pcv and thermostats for street strip cars ?

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AdamR

AdamR

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Something I havent seen talked about much. What is everyone running for a crank case vent on there street strip engines. My motor is a little nastier then most street motors, lots of over lap and duration and 11:1 compression. I really dont want a PCV valve contaminating the in coming air/fuel mixture. A pan Evac set up wont work well with my mufflers. Will a couple of breathers be enough ? Are there low buck vacume pumps that will live on a street strip car ?

What about thermostats ? 160, 180 ? I have a radiator and shroud from a 340 car and will use a clutch fan. I really dont want to test the rpm limits of the flex fan I have. I would like to go with a Moroso electric water pump and a electric fan at some point. The moroso pump doesnt use the by-pass hose. Can you use the thermostat with out the by-pass hose ?
 
I use 2 breathers Adam. After a trip down the quarter I have to wipe a little oil from around the breathers. No amount that I was ever concerned about it.
 
Two breathers will be enough if your motor is solid and doesn't have a lot of blow-by. Circle track guys use two breathers and seems to work well.

No such thing as a low buck vacuum pump system and stock air pumps do not move enough air.

I run a 180 'stat, warmer motors will wear less on the cylinders. I have done both the under driven belt drive and the electric pump. I tested both at the track and could not find any real measurable difference in my performance. So I went back to the belt drive pump to take some load of the alt. I do run an electric fan and that is were I found the best gain on performance between the too.

You can use a pump without the by-pass hose. If you do you will get more flow thru your radiator because all of the collant will be forced to pass thru the radiator. Which is OK if you are underdriving your water pump because now the flow thru the radiator will be about the same as the high speed pump with a by-pass hose.
 
My motor is nice and fresh so there shouldnt be any blow by.I do have crazy oil pressure tho. On the Dyno at 6900rpms it was making 100psi. I'll try 2 breathers and see how it works.
 
Pan E vacs just dont like mufflers from what I have been told from peopl who have tried it. Flowmaster seem to be the worse to use with a an e vac set up.
 
AdamR said:
Pan E vacs just dont like mufflers from what I have been told from peopl who have tried it. Flowmaster seem to be the worse to use with a an e vac set up.
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Please excuse my ignorance Adam. But I don't understand why mufflers would effect the evac. It still creates a vacuum right? Do the baffles mess it up? If thats the case, will a straight through muffler design work?
 
Straight threws work better from what I have been told. I have no first hand experiance with it though. The more back pressure the exhaust has the less vacume the e-vac system will make.
 
onehellofadart said:
I use 2 breathers Adam. After a trip down the quarter I have to wipe a little oil from around the breathers. No amount that I was ever concerned about it.
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My old 360, though not as nasty as your current engine also used 2 breathers. I also did a quick cheack once a week on all things with a rag to wipe up a almost nil amount.

I think the use of e-vac tubes w/mufflers are not the greatest idea. I could be wrong. But my thought is the vapors of oil cpllect in the muffler. I know they'll coat the pipe, but the muffler seems like a worse place. Possible collection as deep as it could be kind of thing.

The e-vac tubes also work on a vaccum idea of the exhaust rushing past the point of the pipe into the header/collector to draw out the oil vapors. This is an area of more the merry I think. A muffler could slow this up.
 
Sons Dart is a .557 cammed 400 and we still use a PCV valve and a 160 thermostat. Seems to work great on his street car. Ron

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pan-e-vacs don't work well with the back pressure with cambered mufflers or a full exhaust system. Although as long as the pressure is higher in the crank case than in the exhaust it will flow to the exhaust, but that is not how it is designed to work. Ideally you want negative pressure in your crank case for better ring seal. Oil pressure won't effect how many breathers you need.
 
I have a built up 318 for the street and I run 2 breathers. My oil pressure get up to 60-70psi and I have no blow back. I run a 180 thermostat, here in Vegas with temps over 110 in the summer my car runs at 190-195. Peace
 
I use low tension oil rings in my engines to reduce drag and make more horsepower, there's a lot there, and if I don't use a pan evac there is too much crankcase pressure and it pushes oil out the front seal at about 7000 rpm. I used the pan evac system when my car was a street car too, I used a 3 inch exhaust system with 2 chamber Flow Masters. The trick is to use the factory type aspirator valves as the tension to open the reed valves is lower than with the Moroso units. I also used a pie cut on the draft tube to increase the vacuum pull.

It shouldn't suck any oil out of the motor as the actual vacuum is fairly low so don't worry about it coating your exhaust, I've never had any problem.

