-8 lbs boost. Everyone said I was crazy to use 2 750 Edelbrocks so I did. I stepped up the secondary jets to .113, the biggest made. The needles and seats are the larger .110 diameter. The carbs run about as perfect as you could ask. The pipes are dark gray, no soot whatsoever. Throttle response is crisp, no bogs. Total investment in carbs less than $500, 94 mph on gps.
When I go to a 540 next year, then 850's or 950's would be my choice.
Jim

ponponracing
10-06-2001, 03:31 AM
Dyam, powervalves don't really affect idling carbs adjustments. They will affect part trottle mixture conditions, and in certain cases the wot conditions. There are other ways to lean the idle mixture with Holley carbs. Tune them right first, you may drill the butterflies, then you may add v-wires in the metering system, you may also tune the mixture with the idle air bleeds, on top of the carbs.
A good "tuner" may be very helpfull in setting your carbs for blower application. Do it properly or you will need a spare motor......or two.

dyam
10-06-2001, 02:33 PM
Hey ponponracing, thanks for the info.
I'm trying to avoid the second and third motor thing!!
My thinking is, if I install the power valves I can then lean out the primary jets and then reduce the amount of fuel used at part throttle.
thanks for the tip on drilling the butterflies. I forgot about that! I'll try that before I put it in the water next Sunday.
The V-wires and the air bleeds I'll have to find some help on.
Again THANKS for the info!

Unchained
10-06-2001, 07:13 PM
Detroit Jim, Was your boat the one with the yellow, orange, and purple stripes ? That one was a beauty. Put a picture on the jet performance page boats/names post.

ponponracing
10-06-2001, 08:06 PM
Dyam, drilling the butterflies is a matter of obtaining the right butterflies position in relation of the transfer slot. Drilling them when they need to be drilled gives you a cleaner idle.
If you run a heavy boat, don't bother about powervalves, you will be always running low vacuum. If you run a small or very light boat, then you may benefit using powervalves. Look in blowers engines preparation books and you will find how to reroute the vacuum signal to the powervalves. Instead of the powervalves being activated by the vacuum signal directly under the carb., you pick up the signal from underneath the blower itself. If you run powervalves, you have to make sure your carbs are equiped with backfire powervalves protection, since a blower backfire and there go the powervalves....

BLOWNDRAGBOAT
10-07-2001, 09:19 AM
Holley is now selling a special carb, setup and calibrated JUST for blower application's. I just installed a set on a customers blown 572 and all that was needed was a minor jet change to fatten up the motor a bit. Pretty nice carbs.
[This message has been edited by BLOWNDRAGBOAT (edited October 07, 2001).]

DEL51
10-08-2001, 10:23 PM
HEY BDB, What is the initial cost on these carbs from holley? The 468 chev has c port aluminum heads that have been ported,2.19int 1.88ex valves. Roller valve train and 8:1 comp.I need a set of carbs and I am cost consious.Thanks DEL51

BLOWNDRAGBOAT
10-09-2001, 05:24 AM
Why are you running "C" port heads? Give me some details on the heads and intake. What type of header are you running? The carbs run about $450 or so depending on where you buy them.

sgdiv7
10-09-2001, 05:34 AM
I bought two of those carbs last year, cost me $750 a copy. the only bitch I had about them is the metering block and float bowl gaskets holley says they are nonstick. I took them apart when they were new to see what all the sizes of everything was inside and both those gaskets stuck and riped. so I went back to what I always used in the past tranny assy. lube, light coating and they never stick again. I am very happy with those carbs. the only thing I had to do to them when I got them was increase the shooter size and change acc. cam position and of coarse jet them to the motor. carbs are just a tad big for my ap. I was looking twards the future, more ci. some day.
Bill

sgdiv7
10-09-2001, 05:37 AM
Hey BDB, where were you when I bought my hp 950's. LOL
Bill

DEL51
10-10-2001, 01:00 AM
BDB,Thanks for the response. I received the c port heads along time ago and just had them freshened. They had been ported by air flow research back in the mid 80's. I did not have this done myself. I don't know the flow numbers but they did a nice enough job.I would guess they are similar to a smaller canfield 310 cc head.The intake is a stock BDS competition blower manifold and I did install a backfire plate with two springs.I used to run this motor with merlin heads that were ported and larger valves,2.25 int 1.94 ex and 2 1050 dominators,9375's.In its previos state it ran well. I now have a 572 and am setting up the 468 for lake duty.A friend of mine is building a 19ft boat and we have a dominator pump with an A impeller.This is a joint project and I am letting him use the engine.He does have experience driving my previous boat.I was just hoping to get some carbs a little smaller and cheaper than the dominators. we are looking at running 10lbs boost max,probably 7-8 if I can get the pulleys right. Thanks for your time.DEL51

