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Antique Gas Engine Discussion

Engine Blowby


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  #1  
Old 07-25-2005, 02:14:58 PM
TomH TomH is offline
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Default Engine Blowby

Starting to get a little blowby on my 2-1/2 HP aircooled associated. As I am fairly new to this hobby, (only have this engine and a 1-1/2 HP M) don't know too much about 'em. What could be causing this blowby, and how could I fix it? Is the cylinder wore or could it be the rings are bad (or maybe both)? Apreciate any and all help.

Tom
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Old 07-25-2005, 04:11:23 PM
Joe Morris Joe Morris is offline
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Default Re: Engine Blowby

Tom, If you haven't been having blow by proir to this time it is a good possibility that you might have flooded the engine more than once and washed the oil off the rings. This can cause some blowby especially if the engine has a lot of hours of running on it. It is for sure that with all the years of age of the engine that the cylinder has some wear on it. But blowby dose'nt come suddenly. Sometimes new rings will help but not every time due o the fact that new rings are perfectly round and the cylinder in slightly oval so until new rings seat into the oval shaped cylinder there will still be some blowby. At least that has been my experience. Hope this will help a little. Joe Morris
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Old 07-26-2005, 01:53:09 AM
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Ray Cardoza Ray Cardoza is online now
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Default Re: Engine Blowby

Are both engines all original? If so it could be a slightly out of round cylinder or bad rings. If the gaps on the rings are all aligned that could cause some blow by too. good luck
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Old 07-26-2005, 01:09:51 PM
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Forrest A Forrest A is offline
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Thumbs up Re: Engine Blowby

Rings may be stuck in ring grooves. Remove the rings and clean the ring grooves of all carbon deposites. Check end gaps by placing rings in cylinder without piston.

Forrest A
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Old 07-26-2005, 01:41:39 PM
Joe Morris Joe Morris is offline
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Default Re: Engine Blowby

Here,is something about old iron that I have learned from experience. If you buy an engine that is running ok with reasonable compression. DON"T pull the Piston if you can avoid it. WHY? because if you pull the piston and clean up the rings and grooves at the same time you are doin'g this you will get them out of their original position as far as the way they are worn / seated into the slightly oval shape of the cylinder. This also welcomes some loss of compression. I once bought a small Witte that had real good compression . But I decided to pull the piston and clean it up and check it out. Opps, wrong thing to do, When I put it back together it had a bad loss of compression. So after that when I had to pull a piston for any reason I made it a point not to move the rings in their grooves. Of coarse this don't matter if the engine is worn out anyway and major surgery is being performed. Just a little live and learn tid bit. Joe Morris
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Old 07-26-2005, 01:50:03 PM
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Forrest A Forrest A is offline
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Default Re: Engine Blowby

At this point it's smoking so maybe a rebore and piston/rings are in order. The other thing I should have added was to mark the position of the rings before removing from piston directly after pulling the piston out of the bore, something I do without consideration, as a general rule.

Forrest A
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Old 07-26-2005, 04:10:06 PM
Joe Morris Joe Morris is offline
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Default Re: Engine Blowby

Forrest. If the engine is smoking that could only mean one thing You have the oiler on too fast, its that simple. It has nothing to do with bad rings. It is an open crankcase engine with no oil in the crankcase of coarse, so you are just over oiling the rings, now, if you have a closed crankcase engine with oil in the closed crankcase and it is smoking it could be bad rings BUT the only way that an open crank engine is going to smoke is from getting too much oil from the oiler. Before you do something drastic try cutting down on the drips of the oiler and see if it don't eliminate most if not all the smoke. Joe Morris
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Old 07-26-2005, 04:12:01 PM
Joe Morris Joe Morris is offline
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Default Re: Engine Blowby

Quote:
Originally Posted by Forrest A
At this point it's smoking so maybe a rebore and piston/rings are in order. The other thing I should have added was to mark the position of the rings before removing from piston directly after pulling the piston out of the bore, something I do without consideration, as a general rule.

Forrest A
Sorry Forrest I should have headed the reply to Tom JOE
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