Crankcase evac question

[BTR69]

Curious on crankcase evac systems. About to put the money into one and looking for what works best for most of y'all. Looking at preferred brand/model and also belt driven vs electric. Seems to me less pulleys running off the crank would be a better option, but do the electrics pull enough vacuum?
Will be going on 355CiD SBC. Roughly 450 hp, powerglide & 3400lb car.
Primarily raced, but will ne street driven a time or two monthly.

[Tom Goldman]

I'll give you my take on them since Stock and Super Stock is limited to a collector probe vacuum evacuation system . ….Pumps are not allowed.
Everyone I know who tried an electric pump has eventually put on a belt driven system . much depends on displacement ,rpm and ring packages.…...Most electric pumps seemed to only pull 4-8' of vacuum at higher rpms.
I know most of my S/SS friends would love to pull that much vacuum with a header type vacupan setup .
bottom line is ,its probable better than nothing or a vacupan setup . especially for a mild lower rpm engine.

[RULER]

Not legal in Stock Eliminator, last time I checked

[weedburner]

Originally Posted by BTR69

Curious on crankcase evac systems. About to put the money into one and looking for what works best for most of y'all. Looking at preferred brand/model and also belt driven vs electric. Seems to me less pulleys running off the crank would be a better option, but do the electrics pull enough vacuum?
Will be going on 355CiD SBC. Roughly 450 hp, powerglide & 3400lb car.
Primarily raced, but will ne street driven a time or two monthly.

My 355 sbc powered street/strip car uses a hybrid pcv/electric crankcase vac setup. Pcv provides all the vacuum around town and on the hiway, only use the electric pump when spraying. Here's a link to a page about my system (put up the page 7-8 years ago, still use basically the same system today)- http://grannys.tripod.com/evac.html



The above data/graph is from a NA WOT 3rd gear pull (2650-6000rpm / 43-99mph) using only the pcv valve shown on the webpage as it's crankcase vacuum source (electric pump was not switched on for this pull).

...Yellow trace is crankcase vacuum
...Red trace is engine rpm
...Blue trace is the WOT switch for the nitrous (nitrous system was dis-armed)

When I started rolling into the throttle at the 4 sec mark, crankcase vacuum was 12.3"Hg. By the end of the ~6 second pull, the crankcase still had 3.9"Hg of vacuum left. As you can see, there's no reason to even turn on the electric vac pump unless it's going to make a pass.
This is a well sealed flat top 355" sbc street engine w/ gapless rings. Well over 800hp on 91oct pump gas when spraying, spins past 9k.



Here's a link to the car's webpage... GSS Shop Mule Webpage

[Eman]

I use the header evac system on my car. What I have seen is if you have restrictive mufflers a header evac system doesn't work as good. On the electric smog pump setups they don't pull much vacum. They also don't like the fumes/crud pulled from the crankcase and have a tendency to fail. especially if mounted so the fumes go into the motor. If the electric is your only vent when it fails it will offer no engine breathing. The PCV/electric vacum deal looks interesting for a street driven car. I've run with a 355 at your HP level with only alve cover breathers and no problems.

[cad]

Id recommend a GZ Motorsports vacuum pump.

[BTR69]

Thanks for the info. I've heard the collector evacs aren't a good idea with mufflers. I''l be running mufflers since will see very occasional street use. Likely will give an electric a shot.