Crankcase Evacuation Systems

[mowog1]

I continue to have excessive blow-by on my bored/stroked Rover 3.9.

It has about 5000 miles on it.

I'm looking into a system such as one of these.....thoughts?

http://www.summitracing.com/search/part-type/crankcase-evacuation-systems?SortBy=Default&SortOrder=Ascending&tw=evac&sw=Crankcase%20Evacuation%20Systems

[crashbash]

rick
search phillip leonard on this site. he had the same problem even after venting both valve covers to catch tank. his engine builder clancy schmit came up with venting the block at the mech fuel pump blanking plate to catch tank also and cured the problem I believe
bash

[MGBV8]

I had Jim Blackwood drill & tap a hole in my block off plate 2-3 years ago, so that I could run a 3/4" hose to a catch can. Helped a lot. I still think my head gaskets are leaking into the lifter valley.

[BlownMGB-V8]

To deal with blowby it helps to thoroughly understand what is going on. We always have some blowby. It is less at idle and can be considerable at full tilt-n'-boogie. In betweeen it, well, varies. It is handled differently by different systems but the one thing that never changes is that relationship and the fact that you have to give it somewhere to go. If you do not the pressure will build up and do nasty things like blow oil out of every seal and orifice. If you do, all is well. But today just relieving the pressure is not good enough. We want to be responsible citizens and minimize pollution, so we recycle. We do this by plumbing the blowby back into the intake tract and thereby burn the oil it carries out with it (the gasses have already burned once so there isn't anything to be gained there).

A PCV system seeks to move fresh air through the engine in a positive manner. This was done primarily to remove blowby components that could combine with oil and moisture to produce acids and sludge. Exactly how it does that is a little complicated but not really important here. What is important is dealing with the gasses. There are two ways for them to get from the crankcase to the intake tract. Through the PCV valve which is too restrictive for higher volumes of blowby such as during high power delivery, and through the large diameter vent line that commonly goes to the air cleaner. This line is essential for high power operation, and is sometimes supplimented by other lines such as at the fuel pump block off plate. All these can be plumbed to a catch can to act as an air/oil separator to save the oil that gets carried out with the blowby but the vent from the catch can has to be large enough to allow full flow, and still should properly be plumbed to the air cleaner in a street application.

Jim

[MG four six eight]

Rick,

Is it using oil also?

Bill

[mowog1]

It does not appear to be burning oil. Nothing notable from the tailpipe.

The underside of the car is now well rust-proofed....courtesy of the blow-by.

I've found oil around the rockers, at the oil filter housing, seeping into the valley. It seeks any weak spot to escape.

[MG four six eight]

Sounds like you may have a ring seal concern. I've seen this before when I have torn down low mileage engines  for diagnosis and actually saw where there are no wear marks across the full surface of the 2nd compression ring!

A cylinder leak down test is a good way to diagnose a ring seal concern. http://www.hotrod.com/how-to/engine/116-0406-cylinder-leakdown-tester/

Hopefully it's not a ring seal issue, however if you do have excessive leakage past the compression rings normally a fresh set of rings and re-hone will fix it.

Bill

[mowog1]

Thanks.

[tr8todd]

How big is your cam?  If the cam is too big, you will dump too much fuel and wash down the cylinder walls at lower rpms.  If this was the case during initial break in, the walls can become scored and the rings will never seat properly.  Its been a recurring theme on a certain engine builders stroker engines.  I've also seen an issue with the expensive gapless rings, but that issue always has massive oil consumption as well as blow by.  If you think the rings may not be seated properly, and the leak down test proves it, check the bores with a boriscope.  The last one I had to deal with was so bad after only 600 miles, the block had to be tossed.  In fact the only thing we were able to keep out of the bottom end was the offset ground 4.6 stroker crank.

[Nexxussian]

I have considered running a "Pan evac" system on other projects in the past, but I have been wondering if anyone has run a vacuum pump on a street car?

I was thinking of regulating the crankcase vacuum down to 8" - 10" of vacuum, which should allow me to run the pump slow (relative to the crank) which should help it last longer.

Just curious if anyone has run one for any length of time on the street?

[BlownMGB-V8]

I've run intake vacuum to the crankcase and have not been satisfied with the results, as it is possible to draw enough air past the seals to affect the idle speed, and this also has the potential to draw dirt into the crankcase.

Jim

[DiDueColpi]

I think you,ll be tearing down your engine to fix the blowby problem Rick.
It shouldn't be putting out anywhere near that much blowby.
An evac system will just treat the symptom and not cure the problem.
 The good news is, a simple rehone will probably fix you up.
You can even reuse the rings if they measure up OK.
Just make sure that you use the honing procedure that matches your ring choice.
And then break the engine in accordingly.

Live like you mean it
Fred

[tr8todd]

I know of several stroker Rovers running vacuum pumps.  Heres one in the owners cars section.
www.britishv8.org/Triumph/LorenzHassenstein-TR8.htm

[crashbash]

Rick, do you know what type and brand of rings used in this engine build ?

[Nexxussian]

Jim, thank you.

[Nexxussian]

Todd, thank you.

Do you know of a way to search a specific section of the forum, such as the build logs / owner's section?

I've tried and I don't find a feature to narrow it with the on site search feature and searching "vacuum pump" or variations through Google, limited to this site returns tens of thousands, or nothing.

I wouldn't mind so much, but so far, the results haven't proven relevant.

[Jim Stabe]

How many miles do you have on the engine?  Edit - I just reread your original post and it has 5,000 miles.   Shouldn't have any significant blow by unless something has gone awry inside - broken ring or piston. What components was the short block assembled with and what kind of clearances were used? Has this come on suddenly or has it always been like that? Any detonation events?

[mowog1]

I will dig my paperwork out....this is a hybrid engine built by D&D.

Has done this since I first fired it up.

[Jim Stabe]

My guess...engine was put together incorrectly. Hope the warranty isn't up

[BlownMGB-V8]

Sounds like rings upside down or something similar like a poor honing job or cylinders out of round. An easy mistake to make but also an easy one to avoid, and something that an experienced engine builder should never be guilty of. With luck, maybe it is just the rings and you can install a new set and be done.

Jim

[roverman]

If it hasn't been mentioned, a wet/dry compression or leak-down test ? If rings are leaking excessively, plugs should have oil/carbon build-up. If  your build used oem style pistons, they may not have adequate oil return passages, for the oil rings. I consider this a design flaw, of some oem RV8 pistons.  Good Luck, roverman.

[mowog1]

I've not yet done wet/dry compression nor leak down.

I pulled the plugs.....they all look similar to this one from #3 cylinder.

[BlownMGB-V8]

That's pretty clean. Not burning oil anyway.

Jim

[DiDueColpi]

Hey Rick,
can you get a better picture of the plug?
Looks like the electrode might have some oil buildup on it.
But your Oak table looks fabulous!! {;-)

Live like you mean it.
Fred