351C & C4 vacuum question

[dwm9ersfan]

The motor in my car has a pretty good lope to it and I am wondering if low vacuum may have something to do with the shifting issue I am having. Also thoughts on adding a electric vac pump to the system.

 

[giantpune]

I'll start by saying that I haven't actually tried it, so I could be completely wrong. But I dont think adding a vacuum pump or canister will help in this situation.

The transmission modulator is what makes the transmission respond to changes in load and throttle position. It needs to see a "live" vacuum signal from the engine, like the vacuum advance on your distributor. The purpose of an electric vacuum pump is to keep a supply of vacuum to run brakes and other accessories that are not tied that closely to your engine's current state.

 

[will e]

giantpune is correct, you don't want to use a vacuum pump or even a canister, for the transmission modulation.

What vacuum are you getting at idle?

 

[turtle5353]

I am running a healthy 408 Stroker Cleveland and it has plenty of vacuum to run the modulator. Doesn’t take much.

 

[will e]

Does the transmission shift differently at WOT than it does just cruising through the gears (or basically idling down a residential street)?

 

[Don C]

What is the reason for the lope? A lumpy cam, or something else?

 

[DAverkamp]

The motor in my car has a pretty good lope to it and I am wondering if low vacuum may have something to do with the shifting issue I am having. Also thoughts on adding a electric vac pump to the system.

Darrel, the “squealing noise”you described back in your post the day after you got it doesn’t correlate with your engine now stalling or whatever it’s doing. We don’t know what dist you have so maybe a few pics will help and do you have any paperwork from the seller on what’s all on in your car? Your new issue sounds like timing/vacuum advance settings, etc. It also sounds like you still have to keep birddogging for a good hotrod shop that knows our cars.

 

[algon]

Have you tried adjusting the vacuum advance module yet?

 

[victorguarrera]

I am running a healthy 408 Stroker Cleveland and it has plenty of vacuum to run the modulator. Doesn’t take much.

I am in the process of rebuilding my 351c with a 408 stroker, are you happy with it, does it have good power, I had a thumper cam in the 351 and not much vac. for the brakes at idle but above idle all good. Does yours with the 408 stroker have any problems like that

 

[turtle5353]

I originally had a big mutha thumper cam and it was absolute garbage in every way. I actually went with a little bigger cam with more lobe separation and my motor ran REALLY well! I love my stroker 408. Great street manner and it pulls like a freight train clear past 6800rpm. I have rev limit set at 6800 and it’s still pulling well. Check out a few of my videos on YouTube. And one in my signature. It’s a tire destroyer! Lol.

 

[Bentworker]

The motor in my car has a pretty good lope to it and I am wondering if low vacuum may have something to do with the shifting issue I am having. Also thoughts on adding a electric vac pump to the system.

Get a vacuum gauge and see what it reads at idle.

What shifting issue are you having? Is there another thread where it is described.

 

[autonomousbronco]

I originally had a big mutha thumper cam and it was absolute garbage in every way. I actually went with a little bigger cam with more lobe separation and my motor ran REALLY well! I love my stroker 408. Great street manner and it pulls like a freight train clear past 6800rpm. I have rev limit set at 6800 and it’s still pulling well. Check out a few of my videos on YouTube. And one in my signature. It’s a tire destroyer! Lol.

What cam did you ultimately go with and do you think it would work with a 351c that although I put aluminum 2V heads on it with roller rockers it's not a stroker?