Thread: Chevy 350 TH Shifting Problems and More???

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Originally Posted by DennyW

Do you know what the engine vacuum is warmed up, and idling ?
Do you have the vacuum hose going to the right place ?
Is the trans modulator adjustable ?
Does the trans have a shift kit in it ?

I did not check the vacuum. What is the optimum range I should see at the carburetor?

I have the vacuum going to one of the small ports on the front of the carburetor. The one on the back of the carburetor is plumbed to the power brake booster.

The modulator is adjustable, and I failed to mention previously that I had adjusted it all the way out in increments of a 1/2-1 turn and did not get any noticeable difference. The vacuum modulator is a single red band adjustable.

I don't believe this transmission has a shift kit. I will have to look back for receipts since my Dad past away last year and he would've been the only one who knew.

Originally Posted by DennyW

((I don't know what cam you are using for one. If it's stock or close to it. You should be getting 14 to 18 inches.))

I have the vacuum going to one of the small ports on the front of the carburetor. The one on the back of the carburetor is plumbed to the power brake booster.
(( There again, I do not know what carburetor you are running. But, the port you hook to, should be main vacuum, not ported. The best place is to port it right to the intake manifold. This can be done by using a vacuum Tee.))

The modulator is adjustable, and I failed to mention previously that I had adjusted it all the way out in increments of a 1/2-1 turn and did not get any noticeable difference. The vacuum modulator is a single red band adjustable.
((Once you check things out, you can then adjust the modulator to the stock settings...))

Below are three pictures of the setup. The vacuum line is going from the modulator on the transmission to the port on the front of the carburetor (smaller of the two black lines in the circled area). The carburetor is a Summit Racing M2008 Series. The last picture is the connection that goes to the power brake booster.

Originally Posted by DennyW

You have the trans modulator hose on the ported port. Wrong one.

https://static.summitracing.com/glob...rb%20instr.pdf
The blue cap is full vacuum.

I will get it hooked up and try that out, thank you. I will let you know of the results when I can.