carb q's

[quiet riot]

I'm looking for recommendations for a carb. Specifically about size and diff versions. Thought about bg mighty demon or holley hp. Or maybe trying to use my current carb.
I'm currently running a 700dp on my 351w spinning 5k on a jet. The new motor is a 408 stroker, afr 205 race heads, victor jr intake, close to 12:1 comp 570 lift hyd roller. hoping to spin it closer to 6k.
Should I just tweak on the 700dp (or have a guru work it over)?
Do the holley hp's, demons, or a tweaked dp give much of a performance gain?
Has anyone tried the proform housing like summit advertises on a standard holley dp?
What size should I look at? The current 700dp worked great outta the box on my 351. Holleys calc says 700 should be ok with 400 inches at 6k but other things like cam, comp, etc also play into it. I saw a 383 test from a mag that got the best gains from a 950 hp (400+ motor) when compared to many other carbs even though the motor should have been better with a 700 cfm or so. Not sure how subjective this test was or how much tuning was done to each carb. I'm hoping to push 600 hp outta this motor if poss.
Thanks,
jd

[HOSS]

Everyone I know who has run a Demon says its and awsome carb. A 750dp Demon would actually flow 925-950. Why not look into a Dominator?

[quiet riot]

I dunno Hoss, are they any better for my app? Just for a quick comparison though:
mighty speed demon = $460
holley 750 hp = $650
working over current carb = ?($300)?
dominator 750 = $650
Whats people op's?

[Blown 472]

My buddy just pulled his pos demon off and bought a hp 950, the damn demon did not have air bleeds installed, they came in a bag and if you needed them you were to pound them in. demons are shit, save your self some headaches and buy a hp holley.

[Hotcrusader76]

Quiet Riot...
Here are some thoughts on carb recommendations for your application as indicated.
From an unbiased out-of-the-box point of view look into getting an HP950 Holley. I say this because those carbs out of the box on SBF have worked wonders on ETs seen on the track.
One of major reasons this carb is a better bolt on affair over a Demon is because of the booster passage size (0.150"). Anything more in size, I.E. Demon's 750 Mighty and Sea Demon (0.160") you're going to be running pig rich.
If you really want to go with a Demon, then purchase the 750 Might Demon#5402010GC or 750 Sea Demon#1402010EM and then plan to change out the 0.160" boosters with 0.140" Demon versions #128141. Demon doesn't sell a 0.150" version so the 0.140" version with higher jetting will work fine. Don't forget you need to get the tool in order to remove the spin nut on those Demons.
Nonetheless, when you break down the cost involved to properly set up the Demon you could have had a HP950 or even a professionaly prepped carb at that.
With regards to the Proform bodies, adding the mechanical secondary version part number to your 700DPs throttlebody will now make it a 750cfm carburetor. The airbleeds will need some major adjustment on your application because the main circuit side is set a little richer than what you'll need for that SBF. Start somewhere around size 35 on the main airbleed and 70-72 on idle. The boosters found on Proforms are typically toleranced around 0.139-0.143" depending on the quality assurance during it's rebuild. That can be good and bad, which definitely reflects client feedback with regards to that product.
Here is link to a proform build-up http://www.truckworld.com/How-To-Tech/02_holley_upgrade/holley_upgrade.html
All in all there is some contrast to different options, good and bad. If it were my carb I would go with the HP950 or even a builders hybrid 950 with doesn't use HP components is cheaper on the wallet.
HP950 Holley - $670.00
Mighty Demon 750- $515.00
Sea Demon 750- $500.00
0.140" Boosters- $90.00
Demon Booster Tool- $35.00
Custom 950 carb- $595-700.00

[TIMINATOR]

