Yesterday I wrote:

"I’m having problems with acceleration. It is a freshly rebuilt 350 with a Qjet. I’m thinking that it might be the vacuum advance. On a 1970 350/300, was the vacuum drawn directly off of manifold vacuum or from a metered carb port. Any advice on the problem would be helpful."

I can't believe that no one out there could help me. Not one reply to my request.

 

It comes from a ported tap. It isn't metered except that at a properly-adjusted idle, it's off(zero vacuum).

 

You need to be more specific about what type of acceleration problem you're having. Is it a bog or stumble? Is the engine breaking up at high rpm? What's the configuration of the engine? Is the carb new, rebuilt,original? Cam specs? How is your timing set up? What ignition are you using? Give us a little more to go on and it's possible we could give suggestions.

 

It is a stock set up. Rebuilt Qjet. Single point distributor, timing set at 8 degrees BTDC. It does not miss or stumble at high RPM, just when accelerating and then only until the RPM increases to above about 2000 RPM.

 

Sounds like a fuel problem. Either bad pump or restricted line. Could be inside the carburetor if it wasn't built properly or sat a long, long time.

 

It sounds like you have some tuning issues. First real;ize that a stock 300 hp smallblock pushing a 3400 pound car is not going to be a rocket ship. That being said try the following. Set your timing up so that, without vacuum advance, you get 36 degrees advance by 3000 rpm. You can read Lar's papers in corvettefaq to see how to do this. You may have to change springs in the distributor and make some changes to the slot that limits mechanical advance in the distributor. In the end you should be around 12 degrees advance at idle and 36 by 3000 rpm. On my car, with a limiter bushing in the distributor, I run around 16 degrees at idle and 36 degrees by 2800 and it feels good. Once you've done this make sure your points are adjusted correctly and that they're clean. I have a Crane XR1 conversion on my car so I can't give you a lot of pointers on points (no pun intended ) other than make sure they're a quality set and that they're working right. Then move on to the spark plug wires. Make sure all the wires are secure and that they are all separted from each other so you don't get crossfire. Lastly I would check the carb. If it's the original carb it's probably in need of a rebuild. Other than Lars on this forum I don't know of many people or places that can do justice to a Q-Jet. Maybe others here may be able to help in that area. I've had two q-jets on my car, the original and a replacement that I bought from GM when they were still making them. Neither one worked as well as I thought they should. I changed over to an Edelbrock square bore carb and couldn't be happier. I'm sure you'll get many varied opinions here about carbs. I'll just say that I'm not a fan of Q-jets and, unless you're looking for every ounce of horsepower, I've felt that the Holleys weren't worth the effort involved to tune them correctly. Like I said, you'll get a lot of opinions on this topic. This is just mine. So, in conclusion, I would say that your best bet is to get what you have to work correctly and then assess whether it provides the performance you want. If it doesn't either you're going to have to modify the engine or replace it with a more powerful one. Good luck.

 

Your description is still a little sketchy. Is it, like vroooooom ugh ugh,,, or is it more, vroom ugh vroom ugh vroom ugh, or is it just a very slow but steady, v . r. r. o. o. o. o. o. mmmmmm... ? It could be something as simple as your accelerator cable or pedal not properly adjusted so you are not truly getting "full throttle" even with the pedal to the floor. We actually see this problem a lot. A perfectly running engine that doesn't put out full power because the throttle is not open all the way.

 

All very good suggestions. I will go back to the basics and start tuning from scratch. I never thought about the springs in the distributor, I'll give that a try too. Thanks everyone, I'll let ya'all know how it turns out. Be Safe!

 

I never thought of that. I'll look at the cable and see if it is adjusted correctly. Thanks!

 

That's what you get with all the crap being posted, geniune questions and such get flushed to page 2 in a hurry, sorry it had to happen to your thread. Seems like when you want something answered you have to result to TTT

 

Ive always thought it would be best to have a general c3 and a tech area. But everyone always shoots it down in the vote.