Quadrajet intake gasket is wet, erratic high idle.

[pontiacgp]

II had it as low as 900 warm in park, and it ran it's best on the 305 that way. But again, what the owner of the carb must to do make it run right on his 350, is different than the settings I had to make it run well on the 305. I set it where I know it would run decent as soon as he got it. It's his job to figure it out and tune it precisely to his and his engine's liking.

I asked if you could adjust it lower, if you can't adjust it lower then there is a problem with the carb

 

[MrSony]

I asked if you could adjust it lower, if you can't adjust it lower then there is a problem with the carb

I could adjust it lower, yes. I left it at 1000 after I fixed the issues with the fast idle and what not.

 

[pontiacgp]

how low can you get it to before the engine stalls?

 

[Bonnewagon]

OK- understood. But be aware that you may need to go help him get it adjusted properly if he can't or doesn't know how to get it to his liking. 900-1000 in drive is more like 1200-1300 in park with no load and you are effectively out of the idle circuit. If it runs best at that rpm there may be an idle issue. I have taken a lot of Q-jets apart and the difference in jet/rod sizes in not as great as one would assume. A carb for a 301 and a 455 are only a few jet sizes difference. In fact I often use a known good 400 motor carb as a test mule on all kinds of motors. I can always get it to run perfectly at 500-650 idle rpm if everything else is correct.

 

[pontiacgp]

Mark, that's the test I always do after a rebuild or a change of rods, see how it runs at 500 rpm....

 

[MrSony]

In a perfect world, I'd have a stock, modified, and balls out race version of every engine ever made from GM, Ford, Mopar, etc to test carbs on and just rev all day long. But, until such a day comes, I'll have to deal with what I got. Or at least until I get my Buick rebuilt. It was a good test mule while the trans was busted 😛

 

[pontiacgp]

In a perfect world, I'd have a stock, modified, and balls out race version of every engine ever made from GM, Ford, Mopar, etc to test carbs on and just rev all day long. But, until such a day comes, I'll have to deal with what I got. Or at least until I get my Buick rebuilt. It was a good test mule while the trans was busted 😛

from a 78 350 to a 305 there isn't a difference when setting the idle on a quadrajet. I strongly suggest that you invest in the Cliff Ruggles book on quadrajets. Many of us refer to it when working a quadrajet.

 

[MrSony]

from a 78 350 to a 305 there isn't a difference when setting the idle on a quadrajet. I strongly suggest that you invest in the Cliff Ruggles book on quadrajets. Many of us refer to it when working a quadrajet.

I do have the book. It's very informative. Only so much one can learn from pictures and words, though.

 

[Bonnewagon]

While Cliff's book is very good- I consider Doug Roe's book to be the Q-jet bible. His explanation of the physics of carburetion is spot on-so even an idiot like myself can understand how they work. He spends a lot of time on a thorough stock overhaul and only later does he delve into high performance modifications. I am always referring to his secondary metering rod charts.

 

[Longroof79]

I have the Doug Roe book sitting on my shelf next to my Holley manuals. 🙂