Rochester Quadrajet set up help

[Patrick H.]

Re: Rochester Quadrajet set up help

Don,

What jets and rods are you now using all the way around?

Patrick

[Don W.]

Re: Rochester Quadrajet set up help

Patrick,

Only the primaries were an issue and the secondaries were not touched. The primaries were changed as stated above and the rest is as in my original post and whatever summit provides in their re-build carbs.

Thanks for your help on this and other items.

If you want more info, I can check with Joe and get back with you next week.

Don

[Patrick H.]

Re: Rochester Quadrajet set up help

Patrick,

Only the primaries were an issue and the secondaries were not touched. The primaries were changed as stated above and the rest is as in my original post and whatever summit provides in their re-build carbs.

Thanks for your help on this and other items.

If you want more info, I can check with Joe and get back with you next week.

Don

Just wondering which primary rods you had in there presently.
Apparently it's whatever was in there originally, so you don't know for sure?

[Anthony D.]

Re: Rochester Quadrajet set up help

Try this site. I bought some parts from them in the past.

http://www.carburetion.com/quadrajet.asp

[Don W.]

Re: Rochester Quadrajet set up help

my new primary jets are 0.073" with a 0.036" metering rod. There was a 0.097" needle and seat which is now 0.130"

[Patrick H.]

Re: Rochester Quadrajet set up help

my new primary jets are 0.073" with a 0.036" metering rod. There was a 0.097" needle and seat which is now 0.130"

Thanks for the info.
Just comparing it to what I've matched up previously.

Patrick

[Clem Z.]

Re: Rochester Quadrajet set up help

he std Q jet N/S dia. is .129 and for performance applications you should use a "WINDOWED" needle seat so the fuel does not have to go up passed the needle to get into the float bowl. since a Q jet has only one N/S unlike a holley that has 2 it needs to flow enough fuel for all 4 barrels

[Don W.]

Re: Rochester Quadrajet set up help

Patrick,

It is also critical as to what air bleed sizes the carb rebuilder installed and that impacts all other settings. I don't know what size air bleeds were installed but, the dyno with air/fuel ratio shows we are set up in the right area.

Don

[Patrick H.]

Re: Rochester Quadrajet set up help

Patrick,

It is also critical as to what air bleed sizes the carb rebuilder installed and that impacts all other settings. I don't know what size air bleeds were installed but, the dyno with air/fuel ratio shows we are set up in the right area.

Don

I don't know that I've ever heard of anyone swapping the air bleeds or ever seen any available for purchase.

Yes, your A/F ratio looked good.

Patrick

[Clem Z.]

Re: Rochester Quadrajet set up help

you have to becareful with the air bleeds on a Q jet because some are in the top and some are in the main body so you can not just interchange parts

[Jeffrey A.]

Re: Rochester Quadrajet set up help

Don

Here is a name of a company that has a lot of parts of Rochester Quadrajet Carbs. I have bought parts for my Quadrajet. The person to talk to is Jim. They are great to deal with. Good Luck Jeff

[FONT='Arial','sans-serif']Carb Junky's LLC[/FONT]
[FONT='Arial','sans-serif']Professional Carburetor Restoration[/FONT]
[FONT='Arial','sans-serif']info@carbjunkys.biz[/FONT]
[FONT='Arial','sans-serif']www.carbjunkys.biz[/FONT]
[FONT='Arial','sans-serif']770-235-0775[/FONT]
[FONT='Arial','sans-serif']1-866-961-CARB (2272) Toll Free[/FONT]
[FONT='Arial','sans-serif'][/FONT]

[Don W.]

Re: Rochester Quadrajet set up help

Patrick,

On the air bleeds; this is not a '69 matching numbers carb. It is a rebuilt aftermarket 4MV that covers several dozen applications. So, as I try to match up the jets, etcs against the original '69 config, I can't verify the air bleeds are as in '69 or something totally different.

Don

[Patrick H.]

Re: Rochester Quadrajet set up help

Patrick,

On the air bleeds; this is not a '69 matching numbers carb. It is a rebuilt aftermarket 4MV that covers several dozen applications. So, as I try to match up the jets, etcs against the original '69 config, I can't verify the air bleeds are as in '69 or something totally different.

Don

I know; I've just never heard of anyone needing/wanting/having to replace them, nor seen them available for sale. It has never crossed my mind. I wonder how much difference it would/does make?

Patrick

[Clem Z.]

Re: Rochester Quadrajet set up help

I know; I've just never heard of anyone needing/wanting/having to replace them, nor seen them available for sale. It has never crossed my mind. I wonder how much difference it would/does make?

Patrick

it is a "fine tuning" tool used to change the air/fuel mixture

[Don W.]

Re: Rochester Quadrajet set up help

I was looking thru "my posts" and I don't see where I should have posted my final results.

2 dyno runs; 1st run to check baseline status, air/fuel mixture, etc. Carb primary jets and larger needle and seat changed; float level corrected by 1/4"

Results:
dyno used to reset idle mixture
dyno used to reset timing from 4 degrees to 16 degrees BTDC; vette mechanic reports '80's engine rebuild likely had pistons changed to ~ 8 - 8.5:1 (due to 16 BTDC)

• + 16 HP from 1st run to 221 rear wheel HP
• + 17 ft-lb of torque to 310 ft lbs torque 2 rear wheels

fuel economy test shows 14.43 mpg highway

Don