new heads = blow by, HELP!
Thread Starter
Instructor
Joined: Jun 2013
Posts: 225
Likes: 1
From: hanceville al
new heads = blow by, HELP!
Just got a new set AFR heads milled to 58cc and comp 1.6 RR installed and now I have extreme blow by. I had oil coming out of my oil tube until I put a valve cover vent/filter on the passenger side CCV and capped of the TB port. It is a 90 speed density so I don't have to worry about un metered air, I'm also running the FAST ez 2.0 system. When I remove the PCV after the engine warms up smoke pours out of the valve cover like a choo choo train. After the VC vent was installed no more oil coming out of the tube but smoke coming out of the new valve cover vent. This was not a problem before the heads, I did a compression check but found all cylinders were between 160 and 175 psi. Any clue what could be causing this?
Melting Slicks
Joined: Jan 2014
Posts: 2,192
Likes: 381
From: Lunenburg MA
The bottom end may not be up to the increased pressures from the new top end. Compression isn't the whole story when it comes to blow by. I'd do a leak down test and be thinking about rebuilding (or a new) short block. It's not an uncommon problem with tight high compression heads on an old block.
Thread Starter
Instructor
Joined: Jun 2013
Posts: 225
Likes: 1
From: hanceville al
Crap, that's what I was afraid of, thanks jv999. What do you think of a 383 with an 52mm TB, ported plenum, ported edelbrock high flow runners and intake. Think it will flow enough for a 383? According to the bench flow sheet they flowed 243cfm on my AFR heads.
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Are they the 180, 190, or 195 CC heads? The 195s are supposed to flow 286 CFM according the AFR. If you have the 195s, it will be enough for a 383 but your intake is holding you back. You'd be better off with a Miniram with a 383 and AFR heads.
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
Those high flow runners will need cleaning anyway. I had lots of flashing around the ports that edlebrock never cleaned up ( another member here said the same about his runners). Its a good product but just not finished like it should be.
Last edited by ghoastrider1; Jun 11, 2016 at 04:55 PM.
Burning Brakes
Joined: Aug 2006
Posts: 1,061
Likes: 99
From: Seattle WA
The bottom end may not be up to the increased pressures from the new top end. Compression isn't the whole story when it comes to blow by. I'd do a leak down test and be thinking about rebuilding (or a new) short block. It's not an uncommon problem with tight high compression heads on an old block.
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