My engine has way too much blowby - Hot Rod Forum : Hotrodders Bulletin Board
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Old 08-21-2012, 11:12 PM
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My engine has way too much blowby

even with my pcv valve and breather hooked up there is still a lot of blowby leaking out through the breather, the pcv is sucking a good amount of air

the rings are new and zero smoke out the back, just a crap load of blowby

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Old 08-21-2012, 11:19 PM
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when you say new piston rings did you rebuild the engine or did you just hone and put a new set of rings, ive seen several times people hone the cylinders out and remove to much material to where the engine has blow by because the rings aren't sealing properly because the bore is a tad to large not saying you did that im just saying ive seen that in the past
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Old 08-21-2012, 11:41 PM
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the block is a high nickel block that has been bored 60 over by the machine shop and fitted with 60 over pistons and rings, makes great power and runs fine

just a lot of blowby, the engine runs as if the pcv valve weren't in there(which it is) and is blowing crankcase pressure through the breather
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Old 08-22-2012, 12:35 AM
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First off how many miles are on it? Second what type of oil is used as well as weight? Lastly was the bores scrubbed clean with a heavy duty cleaner and stiff bristle brush before the block was assembled?
Many times someone gets a block back from the machine shop. They give the block a standard wash job before assembly not realizing that's not good enough. When the block is honed the bores are impregnated with the grit that comes off the hone stones. Unless the bores are scrubbed with heavy duty cleaner and brush this grit remains in the bore. The engine is assembled and the piston rings and oil break this crap loose from the bores. The grit causes rapid wear on the rings robbing them of more than half of there usable life span.
Also I should ask what type of rings were used? Cast Iron? Moly coated?
Are you certain the ring was installed right side up? Most rings have a mark on them to indicate which side is up, if they are installed upside down high blowby results. Which pistons were used?
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Old 08-22-2012, 12:42 AM
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i'm not sure about what pistons and rings were used, but i cleaned everything real well(as best i could anyway) , and after assembly i filled it up with 5 gallons of conventional 10w-30 pennzoil with the comp cams additive for my new cam

there is no smoke out the tail pipe indicating oil or anything, clean as a whistle, even on hard acceleration and deceleration

real good power too
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Old 08-22-2012, 01:23 AM
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LOL, I meant 5 quarts
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Old 08-22-2012, 05:34 AM
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Run a cylinder leak down test and submit an oil sample
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Old 08-22-2012, 08:11 AM
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My engine has way too much blowby

One solution would be to get a new 14" air filter assembly with PVC nipple in the base or if yours has the knock out just get the nipple. Then get a breather cap for the valve cover that has a nipple on it. Install a clear hose from the air filter base to the breather cap. Another thing to do is pull the right side valve cover and see if there is a baffle under the cover where the breather cap fits. If it does not have a baffle attached to the valve cover try these from Summit Racing. Summit Racing SUM-G3413 - Summit Racing® Valve Cover Grommets - Overview - SummitRacing.com
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Old 08-22-2012, 09:33 AM
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I've seen some PCV grommets that were solid at the bottom, needed to be cut. Is yours pulling air or do you mean the carb is pulling a good vacuum? You have an air return in the other cover?

I'm with DV on the rings and or hone pattern being an issue.
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Old 08-22-2012, 04:40 PM
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well i just hooked up a breather with a nipple that connects to the air cleaner and that seems to of solved my issue

that or it's simply masking it, anywho i meant the carb was pulling good vacuum and the pcv valve was okay

I tigtened all the valve cover bolts extra tight so nothing would seep out
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