70455goat

Hey Lars, great post. Normally, I take my engines to a pro to dial them in. I do a lot of work myself, but every time I have tried to dial in my own engines, they run worse, use more gas, and usually wind up pi--ing me off.

I had my son's 350 in his 69 chevelle rebuilt with all good performance parts from bottom up adn replaced all bolt on items under the hood. I couldn't believe how crappy the car ran when I got it back. I took it to a guy in the area known to have the best carb shop. It costed me $400, but it was probably the best $400 I spent. He found 2 different size secondary jets in a brand new Edlebrock carb. recurved the elect. distributor to match the cam, changed the gap on the plugs, and a few other tricks and the chevelle seemed like it had an extra 100 horsepower.

I have a question, what is the difference between manifold or ported vacuum? Is it the difference between taking it from the base of the carb or from the manifold?

 

05GTO

Manifold vacuum is highest when the throttle blades are closed and rolls off as the blades open.

Ported vacuum is zero at idle, and rises slightly under part throttle and then goes to zero at wide open throttle.

__________________
Randy

70455goat

Lars,
Where do you connect to get ported or manifold vacuum?

Second question: I was checking my stock Q-Jet the other night and when I open the throttle, the secondaries don't open. I hit the throttle on a hard romp and they looked like they wanted to but just barely moved. After looking at the carb, I noticed the lever on the passenger's side of the carb (that keeps the rear flaps from opening) was not releasing. If I manually lifted the lever and hit the throttle, the 4 barrell opened up completely.

Is something wrong witht the release lever?
What makes the lever release so the 4 barrel will kick in?

Thanks for all the great info.
Dale

Rukee

Ported vacuum will be on the carb, one of the ports at the base of the carb. Manafold vacuum will be plumbed into the intake manifold.
The secondaries will not open untill the motor is warmed up and the choke is fully open. You should be able to hold the choke plate fully open and then that locking lever should move out of the way and allow the secondaries to open.

70455goat

Thanks, I don't think my choke is working because, it doesn't idle up at start. I have to keep it running when it first starts. It stays running after a few seconds, but never has a high idle. Could the choke cause the 4 barrels from kicking in?

Rukee

If the choke doesn`t fully close, or the fast idle cam isn`t adjusted right, it will cause your no high idle, if it doesn`t fully open, it`ll cause your no secondary action. It may just need some lube in the linkage or possaibly the choke stat is bad or way out of adjustment.

70455goat

Thanks. I will be checking the carb out this week end. You have been a lot of help.

70455goat

Hey Lars,

Thanks for all of the info. Another question: How are you at auto trannys? When I give my goat enough gas to down shift (I don't have to be romping hard even), it won't shift back into the higher gear until I am almost letting completely off of the gas. Like if I punch it and it downshifts into first, it is almost like I have the shifter pulled into first until I let completly off of the gas. But when I am just cruising easily, it upshifts perfectly. It did seem to shift a little better after I drove about 40 miles home from work the other night. I thought of maybe a vacuum leak, but wouldn't it have problems shifting altoghter?

Dale,

Rukee

When was the last time the fluid and filter were changed? If it`s a turbo 350 in there you could try to adjust the detent cable. There should be a little like a horse shoe sleeve thing on the outer cable at the back side of the bracket that holds it at the carb. Pull that adjusting sleeve up with a screwdriver or whatever then roll the throttle to wide open, let the detent cable slide in or out where ever it wants to be, then while still at WOT push the adjusting sleave back down to lock the detent cable in place. If that doesn`t help, check the vacuum hoses and module at the tranny for manifold vacuum. If it has vacuum check to be sure there is no tranny fluid leaking into the vacuum line, if none, then check inside the hose nipple there, some vacuum modules are adjustable with a thin screwdriver, you may be able to adjust it in or out to make it up shift better to your liking.
If it`s a turbo 400, check the kickdown switch at the gas peddle (electrical) to make sure it`s adjusted right and doesn`t stick in the kickdown position. I`ve seen some that stick and won`t slide easly back and forth

cpeahl

Same here. 69 convertible, thanks for a great article