I just picked up my 500hp 355 SBC. The engine builder said I should go with a Summit evac kit venting to the exhaust rather than the pcv to the carb. Your thoughts-
I would like to hear from guys who have actually successfully run them on the street with mufflers. All of the kits, Summit, Jegs, Moroso, etc., all have a disclaimer saying not to be used with mufflers.
Yeah, that’s a good amount of HP out of a 355. I would expect a high compression ratio to achieve that. Probably a lot of crank case pressure that a PCV can’t properly evacuate so; the draft tubes might be your best option...... Sent from my iPhone using H.A.M.B.
I agree, and also could be low friction rings that would free up horsepower but also increase some blowby. The problem with running the crankcase evacuation system with mufflers is that it's going to be pulling oil vapor out of the crankcase as well as blowby. That's going to eventually saturate the muffler packing with oil and ruin them. However, if you're running a muffler without packing, like a Flowmaster 40 series, I don't see an issue with it. We used to like loud ass mufflers, so we'd take Cherry Bombs chop them down to 12", pull the fiberglass out of them, and then weld them back together. Really made that 150 hp sound tough haha. Another thing to remember with the crankcase evacuation system on the street is that the engine is going to use use oil. So you have to be vigilant about checking the oil often so that you don't run it low inadvertently. Even though it's a fresh engine, it's going to use oil.
Thanks. Do you have any suggestions? Can I run breathers in the valve covers to some king of catch can? But then I'll have to run some type of vacuum to draw, correct?
You could certainly try that, in using an oil catch can in between the breather and the line to the exhaust. I know my buddies that have supercharged mustangs all run oil separators with success, using them to keep that oil vapor back out of the intake charge. I've even thought about putting one on my turbocharged BMW. Ultimately, high cylinder pressures, whether it be by forced induction or high static compression with low friction rings, or even the opposite end of the spectrum with a tired old engine with worn rings and lots of blowby, your crankcase is pressurized and you need to vent that pressure somewhere. If that's the nature of your engine, then so be it, that's the way it is. I don't see any issue in running a catch can, or even not running a catch can if you have an exhaust system that doesn't mind the presence of raw oil. Have you considered any mufflers that don't contain any packing material? I feel like the would be the easiest solution.
To work with mufflers they would need to be run behind the muffler. That type of evacuation needs to not be impeded and is used mostly on open headers. If I was worried about it i would run a vacuum pump. The race ones are not too pricey for most guys running a high horse motor, or you can get one that is not as purdy from a '70s era Ford, it was called a smog pump. it will be belt driven in either case and will use a little torque. The other option is to run it dry sump. That is expensive but it is your absolute best option. You can find the stuff on a site that sells used roundy round parts.
Thanks for your input, it's much appreciated. I'm running Cherry Bombs right now when I'm not running open headers
Pan evac does not work well at an idle. PCV system does. Pan evac works well at high rpm. PCV does not. Run them both. That's the way racers did it for years.... Jenkins Vega P/S used that setup.
Bub - Do BOTH..! The PCV works at low rpm, where the pan evac. takes over and works the higher rpm range. BUT...does very little at low rpm...where the PCV works well. If you are using low tension rings, a vacuum pump is the best way to go. Suck out the air..! A plain "open breather" system is...ok, especially at lower rpms, but the header/evac. system works a bit better at higher rpm. Mike
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