Pan evac with factory manifolds

[Racing68]

I'm getting ready to start a pull truck project for a customer where he has to use factory intake and exhaust manifolds. Has anyone successfully used a pan evac system using factory exhaust manifolds and a bullet style muffler that must exit behind the cab.

[Kevin Johnson]

https://www.google.com/search?rlz=1C1CH ... N3caOWGdr0


Hundreds of hits on Speedtalk.

[engineguyBill]

Too much back pressure with the factory exhaust manifolds, pan evacuation system will not work efficiently (nor at all).

[cjperformance]

Evac u pans work fine with stock manifolds, you fit the vac spike/valve in the pipe at least 12+" downstream of the manifold flange.
I have done it, i didnt think it would work very well but it works perfectly fine.
A very restrictive system 'downstream' of the vac spike will however reduce effectivness depending on level of restriction.
On another note, on a BBC with 4into 1 pipes , 3 inch dual system to rear if car and using 3"ultraflow mufflers that vac u pans still work

[MadBill]

I've been pondering such a system for my in-progress 495" BBC with 3.5" pipes and 40 Series FlowMasters Craig. What range of vacuum are you seeing?

[cjperformance]

I've been pondering such a system for my in-progress 495" BBC with 3.5" pipes and 40 Series FlowMasters Craig. What range of vacuum are you seeing?

Bill, the best i could get out of the BBC with full system was 2.5"hg BUT that was NOT a fresh engine, this was a going car that had been used for drag only and I had converted it over to use as a streeter as well. I definetly would have seen more with a fresh engine.
With stock manifolds on a 460" BBF using aprox 40" of pipe off of the manifolds, the 1st 10" being 2.5" then the rest 3" it saw just under 7.5"hg

[GARY C]

I never measured what my Nova was pulling, it had headers and full exhaust with Dyno Max straight through muffs but it pulled enough to keep the rear main form leaking at rpm... SBC nitrous engine.

[stokerboats]

Would an X pipe help scavenge in this application?

[cjperformance]

Would an X pipe help scavenge in this application?

If the csa thru the x is not too small then it wont hurt but isn't going to help either. Then again , most things are worth a try to prove!

[GARY C]

Would an X pipe help scavenge in this application?

I ran mine with straight and x I wish I had measured both, I think you could maximize it's effect by finding a way to pull or blow air through the header or piece of pipe the tube it is going in and use a manometer to find the best angle before welding.

I had clear hose on mine up by the engine so you could see it move moister as the engine warmed up and the drivers side clearly worked better until I re positioned the pass side.

[Racing68]

Evac u pans work fine with stock manifolds, you fit the vac spike/valve in the pipe at least 12+" downstream of the manifold flange.
I have done it, i didnt think it would work very well but it works perfectly fine.
A very restrictive system 'downstream' of the vac spike will however reduce effectivness depending on level of restriction.
On another note, on a BBC with 4into 1 pipes , 3 inch dual system to rear if car and using 3"ultraflow mufflers that vac u pans still work

This is exactly what i wanted to know, thank you.