Thread: leaky heads

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Heres one for ya . I have a set of small block heads 186 castings , they will not hold a head gasket for nothing . Ive put them on two differnt 350's and tried 2 differnt gaskets the first was fellpro economy you know the blue ones tried 2 sets . then tried the fellpro 501D severe duty gaskets 2 sets . i keep getting coolant in the cylynders usally an passenger side , but olso #3 . Both blocks are fresh decked and flat i know i checked them a dozen times . The heads are fresh from the machine shop and also flat i checked them to . the shop said he took
.020 off them . they were magged and had a valve job also . Is it possible theres not enough metal left between the outer water passage and the combustion chamber .

I had a 350 push out .060 put it all together fired it up to break in the cam. after about 15 min I noticed green liquid on the floor. I paid to have the block magnafluxed. I tore it down thinking I did somthing wrong. with the heads off I could see antifreze coming through the cylinder walls in two cylinders. I brought it back to the shop and they swore they checked it......They finely sleeved the two cylinders and everything was good. I was out the gaskets and time ...

I guess i'll takem back and talk to the machine shop guy and get him to recheck them for cracks . there either cracked or decked to much , the imprint on the head gasket shows less than a 1/16" between the fire ring and the outer water passage so its not like the ring is overlaping. also i did several compression checks and on all cylinders and all where exactly the same .

you say you check it to see if flat how did you check this ? did you look at the print out of the old head gasket on deck/heads to see low spots if any? reading old head gaskets will tell you alot. are the deck pins holding heads up .you would have a hard time over decking a sbc things like pistons would be coming out of the deck @TDC so it would have to be .025+ before you may see this .i would say the head chamber is crack or heads crack under a valve seats. heads need to be look at better

Thanks for the response. I checked the heads and deck using a precision straight edge and a feeler gage checking horizontally , vertically , and diagonally in multyple spots. I never thaught to check the dowl pins but im gona. I'll go look at the gaskets again just to be sure. I never had this problem before , its driving me nuts. If head chamber was cracked wouldn't i loose compresion in that cylynder? You got me thinking theirs a possible crack under the valves . I was thinking about sealing off the two water passages on the intake side, and filling heads with coolant let em sit on the head stands and see what happens.