I have an automatic 73 smallblock with an edelbrock performer intake manifold (1991 vintage), holly 390 cfm carb, slightly upwards of 9.5:1 compression (forged pistons) and a 260 cam. aftermarket electronic ignition modified original distributor.

the smallish flow carb was installed when i lived at 7000 feet above sea level. the shop that rebuilt my engine said its all they use way up there. i think that is WAY puny for SE michigan's elevation.

I'd like to replace this carb with something that will 'just hook up' to the existing throttle linkeage. I asked in the C3 general forum about finding a shop here in SW michigan, and reponses have led me to do this myself. I'm not afraid to wrench, having done a lot of the restoration on this car (rear end, front ent, steering, brakes, instruments, etc). but i am not a carb expert in any way.

I have the original rochester, and might want to have that rebuilt, (so can install and hook up ram door or whatever its called), but I bet the height of the intake manifold is too high for the rochester to fit. the holly i had allowd the use of the original air cleaner - is there a way to hook up the ram air door to such a setup? how does that work anyway?

so - opinions please. model numbers are helpful. i am a newby when it comes to carbs. tips on dialing one in are helpful too. i liked the holly, it seems simple - contrasting different carb choices would be helpful.

also: where should I start WRT timing with that cam at this elevation (about 900' above sea level). we typically run more advance at 7000'. or is this just "dial in the advance until it pings, then back off till it doesn't ping".

thanks in advance for helping a new, carb ignorant member.

 

Get your Qjet rebuilt, or have a go at doing it yourself and use that...best carb for the job IMO.
If you have a standard performer intake there shoudnt be an issue with hood clearance.
If you want to have the carb rebuilt for you, PM Lars here on the forum and ask him for his services paper, lists all the fab stuff he can do to help make your car run like it should!

 

What do you mean by the ram door? Are you talking about the choke on the front two barrels? The flap on the front two barrels is the choke, and is very useful for cold starts. The flap on the back two barrels is typically vacuum operated and opens when there is enough air flow to support the secondaries opening. Can you post some pics?

The choke I had on my Q-jet was controlled by a bi-metallic spring that screwed to the manifold. Does your manifold have that provision?

Ken

 

No, he is talking about the cold air induction hood on the 73-75 Corvettes.

For the OP, bolt the Q-Jet to the Performer and use the original air cleaner. I ran that set up on my '75 for about 7 years.

 

the ram air from the factory only works when you have the acc pedel fully depressed (enough to trip the electric switch at the acc pedel).
options: 1) if the solenoid still works and the factory function is okay with you, leave it. 2) if the solenoid has failed (use 12v source to test), you can r/r but they are getting costly $$$ now. so you can remove the "flapper" door and have the cold air scoop funtional full time.

if the holley fit under the hood, the q-jet will fit. they are the same height.

i recommend that you rebuild your original q-jet. sounds like you have plenty of aptitude - just need some info. get some books, e.g., roe, ruggle, also do search and download lar's papers, and . . . . good luck

 

Have a 73-350 with a Torker II and Holley 650 DP, nice combination. The hood on a 73 is a little higher so you have more options.

 

Why would you want a lower CFM carb at high altitude? This doesn't make sense to me. At high altitude the air is thinner, meaning there is less oyxgen to combust with the fuel. Therefore, to get more oxygen into the motor for proper combustion wouldn't a larger CFM carb with smaller jets be the right way to go?

Not that it matters for you now, it just seems strange.