We are moving our Gen IV BBC from nitrous with a vacuum pump and Cometic C5381 rear main seal to a new ProCharger combination.

What are you "Blower Guys" going for a rear main seal at over 20 PSI boost?

Thanks...

DG

I have always just ran the FelPro rear main seal Part Number: FEL-2918. I normally run 30lbs boost and also log pan pressure. No vacuum pump and will see anywhere from .750lb to 2 lbs depending on how much alcohol is in the oil. The more alcohol will cause lost of ring seal, that's why is goes up. Never had any issue with rear main seal leaks.

Same here, just ran a good old Fel-pro 2918, up to 30# boost at 8400 rpm, no leaks.

Steve, I never logged pan pressure. I assumed if it didn't bulge out it was good to go!

Pan pressure is great info, tells you about ring seal, lost due to oil, puke tank full or filters need cleaned. You will also see it go up and down based on how rich or lean you are running, again due to ring seal loss. When you hurt a piston it really spikes up

I get all that, just never had it on my car. Never hurt a piston either.

What's really needed is a crank crack dector!

If you find that crank crack detector let me know we broke on at front journal in Charlotte in the A/Fuel car. Then found most will break that same spot after 50 runs. Hell if find one just get two I will take the second one.LOL

I'm no top dragster guy and never ran one in the 3.90 range, but I have run some 14:71HH bbc motors, tickled 28 psi a few times, and ran on one in the 4.20 range for a few years, but ALWAYS with a vacuum pump. My primary reason there is to keep the oil clean and remove all the methanol. I guess it helps with ring seal and what not but i never was concerned about that. We use the 4 vane Moroso pump, turn it 60% of crank speed, always showed at least some crankcase vacuum, and the oil always looked great. Moroso makes a "promod" vacuum pump that looks to be about 1.5X bigger than the standard series but I've never had reason to use it. The larger pump would move much more air than the standard size.

My question to the folks who don't utilize vacuum pumps on blown applications is why not? Have you tried it and had negative results? Simplicity? Cost? Did you record/monitor down track crankcase vacuum? Oil is getting expensive these days and I can't see how changing the oil every time I go to the track is a good idea.

quote:

Originally posted by Triple Nickel:
Moroso makes a "promod" vacuum pump

Summit 1200.00. I use the 4 vane on mine too..

Dave

David

Here is one from a company that I get mine from. It's one piece and you have to cut it to get it around the crank.
Seal

I've used them for several years now and they work great.

Dave