318 deck is .004 warped

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Watchthis

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My 69 318 block is measuring untrue by .004, will the head gaskets seal? I have already blown a head gasket on this moderate build. Sent the heads out and found the problem bank was warped .005. I have now had the heads milled and checked the block before putting them back on and have found this .004 gap right between the 4 and 6 cylinders. This is where the gasket blew. It is also where the head was out by .005. It's understandable that with the head out .005 and the deck out.004, equalling .009, that that was the problem. The question now is, will the head seal with the deck out .004. I really don't want to pull this motor again. Lol
 
I'm betting if you use a fel pro head gasket (they are about .038 thick), it will seal. Some of the "thin" gaskets, like MP's orange have been noted to leak easily. I've never had a parts store felpro leak. I've done numerous "heads off" projects, and certainly not all of them were true. Just my opinion.....
 
FWIW, the standard test is for decks to be .002" or less. But, IMHO, it would not be risking a lot to try it again with a Felpro gasket; as above, they seal pretty well. If 'twere me, I spray a coat of KopperKote on too.
 
If it's really going to nag at the back of your mind, you may be better off just surfacing the block means it's out. But you fall into the .004 tolerance set by the info giving in the above post by SGBARRACUDA.
 
I find it odd that it is a dip between two adjacent cylinders, not a condition that runs the length of the deck of the block. Has this block ever been surfaced?
 
JBurch said:
I find it odd that it is a dip between two adjacent cylinders, not a condition that runs the length of the deck of the block. Has this block ever been surfaced?
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I caught that too. the low spot is between cylinder 4 and 6? Usually that occurs from a blown head gasket between those two cylinders.
 
I would say that .004 over entire length of head would probably seal but that much between cylinders? I say no way. Something is wrong, as in got driven for long time with bad gasket or juiced, bottle, etc. That sounds like what I have seen from too much boost on close to stock engine, with crappy gaskets.
 
SGBARRACUDA said:
I caught that too. the low spot is between cylinder 4 and 6? Usually that occurs from a blown head gasket between those two cylinders.
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I didn't catch that..... that is suspicious
 
Question to the OP: Is this low spot just in a limited area, top and bottom, or does the block gradually get lower from end to end as you move towards the middle?
2nd question: Is the flat edge true?
 
Not flat is one thing. low between two cylinder is another. I'm not sure it will seal long term. Only one way to find out...
 
Probably get crucified for this...........

Borrowing some thing I read about big block chevies decades ago and the fact that due to intake port lay out the head is "missing" a head bolt, so the gasket goes a long way not well clamped and in high static compression ratio engines it was/is a high gasket failure area. Some guys would (maybe they still do) would prick punch the area to grab a hold of the gasket to prevent failure.

The point: "Watchthis" you could give this a try, the prick punch pattern should be such it provides the maximum grip on the gasket to reduce squirm of the gasket between the 2 cylinders. Don't get in the way of the fire ring.

I offer this up as a possible low buck/no buck repair; other wise it's pull the engine out and have the deck surfaced. Choice is yours, and what makes you feel comfortable.

Good luck.
 
First of all, thanks for all the reponses. To answer a couple questions, the dip is between 4 and 6. When measuring straight across from front to back, it's .003 out. When I measure on a diagonal it's .004 out. I don't think this block has ever been previously milled. If it has been milled, would it be marked someplace? There has only been one other person to ever tear this motor down, other than myself. Unfortunately he has passed away. He did turn the crank though. I'm tempted to put it back together but I hate to throw away another $100 of gaskets. I don't know if I previously mentioned it, but I have purchased head studs to replace the bolts. Not sure if the higher torque will help or not. The studs torque at 110 lbs.
 
Sounds like you are at a good place to gain some compression. If the engine is still in the car though it would be tempting to get around taking it out and tearing it down to deck the block.
 
moper said:
Not flat is one thing. low between two cylinder is another. I'm not sure it will seal long term. Only one way to find out...
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Exactly! I would venture a guess that 90% of Mopar V8s were cut unlevel. They were terrible about it. Unlevel is one thing. It can be off plane and seal just fine. Low tween cylinders is a totally different animal. I always include decking the block into the cost of any engine build. Budget or otherwise. It's just a good idea.
 
