So i'm doing a top swap and before installing everything i like to test it. While testing i found that some of the cylinder valves leak, what should i do?
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12-04-2014
So i'm doing a top swap and before installing everything i like to test it. While testing i found that some of the cylinder valves leak, what should i do?
12-04-2014
Install them and let all your cares go away.
Or get them re-worked, but that in itself could be another downer as likely the heads are cracked between the valves on some cylinders like half of the used heads are. You can run them as is though and nothing happens, most of us have cracked heads without even knowing.
12-05-2014
Well praying its not cracked could i try lapping the valves
12-05-2014
Yes... But have you determined what's leaking? Seals or valves not seating? That'll let ya know what to do... Also what are your plans for build? That'll guide you on how far you might want to go with those particular heads.
12-05-2014
In a dark room, take a flashlight and shine it at the valve seats and then look in the port and see if you can see light between the valve and the seats, if you do, than a valve job is in order.
12-05-2014
98% chance your heads are cracked.
The heads are cracked in every 3800 ive ever delt with. I've never cared.
12-05-2014
^^^this^^^Originally Posted by darkhorizon
really doesn't matter unless ridiculously cracked! It's a hairline between the thin bridge of material separating the valves... No worries!
12-05-2014
That says something for these 3800 motors, that they'll still run with cracks in them!
12-05-2014
Okay thanks, ill try lapping them and see what light goes through then probably just get frustrated and put on the likely cracked heads lol
12-05-2014
And yeah 3800 engines are awesome
12-06-2014
Nearly everytime I install springs, I find there is leaking. If you tap the valves with a rubber mallet.. it'll usually seal them up.
12-06-2014
Bill, do you mean up top, valve stem/retainer? That must snap the valve, almost shocking it?
12-06-2014
Do like bill said, A lot of times the valves are being held open by carbon/deposits. If you have a friend handy take the head to the car wash. Stick the wash wand in the port and pull the trigger while the other guy bangs on the valve tip. If that doesn't fix your sealing, you would probly need a valve job. Lapping will rarely fix any sealing issues, and just put a lot of wear on the seat and valve. (Access to a valve refacer would be handy after you lapp)
The only way to get around the cracks is to find a good pair and put some seat inserts in. Induction hardened cast iron does not make a good ex seat. Gm knows this. Planned obsolescence.
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