Help with final check on deck clearance before decking block

[Kapper]

The shop just called asking what I want to deck the block to. They said there is currently 0.045 inches of deck of deck clearance with the 4.2 crank, 4.0 rods, and IC944’s. According to the calculator, I need to deck the block to .01 to get the quench and CR in the right ranges.

To me, .035 seems like a very large amount to take off the block.

Before I have them deck the block to .01 I wanted to have someone take a look and tell me if I am making a mistake somewhere.

Anyone see any problems with my calculator results or with shaving 0.035 inches off the block to get the .01 clearance?

Im using:
4.0 block bored over .030
4.2 crank
4.0 rods
IC944’s 21cc pistons
Comp Cams 231-4 cam
Shop said Head Gasket will compress to .039
Cylinder head combustion chambers are 58cc but I plan to polish them out to 60cc’s if needed.

With these values the calculator says I should have .049 Quench, 9.4SCR and 8.21 DCR
What do you all think, should I be concerned about shaving the .035 off the deck to get the .01? If everything looks ok, I'm going to have the shop start the work ASAP.
Thanks for any help. God bless!

[Muad'Dib]

Its expensive but worth doing IMO. Plus there is no known head gasket that compresses that low. .044 is the smallest. I would also go with 0 Deck.


On another note... are you sure they arent mocking it up with 4.2 rods or something? Its my understanding that with 944's and 4.0 rods the deck shouldnt need much if anything shaved at all...

[Kapper]

Its expensive but worth doing IMO. Plus there is no known head gasket that compresses that low. .044 is the smallest.

So you don't see any problems with taking that much material off the block?

The head gasket is a Victor Reinz that is shown in the FAQ section to compress to .044 but the guy at my shop measured it and believes it will go down to .039.

Even with the .044 gasket and .01 clearance the calculator gives .054 Quench, 9.4SCR, and 8.21 DCR with 59cc cumbustion chamber.

Do these all look acceptable? Should I deck it to .00 to get the quench back below .05?
Just dont want to ruin the block at the tail end of their work.

Thanks again.

[Muad'Dib]

Again, i think something is off unless i just dont know enough about a long rod stroker. That seems like a lot to remove using the 944 / long rod combo.. im under the impression that it should be something more like .02


Either way i would still go to 0 deck to get quench down to the gasket thickness which will be .044.

[SilverXJ]

Thats a lot of deck clearance with the IC944 pistons. IIRC they usually only need .020" taken to get around 0 deck. They can't be using 4.2L rods of the piston would be in the hole .248 more. Really, KB should have made the pistons a bit taller.

[IH 392]

You could measure 20 of the same blocks and not come up with the same thing twice, sounds like you got a particularly tall block?, but I agree I'd deck it right to 0 and use the thin gasket.

[Kapper]

We found that the rods are not to the factory specs because they have been rebuilt. The shortest rod 6.113 was the one being used to measure the deck height. That explains .010 of the .045 deck height. The longest rod is 6.119 and the rest are somewhere between.

We checked the rods, the pistons, the block, and the crank and everything seems correct. At least we don't have the wrong parts. Thanks for the help guys.

[Kapper]

It just occured to me that when taking this much off the block (.040) to get the block to .005, the pushrod length will need to be different. Do I now need to buy adjustable pushrods? Is there some other way to fix this?

[Muad'Dib]

Not adjustable pushrods.. but the right length pushrods. Buy a length checking tool or rent one and find what length then get the right ones from smithbros, trend etc.

Check my build thread .. lots of info there.

[Kapper]

Not adjustable pushrods.. but the right length pushrods. Buy a length checking tool or rent one and find what length then get the right ones from smithbros, trend etc.

Check my build thread .. lots of info there.

Thanks I will check that out.

I just notice your in Bend...I'm in Salem just over the hill from you. We should go wheelin some time after I'm up and running.

[gradon]

If you enter the 1.353" pin height of the IC944 and 6.123" 4.0l rod length, and with the middle ground 9.453" deck height(spec is 9.450-9.456"), you'll have a .0295" deck clearance. KB specs the piston so that you have to take .020" off the deck to get a .010" deck clearance. I'd agree that in most cases, the KBs should have a .030" deck clearance prior cut, so your .045" is out of the ordinary(normal for the 4.2 rod and aftermarket 4.0 piston strokers).

[Kapper]

If you enter the 1.353" pin height of the IC944 and 6.123" 4.0l rod length, and with the middle ground 9.453" deck height(spec is 9.450-9.456"), you'll have a .0295" deck clearance. KB specs the piston so that you have to take .020" off the deck to get a .010" deck clearance. I'd agree that in most cases, the KBs should have a .030" deck clearance prior cut, so your .045" is out of the ordinary(normal for the 4.2 rod and aftermarket 4.0 piston strokers).

This makes the .045 deck clearance more acceptable because if I take the .030 clearance you mention and add to it the .010 difference between the stock 6.123 spec and my actual rod length of 6.113 it explains where .040 of the total is coming from.

Although, I must be missing something because when I add 1.353 to 6.113 (actual) I get 7.466. Then when I subtract this from the total deck height 9.453 I get 1.987. Am I missing something else that needs to be taken into account to get the .0295 deck clearance to started with?

Thanks for the help.

[gradon]

Deck Clearance = Deck Height - (Stroke of Engine/2 + Rod Length) - Piston Compression Height

[Cheromaniac]

Then when I subtract this from the total deck height 9.453 I get 1.987. Am I missing something else that needs to be taken into account to get the .0295 deck clearance to started with?

Yeah, you need to subtract stroke/2 or 1.948" so that'll leave you with a deck clearance of 0.039".

[dragginwagon406]

Mine started at .030" in the hole with IC944 pistons. Took .022" off the deck and ended up .008 in the hole.