As for the thermostat and bypass, If you run a thermostat you'll need the bypass hose. If you don't run a t-stat just gut an old one and use the orifice as a restricter. This is what I did. I'm also a big fan of electric fans though it might require you to purchase a couple before you figure out how much or how many you'll need to keep it cool in traffic.
 
Have you thought about just a simple catch can? I'm using a home-made one on the 440 in my Chrysler. Stops alot of stuff getting back to the carb from the PCV. The 340 in the Duster doesn't seem to need it, but it is a pretty mild build as far as I can tell.

As far as thermostats go, I can't figure out why people keep talking about running these cool stats - 160-180. Why not run it at a nice efficient 190 or 195 if the rad and rest of the cooling system is up to it? I run a very small plastic fan on the Duster that keeps it down to about 210 in stop and go traffic, 95 degrees ambient. I think I could get away with no fan at all if it wasn't for the summertime temps around here.
 
Adam, If the idle is a concern I could see not wanting a PCV..But really, it does no harm in any other case. The "dilution" is very minor. You can run the evac systems, but like Guitar said, you will need to ge the right valves for your exhaust, and they dont work at all at low speeds when set up right. Years ago there was a super clean burning Pontiac in PHR I think that used valves to help dilute the exh before the cats. You can buy the valves seperately, but you'll need to research at what level of vaccum they open at. I hate just breathers on anything but a race car. You're constantly wiping and cleaning, and nbo matter how good you are about it, you'll end up with big dirt and dust collections below and around them at cruise nights.
As far as thermostats, the hottest you can control the temps at, the more power it will make. With aluminum heads, I'd aim for running temps between 190-200°. Lower and your valve lash changes the wrong way, not to mention idle quality and mix.
 
This is unique, but here is a system I ran and it worked quite well. I can't remember who recommended it, but it was an old school racer trick. I ran a mechanical fuel pump (suction side) to two in-line PCV valves, one on each valve cover. The outlet side was vented into the atmosphere. Obviously, I was using an electric pump for fuel supply. I also ran a full exhaust with this system. I don't have dyno results to show any horsepower levels before or after. I do know that after I went back to a conventional breather set-up (no PCV), I developed an oil leak from the pan. The motor maybe saw 1500 miles with this set-up and I never noticed any problems. This was on a 406 SBC, 10.5-1, .550 cam with a tunnel ram, so it had the potential to make a lot of cylinder pressure. Just another option to consider. :toothy7:
 
On the flip side, I run a pcv valve, with no issues.

I don't run a T stat, but do use a restrictor plate in place of it.

I had trouble finding one for a mopar, so I just broke the middle out of an old T stat.
 
The deal with not running a thermostat is that you can better control the temperature of the engine with electric fans and pumps. As for the lower thermostat temps, you are wrong. If properly jetted your engine will make more power at lower temperatures.

David Reher even did an article in National Dragster about it. I know he's a Chevy guy but he does know a thing or two about race engines.

What I do with my car is warm it up to 180 when I first get to the track then cool it to 130 before I pull into the water box. I leave the line at 140 to 150. This is where it runs the best. Any colder and it will stumble. Any hotter and it doesn't run as quick.
 
You don't think so what?

My motor is the same way... If I come up to the line below 160, it'll run almost a tenth faster than it would if it's over 160.

If I come up under 160, at the end of the run it's around 180. If I come up over 160, at the end of the run it's over 200.

If I come up when it's cold, say 140 or so, it'll bog off the line.

I've got a 160 thermostat in there, that could have something to do with the 160 mark.
 
Heat is energy, that's a fact. However if you are leaving it in the engine it's wasted and it just dilutes the incoming air fuel charge. Colder air is denser air, The denser it is the more oxygen is in the air. The more oxygen you can get into the cylinders the more power it will make with proper jetting.

The reason the OEMs run 195 thermostats is for fuel efficiency and emissions, not for maximum power.
 
So we are attributing 1/10 sec to 10 degrees engine temp. And this is objectively confirmed or tested how? I still don't think so.

OEMs were using 190 and 195 deg stats LONG before emisisons standards ever played into it. I guess you guys know better how to operate an engine than the people who desinged and built it.

And OBTW, if the flow through your heads is staying in there long enough to be affected by as much as FIFTY degrees temperature difference, It must not even be running.
 
Ace said:
OEMs were using 190 and 195 deg stats LONG before emisisons standards ever played into it. I guess you guys know better how to operate an engine than the people who desinged and built it.
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You cant really compare a stock motor to a race motor.
 
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