QuestionAs an old classic car guy, I no longer tinker with them. My son has caught the bug, He has a 1987 Olds Cutlass Supreme that was modified to a V8. He recently bought a 1962 Rochester 4GC Carb at a cars and parts show. The seller said he needed a Heat Riser to attach the carb. to the intake manifold.
1. Where can he get one for this carb? Cost? Assembly instructions?
2. Does he need the heat riser gasket kit as well?
He had a V6 in it when he bought it. Converted the original carb to a Holley Manual -too much hassle.
He can be emailed at if you need more information.
Thanks.
Mark
AnswerHello Mark,
I'm old enough to remember these cars new.....and considered them a smog choked low point. Now they're collectable and I understand why.....just like we like to collect '60s and older because we grew up with them, so do the younger guys collect '70s, 80's and even 90's.
In your case, there's a huge difference between how cold start warm up (heat riser) was done in the sixties versus the eighties. Basically, the former was more electromechanical and the later more electronic/electrical. Here's what to consider:
Simply speaking, a heat riser system uses a bimetallic spring and butterfly valve on the exhaust manifold (usually RHS) which closes when the car is cold. The closed valve backs the exhaust gases through a passage in the intake manifold under the carb. and exits through the other exhaust manifold. As the car warms up, the exhaust manifold spring/valve opens and exhaust then works normally. Additionally, on automatic choke equipped cars, there is a dashpot on the intake manifold into which a second bimetallic spring is mounted, attached to a rod that is inserted into the choke butterfly valve. When cold, the spring/rod keeps the choke closed for easy starts and gradually pulls the choke open as the car warms. Crude by today's standards, it worked (usually)
So, to use your '62 carb, you'll need to replace both exhaust manifolds to the earlier type, replace the intake with an old style with the crossover and get the choke pull-off spring and rod assembly (or electric version if so equipped) plus gaskets. Also, you need to check if the transmission is the type that works independently from the engine like a 700R4, etc. If your transmission has a feedback loop to the engine, you'll have to replace it with one that works stand-alone and modify the engine controller accordingly. Easy!?
What you're running into is the change in modification procedures for 60's cars vs. 80's cars. Gone are the days when you could swap a manual for an automatic or vice-versa in a weekend. Electronic engine and transmission controls with interconnected feedback loops help efficiency but sure are complicated!
What I'd recommend is to forget the 60s' carb. and get a new one designed to work with your car. Summit Racing Equipment carries a number of kits to do this and Edelbrock carbs make a reproduction Rochester updated for todays cars.
Good luck and keep encouraging your son. We need these future gearheads!
Best,
Bob
