5.0 deck clearance questions, possible problems - Ford Mustang Forum
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post #1 of 16 (permalink) Old 05-19-2010 Thread Starter
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5.0 deck clearance questions, possible problems

At the and of last week I picked up my 5.0 HO block from the local machine shop. It was cleaned and got a fresh 4.030" bore. At the beginning of this week I installed two of the new pistons, KB116 hypers and here is the link:

KB Pistons for Automotive Applications

I became very confused when I measured the deck clearance. Well, not so much at the actual measurement, but the fact the it was different at the intake side of the piston and the exhaust side. The top of the piston on the intake side measured ~.005" below the deck, on the exhaust side it measured ~.014 below the deck! Is this normal, what should I do? Am I missing something?
I have been taking the measurements with a straight edge and a feeler gauge.

Any help is much appreciated!

'94 Laser red 'vert. Still a 5-oh... for now
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post #2 of 16 (permalink) Old 05-19-2010
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if you just had the block bored, and no other machining services performed, it would seem that the cylinders were not machined at a perfect right angle to the deck of the block.

If it's not broke, you're not trying hard enough.

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post #3 of 16 (permalink) Old 05-20-2010
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Quote:
Originally Posted by YLDPONY View Post
At the and of last week I picked up my 5.0 HO block from the local machine shop. It was cleaned and got a fresh 4.030" bore. At the beginning of this week I installed two of the new pistons, KB116 hypers and here is the link:

KB Pistons for Automotive Applications

I became very confused when I measured the deck clearance. Well, not so much at the actual measurement, but the fact the it was different at the intake side of the piston and the exhaust side. The top of the piston on the intake side measured ~.005" below the deck, on the exhaust side it measured ~.014 below the deck! Is this normal, what should I do? Am I missing something?
I have been taking the measurements with a straight edge and a feeler gauge.


Any help is much appreciated!
Wow somthing is not right. sounds like the machine shop did somthing wrong
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post #4 of 16 (permalink) Old 05-20-2010
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Man if you can send those hypers back then do it.
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post #5 of 16 (permalink) Old 05-20-2010
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you need to have it paralell? decked. that will square the top of the block to crank center line.
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post #6 of 16 (permalink) Old 05-20-2010
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BLOCK WORK 101
anytime you are having block work done, you should alignhone the mains, DECK the block 0 deck for better comp. bore and hone with plates, bore off the thrust/true bore to get proper alignment of cylinders to crank. there should be no gap going parallel to the wrist pin, side to side there may be a little gap, but VERY LITTLE that is why decking is also refered to as squaring the block. This is just my opinion.

86 lx 306 ported bigvalve e7te's 1.72 rr custom split lift split duration unltradyne pro-m 70mm t-body mac flowpath block was alignhoned bored off the thrust, lifter journals bored and bronzed cobra intake t-5 4:30's about 11.5:1 comp true flat top forged pistons. DAILY DRIVER

1994 GT 2 engines in the works 1st mild 302 gt40p top half good block work mild cam. 2nd 377 or 383 stroker have to make a choice soon, it will be blown or juiced yeet another choice.
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post #7 of 16 (permalink) Old 05-20-2010 Thread Starter
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Thanks for all the advice guys.
Last night I was trying to figure something out, and it hit me why I was getting different measurements on the two sides: Piston rock. The pistons were fit fairly tightly (by the machine shop), .0025"-.003" but they still have a little rock. Now that I realized this I measured the deck clearance parallel to the wrist pin and the pistons sit between .008" and .012" below the deck, too much from what I understand.

So here is my tentative plan:
I have the 4 corner pistons installed (1, 4, 5 and 8). I was going to haul it back to the machine shop and tell him I want it decked to as close to 0.000" deck clearance clearance as possible. Does this sound like a plan?
Oh, and I have Fel Pro .039" head gaskets, is 0" deck fine with these?

Thanks again for all the help!

'94 Laser red 'vert. Still a 5-oh... for now
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post #8 of 16 (permalink) Old 05-20-2010
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with a .039 gasket, .000 deck would be about as perfect as you can get!
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post #9 of 16 (permalink) Old 05-23-2010 Thread Starter
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Okay, I took the block up to my machine shop yesterday. I had the four corner pistons installed. I told him that I wanted zero deck clearance, it would be okay if a couple of slugs peeked over the deck as much as .002 but I wanted none below.
So they will measure it, disassemble what's there and machine the deck

I really need to post some pictures of this project on here...

'94 Laser red 'vert. Still a 5-oh... for now
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post #10 of 16 (permalink) Old 06-10-2010 Thread Starter
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Maybe I should start another thread to get input on this, but I will try it here first.

As I planned I had the block decked to 0.000" deck clearance. A couple of pistons sit a couple thousandths below the deck now, but they're close

Now for my next question/possible problem:
I have all the pistons installed right now and the rings seem to have quite a bit of friction on the fresh bores. I used the pre-gapped rings but also had my machine shop make sure they were correct. They opened up the top ring up a little bit to achieve .028" end gap. I also had them fit the pistons when the block was bored.
So here's my question: With all the pistons in place it takes ~30lb/ft of torque to turn the crank. Is this too much? Before the pistons were installed the crank turned feather-smooth, so I know it's not that. I coated the bores with a light coat of 30W oil before installing the pistons.
So should I be concerned, or is this an acceptable resistance? I am using Hastings plasma-moly lings by they way.

Any input is much appreciated!

'94 Laser red 'vert. Still a 5-oh... for now
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About 24-25 lbs is the norm. But depends on a few factors. Ring tension being one of them. I wouldnt be too concerned with 30lbs.

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post #12 of 16 (permalink) Old 06-10-2010 Thread Starter
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Thanks much, that is good news indeed. I thought maybe a light coat of 30W wasn't enough so I added another thick coat. I thought I'd let it sit a few days like this and measure the required torque to turn the assembly in a few days, maybe it will be reduced with some added lubrication.

Quote:
Originally Posted by YLDPONY View Post
With all the pistons in place it takes ~30lb/ft of torque to turn the crank.
Edit: ~30(lb)(ft)

I have no idea how I made that mistake

'94 Laser red 'vert. Still a 5-oh... for now
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glad to hear you got it straightened out

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Best so far: 10.92 @ 123mph with a 1.49 60ft
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post #14 of 16 (permalink) Old 06-10-2010 Thread Starter
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Quote:
Originally Posted by need4spd90 View Post
glad to hear you got it straightened out
Edit:
Got one problem straightened out

But thank you, I enjoy seeing these things get done right instead of just thrown together.

'94 Laser red 'vert. Still a 5-oh... for now
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well hopefully there will be no more surprises lol

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Best so far: 10.92 @ 123mph with a 1.49 60ft
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