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Does anyone have any real world experience on this subject. I am haveing a problem when I put it in 3rd gear and load the motor the blow-by gets bad. It will fill a half a quart bottle up after one 1/4 mile pass. Is there any solution? right now I am running total seal seconds and the rings that came with the cimas everywhere else. Help

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12.70 @ 104

The secret to blowby can often be remedied by crankcase ventilation. I also run TS second rings, however, I run 2x 3/4" breather pipes from the rocker covers and one 1/2" pipe from the fuel pump take off to a homemade breather tower (1 quart content, baffled, with a 2" K+N air filter for a breather). This setup seems to work, especially as any oil collected in the breather gravity drains back into the crankcase via the fuel pump take off. The secret seems to be slowing the air velocity and the larger the breather pipe, the less the velocity. Hope this is of help.
matt

I already have a breather but that doesn't fix a blow-by problem. I pick up half a quart of oil after a 1/4 mile run. There is something wrong with that. I see a huge breather as a bandaid. I want to fix the blowby problem, because there is nothing that pisses me off more than a oil mess after running hard. Thanks for the reply though.

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12.70 @ 104

What type of crank/pistons/rings are you running? Crankshafts without the 411 main bearing will flex enough to rock the piston and distort your ring seal. 92mm cylinders are also quite thin and distort easily. Total Seal rings would be a wise investment too. Don't rule out valve guides or a bent rod either.

Breathers are band-aids. Get to the source of the blow-by.

Hi, I did not read were you said how much boost? or how old is your engine. And how much hard driving do you put on it, with that in mind some things may explain it self.

It is a 1776 that was just built. It doesn't have many miles on it but it really won't get many because it is in a buggy. The crank is a demello an the pistons are cima with total seal second rings that blow-by worst than the original cima second rings. THe boost is 15psi and when you get it up into 3rd gear the blow-by really kicks in. I can fill up a 1/2 quart bottle in one quarter mile run. Any help?

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12.70 @ 104

Definetly a ring seal problem. I don't like the chrome top rings that come standard with Cima/Mahle sets. I have had real good luck using Grant cast iron top rings and the TS 2nd ring. They seal fast and better than the chromes.

While hanging out with Brian Heyrstay and Gary Berg for a few races with the G dragster of Brian's last year, I saw 1st hand the value of the crank case vacumn pumps. Besides eliminating blow by, it picked up more HP. His was running about 7" of vac. I'll see if I can find out what ring package is used in his 1688 rocket.

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Tom Notch
Tom's Old VW Home

Tom I don't think that the buggy that this motor is in can take any more stuff to be bolted on it. Right now it has a dry sump tank, Fuel injection, oil filter, turbo. I am running out of room out back. i have heard that a vacume pump will really help out on the H.P. department. A buddy of mine runs one and he picked up 3 tenths just by bolting it on. His car went from a 7.00 in the 1/8 to a 6.70. If you can get me some info on the ring setup on that rail i would appreciate it. Thanks, Chuck

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12.70 @ 104

you say you are picking up a pint of oil per run- this means you must have some sort of breather system for the oil to collect in. Is the breather mounted too low? This may be a dumb question, but if the breather is mounted too low, then the velocity of oil/air mist will not be slow enough and large amounts of oil will collect. I used to run a breather system that was mounted at about distributor height. This gave nothing but problems with oil collection (especially if you use the fuel pump take-off as a breather). I mistook this for worn rings but this was not the case. I then switched to a homemade baffled breather tower mounted as high on the firewall as possible (3" higher than the fanshroud). It had 2x 3/4" connections from the rocker covers and 1x 1/2" connection from the fuel pump take off that also acted as a drain back for the collected oil mist. Problem solved, no tear down necessary for me. If you find that after adequate crankcase ventilation and installed height of your breather your problems still persist, then your piston rings are not sealing properly. Some of the cheap breather boxes on the market are just that- cheap. The pipe fittings are way too restrictive for competition use. 1/2" fittings are not good enough for high rpm/boost levels. They do not slow the volume of air/oil mist correctly and as a consequence oil collects in large amounts.
matt

