Crank case pressure
- Thread starter 35regal
- Start date
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stumper
Well-Known Member
My car uses them (had been in for 4-5 years). I just had an issue with it last year where the check vavlers went out and was resulting in no vacuum and pressure in the motor (leaks). When I found the check valves were bad I called Moroso. They explained the (not for street use claim) to say that the negative effect of using mufflers with this set up is that it will cause the check valves to fail prematurely from backpressure. The more restrictive the muffler the worse it is. When the valves are working the system will work fine pulling vacuum albeit it a bit less than if there are no mufflers.
I was running Flow Master 50s which are very restrictive mufflers and went to Dynomax Ultraflows which are a straight through design, replaced my check valves and have all kinds of vacuum again - and no leaks!
Long story short - you can use these for the street and they will work fine. They will pull vacuum in porportion to the amount of restriction in your exhaust system so the more free flowing the better. The check valves "DO FAIL" after some time - and in relation to the amount of restriction in the exhaust so check them periodicly.
I was running Flow Master 50s which are very restrictive mufflers and went to Dynomax Ultraflows which are a straight through design, replaced my check valves and have all kinds of vacuum again - and no leaks!
Long story short - you can use these for the street and they will work fine. They will pull vacuum in porportion to the amount of restriction in your exhaust system so the more free flowing the better. The check valves "DO FAIL" after some time - and in relation to the amount of restriction in the exhaust so check them periodicly.
1968FormulaS340
Well-Known Member
I had that system on my car when I got it. When I changed to manifolds I went with a standard PCV valve.
Upon removal I did see that one of my check valves had failed. This was with 3" exhaust, unknown mufflers and about 2000-2500 street miles.
So like stumper said, you will need to keep an eye on them.
Upon removal I did see that one of my check valves had failed. This was with 3" exhaust, unknown mufflers and about 2000-2500 street miles.
So like stumper said, you will need to keep an eye on them.
stumper
Well-Known Member
I think the first step should be to determine if you "need" to use the header evacuation system - or if a conventional PCV/vent would suffice. The latter takes the issues of using the former out of the equation - if it keeps the crankcase pressure neutral or negative. Unless your motor build is towards the radical end of the power spectrum you can probably get by with a more conventional system and not worry about the check valves - or the smokey exhaust..
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