1986 Carb Help

[iroccopz28]

I have a 1986 Iroc-Z Z28 Camaro with a 305 LG4 and a 5-speed transmission. I believe that it has a compter controled Rochester 4bbl carb on it. What I am trying to find out is if there is any way that I can take a Carter Thermoquad carb that I have and make it work on this car. Does anyone know if I can make this carb work with this car.

I wrote to edelbrock asking them if it was posable to make a non computer controled carb work on a car that originaly had a computer controled carb on it, and all they could tell me is that they didnt sell a computer controled carb . So I would greatly appreciate it if someone has some good information about this.

Thank you for your time,
Jim
[email protected]

[hotrod_chevyz]

If you run a non computerized carb such as the thermo quad,you will have to switch to a earlier year model distributor.The reason for that is the TPS is built into the carb.That controls the ignition timing advance,wich is required for the engine to function properly.The distributor on your car now is electrically controlled by the computer,via information fed back to the computer from the TPS inside the carb.So a vaccume advance HEI distributor would have to be installed because it predates computer controlled ignition timing.A single hose replaces the entire computer essentially.

So you would have to get a chevy 305 or 350 distributor from a 77-79 year model car,or buy a new one for that year of car

some problems you might run into are

1:improper linkage alignment for the throttle cable and transmission detent cable

2: the thermo-quad is a spread bore carb and a adapter will have to be bought,alond with a shorter air cleaner

3:to my knowledge a thermo quad has never been put originally on a 305,therefore isnt properly jetted,and will gas out anybody driving behind you,as well as fowl spark plugs,and cause inconsistent ignition.

a earlier year q jet and older HEI distributor would be your best bet.It will run way way better,and parts and rebuilds will be way cheaper.My q-jet rebuild kit costs ten bucks.The distributor new is 170 dollars,but you get like 70 bucks core on them.I believe i ordered a 1977 monte carlo distributor and carb for mine,before i went with a high rpm intake and carb,and to be honist,it really didnt add any HP.

[hotrod_chevyz]

the qjet and stock intake ran as good as my torker intake and carter afb.But my carb as it sits runs no better than my qjet did,but it costs over 60 bucks to rebuild.

[FormulaLT1]

What he said plus welcome to the forum.

John

[iroccopz28]

Thank you for the information. Thats the most information that I have been able to get from anyone. I have been looking at an edelbrock performer intake (edl-3701) and cam (edl-3702). Maybe it would be less complicated to go this way and rebuild my carb. Although I have heard that these rochesters aren't worth rebuilding, but i havent had much experience with them yet.

Thank you again for the information. I will write it down (or print it) and keep it on hand incase I feel darring.

Also thanks for welcomming me here FormulaLT1, I hope I can be a help to someone else at some point.

[hotrod_chevyz]

I would stick with the carb you have perhaps rebuild it.It is more than efficient for the application it will be serving.For the price of the TPS inside the carb,you could get a new vacume advance distributor that will add some power and cure any sensor or computer related redundancies.With the new distributor installed,you will have no need to replace the TPS and other electric components inside the carborator,as they will be rendered useless with the earlier distributor installed.But in the same time the fuel will be used more efficiently,therby reducing emmisions.

[hotrod_chevyz]

Your welcome and welcome to the forums.A great amount of knowledge can be attained by investigating past threads and articles,as well as improve your knowledge and capability of using and understanding terms used in automotive discussions.By browsing threads of the past,you may find and utilize information you never knew you needed.

[iroccopz28]

So if I was to use the same carb i would want to look into a new distributor? Should i actually be looking for a new one with vacumm advance, or would i need one out of an older car like we talked about before. That idea sounds like it makes a lot of sense. Thanks again, you have been a great source of information.

[hotrod_chevyz]

i ordered a 1977 monte carlo distributor for mine any vaccume advance distributor will work as long as its for a 305 or 350.Once you do that when you go to rebuild the carb there will be no need to replace the throttle position sensor,therfore the twenty dollar carb rebuild kit from a local parts house will have everything you need to make it run as good as it can.And you dont have to worry about inspection because the emission system is still in tact that way.Good luck and your welcome let us know what the outcome is.

[iroccopz28]

Awsome, you have been such a big help. At leaste now i know what i should be looking for. It makes it difficult to look for parts when you dont fully understnad what it is that you should be looking for. I am glad that I found this site, because without it i would still be pulling my hair out trying to find some usefull information. Thanks again.

[camaronumerouno]

i have the same car...an 86' z28 with the computer controlled q-jet, except with minor mods...and i had planned to buy either a 600cfm performer edelbrock or a Road demon jr. 525cfm with vacuum secondary and electric choke...either way i will also be purchasing an edelbrock performer intake....will I have to go through the same deal (with the distributor replacement and all,) as iroccopz28 if i go this route ??

[hotrod_chevyz]

Yes you will Mike and your welcome again and good luck James.

[hotrod_chevyz]

If you dont go with a earlier style HEI distributor (late 70's)your car will not have proper timing advance,and you could possibly damage the engine or it will just run like poo Mike.And be sure you get the right CFM carb,most hi performance carbs are not properly jetted for a 305 and that can make it run really bad.Unless you have Installed bigger heads or a hot camshaft,you will gain no ground by putting any intake and carb other than the one the factory specified.All they will do is make your car worse on gas and it will actually be slower and harder to start.Sure will make it look better tho.