Vacuum Issues

[monte0185]

I just got a pro street truck and noticed its got a leaky rear main seal. My guess is its got some pressure inside the engine pushing it out and the cams to big for any decent vacuum. Back in my Drag racing days we just run the moroso crankcase evac system off the headers but this has mufflers so I dont think thatll work. what about a vacuum pump? Its got a rigged up manual brakes on it now I plan on going to a hydroboost setup for that but still need something for a PCV system. Ideas please and pics would be great as well.

[Marv D]

I've ran the header evac kits on the street motors with mufflers. A pretty freeflowing exhaust system tho (3" through 3" mufflers then turndown at the rear end) It certainly worked better than nothing. I'm about to put a (well used) Aerospace vacuum pump on the street but I honestly think longevity is going to be an issue.

I guess question is,, your carb has no provision for a PCV?

[cableguy0]

If its pulling enough vacuum for even rigged up brakes a pcv should work. 8-10 inches of vacuum should be fine. I agree with Marv though I doubt a vacuum pump will last any huge length of time on the street and they aren't exactly cheap to be replacing often.

[monte0185]

Originally Posted by Marv D

I've ran the header evac kits on the street motors with mufflers. A pretty freeflowing exhaust system tho (3" through 3" mufflers then turndown at the rear end) It certainly worked better than nothing. I'm about to put a (well used) Aerospace vacuum pump on the street but I honestly think longevity is going to be an issue.

I guess question is,, your carb has no provision for a PCV?

It appears I do have a pcv valve it was hidden in the pass side behind the spark plug wires. Im going to try to find one of the low vacuum PCV valves and replace it cause I dont think its working well. Or i just need to replace the rear main seal. Guess well see.

Originally Posted by cableguy0

If its pulling enough vacuum for even rigged up brakes a pcv should work. 8-10 inches of vacuum should be fine. I agree with Marv though I doubt a vacuum pump will last any huge length of time on the street and they aren't exactly cheap to be replacing often.

Cheapest I found that may work was like 100$. Right now Im running manual brakes and although they work decent Im swapping to Hydroboost. I have a setup on a parts truck im gonna rob. LOL

[BR3W CITY]

I made the jump to HB due to the cam on my LQ4. Going from manual to HB is a shock, since the pedal feel is so drastically different, and the raw clamping force of the brakes is about 2.5x what you'll ever put out by foot.

I've never had an issue pulling enough vac for my PCV system, but I will be adding a catch can just to prevent the little bit of oil that could make its way into the intake.

[monte0185]

I have HB on my dually so shouldnt be too much of a shock to my system. LOL Here are my toys..

[BR3W CITY]

Your tow rig is pretty much what I'm hoping to find. A fairly clean CC DRW.

[cableguy0]

Do you have a breather on the opposite valve cover from the pcv? Also is the rear main the only thing leaking. Generally excessive crank case pressure will pretty much push oil out from everywhere. I would be suspect of a bad rear main especially if its a 2 piece seal.

[Rannos]

Originally Posted by cableguy0

Do you have a breather on the opposite valve cover from the pcv? Also is the rear main the only thing leaking. Generally excessive crank case pressure will pretty much push oil out from everywhere. I would be suspect of a bad rear main especially if its a 2 piece seal.

This is very true. The sbc in my truck now is set up for a good bit of nitrous and my machinist suggested I run a vacuum pump. The truck is street driven so I did not use one. It blows oil out EVERYWHERE except the rear main seal. I've tried PCV's and they didn't help (I didn't try a low vacuum one tho). Seems to do best with free flowing breathers and limited baffles but the breathers get oil soaked fast. I am planning to use one of the electric vacuum pumps off the old caddy's to try and sort it out.