I vote for a Holley 800dp,but then again if you really want to go fast,get a REAL roller and quit messing with the wannabe roller. As the oil heats up(and it does,cooler or not),thins with age and the lifters wear internally(they do),the bleed-down rate increases and the lift and duration get less and less. This is worse than you might think because as the lifter bleeds, the intake closing point moves more and more advanced and the power drops off at high RPM. The dyno rats say no, but they closely control the oil temp,start with new oil on every engine,the lifters on your new motor are new(duh),and the pulls are of a short duration(12-20seconds). They look good in the magazine,dyno and on drag motors that run through the gears up and down, but down the lake for 30 seconds+,the power falls off.The heavier the valvetrain(BBChevy),the higher the rocker ratio(BBChevy1.7,BBFord 1.73),the worse it gets. I worked with a hydraulic roller on my tall deck 572 in the Eliminator for 2+ MONTHS testing 2-3 times a week,then put in a solid roller and gained 6+ MPH. I bought the KIT,that was recomended by the company as a jetboat cam,then tested with different springs(lighter,different rate),different preload,thicker oil viscosity,and an oilcooler until I was sick of the hassle. To be fair,mine was a worst case scenario because I run long (heavier) valves,BIG diameter(heavier)valves,a tall deck block,(longer,heavier pushrods),the BigBlocks 1.7 rocker ratio,and I DONT want to hear my lifters collapsing on a speed run. After a run of 15 seconds or so the lifters were all collapsed and NOISY! During the tests,on DIFFERENT occasions,2 separate lifters swedged wider from the excessive clearance, locked themselves in the block,and caused bent valves,requiring the removal of the motor twice for removal and repair of the lifter bores! After working closely with the cam company for the 2+ months and following all their recomendations,they offered to refund ALL of my money for their product,paid for the other parts damaged and ALL the gaskets! THATS when I switched to the solid roller and gained the 6+ MPH. That was 2 years ago,NO TROUBLES SINCE!Your results may vary. P.S. also had problems with the Hyd.Rlr in my new Vette too. TIMINATOR :(

[Hotcrusader76]

Oh yeah....
I personaly like the Demons over the Holley once they're prepped to work correctly. To bad it costs me an arm and a leg to get one set-up right.
1. Larger fuel capacity
2. Billet metering flows more consisent than cast versions
3. Better air-balance when comparing out of the box versions
4. Stronger billet baseplates when compared to cast versions
I am in the works of getting our first shippment of Demons sent to us over here. I've been trying to get them as kits so we can assemble them ground up like we do for our Holley's, but I guess they don't have phones in the sweat shops who make them....hmmm ...I dunno...so it looks like I'll have to take them apart to clean them myself. :rolleyes:
~Ty

[quiet riot]

hot crusador, so are those your prices? You carry the hp 950's? Pm me with some more info on the adv of having you do a custom 950. Thanks for the info.
Timmy, I hear what your saying. Concerns like yours made me call the cam manuf and record the part where they promised me the setup they gave me would work great without prob's. Like I said in my post about "running roller cams", if I find this to have issues down the road I'd rather switch to solid and adj valves than worry about breakdowns (or big power letdowns.)
Then again, I'm not going for all out performance. If I was I'd be in a big block air entrapment hull with a prop. :D
shsssse, don't spill this into the jetboat forum. :wink:
jd

[Hotcrusader76]

Quiet Riot...
I'll post this for everyone here since my prices are favorable to all ***boaters.
Because you're not racing this sled, the 950 Hybrid (Non-Hp) is what I would recommend. The TPC 950 with a slabbed/Nickel plated shaft and low profile button screws on the throttleplates would definitely make up for lost ground on CFM in comparison to the "HP" 950. Nonetheless it's a flawless build.
I overhauled Froggys 950 Hybrid with slabbed shafts and profiled boosters which gained him some incrediable numbers on his 21' Ultra 509BBC (Now Clownpunchers boat).Here are his numbers (http://www.tpcracing.com/testimonials.html)
One of our 950s (using a 4779 mainbody not an HP version) would run you $655.95 for an auto version and $675.95 for a Marine. Otherwise the Marine "HP" 950 runs $850.00.
Personally you don't need the HP version. Stick with a Hybrid 950

[Blown 472]

spam o ram, over a hundred hp gain??

