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  #46  
Old 07-20-2010, 11:28 AM
NeedForSpeed NeedForSpeed is offline
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Re: 11:1 Engine Rebuild

Quote:
Originally Posted by Cam View Post
From what I understand they should not be out of round.

The entire engine (except parts I have replaced) has 187k miles on it. It had no bearing failures.
Round is better
Looks like the crank worked fine out-of-round,
It comes down to whatever you can live with, as it seems the engine was able to live with it.

As for machining the deck surface, with 187K, the surface is not likely to 'clean' with a .0015" cut, considering aluminum and 'floating' cylinders. The idea is to cut the same from each deck, unless going to the trouble to measure each corner and 'blueprint' the deck.

LAN has done a few, he would have a better perspective than I would. However, .006 sounds very reasonable for clean, flat and true

Did LAN supply the pistons? If so, ask him about the deck surface, he should be happy to comment about the .006" cut.
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  #47  
Old 07-20-2010, 12:27 PM
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Re: 11:1 Engine Rebuild

I have asked LAN about the cut, and he said I would have to feel for contact between the pistons and heads. He didn't seem to think it would be a problem though.

As for being out of round, with the oil clearances where they are, I am going to say it is going back together as-is. Like you said, it worked before. And I am not taking it much past the stock RPM range, and even with the increased compression, it should survive.

I am masking everything off (heads and block) for paint now. Once the enamel is fully cured I will begin reassembly. I know there are a couple tiny pieces I will be forgetting, but save waiting for parts this build is about to begin.

I will post pictures of my progress as I get the chance.
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  #48  
Old 07-20-2010, 12:49 PM
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Re: 11:1 Engine Rebuild

Quote:
Originally Posted by Cam View Post
I have asked LAN about the cut, and he said I would have to feel for contact between the pistons and heads. He didn't seem to think it would be a problem though.

As for being out of round, with the oil clearances where they are, I am going to say it is going back together as-is. Like you said, it worked before. And I am not taking it much past the stock RPM range, and even with the increased compression, it should survive.

I am masking everything off (heads and block) for paint now. Once the enamel is fully cured I will begin reassembly. I know there are a couple tiny pieces I will be forgetting, but save waiting for parts this build is about to begin.

I will post pictures of my progress as I get the chance.
Sounds good

LAN knows the piston specs, so, whatever he says. If Piston has stock compression distance [pin center to top] and you are using stock headgasket, .006" removed may be perfect for octane tolerance with 11.1:1.

Again, whatever LAN says, he would know the specs

Waiting for pictures
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  #49  
Old 07-20-2010, 12:52 PM
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Re: 11:1 Engine Rebuild

Bet these guys would have the answers---IF they would share.

http://www.youtube.com/watch?v=KhGu0...eature=related

Oh, to have some major bucks.

Lee
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  #50  
Old 07-20-2010, 01:06 PM
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Re: 11:1 Engine Rebuild

They are taller than the stock pistons, IIRC. I can verify that though pretty easily. When I put the short block together I am going to measure to the best of my ability how far the piston protrudes from the decks, and then subtract my clearances on the head.

Depending on what I see, I may shim the heads (I could probably get myself some .006" titanium and seal it to the block after gasket matching it). The other option is find an aftermarket HG that is slightly thicker than ours. (COMETIC?)

I may have plenty of room...we shall see once the short block goes together.
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  #51  
Old 07-20-2010, 01:16 PM
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Re: 11:1 Engine Rebuild

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Originally Posted by Cam View Post
They are taller than the stock pistons, IIRC. I can verify that though pretty easily. When I put the short block together I am going to measure to the best of my ability how far the piston protrudes from the decks, and then subtract my clearances on the head.

Depending on what I see, I may shim the heads (I could probably get myself some .006" titanium and seal it to the block after gasket matching it). The other option is find an aftermarket HG that is slightly thicker than ours. (COMETIC?)