DEL51
10-10-2001, 01:06 AM
Originally posted by DEL51:
BDB,Thanks for the response. I received the c port heads along time ago and just had them freshened. They had been ported by air flow research back in the mid 80's. I did not have this done myself. I don't know the flow numbers but they did a nice enough job.I would guess they are similar to a smaller canfield 310 cc head.The intake is a stock BDS competition blower manifold and I did install a backfire plate with two springs.I used to run this motor with merlin heads that were ported and larger valves,2.25 int 1.94 ex and 2 1050 dominators,9375's.In its previos state it ran well. I now have a 572 and am setting up the 468 for lake duty.A friend of mine is building a 19ft boat and we have a dominator pump with an A impeller.This is a joint project and I am letting him use the engine.He does have experience driving my previous boat.I was just hoping to get some carbs a little smaller and cheaper than the dominators. we are looking at running 10lbs boost max,probably 7-8 if I can get the pulleys right. Thanks for your time.DEL51
For now we intend on using water injected bassett headers.These have 2.5inch primary tubes and 4.5 inch collectors. They exit over the transom

BLOWNDRAGBOAT
10-10-2001, 07:47 AM
Just double check with bassett and make sure they are sending you a set thats compatable with c-port heads. Sometimes, depending on the heads, a special header flange designed for c-port heads will be needed. Just a precaustion.

DEL51
10-10-2001, 11:31 PM
BDB, I have used these headers with these heads in the early 90's. Do you think the edelbrock carbs will be good? They are cheaper.What do you think about ligtning water jacketed headers? How much do they run.I am starting a new post about alcohol and would appreciate your input.Thanks, DEL51

BLOWNDRAGBOAT
10-11-2001, 08:29 AM
The edelbrock carbs are basically a carter AFB style and I EVEN though I think ol' CHET is a goon, I wouldn't even let him run those carbs. Let edelbrock stick to cars and trucks. As far as lightening, I LOVE thier products. They make some kool shit. I even started making my own rail kits based on thier design.(DON"T TELL THEM) I would have to say that using thier headers and exhaust products would all depend on what it's being used in and how.

BradP
10-11-2001, 11:19 AM
Blowndrag, I really like my Lighting headers too except for one thing. What's the trick for those two damn bolts that no wrench except an open end will fit and you can't get tightened down?

BLOWNDRAGBOAT
10-11-2001, 11:56 AM
Hey Brad!!! I use ARP header stud kits. And modify (shorten) the two hradest to get two. I also use a special offset snapon wrench thats got the perfect angle to tighten the nuts. Make sure you use 271 loctite. You should be able to tighten them once and for all.

BLOWNDRAGBOAT
10-11-2001, 12:07 PM
Damn dude I forgot to give you the rest of the story.... I like to use the 12 point version since you can tighten them with less wrench movement if that makes sense to you...ARP part number 400-1403 for the long kit. Studs are 1.6inches long. The bolt kit number is 400-1202. ARP's number is 805-278-7223

BradP
10-11-2001, 03:50 PM
Just as I thought, just throw a little more money at it! LOL
I just can't figure out why the radius just at those two bolts has to be that tight, runner lenth/angle at that point that critical?
Thanks for all the great info.
[This message has been edited by BradP (edited October 11, 2001).]

BLOWNDRAGBOAT
10-11-2001, 05:11 PM
Isn't it funny how money makes problems go away...O.J. even proved it!!!!! I don't know why they lightening does that. I guess thats just the way they make em. Have you tried using the smaller diameter 12 point header bolts? They also make a set of positive locks for headers bolts that keeps them from backing out.

BradP
10-12-2001, 12:23 PM
The 12 point bolts i have are too long, can't get a box end on them past the tube. Have 6 point small head bolts on now and can still only get teh open end on 'em. I guess lightening just like sto torture us.

dyam
10-12-2001, 02:52 PM
Brad:
I'm using stainless allen head bolts. It's still a bitch to get to but it's better than regular bolts.
I still have to use a special allen wrench that allows you to be slightly off straight and still tighten them. Not perfect but it works ok.
Hope this helps.

turbo
10-24-2001, 05:24 PM
unchained how did you take that intake pressure on your pumps intake. drill hole somewhere in intake or in hand hole. I would like to check mine. I installed pro loader and wondering if I really needed it.

Unchained
10-27-2001, 04:12 PM
Turbo, On the Dominator pump there is a factory tapped hole on the right side of the pump intake. It would be easy to drill and tap a hole for 1/8" pipe thread in the intake on any pump. On the Dominator the hole is 4" forward of the bowl flange and 5" below the hand hole flange. To go fast you want 30 to 40# of intake pressure at top speed. The racers go higher pressure but it can cause shut down handling problems. Be careful, shim the shoe a little at a time. Maybe .040" increments.

dyam
10-29-2001, 12:01 AM
OK- I finally got the boat back in the water, after shimming the ride plate down a bit and rejetting the carbs from 80s to 72s and adding 6.5 power valves>
It runs a lot cleaner on the bottom and comes out of the hole quicker but it still gets black soot on the stern just above the exhaust tips( they exit below the water line).
Is this something I can experiment with and make go away or is this just something I need to get used to?
No I didn't have time to check the plugs, but if everything is perfect, will I still get the black mess on the stern?
Any comments will be appreciated!!