Mike Brichta Posted June 3, 2014 Share Posted June 3, 2014 I am looking to rebuild a Q-Jet for a GM ZZ454 engine and was wondering what size primary jets should I use. Thanks!! Mike Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted June 3, 2014 Share Posted June 3, 2014 you just can't go changing the jets in a Qjets, when I get home tonight I'll look for the link for tuning them, great article changing jets effects everything on a Qjets, idle, cruise and WOT Quote Link to comment Share on other sites More sharing options...
Mike Brichta Posted June 3, 2014 Author Share Posted June 3, 2014 Hey Sam, Thanks for the quick reply. I've done this successfully many times before just not for a Big Block engine. For small blocks I usually use something between a .068 and .072 jet size. I was just wondering what a big block engine would need. I know about the jet size changing all of the things you mentioned in your reply but if you find the article I would love to see it. Thanks!! Mike Quote Link to comment Share on other sites More sharing options...
wallaby Posted June 4, 2014 Share Posted June 4, 2014 One of the great things about the Q-jet is it doesn't care what size engine its on. If it's dialed for a 350, it will be dialed for a 454. The only difference is that one engine combo might be happier with a richer mixture than the other under power. Most engines live in a narrow happy band at cruise, so if the 350 was good at cruise, the 454 will most likely be happy with that same carb at cruise. You could go with a 72 and use a fatter rod; it will still hold the lean part-throttle mixture, but richen up more on hard throttle. It's pretty complicated just messing around trying to find what's best. Changing just the jet will alter everything, as stated above...changing just the rod will affect cruise and idle, but not WOT. I have found that throttle response is better with a leaner mixture, but you need the carb to richen up quickly to avoid pinging. Don't automatically think that bigger is better. Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted June 4, 2014 Share Posted June 4, 2014 Mike, this is very informative http://www.corvetteclub.org.uk/files/downloads/how_to_tune_a_qjet.pdf Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.