I may have plenty of room...we shall see once the short block goes together.
My guess is that the new pistons are not 'taller' with respect to the spec that matters for piston to head clearance

You would not be able to visually see the difference to say the pistons are taller than stock, that must be measured.
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  #52  
Old 07-20-2010, 01:46 PM
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Re: 11:1 Engine Rebuild

I have the tools to measure that, as well as a spec sheet that came with the new pistons. Being that they are 11:1 pistons as opposed to 10:1, the diameter was increased, and I believe the height as well. I have my old pistons still and my new ones laying in the garage wrapped in foam. I will go check them once the paint on the block and heads is applied. I am almost done masking...what a tedious process.

With respect to LAN, I will not post any actual dimensions on the pistons. Only whether or not they are changed. Pics are a different story though
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  #53  
Old 07-20-2010, 02:55 PM
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Re: 11:1 Engine Rebuild

You might want to take thermal effects into account and consider laying the head back a tad to ensure that the pistons tops don't come in contact with them.

-Bill
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  #54  
Old 07-20-2010, 03:23 PM
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Re: 11:1 Engine Rebuild

That is what I am worried about. By taking the material off the decks, the heads have moved close to the CL of the engine. Pistons will not have moved though, tightening up the room between the pistons and the heads.

What do you mean by laying them back a tad?
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  #55  
Old 07-20-2010, 03:59 PM
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Re: 11:1 Engine Rebuild

METHYL ETHYL KETONE!

the answer for all your paint mistakes

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  #56  
Old 07-20-2010, 04:05 PM
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Re: 11:1 Engine Rebuild

Quote:
Originally Posted by Cam View Post
That is what I am worried about. By taking the material off the decks, the heads have moved close to the CL of the engine. Pistons will not have moved though, tightening up the room between the pistons and the heads.

What do you mean by laying them back a tad?
Assume the very top of the piston will travel beyond the top of the deck/head gasket thickness. Take a grinder and gently remove material from the head where the piston might contact it. Yes, you're going to increase the amount of cc's of volume, but better that then beating the crap out of your bottom end (note: I'm not talking about a potentially severe interference here. A very, very minor interference, given the speed that the piston head is moving and the number of cycles each one goes through even in a short drive around town. will result in a combination of deformed piston heads and load transferred to the bottom end which can result in messed up bearings. I honestly don't think you'd even see a noticeable deformation in the rods)

Hope this makes sense.

-Bill
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  #57  
Old 07-20-2010, 04:15 PM
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Re: 11:1 Engine Rebuild

Makes perfect sense. I will have to make a judgement call once my short block is all together. Won't be long now. Paint is drying. I can handle it in 3 hours, but I probably won't start assembling it until tomorrow or thursday.

I really don't want to remove material off the pistons, they are thermal coated and that was not cheap. Is shimming a viable option? I just measured my head gaskets and they are .066" thick...same as cometics maybe they would throw another layer of steel in there for me...?
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  #58  
Old 07-20-2010, 04:16 PM
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Re: 11:1 Engine Rebuild

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Originally Posted by NeedForSpeed View Post
. The idea is to cut the same from each deck, unless going to the trouble to measure each corner and 'blueprint' the deck.
these motors' deck surfaces should always be flycut squared to the crank centerline and case seam.......always. It's not tedious with the right equipment. fly cutting "from the hip" is not good. Same goes for the heads(except to the cams journals)

Do not gamble....measure the compression height of those pistons and calculate your CR properly.

One should not use a shim on the head gasket to obtain proper deck clearances on the pistons. Not that it can't work, it's just not the right way to be doing this on such a motor. Proper way to do it is to flycut the pistons to achieve the right clearance.

CC chamber, measure CH and DH, calculate requires specs(CR, piston height, etc, etc). Machine/correct CR as needed and rebalance.


Just my thoughs in a nutshell over dinner here
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  #59  
Old 07-20-2010, 04:21 PM
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Re: 11:1 Engine Rebuild

Thanks for the input Boxersix.

I am trying to get a hold of cometic. Since they make custom gaskets, I am going to get a price quote on some EG33 gaskets .070" thick. Just in case I need them.

By flycut the pistons are you talking about removing height off the dome?
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  #60  
Old 07-20-2010, 05:34 PM
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Re: 11:1 Engine Rebuild

Best to alter the head rather than the piston IMHO. I personally would make the measurements and add a safe amount of expansion clearance and order a custom gasket from Cometic.

Tom
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