Vacuum Pumps: Plumbing Arrangement

[weedburner]

Back-to-back dyno data on an otherwise same engine doesn't really tell the whole story.

With/without data on an engine built to run without crankcase vacuum won't show much difference.
With/without data on an engine built to take advantage of crankcase vacuum won't show much difference either, other than blue smoke.

Crankcase vacuum allows you to get away with less ring tension, which in itself is worth some HP. Fixed orifice pcv valves pulling crankcase vacuum are a big part of how modern oem's are able to reap the benefits of low drag ring sets.

Grant

[skinny z]

Fixed orifice pcv valves pulling crankcase vacuum are a big part of how modern oem's are able to reap the benefits of low drag ring sets.

Grant

Seems there ae some race minded folks that use the PCV valve similarly.
And in that case, racer or OEM, is the crankcase sealed or, as in a conventional PCV system, is there a breather on an opposing valve cover? That to me would defeat the purpose.
FWIW, as I think about, I don't believe my 2006 LM7 powered Chevy truck has a crankcase breather. I may have missed it although with emissions being what they are, I doubt anything gets vented to the atmosphere anymore. Other than the tailpipe.

[Dave B]

But if you have a engine designed for vac pump ,imo quite a bit can be learned. We just recently dyno tested a 380 inch sbc. We tried a new vac electric , new 4 vane from company we never tried before. Base engine made 893 hp after broke in. With electric pump that only pulled 11" it made 916 hp. With 4 vane it made 20" and went 922 hp. Then we went to our base line Star pump and 25" vac it was 930 hp. I dont think 5" vac should of gained 8 hp ? Was it because quality of pump ? idk. This engine makes peak hp at 9800 rpm ,so its no cookie cutter base engine. Ring package was thin and base radial tension was reduced even more than ring company reccomended.

[bob460]

But if you have a engine designed for vac pump ,imo quite a bit can be learned. We just recently dyno tested a 380 inch sbc. We tried a new vac electric , new 4 vane from company we never tried before. Base engine made 893 hp after broke in. With electric pump that only pulled 11" it made 916 hp. With 4 vane it made 20" and went 922 hp. Then we went to our base line Star pump and 25" vac it was 930 hp. I dont think 5" vac should of gained 8 hp ? Was it because quality of pump ? idk. This engine makes peak hp at 9800 rpm ,so its no cookie cutter base engine. Ring package was thin and base radial tension was reduced even more than ring company reccomended.

What new vac pump did you try?

And what's the max vac should you run in a street/strip car?

[JC565Ford]

What new vac pump did you try?

And what's the max vac should you run in a street/strip car?

For what it's worth, the 565 Ford with the GZ pump installed didn't make any more power running 12" of vacuum, or 9.5" of vac. Since it's an endurance engine, I ran it for two years at 9 -10" of vac.

With the rebuild coming up, we'll see what it likes this time around.

[Dave B]

But if you have a engine designed for vac pump ,imo quite a bit can be learned. We just recently dyno tested a 380 inch sbc. We tried a new vac electric , new 4 vane from company we never tried before. Base engine made 893 hp after broke in. With electric pump that only pulled 11" it made 916 hp. With 4 vane it made 20" and went 922 hp. Then we went to our base line Star pump and 25" vac it was 930 hp. I dont think 5" vac should of gained 8 hp ? Was it because quality of pump ? idk. This engine makes peak hp at 9800 rpm ,so its no cookie cutter base engine. Ring package was thin and base radial tension was reduced even more than ring company reccomended.

What new vac pump did you try?

And what's the max vac should you run in a street/strip car?

Tried cvr stuff. I think in street stuff 10-14" would do what you need without beating pump to death. Most guys now days will go .043 ring or even .039-.039 - 2 mm oil. I like .027 stuff my self and we even relieve radial tension more than how they come std.

[Dave B]

20240322_152914.jpg

Star pump and tank, hands down nicest and best performance pumps on the market.

[289nate]

I have an old aerospace vacuum pump set up I bought used. Ran it with a mild 289 and old school thick rings. Made no difference at the track which wasn’t unexpected. I had the relief valve set for 11 to 12 inches of vacuum. Was told to keep it there to be safe with the wet sump street strip application.

The guy I purchased it from switched to a different more efficient pump. I believe it was Star. I would be pretty certain a fair amount of the gain Dave realized with the Star pump was due to less drag to turn it.

I will likely eventually try the vacuum pump set up again on the new motor. I would not expect much of a gain. my account for a little bit since this engine turns higher and uses modern thinner. Metric rings. Still wet sump so I will have to limit vacuum.

[skinny z]

I have an old aerospace vacuum pump set up I bought used. Ran it with a mild 289 and old school thick rings. Made no difference at the track which wasn’t unexpected. I had the relief valve set for 11 to 12 inches of vacuum. Was told to keep it there to be safe with the wet sump street strip application.

The guy I purchased it from switched to a different more efficient pump. I believe it was Star. I would be pretty certain a fair amount of the gain Dave realized with the Star pump was due to less drag to turn it.

I will likely eventually try the vacuum pump set up again on the new motor. I would not expect much of a gain. my account for a little bit since this engine turns higher and uses modern thinner. Metric rings. Still wet sump so I will have to limit vacuum.

Although I started this thread for the benefit of a friend it has me to thinking about my own rig.
Once I'm back at it and producing time slips, this will one of those that fall into the "what to do next?" category.
Engine, transmission and gearing are a fixed element now. Weight, suspension are the same as the iteration before this one. The converter is still up in the air as is the rear tire. But details like a vacuum pump may be something to work with as the car is developed. Need a proper CAI too.

[Dave B]

20240329_114142.jpg

Another setup but pricey.

[skinny z]

It certainly LOOKS pricey.
But as the saying goes, "how fast do you want to go?"
Larger diameter tubing too which I see looks to be part of a well designed system. It may have been covered here already but I'll ask is the large diameter about volume rather than speed?

[Dave B]

Kevin
#12 (3/4)" Id line seems to be industry std. Some guys run a line to each valve cover. A good pump works fine with a single line imo.