Matt I understand the whole breather concept but even if you put a hugh breather system on it is still blowing by at the rings. A brather is not a solution it is still a bandaid. I turn 7500 rpm's on one of my street motors and have NO breather what so ever on it and it is dry as a bone. The cylinder pressures are not high enough that there should be a blow-by problem. I could see if I was making 1000 hp then there could be a problem. I mean look at a v8 that makes 800hp that is 100 hp per cylinder and they don't have blow by problems. Keep in mind I am still only making 50 HP a cylinder, this is no where near high enough to have to worry about blow-by.

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12.70 @ 104

Breathers are NOT bandaids. All motors require some sort of crankcase ventilation especially high HP motors. Blowby is a completely different subject.
I have never had any trouble with the Cima/Total seal combination. I run a max of 25# of boost. One key is to make sure the breather box is above the motor so the oil drains back. Your valve covers fill up about 3/4 full of oil at 6000 rpm and the rockers alone will sling it up the breater tubes plus any crankcase pressure that is developed from the pistons moving down in their bores.

Marty, words of wisdom indeed. That was the point I was trying to make. Chuck, if you are still worried, try doing a leak down test with compressed air. Check the readings on the gauge and if they are reading more than 10%, then I suggest you either remove one rocker cover or your oil filler cap and listen with a stethoscope or plain piece of rubber tube for air hiss in the crankcase. A small amount is normal, but large air hiss is indicative of knackered rings/bad ring piston seal. It's a fail safe method.
matt

Hey guys, great thread. I have a turbocharged 1.7L type 4 in my 914. I just did my first track event, Watkins Glen NY, with the 914. At 6000 rpm redline, I would see a little oil collect in my breather tank, approx 1/2 to 1 pint after 8 full laps. At 7000 rpm, I could put approx 1/2 quart in the tank, so as rpm increases, so does oil vapor in the air stream.

My question is, is it okay to allow collected oil in the breather tank to drain back into the engine? I have been told not to because of contamination. But if the oil in the breather tank is being blown up from the crankcase, wouldn't it be just as clean as the oil in the crankcase ?

How many of you guys drain right back into the case?

Also, any info on case vacuum pumps, suppliers, kits, etc...

Regards,
Ed

If you run a quality air filter on your breather system, then contamination will not be an issue. The entire breather system will then be sealed to prevent any incoming dirt from entering. I run my system so the oil drains back and have zero problems. Baffling inside the breather tower helps the oil collect as a liquid in drops rather than as an oil/mist vapour. It is a really good idea to run at least 3/4" bore hoses from your rocker covers if you are running high rpm/boost. This slows down the velocity of the oil mist and as a consequence, the oil is far more likely to fall out of suspension rather than collect in a reservoir. This is particularly important on turbo engines as ring blowby is always evident (just as it is for normally aspirated) and is inherent to engine design. On an engine that is considered to be ring sealing as good as it gets, there will always be at least 2-3% piston ring blow-by. Add boost, and blow-by will increase by a factor determined by how much boost is being produced/cylinder pressures. I cannot over-emphasise the importance of a good breather system! As a bonus, a good breather system will aslo do the environment a favour!

How about trying this. I have read about it and it make perfect sense.
When and if you strip th engine down, why not "gas port" (I think thats the name) your pistons. By this I mean to drill tiny 1mm holes in the edge of the piston, down to behinde the compression ring (first ring). This will have the effect of letting the pressure inside the combustion chamber push the compression ring out and thus seal the bore more effecently. Where in a normal piston the pressure has to travel down the bore and then behind the ring, which will take longer, and thus you have a loss of pressure and then power. So this might help in 2 things, with power gains and then blow-by.
Any thoughts on it?

Cheers john