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Help re-installing cylinder head


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Hi Guys-

Long time, no talk.  Working on the 87 Laredo.

 

I had a shop rebuilt and assemble my 2.5 a couple of years back, and I had to take the head off because it was blowing smoke, turned out to be a couple bad valve stem seals.  Put the head back on myself, but unlike the Chevy v8's I have had apart, there were no dowels, so I used 4 studs in the corners to line up the gasket and head, tightened up in order to specs, and put RTV on the bolt it needed to be on.  Immediately, I'm leaking antifreeze, but, not wanting to take the head off, I drove it and put up with it that way, and topped off the coolant.  At warm up, and after shut down is when I would see the leaking.  It wasn't blowing white smoke.

 

A mechanic friend of mine suggested that the studs in four corners wasn't a very precise way to put the head on, and thought there should be dowels.

 

That brings us to this weekend - I pulled the head off again (don't you love re-doing things, over and over?), and it doesn't look like the block has dowels.  So, just so I don't ever have to do this again, what is the best way to get this lined up right?  I'm going to take the head to a shop and have them check it out, just to make sure it's not warped or cracked.  It was leaking from the driver's side rear corner, I could see the trail down the bellhousing, and the bolt threads were all wet.  Getting this head on, on the bench, seems very doable.  Reaching up and over the fender, it's another story!

 

Thanks!

 

Tom

 

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Could be, but when the block was rebuilt, it was magnafluxed, and didn't leak until I had to pull the head and put it back on.  I guess we'll know once I take it to the head shop.

 

From what I'm reading on the internet, these vintage 2.5L's didn't have dowel alignment pins. 

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If you have the head off.....Get a known "Straight Edge", a carpenters square springs to mind, and check you block and your head....a gap of even half a MM can be cause for concern.

 

On the other hand.....there is a manufacture who makesa a thicker HD gasket for the 2.5....maybe that would help...... . :MJ 1: .

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One or two of the head bolts penetrate into the water jacket and have to be sealed. You wrote that you used RTV on the bolt that needs it, but I wonder if RTV is the correct sealer. According to my FSM for the I-4 engine, the head bolt at the left front position (#8 in the FSM illustration) should be sealed with "Loctite Pipe Sealant with Teflon 592 or equivalent." RTV is a gasket sealer, not a thread sealer. Back in the halcyon days of my youth, we used a sticky black Permatex product for the head bolts that penetrated the water jacket, but I don't remember the exact name for the product.

 

Also, the head gasket can only go on one way. Be sure the side marked "TOP" is facing up.

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Thanks, Eagle.  The right rear was leaking, but I was following the FSM as to what bolt to coat in sealant.  I can't remember what kind I used.  I will be sure to use what they call for, or an equivalent.  Appreciate it!

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I'm gonna let the head shop check it out.  If it checks out OK, I'll have to be more careful in getting the gasket and head down using the "stud method."  Frustrating!

Studs are just as accurate as dowels. The interface of the head to the block, horizontally, is not critical to the thousandth of an inch. You just want to cylinders to line up under the valves and the water and oil passages to line up well enough to allow passage of coolant and oil.

 

Also, pay attention to torque. The bolt with the pipe sealant gets a lower torque than the others. Also, be aware that the torque values for the 1984 thru 1987 engines were different from 1988 and newer.

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I'm gonna let the head shop check it out.  If it checks out OK, I'll have to be more careful in getting the gasket and head down using the "stud method."  Frustrating!

Studs are just as accurate as dowels. The interface of the head to the block, horizontally, is not critical to the thousandth of an inch. You just want to cylinders to line up under the valves and the water and oil passages to line up well enough to allow passage of coolant and oil.

 

Also, pay attention to torque. The bolt with the pipe sealant gets a lower torque than the others. Also, be aware that the torque values for the 1984 thru 1987 engines were different from 1988 and newer.

 

 

How much lower torque on the sealed bolt?

 

My Comanche is a 1987, but the block came from a YJ from the same era, not sure of the year (87-90).  Should I be able to tell the year of the cylinder head from the stamping?  I thought I saw an 88 on there, but I'm not sure if it's that simple. 

 

Thanks again

 

Tom

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Ok

Just about to take the head to the shop and it looks like its a casting (d12) 408, used from 87-90. Are we sure the torque value change splits from 87-88?

 

Thanks

 

Tom

You didn't believe me when I wrote that my info came from the FSM?

 

 

 

ETA: I don't understand why the first page is upside down. It's oriented correctly when I view it in Photobucket.

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Ok, got the head back from the shop.  They did a light milling on it, and said it was good.  It cost money, but I wasn't putting the head back on without verification.  New bolts on the way from headbolts.com, new Felpro gasket ready to go, I have to get the pipe sealant and put it on this weekend.  Here's hoping....now onto the next question thread -- vacuum leaks. 

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