I have a c3 corvette that for some reason someone put a 350 l98 with a rochester carb in it(auto 3 speed). Any one got this set up in their car? the engine seems almost stock except it sounds like it has a big cam(its very choppy) and is no longer fuel injected. The car has little power from a dead stop. But it will get a little loose in the rear at 50 if you drop it in 2end and give it all she's got. Any ideas? I've never worked with a engine modified this way. I'm thinking its a problem with my timing curve.

 

Need more info like what carb & CFM, manifold, cam, CR, ignition system, etc.

 

The carb is a rochester quadrajet 650 with vacume seccondaries on a Edelbrock intake manifold The distributor has a vacume advance and It looks to be the one that came on the original l48 that came in the car (timing set to 6 degrees TDC). The cam is where I am lost. I do not know any information on it because I bought the car like this.

 

Is it a dual plane manifold? I thought Qjets were 700+ CFM. Need to be sure that the carb is set up properly. Get a factory service manual or HP Books Rochester Carb book or Cliff Ruggles Rochester carb book. Probably could use a little more timing too.

 

It is a dual plane manifold. I'm fairly sure its a 650 but I could be wrong. This is actually the first non fuel injected car I have worked on. I'll get my self that book and try some more timing. I'm sure whatever it is must be simple because it is running great. Just not impressive off the line.

 

Your rear end ratio will affect off the line performance as will tire size although not as much. If it's that good at 50 in second, about a half-point (3.08-3.55) will improve your take off performance. Better yet go to a 200 4R and a 4.11 rear. You'll have neck-snapping take offs and the overdrive will make it driveable on the freeway. My 79 has a 3.55 behind a 200 4R and I'm turning about 2200 rpm at 75mph,I have decent take-off. Anything less then perfect traction and the 265's will spin pretty hard.That's with an 850 cfm carb on a 350 motor,I expect it will crisp up quite a bit when I put a 625 cfm on it.
I'm guessing from what I read in your posts your cam was chosen using the "more is better" theory(sorta like my 850 carb.) To get the full advantage you need to open up the exhausts,raise the compression at least a point,two would be better, and lower your take-off gear ratio. If you lower the overall gear ratio very much you will turn what sounds like a pretty nice car into a gas hog.
Probably your best course of action would be to change the cam to one take makes torque a little lower in the rpm range (at least the cheapest). If you have another set of wheels and the vette is strictly for fun then go the gas hog route! Good Luck!
Ron










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This car is just for fun so gas is an after thought. I just had my neighbor who is more familiar with older chevy engines take a look and I learned how to read a vacume gauge correctly. My timing needed to be advanced to about 10 degrees TDC. He also adjusted the vacume secondaries to open quicker. It sounds much meaner now. I unfortunately can not test it out until some of this snow melts. We got over 3 ft last week here in VA. I'll have to look and see what my rear end gears are. This may be a 2 part problem

 

Another area to check is the mechanical advance. The stock distributor came in very slow. Lighter springs/heavier weights will speed it up and help low end.

 

ok the snow is melting here so I dug the last bit of snow up and go the car out of the snow. some one chime here but forward the tires bark a little and I take off much better under full acceleration tires are 255. second gear is about the same as it was before... but in reverse I can smoke the tires off with out hesitation. I think I'm now at a gearing issue as suggested above??? I want to see smoke going forward and feel whip lash in my neck under hard acceleration.

 

I was going to sugest setting your timing to 10 TDC but your neighbor beat me to it.

Next thing would be change the gears to 3:55. This will make a big difference off the line and still be good during a roll.

Schoon