Guest tony78_280z Posted December 15, 2005 Share Posted December 15, 2005 I got this set of heads in great condition. No play in valve stems, every piece and part looked great. So of course I made them better by tearing them apart and porting them out. Of course I did some extensive research on the project first. But the purpose to this thread is not my knowledge, technique, or out come, but to ask a specific question which I will surely get to after a few more details. On this project I used grinding stones instead of carbide cutters, and did it with an electric dremmil. This of course added alot more time to the chore (At least 20 hours), but being my first set of heads I thought it better to take it slow and easy and make percise and calculated cuts. Needles to say there were a few times when the stone snagged and the dremmil jumped and it slid accross the valve seats. I couldn't take a picture of the damage to display to you, because the camera couldn't capture what the naked eye could see. The injuries are more like tiny scratches on the shinney surface of the seat than actual metal gouged away. Of course my immediate thought is that I'll need new seats ground into the heads. But I'm getting conflicting information. Some tell me that the scratches are so minute that they could be buffed out with lapping compound. And others say lapping the valves is a "time honored, waste of time" My goal with this project is to be as budget minded as possible. If I wanted to spend hundreds of dollars I'd just buy some vortecs and be done with it. These perfect (although not the most desireable) heads fell into my lap. And My goal is to spend as little as possible on them yet make them a little more desireable. What say you all? Shall I lapp the valves and give it the trickle test? Or not waste my time and go ahead and get the seats cut? Or can I have the cylinder head shop cut only the seats that were damaged, and leave the others alone? (The shop charges by the seat. And I do not know if they will inspect each seat and give my their honest opinion) Aside note: The "General Engine" shouldn't be lumped in with the Trouble Shooting. Or there should be a forum for "Any and All Engines". Quote Link to comment Share on other sites More sharing options...
MONGO510 Posted December 15, 2005 Share Posted December 15, 2005 If you can feel the scratch you will probably have to grind it. If not, then lap it and then check with prussian blue. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted December 20, 2005 Share Posted December 20, 2005 what is prussian blue? Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted December 20, 2005 Share Posted December 20, 2005 Tony: I don't work in a machine shop, but have and also done some porting on heads. When you are working in the valve bowl area, directly behind the valve, through the valve hole... you MUST be careful!!! Like you said, the bit can catch and slip and result in the seat being scarred. Now that it has happened, here's how you can tell if you need to have the seats reground. Get a lapping stick and some lapping compound, they are cheap and if it doesn't work you'll only be out a couple bucks. Attempt to lap the valves that are damaged. After you do, you should see a consistent width band of clean metal around the valve seat. It wouldn't be the full width of the valve seat, but it should be at least half the width with a little above and below not touched. If you can still see the gouge, you might have trouble. What the user MONGO510 was talking about, prussian blue, is also called machinist blue or machinist dye. It can be purchased most places where you can purchase lapping compound. You apply the machinist dye to the valve seat before lapping and if any blue dye remains after lapping there will still be an air leak. (the valve will not fully seal) The prussian blue is just a way to be able to see easier. If it appears that the gouge is still there, lap some more. If you have to, you can chuck the lapping stick up in a drill and try it that way. If that doesn't work you may have to have the machine shop regrind the seat. As to whether or not all the seats need reground or just the damaged ones, when you regrind a seat, the valve sits slightly deeper in the head. Because of this the combustion chamber is slightly (very very slightly) enlarged. For a racing engine that is blueprinted so all the cambers are exactly equally sized this could be a problem. But for a home port job it is probably no big deal. The valve bowl is the most important part of the porting job. The greatest increases in air flow come from correctly porting this area. But the best and often only way to get in there is from the opening where the valve goes so you must be super careful. Some times I put duct tape over the seat while I'm working in that area. Hope this helps Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted December 20, 2005 Share Posted December 20, 2005 Duct tape, why didn't I think of that? How come that wasn't mentioned in any of the books/threads I read? Thanks for the info. Quote Link to comment Share on other sites More sharing options...
BrandonsZ Posted December 20, 2005 Share Posted December 20, 2005 You have to lap them if you replaced the seats anyway so why not just lap them now and then if they didn't fix then replace them. Sounds like a plan and you could get prasctice lapping valve seats without worry. Quote Link to comment Share on other sites More sharing options...
Here comes trouble Posted December 20, 2005 Share Posted December 20, 2005 Prissian Blue is a machinist lay out dye (lacquer) and goes by the name of Dyekem Blue.($5.00 a bottle and you will need it to lap) Get your self some lapping compound in a sticky cream form that will help prevent the lapping compound from seeping into the vave guides .(big NO-NO). Equip and improvise a forward reverse hand drill with a suction cup a little smaller than the valve heads. Swab the valve and seat with Dyekem Blue and let it dry.... Put a light coat of lapping compound only on the machined ring surface of the valve and it will transfer itself to the valve seat..... Place the valve in the guide hole and position the suction cup on the top of the valve. Run drill forward and reverse with frequent inspections of the valve and seat to check lapping action in removing scratches and the spread of the lapping compound towards valve guides. Re-apply lapping compound and dye as needed. The Dyekem Blue will eventaully wear off except in the scratched valve seats. By this time you should be able to tell the extent of the scratches in the valve seats and if the lapping will remove them and also what effect the lapping is doing to the machined ring of the valve. If you are successful at this... you can re-install the valves with springs... To check seal of valves turn the cylinder head upside down and level. Fill the combustion chamber with some solvent to see if the valves leak to determine which valves are sealing and which valves need more lapping. I have done this on budget heads and eventually got all the valves to hold the solvent for over 24 hours without leakage or replacing valve seats but I replaced a lot of valves with other used ones before I got a satisfactory seal with a lot of time consuming lapping and INSPECTION of seat and valve. This is a budget repair not a race three grind valve modification to assault the track record Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted December 21, 2005 Share Posted December 21, 2005 Thanks for the info! Another question. When lapping, I assume that the valve seat needs to be lapped with the valve that will go into that seat. Is that true? Does that not lap both the valve, and the seat? Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted December 21, 2005 Share Posted December 21, 2005 it does indeed, and yes you do use the valve thats going to go in that seat Quote Link to comment Share on other sites More sharing options...
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