I'm running 302 heads that were just milled .006 to true them up. Compression is not a problem right now. With my pistons and these heads, the compression calculator is showing 9.5:1 now. I do have to cc these heads to verify the chamber size though. 10:1 would be awesome, but I really don't want to pull the block and disassemble it again. That being said, I don't want to throw away $100 worth of gaskets , if it doesn't seal. I have a set of .028 compressed thickness head gaskets that I was planning on using. I don't know. I guess I'll ponder some more aND make a decision as to gamble or not gamble.
 
RustyRatRod said:
Exactly! I would venture a guess that 90% of Mopar V8s were cut unlevel. They were terrible about it. Unlevel is one thing. It can be off plane and seal just fine. Low tween cylinders is a totally different animal. I always include decking the block into the cost of any engine build. Budget or otherwise. It's just a good idea.
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Well said! Any good engine build should include checking machined surfaces with a precision straight edge and a feeler gauge. 2 simple tools that can prevent problems later. Often a simple milling of a thousandth or two will true up the surface and prevent sealing issues. Make sure you tell your machinist what kind of gasket you are using. Some gaskets require a different smoothness to seal properly. tmm
 
Watchthis said:
I'm running 302 heads that were just milled .006 to true them up. Compression is not a problem right now. With my pistons and these heads, the compression calculator is showing 9.5:1 now. I do have to cc these heads to verify the chamber size though. 10:1 would be awesome, but I really don't want to pull the block and disassemble it again. That being said, I don't want to throw away $100 worth of gaskets , if it doesn't seal. I have a set of .028 compressed thickness head gaskets that I was planning on using. I don't know. I guess I'll ponder some more aND make a decision as to gamble or not gamble.
Click to expand...

A thinner gasket will have a harder time sealing the defect...

The proper thing to do is have the block decked properly...

then you can use any gasket that you wish and it should work...

If you don't, you may keep blowing gaskets...

Do you want to keep fixing it, or fix it right this time???
 
OP, about your measurements, was the deck flat between cylinders 2&4 and between 6&8. If those areas were down .001-.002" as well as the area between 4&6 being down .003" and .004", then the warpage is a lot more gradual, and the sealing chances go way up, IMHO. .002" off localized is not usually a problem for sealing.

With a deck mill job at a machine shop, I would not expect any markings to be there.

I agree on the thicker head gasket giving a better chance to seal. Going from .028" thick to .051" lowers the SCR by about 0.3 points.

And yes, the studs do increase clamping force.

I have gone ahead and done things like this in the past, they worked out better than 50% of the time if I thought it out and felt it had a decent chance to work. But it sometimes doesn't work out, so there you are..... Are you keeping this motor for a long time? If so, then that says take it out and mill it.
 
When you see a brand new block being machined, you see the big fly cutter skim cut the decks with no torque plate tension. This, coupled with the years of head bolt tension on a block (maybe not all equal) would distort a deck over time.
[ame]https://youtu.be/wr4_B9EXWSo?t=265[/ame]
 
I was going to say, .004? bolt it together and run it. The only tempermental engine I ever witnessed was a Ford Modular v-8. 4.6 on an F-Series, replaced the head gasket, still leaked. replaced the head, still leaked. Ford tech rep made me pull the engine and mount it on a stand, he checked the deck and said it was .001 out and to replace the engine assembly. Ah yes, my days as a Ford tech,... :)
 
Problem solved. I took a gamble, since I had the gaskets, and the white smoke is gone. Just incase anyone has ever wondered about the quality of Speedway/procomp head studs, I used them on this project. They were $70 and went together perfectly. I used these studs along with a Mr. GASKET .028 ultra seal head gasket. The combination seems to be working fine. I've already made a couple of 6500 rpm passes and it's holding together fine. Thanks for all the information that you guys provided.
 
Thanks for posting your solution, glad it worked out.
 
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