Im building an engine that should put out around 380-405 HP. Can I modify a 1850 600 to do the job or am I better off getting a bigger carb? If at all possible I really want to keep the smaller carb for responsiveness, but I don't want to cut myself short of potential horsepower being unused and/or running out of breath at the top end (which should be around 5500, maybe 6000 tops).

Ive read about thinning the throttle blades and shaft for extra cfm, but dont know if this alone would cut it. I also thought about going to a squarebore.

Im open to suggestions and comments.

 

holley 1850 is a square bore carb. 380+hp at 5500 rpm is a pretty big engine(a guess). Maybe a 750 would work better. Engine size and rpm range is the info we need to figure what size carb will work.

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82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

 

while the 1850 would probably work...techically...you'd be much better off going to a 750. the 600 will be a bottle neck.

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

 

yeah i would say normally go to a 750, BUT for all intents and purpaces, the race motor was limited to a 500cfm STOCK holley two barrel.. only mods allowed were to the metering block. anyways, it supported a 450 hp 355 engine that breathed up to 7000 at the end of the straights

Steve

 

FWIW, 2-bbl & 4-bbl CFM ratings are apples & oranges, since they are tested at different vacuum levels.

That said, I'd agree that your 600 would be a limitation to an engine turning over 5000 RPMs.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam and intake, World 305 heads, Hooker headers & y-pipe, 3" Catco cat & 3" cat-back).
57 Bel Air, my 1st car. 0.030 over 396, 9.7 CR forged TRWs, Weiand Action+, Edelbrock 1901 Q-Jet, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlock header mufflers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, LT MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1/95.5 @ 5800' Bandimere.

 

Well theoratically you can put a 500 cfm carb on a 2000hp motor. Of course if you do..it won't make anywhere near 2000hp.


five7kid is right tho..2bbl carbs test at 3" of vacuum, same as FI. 4bbl carbs are rated are 1.5". A 500cfm 2bbl works our to 300 or something when measured like a 4 bbl..I'm not sure exactly, the conversion is NOT linear.

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

 

Hey, thanks for all the replies guys.

First, I want to correct myself. When I said I was thinking of going to a squarebore (typo), I meant to say spreadbore. I was thinking of using a spreadbore 650 DP if that would help. The car is eventually going to have a manual tranny, so the DP would probably work okay.

Second, I was leaning towards building a 355 similar to the Miserly Mouse featured in the April 2001 issue of CHP. I like this engine because it is built with budget parts and uses 87 octane gas. They claimed 390 HP at 6000 rpm using a basic 9:1 shortblock, vortec heads, performer rpm intake, Comp 268 cam and of all carbs; a 625 cfm Road Demon. They even tried using a 750 cfm but had no substantial increase in power. Im thinking that I could save money and get similar results by using a Holley 600 and hopping it up a little with some "creative" grinding and machineing. Surley I could get an extra 25 cfm out of it to match the Road Demon.

So tell me what you guys think. Am I just wasting my time or do you think it would work pretty good? Also any tips on modding the carb would be appreciated. Like I mentioned before, I have read a little about thinning the throttle blades and shaft to increase cfm. If there are any more mods please let me know.

Anyways thanks in advance and sorry about writing a novel.

 

btt

 

I was leaning towards building a 355 similar to the Miserly Mouse featured in the April 2001 issue of CHP. I like this engine because it is built with budget parts and uses 87 octane gas. They claimed 390 HP at 6000 rpm using a basic 9:1 shortblock, vortec heads, performer rpm intake, Comp 268 cam and of all carbs; a 625 cfm Road Demon. They even tried using a 750 cfm but had no substantial increase in power. Im thinking that I could save money and get similar results by using a Holley 600 and hopping it up a little with some "creative" grinding and machineing. Surley I could get an extra 25 cfm out of it to match the Road Demon.[/B][/QUOTE]

Well acording to the calculations 5500 rpm could be achived with a 550ish cfm carb, 6000 could be achived with 616.13cfm. Now actualy geting full power with a smaller cfm carb is another story. Ther is a carb that is designed for exactly what you plan on doing,
holley "80670" 670cfm. That carb will give you plenty of flow with no fine tunning, unless your very picky. I would get the cfm calculator at www.engineprosoft.com/ "free"
and see what you can get as a stock carb instead of tunning a smaller or bigger carb for your needs.
SSC

 

Well acording to the calculations 5500 rpm could be achived with a 550ish cfm carb, 6000 could be achived with 616.13cfm. Now actualy geting full power with a smaller cfm carb is another story. Ther is a carb that is designed for exactly what you plan on doing,
holley "80670" 670cfm. That carb will give you plenty of flow with no fine tunning, unless your very picky. I would get the cfm calculator at www.engineprosoft.com/ "free"
and see what you can get as a stock carb instead of tunning a smaller or bigger carb for your needs.
SSC [/B][/QUOTE]


I agree, I would think the 600 would give a bit more throttle responce. If it were a track only car, I would say 750, but a street car doesn't live at WOT.


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1992 Pontiac Firebird 350/Six Speed
1987 Toyota Pickup 383/500+ HP

 

Check these two threads before you buy a carb.

https://www.thirdgen.org/messgboard/...ML/000558.html
https://www.thirdgen.org/messgboard/...ML/000660.html


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People who think they know it all,,, are especially annoying to those of us who do.