AVP head

ratwell · Post by **ratwell** » Wed Dec 22, 2004 10:57 am

I've got a new AVP head that's leaking down 50% on the exhaust valve. I've got some grave concerns about install it and hoping it will fix itself.

Does anyone have a recommendation besides send it back and buy a head from someplace else?

HAM Inc · Post by **HAM Inc** » Wed Dec 22, 2004 11:53 am

Don't install it. If the valve is leaking that much, something is bad wrong. I'm assuming you checked it with a leak down tester? If so try tapping the valve lightly with a brass hammer. If this doesn't bring the leakage down to 2% or less then you have a problem. If the seat is not concentric the valve can grab it and yank it out of the head, (this can be catastrophic). At the very least you'll burn a valve.
If the shop that did the work won't make it good, then you'll know not to use them again!

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Wed Dec 22, 2004 11:56 am

Damn....... 50%?
DAMN!

If you goahead and install it you may as well be pissing up a rope..

ratwell · Post by **ratwell** » Wed Dec 22, 2004 11:59 am

HAM Inc wrote:Don't install it. If the valve is leaking that much, something is bad wrong. I'm assuming you checked it with a leak down tester?

Yes. Here's the leakdown gauge in action: http://tinyurl.com/5koxg

If so try tapping the valve lightly with a brass hammer. If this doesn't bring the leakage down to 2% or less then you have a problem.

The other cylinders on this never run engine (rebuild) are leaking 4-6% which I would expect before doing the test.

If the seat is not concentric the valve can grab it and yank it out of the head, (this can be catastrophic). At the very least you'll burn a valve.

I'm afraid of burning it.

If the shop that did the work won't make it good, then you'll know not to use them again!

Thanks for the advice.

HAM Inc · Post by **HAM Inc** » Wed Dec 22, 2004 12:03 pm

If I did a pair of heads that leaked a low of 4% and a high of 50% I'd fall on my sword!

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Wed Dec 22, 2004 12:09 pm

And people still wonder why good heads cost..............

This is a great illustration.

ratwell · Post by **ratwell** » Wed Dec 22, 2004 7:05 pm

The heads came with a longblock. This is a budget repair for a friend and I'm not quite ready to write these heads off yet although as you both confirm they are very scary.

Good work that's error free and guaranteed costs money. No doubt about that.

Bobby74 · Post by **Bobby74** » Thu Dec 23, 2004 3:15 pm

try lapping the valves to see what type of contact area the valves are making with the seats. If you're lucky, you might be able to get by with re-lapping the valves. If its too far off, you'll have to get the seats and valves ground to the same margins.

turboteener · Post by **turboteener** » Wed Dec 29, 2004 6:44 am

Do not lap valves on a good valve job or on any engine you care about. The valve lapping compound will embed itself in the seat and valve and promptly kill the valve seal over the (short) life of the engine.

Post by **Piledriver** » Thu Jun 07, 2007 12:25 am

turboteener wrote:Do not lap valves on a good valve job or on any engine you care about. The valve lapping compound will embed itself in the seat and valve and promptly kill the valve seal over the (short) life of the engine.

I know I'm resurrecting an ancient post, but I have to say "Huh?" to this one...

I have ALWAYS lapped my valves in, and have always gotten great service from them, no issues, ever, over many many hundreds of thousands of miles, mostly in ACVWs.

I have never had as much as not having one liquid-tight (solvent) when checking before I replace the ex valves at ~50K. They don't even ooze.

People have been lapping in valves for 100+ years without issue, so once again, I have to say "Huh???"

Perhaps you forgot to clean them off?

blue77bay · Post by **blue77bay** » Thu Jun 07, 2007 2:35 am

not only do i lap valves i also lap cylinders ,no problems here ?????????????
be ultra ultra thorough when cleaning ,then clean again

Class 11 streeter · Post by **Class 11 streeter** » Thu Jun 07, 2007 6:12 pm

I think I remember Len saying he laps valves with a compound so mild it makes DIY off the shelf lapping compound look like gravel.

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Thu Jun 07, 2007 8:24 pm

Class 11 streeter wrote:I think I remember Len saying he laps valves with a compound so mild it makes DIY off the shelf lapping compound look like gravel.

Yes, he uses the same "ajax" trick that I have spoken about here in the past.. There hasn't been a fine enough lapping compound on the market for us in years..

Comet or Ajax mixed with a tad of water works wonders.

Post by **Piledriver** » Fri Jun 08, 2007 4:35 pm

I have a bottle of 5 micron alumina here that should do...

Jotunrunner · Post by **Jotunrunner** » Fri Jun 08, 2007 9:07 pm

lap? huh? ajax? really? -this is something ive never heard of, and never dream of trying without a lot more info. anyone care to illustrate this procedure?