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02-24-2014, 06:59 PM | #1 |
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49-53 minimum cast iron head thickness??
Hey flathead experts...
I have run into a problem with my fresh 50 Merc. 2 exhaust valves just very slightly kissed the head . No damage but what is the minimum thickness for cast iron heads and where and how do you measure it? My heads have been milled flat at least once and probably more over the last 65 years. Also who makes the thickest head gaskets. I have been using BEST graphite. Thanks for the help... |
02-24-2014, 07:48 PM | #2 |
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Re: 49-53 minimum cast iron head thickness??
Rather than go to all the trouble and expense of thick gaskets I'd just find another set of heads. Then I would measure the valve and piston to head clearance before assembly.
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02-24-2014, 09:16 PM | #3 |
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Re: 49-53 minimum cast iron head thickness??
I get it so the valves and pistons don't touch without a gasket. There are other ways to fix the problem that may not be accepted these days. One is doubling up on the gaskets. There are also head gasket shims or spacers or whatever they are called made. I have not done either of these fixes but have heard of them being done.
If you are dealing with stock heads, they are not that hard to find replacements. Neal |
02-24-2014, 10:15 PM | #4 |
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Re: 49-53 minimum cast iron head thickness??
If they are stock cast iron heads, you should be able to find some different ones pretty cheap. If you were closer to Wisconsin, I'd give you a pair.
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02-25-2014, 12:02 AM | #5 | |
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Re: 49-53 minimum cast iron head thickness??
Quote:
I took router and a die grinder to mine. For clearance, I put the heads on the block loose on a couple of studs... Made it so that the valves no longer pushed the heads up... When you add a gasket, that's your clearance... I didn't have to take a lot out, and I must have cut up an old head to find that I had plenty to work with. Karl |
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02-25-2014, 12:24 AM | #6 |
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Re: 49-53 minimum cast iron head thickness??
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02-25-2014, 12:10 PM | #7 |
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Re: 49-53 minimum cast iron head thickness??
Thanks for the reply. Grinding is what I will do. This is not a racing engine and it won't matter at all.
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02-25-2014, 04:35 PM | #8 |
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Re: 49-53 minimum cast iron head thickness??
If you look close you can see where the valve will contact the head first ... (the far side of the valve)
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02-25-2014, 07:13 PM | #9 |
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Re: 49-53 minimum cast iron head thickness??
Thats is exactly where the exhaust valves for cylinders 4 and 8 slightly touched.
I think I will use copper gaskets that are thicker than the graphite. Graphites run about .0050 thick after crush and copper are about .0062 after crush. Looking for another set of Mercury heads now that have not been shaved as much as the ones I used. Thanks for the photo. |
02-25-2014, 07:19 PM | #10 |
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Re: 49-53 minimum cast iron head thickness??
Thanks for your reply. I am looking now locally for a pair of 49-53 Merc heads. Like to stay with Mercuries since my engine has a 1/4" Merc crank motor.
I might be interested in your offer if I can't find anything suitable. |
02-25-2014, 07:43 PM | #11 |
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Re: 49-53 minimum cast iron head thickness??
Seeing that you are going to look for an other set of heads, I'd look for a set of EAB heads, 52-53 Ford. They have smaller combustion chambers =more power. That don't stand much milling or you'll have the same problem. If your lucky enough to find a set that hasn't been milled they will stand .010 mill, probably more. I probably have 1/2 doz. Merc heads in my storage barn, I never use them. Your welcome to a set if you were here. Walt
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02-25-2014, 09:17 PM | #12 | |
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Re: 49-53 minimum cast iron head thickness??
Quote:
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02-25-2014, 10:14 PM | #13 | |
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Re: 49-53 minimum cast iron head thickness??
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02-26-2014, 11:29 AM | #14 |
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Re: 49-53 minimum cast iron head thickness??
My 280 has EAB heads milled .040" they hit the pistons on the outer diameter of the cyl bore. I clearances this with a die grinder. Didn't take much. Had no trouble with the valves. Using a copper gasket I have .045 around the outer dia of the cyl. CR is alittle over 8:1
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02-26-2014, 11:36 AM | #15 |
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Re: 49-53 minimum cast iron head thickness??
I have read that graphite composite head gaskets compress to .0050 and copper head gaskets from Best compress to .0062. Copper may solve my problem but I will continue to look for a set of usuable heads.
I am also running a 3/4 cam with slightly higher lift so that compounds the problem. Typically a stock cast iron head un- cut would have plenty of clearance. Do you have any suggestions on how to spot usuable heads at swap meets? The Portland swap meet is in a month and there be plenty of them there. |
02-26-2014, 11:42 AM | #16 |
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Re: 49-53 minimum cast iron head thickness??
Hello Ol' Ron... My engine is 276 CI with a 3/4 cam. That is probably why I have a clearance issue. I should be able to find iron heads with more clearance than the ones I used. And I will add some clearance just to be sure. I would like to use Mercury heads just because the engine is a Merc.
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02-26-2014, 11:48 AM | #17 |
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Re: 49-53 minimum cast iron head thickness??
I think stock cast iron heads un- milled can be cut up to .0040 with out clearance issues if you are running a stock cam. A higher lift cam could cause a problem especially if the heads have been milled several times in their life. I think that is the problem with the heads I used.
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02-26-2014, 12:05 PM | #18 |
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Re: 49-53 minimum cast iron head thickness??
Init1, you're off by a zero; graphite composites are about .050" compressed, you can cut most stock heads about .040" without worry.
Here's a thread with pictures of how to gauge how much the heads have been milled: http://flatheadsrus.com/viewtopic.ph...t=3538&p=22813 Here are the missing pictures, first one is of a head with a small shave, the second of one that has been shaved pretty far. The milling machine starts cutting into the thermostat housing beyond maybe .030".
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02-26-2014, 12:21 PM | #19 |
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Re: 49-53 minimum cast iron head thickness??
Thank you Ross F-1. The Pics say it all. I will look at heads with a healthy ridge below the thermostat housing.
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02-26-2014, 01:36 PM | #20 |
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Re: 49-53 minimum cast iron head thickness??
Ross F-1 hit the nail for checking all of the 8BA family of heads. This is the only way to tell how much a head has been shaved. If it goes all the way down to the thermostat housing, it has had a lot of meat cut off and can end up unusable for any application. The head deck parting surface should stand near .040" proud of the thermostat housing on most heads at the OEM spec (never been shaved before).
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