Topic: Carb tuning and testing
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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Im finding it hard to locate anyone in the Pittsburgh area to wet test and/or tune my carb.
The Rook 2011-06-26 12:10:06
Anyone able to offer me any help here?
I have an edelbrock 1411 750cfm and I know its a tad too large but dont want to change it out unless absolutley needed. I get that initial hesitation and cant just stomp on the pedal and go, I have to tickle it a little. ( cant blame a fella for wanting to lay a little rubber down on the road can ya???)
Ive rearched here and understand that maybe theres too much air and with the proper tuning it can be remedied........
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Lifetime MemberManteca, CA - USA
Joined: 11/20/2005
Posts: 3623
Vette(s): 1978,two tone,Metalic Rootbeer & gold
1975 L48 4 speed
Hi Dan, I'm certainly no expert, and I've never worked on a Carter AFB or the Edelbrock equivalent but, if you've started with a 750 cfm carb (and I too favor more air) it doesn't seem as though that should perform that poorly, at least I've never thrown on a Holly 750 that didn't work well out of the box. I don't know about spacers and such that some carbs seem to prefer but all I can imagine (forgive me for stating the obvious) is to read the spark plugs and resize the main jets if needed. If the spark plugs don't read rich or lean there must be a more complex reason for the poor throttling. That carb is famous for "easy". Please keep us informed on this story. Good luck buddy.
Jimmy B.
Just can't wait to get on the road again. 
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Lifetime MemberManteca, CA - USA
Joined: 11/20/2005
Posts: 3623
Vette(s): 1978,two tone,Metalic Rootbeer & gold
1975 L48 4 speed
Oh Dan, you didn't say if that was a new carb or one that's been sitting, or it just deteriorated over time.
Jimmy B.
Just can't wait to get on the road again.
Click to see larger views!
It along with the intake mainfold were new on the car about 5 or 6 years ago. To be honest my life was so crazy for so many years that now Im driving the car more than I ever did. This is why Im finding new problems with old equipment...lol
The Rook 2011-06-28 11:06:09
Lifetime MemberManteca, CA - USA
Joined: 11/20/2005
Posts: 3623
Vette(s): 1978,two tone,Metalic Rootbeer & gold
1975 L48 4 speed
The accelerator plunger would be the most obvious suspect to create a hesitation when you depress the throttle, meaning time to rebuild the carb, but sticking/rusty centrifugal advance weights in the distributor or even a bad tune-up can cause the same affect. Maybe even a vacuum leak, but it's always best to eliminate all the possibilities by taking a long ,hard look around before spending money on the process of elimination by buying stuff you might not need right now.
Jimmy B.
Just can't wait to get on the road again.
Click to see larger views!
if you have pretty much a stock motor the 750 is to big, every one that I have talked to guys who have tryed to run a 750 on a small block unless it was a built big in. motor say the same thing and that is they have a hesitation, a friend of mine went through the same deal, he changed the rods, springs, jets, fooled with the pump, waited hours to talk to Edel. tech's, they didn't have the answers either, went with the I believe the 650 runs great, ran a 600 on a 283 I had and it ran great to.
It has a mild cam....The 750 was recomended by an old timer mechanic who has since passed away. He was a chevy 350 expert and did alot of my early on mechanical work.
If he were still alive he'd have that carb in check for sure......
ok, here are a couple formula's to get you close.........350 cu in X 2 - 15%= 595 cfm, for a healthier engine subtract 5%.........#2.......350 cu in X 6000 max r.p.m. X 90% VE /3456 = 546.87 CFM, stock engines run about 80-85% VE and performance engines run about 85- 90% Volumetric Efficiency, with a mild cam and intake with 103 K you are pumpin out stock H.P, my guess a 600-650 CFM carb would work for you.
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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