Do I need to lap new valves on a new head?
I would of course if i had the compound but i want to avoid buying it if i don't need it.
I tried to do the white board felt marker test where you put ink on the mating surface of the valve and see how much rubs off onto the head.
None came off on the head because it was still too greasy but a ring was removed around almost the entire circumference of the valve. I only did this to one of them because i usually go by how much ink transfers. none did but it came off the valve.
Do other people always lap? even new parts?
I know there are still machining errors but i was wondering if they are great enough to merit lapping on new stuff.
I doubt it but your probably supposed to haha, when I put my new topline head on two and a half years ago I didn't even look at the valves and it ran fine, still does too.
I will always lap now, if there is any doubt at all. Last year during a head rebuild on my gasser I had the valve seats ground and valves cleaned up. I was told there was no need to lap as the seat grinding machine is perfect. I threw the head on without lapping or testing. I ended up pulling it off two days later because cylinder 1 was down on compression and cylinder 2 had nothing at all.
It only took a few minutes of lapping and it now runs beautifully. A bit more of a thorough test you can try is the solvent test. Shoot some solvent down the intake/exhaust ports on the head and see how much leaks through the valve seats. If nothing comes through you should have no worries.
A bit more of a thorough test you can try is the solvent test.
That would be my recommendation as well... start with a test and see how you do. Otherwise you're just guessing as to the craftsmanship of the person who put your head together. :wink:
My guy who does my heads works on Maseratis and some of the rarest cars in the world. He does the valve work on a machine that costs $175,000 and he still hand laps all the valves after each cut.
A bit more of a thorough test you can try is the solvent test.
That would be my recommendation as well... start with a test and see how you do. Otherwise you're just guessing as to the craftsmanship of the person who put your head together. :wink:
I shall do this solvent test. Thanks guys. That's exactly what i wanted to know.
(a good test to do before buying stuff)
My guy who does my heads works on Maseratis and some of the rarest cars in the world. He does the valve work on a machine that costs $175,000 and he still hand laps all the valves after each cut.
well aren't you just a fancy pants!!!
I'm kidding of course. Hand lapping is always a must on new valves on old head of course. I will likely end up lapping them after seeing everyone's response.
I always lap them because the compound and time are cheaper than pulling the head if there is a leaky valve. Besides, no matter how "perfect" any part is made, there is always a tolerance for machining anything. That is "plus or minus 0.0005" - so one part could be on the plus side and the mating part on the minus side giving you double the gap you wanted. Lapping zeros this out.
This idea is what Ford at their Windsor Engine plant have conquered with the fitting of the pistons in the block. They have invested in a several story high automated machine for this... They measure each piston and arrange them by size. All are within new specs, but there is variance. The also measure each bore, again all within new specs. The computer then sizes the piston to the bore so the tolerances are all balanced. The result is an engine with a broke-in fit from the beginning. More power and less emissions out the door. Part of the reason they have JD Powers quality equal to Toyota now.
I would always hand lap the valves , when you perform this proceedure you will visually see that there is a 100% contact between the valve and its seat and you will see exactly at what height on the valve this contact is being made, you could never see with a human eye that a valve may be bent .001 by looking at it in you hand, but you will sure see that there is a problem when you hand lap them in the head.
well aren't you just a fancy pants!!!
Nah, he's just the only guy I actually trust to do my head work. He certainly isn't cheap, but not too overpriced (considering the credentials). The only issue is trying to get him to even take my work. Whenever I go there, I feel that I'm giving him work that's 'beneath' him. :wink: