Does anyone know of a shim I could use to increase the valve clearance. I really want to use these Evans heads , but they have been milled so many times before. I am afraid to fly cut the valve pockets and the piston domes more than .060" now and that won't be enough to clear the high lift Schooler cam I am using. These are 59A marine heads with the water outlet at the front. Dennis 704 788 8225.
Speedway has 0.070" inch thick copper gaskets, I think there are even some companies that will make you a set out of 0.120" copper. EDIT: See Cometic P/N C5870-120 is for a 21 stud flathead, hopefully they make a 24 stud in that thickness as well. (These are multi-layered steel gaskets)
Not knowing how much clearance you need, here a few ideas/WAGs. Other than the possible issue w/squish, is there any reason you couldn't use extra-thick copper gaskets? May have to be custom cut, but shouldn't be too bad. Or you could take the time & do it your self. Other than cutting in the heads' valve pocket for some clearance, I suppose you could sink the valves in the block -ya, I know, that will cause some issues as well, but... - & then you'd have to shorten the stems a like amount. That'd buy you some clearance, but you may not want to go down that road. So we're back to head gaskets. Or 'other'. Iffen you really need a lot of clearance, use 2 ultra-thin copper gaskets w/a steel plate sandwiched 'twixt them. I'd want them done on a water-jet & blanchard-ground afterwards. You could drill n cut the holes yourself, then have them ground to thickness & for parallel/flatness. I've seen similar done on a LSR stude V8, but it was done to create clearance for bigger valves, on a *very* small-bore. It worked fine. Just a bit more thinkin' required. & then you may not have to cut into the heads, unless you want a particular contour. Just about anyway you go, you'll have to, or should, deal w/the quench depth #'s. More trouble if you have the pistons already. A possible "crutch" might be to incorporate "Singh grooves". Supposed to help create similar conditions as very tight quench, but requires ~ 0.100" at the quench areas for the grooves to work. Haven't done this one myself, but did look into it for something down the road a bit. Could offset grind the crank for a bit more stroke, if bearing sizes are available, maybe? Or have the cam lift decreased - probably not your 1st choice... . How about a pic of the CC? Always like seeing that. TIA. FWIW. Marcus... Geez, I type slow... .
X2 on Ralphies54 comment: check your total valve lift, subtract the depth now available inside the head. If this is a negative number(sounds like it is), add the COMPRESSED head gasket thickness. If this new number is still negative, & the inside of the heads have not already been fly-cut for clearance, this number +.060 is the amount needed to be removed to be useable. CHECK WITH YOUR MACHINIST FIRST!! If they have already been fly-cut, you probably need to invest in those .120/.125 copper gaskets or look for another set of heads. Hope this helps. However, please note: the new "re-pops" will be way cheaper in the long run!
I went through this exercise a couple of years ago and came across the website of an outfit that made custom steel shims for just this purpose. As I remember, they were quite expensive ($120 a side?). I lost interest in them real quick. You should be able to find them with one of the search engines if this still is of interest.
I'm not the type generally to ask a person the why of things, just do my best to give a straight answer if I have one. But I have to ask: why were they milled so many times before, and if so why do they need to be milled again now?
I meant to say fly cut the valve pockets .o60" i think i could go .090' then the .125" gaskets would be enough. i have never heard of them [.125"] before. Sorce??? You are right, milling the heads is out of the question. The heads are 60 years old. Who knows why they have been milled so much.
I really had my heart set on using these rare heads. THANK YOU everyone. I'm going to give in. It' just going to cost too much to use them. Don't be pissed. I have a really nice set of 8BA Edelbrock that are fly cut and clear the valves without a gasket. I still would like to obtain the .125" shims. I could use the Evans with a stock cam in an other engine.
Could consider obtaining some thickness readings in the areas to be machined. An engine shop that can do the UT sonic thickness testing on engine blocks etc could take readings to see if there is enough meat to work with. It would just take a couple minutes once the instrument is calibrated to aluminum.
ed iskenderian had to make his own head gaskets for his famous model T. he said it took a couple of days' work.
If you know somebody with a CAD program, a steel shim could be cut very cheaply by a laser. That would require double head gaskets.
Obviously this cutting method below may not be appropriate here, at least pending some serious investigation of remaining metal, but i think anyone following this post will be interested. The good posts in this are from O'Ron, one of our greatest Old Masters. I always imagined that the dome cutters used in the day must have required master machinists to make, but this is as easy as some improvs I have done in a driveway. Even the lathe is not really necessary...note that the one pictured was too small to turn! All you need is something that will allow your piece of scrap to be rotated. https://www.fordbarn.com/forum/showthread.php?t=61824&highlight=cutter&showall=1
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