hey folk! i'm stuck in a situation with putting together my flatty. i picked up a complete and rebuilt 8ba engine that was built 15+ years ago. i found it is .080 over with the dome pistons,discovered there is an 8cm merc crank in it, and unknown cam which i'm assuming is stock since there is zero valve interference. with me desiring a higher compression for more ponies, i took my set of EAB heads off of my last engine, had them decked minimal to the warp, and wanted to use them for some performance. (they're very decked at this point) i put the heads on without the head gasket and found the head was lifting from the piston. so i installed the fel pro composite gasket, snugged some bolts, and clayed it. i'm getting readings of .025 to .030. after doing some research, i found that .055 is the sweet spot give or take .005 on piston to head clearance. i also noticed that the combustion area on the eab heads are now way smaller than the origional 8ba heads which i also have a set of. after i clayed the 8ba head that the engine came with, they're around .120 , and the combustion area very well fits the piston area in distance. the EAB heads have alot of decked area in the combustion chamber, which i am not very sure of being good. long story short, i am a noob to specs, and a very bad mathamagician. can i throw in a specific copper head gasket thickness (links please) and efficently run my EAB heads, or should i repaint these lower compression 8ba heads, strip and paint, and install without the benefits of such worthy crank and combustion? theyre truck heads and do not have the oil filter bolts on them. any tech help is much appreciated..... and yes, i've searched. all i come up with is egge pistons in this clearance issue...
I had the same issue. I had to mill relief in the valve pockets in the head in order to get sufficient clearance. Check out my album. I have a pic of my old neighbour working on the heads.
thanks george. no thoughts of stacking head gaskets since it's so close??? or running a copper gasket with a thickness?
http://www.jalopyjournal.com/forum/showthread.php?t=556178&highlight=thick+flathead+gasket http://www.headgasket.com/gaskets.html http://www.flatheadjack.com/
Stacked gaskets are never a good idea....Especially with a flathead. Go with what George said, and have the heads machined. 4TTRUK
Hello If thicker head gaskets will solve your problem, you can buy Cometic head gaskets. Check out their web site, you can order several thickness gaskets, or special order. Very good gaskets..! http://www.cometic.com/ It might help if you post pictures of the two different heads too.. K .................................... Taildragger&fenderless
I checked the Cometic site, and they want more for a set of gaskets than I paid for my first set of new aftermarket heads! Kinda puts things in perspective, ehh?
There's probably a good explanation why flatmotors are different, but on performance OHV8s, .055" is the max piston-to-head clearance wanted. Usually we shoot for no more than .035" to .040". Can someone explain why a flatmotor wants more? FWIW, I just built a Packard OHV8 for myself with .025" squish. In a pickup, it won't be revving high, so I thought I'd go tight. jack vines
yes tubman, it most certainly does... packardv8.. have you run it yet? ive read posts all weekend and only saw one person post about running under the .055 or .050 mark. if i could get somewhere near that mark, i'd run it if i didn't have to dump another 300+ dollars into it. i have a set of 8ba heads that clayed in at .110 up to .120.... i think i'm just going to throw them on and run it since this engine should have been done months ago. talk about moments when i wish i was a machinist and knew more about it! haha
You can probably get a little more clearance with a copper gasket. Otherwise check your valve clearance with the 8BA heads. You'll probably find that you can mill them .060 and get that quench area down. Pretty sure you'll be able to do it. I've run engines with as little as .040 with no problems.
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