Happy Holidays to all! I'm thinking about replacing the old rottenchestor carb on the 72. It's a slighty modified 454 with better pistons and a mild cam. Anybody change carbs out there and what did you use. I'ts not a numbers car and its not the orig. carb anyway. I see in the Summit cat. that Holley has a rebuilt Rochestors and also Jet performance carbs. Anyone have any experience with these?

 

I've always had Holleys or carter thermquads. Edelbrach AFB I believe is nearly identical to the T-quad but updated. Do you still have the original intake? either waythe AFB's spreadbore for sure andI believe availible in a square bore . Your intake should be a spreadbore. Holly's used to have a problem with back firing ruining them but they have solved that problem now. Both are very adjustable and good reliable everyday carbs. You could also go for a high dollar Demon. Cheers

Give a look here....... http://www.shopcarburetors.com/

 

Hi and Happy Holidays, I think there is a site to help you calucate CI vs carb CFM, but can't find it now. A Q-Jet should give you about 750 CFM and that should be enough. Mabye some else can be of better help, PG.

 

Edlebrock has a replacement for the Q-jet that originally came with the 454. I have been using one for about 4 years, and the only change I have made is to install off road spring loaded needle seats in the bowls. That keeps the bowls full on those high speed escapes...

 

The CFM calculator is at:

http://www.csgnetwork.com/cfmcalc.html

I punched in a 454 at 92% efficiency (high for an "average" car, decent for a good cam combo), with a 5000 RPM redline, and got about 600 CFM, 650 for 100% efficiency (high perf cam and/or mild boost). At 6000 RPM, you would need 725 CFM at 92%, and almost 800 at 100%.

Carbs are like politics and religion, everyone will have their own experience, opinion, and evidence. I like Holleys, and haven't had issues. I have used Qjets on boats for years, and (other than gumming with old nasty gas) haven't had issues. I'd love to throw some Marine Demons on the boat, but they don't fit the budget. The Qjet on the Vette had 211k miles on it with one apparent rebuild. It was working fine when I swapped it out for a Holley 4150 just because I had it on the shelf, and it looks good with all that polishy shine.

bill.

 

A well tuned Q-jet is a very good carb IMO. Put a brass float in it and pleated paper fuel filter.

HP Books has a very good book on Q-jets. Covers everything from rebuilding to performance tuning.

 

Thanks guys. I agree with all of you. I have a Holley on my Cuda that I haven't touched in 10 yrs. I use the Edelbrock on my street rod and never touched that either once I but it on. I do have the orig. manifold on and I did order that Rochester book from Midlife Classics Books yesterday. I never had much luck with the Rochestors and nobody has parts for them. Maybe the book will list some suppliers and show me some trick to get this baby to work. The machine shop that did the work on my engine races big blocks and swears by them. Hey Wedge are you running a 454 also and do you happen to have the part number you are using?

 

Rich,
I'll get that part number to you tomorrow, and yes I am using that on my LS4 454. I am also using a Performer RPM manifold with a matching RPM mid grind cam, and a Pertronix breakerless igniton with a 40,000 volt coil. NO problems smokin the TA's into second gear... If you are considering keeping the appearance stock, you might want to pass on the manifold, it will require a taller hood. I needed 3" more clearance, the right side of my car is now a mystery when I drive. Can't see a thing over there. An LS6 low profile intake builds great HP... and you can keep your original hood
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Rich
[align=left]The carb I used is the Edlebrock 1910 Performer RPM Q jet repacement. Works Great.
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Thanks, If I can't get mine to work I'll go for that one.