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Discussion Starter · #1 ·
Hi gang.
I've just noticed that I'm getting some blow by coming out of the driver's side valve cover. The engine is a 408 BB, 1000 miles since rebuild. I've never noticed any blow by until today. I did get an oxygen sensor welded into the header several days ago, but
thats the only change. I am noticing more steam/water dropplets out of the back of the exhaust as well. Of course the weather here is good, mid 70's and low 50's so I don't think its temperature related. Compression is good, no smoke/steam from the back, power is good. I'm stumped.
Thanks in advance.

Brian

[This message has been edited by Brian n az (edited 02-13-99).]
 

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Brian,
Do you have a pcv system on the car ? Without one, you will get a little blow by. Of course, without the motor in front of me, I can't tell you if what you have is too much. I would say put some miles on it and then see what happens, even though, with today's rings, they really should seat almost at start up. Was the motor bored or just honed and new rings ? Give me some more info and I will try to help.

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md
 

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Discussion Starter · #3 ·
Bill:

I had the block bored .030 over (402 to 408)
and installed new pistons (TRW L2240NF) and speed pro moly rings. The end gap on the rings were double checked just to make sure.
I checked the compression after breakin and after 500 miles, the rings are definitly seated. I am running a PVC, on the side that has the blow by. I checked the vacuum from the carb (15mhg at idle) and I get good pull on the PVC. The amount of blow by is not excessive per say, no blue smoke, just a musty oil smell. I would say the blow by is consistant with the smoke you see when pulling a valve cover to adjust the rocker arms. The blow by is coming from the crankcase. I did pull the valve cover and check the rocker assembly (Harland Sharp rollers) and everything is tight and good. My cam is a Comp Cams Mag 280H, [email protected] with .520 lift. Like I said, I never had this problem until I started calibrating my carb with the O2 sensor. I now get 14.5 A/F on cruise and 14 at light/moderate excelleration without the PVC plugged in. With the PVC in, I get ~12.5 A/F no matter what RPM. I'm sure thats is condensation, but I don't know how its getting into the motor. The other side of the motor is clean, no blow by at all.
Thanks for the reply.

Brian
 

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Brian,
Any motor will have a little blow by. It is impossible to get a perfect seal. If the pcv valve is working properly it should not be making your A/f ratio change that much. Are you sure it is the proper one ? I would get an AC Delco pcv valve for the highest performance application you can find, such as an LS-6 Chevelle or Z-28 Camaro. They are different as to the opening times and restrictions. Also, make sure you have a baffle in the valve cover under the pcv valve and under the breather on the other side, this will keep oil from being sucked into the pcv valve and affecting things. Try those things and let me know if it helps.

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

[This message has been edited by BillK (edited 02-14-99).]
 

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I had the same problem, the cause was a leak between the manifold and the head, so check your bolts, threads and make sure your manifold is free from suction through these areas, and make sure your using a good gasket kit.
 

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I had the same problem, the cause was a leak between the manifold and the head, so check your bolts, threads and make sure your manifold is free from suction through these areas, and make sure your using a good gasket kit.
 

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I had the same problem, the cause was a leak between the manifold and the head, so check your bolts, threads and make sure your manifold is free from suction through these areas, and make sure your using a good gasket kit.
 
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