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Head Minimum Thickness spec in FSM wrong?
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=86975		 Page 1 of 1
Author:  minnisp [ Wed Aug 02, 2017 9:11 pm ]
Post subject:  Head Minimum Thickness spec in FSM wrong?
in fsm chapter 9-197 there's a minimum head thickness spec of 3.541

https://1drv.ms/i/s!AjoXnVa96mPNmIsKFFdY8WaJM2PlQg

and on chapter 9-183 there's a minimum head thickness spec of 3.738. That's a huge difference. Am I missing something?

https://1drv.ms/i/s!AjoXnVa96mPNmIsJJ_UDRrPntQ-r6g

My machinist measured my head and got 3.741 and he said the page 197 spec cannot be correct unless you can whack a 1/4 inch off of the head :)

I searched and couldn't find anything on the forum about the 3.738 spec, but the 3.541 spec is all over the forums.
Author:  flash7210 [ Wed Aug 02, 2017 9:23 pm ]
Post subject:  Re: Head Minimum Thickness spec in FSM wrong?
The service manuals are known to have many errors.

Given that the valve seats are almost flush with the head surface, that doesn't leave much room for machining the head.
Author:  minnisp [ Wed Aug 02, 2017 9:37 pm ]
Post subject:  Re: Head Minimum Thickness spec in FSM wrong?
Roger that. I hope people searching will get a hit on this and find out about the discrepancy
Author:  WWDiesel [ Wed Aug 02, 2017 10:45 pm ]
Post subject:  Re: Head Minimum Thickness spec in FSM wrong?
Very good find and point!
I believe the consensus is 0.002 to 0.003 is about the maximum that some have had shaved off of their CRD head and been successful with no problems.
Of course doing this requires going back with a thicker head gasket. :roll:
Author:  GordnadoCRD [ Wed Aug 02, 2017 11:26 pm ]
Post subject:  Re: Head Minimum Thickness spec in FSM wrong?
Your FSM pages listed don't correspond with mine, but the figures do.

On 9-1595 Cylinder head thickness is 3.738" - 3.742"
Yours falls within this spec.

On 9-1616 under cylinder inspection it states minimum cylinder head thickness is 3.541"
I agree, it can't possibly be correct given the actual measurement.

I suspect it's either a data entry error,
or
It's possibly a figure that was forgotten about when they updated the FSM from the 2.5L to the 2.8L, since it's not stated in the Cylinder Head Specs page.
Author:  minnisp [ Wed Aug 02, 2017 11:41 pm ]
Post subject:  Re: Head Minimum Thickness spec in FSM wrong?
yeah that pagination got me too. the pdf page is different than the FSM chapter-page designation.

I think your number makes it easier to find since it's in PDF format because you can go directly there. Glad you pointed that out.

I was wondering if maybe the 2.4 or 3.7 head spec got copied to the 2.8 section by mistake but was too lazy to look.
Author:  GordnadoCRD [ Thu Aug 03, 2017 12:04 am ]
Post subject:  Re: Head Minimum Thickness spec in FSM wrong?
It's possible. I didn't think to look it up. :roll:
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