[quiet riot]

hotc, so would the hp version just give more tuning options vs the 950 hybrid? Is this why you recommend the hybrid? or just money? BTW, I do race this usually a few times a year in the Columbia Drag Boat Assoc (a div of IHBA), but I do my fine tuning to fit in a bracket class with a few hundred hp shot of N2O (adj in 50 hp incr).
My main thing is just a reliable carb that is pretty good for my setup. Keeping in mind, most of my boating is done around sea level, but I do go as high as 8-9k ft to high lakes a few times a year. Currently, my 700dp works fine without jet changes or such. I'm not racing at the high lakes or rivers, and it does run a little fat but the msd seems to keep it in check enough and I can adj the timing from the drivers seat control if needed.
Thanks,
jd

[Hotcrusader76]

The HP does offer superior adjustability, and not to mention it uses the HP style metering which has a three hole emulsion vice the 2-hole (stock Holleys). The HP is a race carburetor and is benifical under those conditions.
If you're running in a competitive class, you can bet your opponent is running an HP or Demon.
~Ty

[quiet riot]

so me being the kinda guy that doesn't get into adjusting stuff to weather/altim's like most do at the races, I'd prob be better off with the hybrid 950, right? I like to watch the other boats and bs between rounds, not hash on the setup. Would I be able to notice a "seat of the pants" difference with an hp or dom? If not I wouldn't justify the expense I guess.
Most the rest of the time, I like to hook the boat up, throw a cooler in and go boatin. I'll get intouch with you within a few weeks when I get closer to finishing the motor.
Thanks,
jd
ps. I do have to run within .1 or so of the bracket's dial in to have a chance, but I bring my own bottle of oxygen for that.

[Dave C]

I had the HP 1000 on two of my motors. It was nice right out of the box and I was happy. I slapped it on, adjusted and I was away.
IMO I don't think the HP was that expensive given how nice it was compared to a regular Holley.
I never used a Demon.
However, if I went to lakes at higher elevations they required adjustments. NO way around that, hence the EFI now
;)
Anyone try the carbs externally adjustable metering plates? (aka Willys) I know a few drag racers that have tried them and they swear by them.
Also maybe Hotcrusader can help with those damn throttle plate shafts that begin to "stick" after some use and won't go back to idle all the way by themselves. :mad: I hate that...

[TIMINATOR]

QUIET;at the most you'll get from a carb change is 20HP, so why spend the $300-$600 to only get 1 MPH? Non-airentrapment hulls usually take 20HP per MPH gain in my experience, no seat of the pants gain there. Borrow a carb and see if you really care anyway before ya spend the cash, or you could buy a set of solid rollers and set the lash at .005 and see if I'm right about the hydraulic deal. TIMINATOR

[Snowboat]

Timinator; why set the lash at .005", isn't that a little tight? I've only tried going from .028" to .020". What happens at that tight a lash?

[TIMINATOR]

Thats the "normal" setting for running a solid roller lifter on a hydraulic roller cam for testing or actual use when you find out it goes way faster! I've done it many times with my customers as an experiment and have never gone slower! Some of them have purchased solid roller cams, some have run the solid lifters on their hydraulic roller cams for YEARS! I did with the C---e hyd rlr in my Vette for about 5 years before I sold it,the buyer ran it like that for 2 more years until the car was totaled. Set the lash once a year. Since hydraulic rollers don't have a ramp to take up the lash, thats why the lash needs to be tight. Oh yeah, the reason that I put the solid rollers on the Vette cam,is because the aftermarket hydraulic roller(220at.050) slowed the car down by 6 tenths and 5 MPH! I worked with it for 3 months too, then put the solids on it and it gained 1.2 SECONDS and 9 MPH!!!! Haven't used a hydraulic roller again till the FIASCO with the boat early last year. Since then I WILL NEVER USE USE ANOTHER ONE!!! Your results may vary. I gave some reasons in the earlier post. I own a race machine shop (FULL SERVICE),I experiment all the time and I DON'T SELL OR INSTALL ANYTHING THAT I DON'T BELIEVE IN OR HAVEN'T TRIED. TIMINATOR :)