93 740 warped head

e777 · Post by **e777** » 08 Nov 2012, 21:35

I'm tempted to buy a one-owner 740 with 214K. Beautiful car but with a warped head, caused by a ruptured hose leading to overheating.

Warped heads is a maintenance area that is unfamiliar to me. So I thought I'd ask that if a car has suffered a warped head is there any potential for such things as damage to the block or other parts? Or anything else I should be on the look out for?

Any input would be appreciated.

Thanks!

Eric

91 240 230K
90 740 270K
86 740 240K

Post by **billofdurham** » 09 Nov 2012, 12:25

A '93 740? I thought they were phased out in '92.

Usually a warped head doesn't cause problems with other parts unless it has warped so far that it is pulling the head bolts.

Warped heads can be machined within certain limits:- Across the head measuring at both ends and then between the cylinders distortion up to 0.01" is acceptable, between 0.01" & 0.02" the head can be machined. Over 0.02" the head is scrap.
Measuring diagonally from right rear to left front and vice versa distortion up to 0.02" is acceptable, between 0.02" and 0.04" the head can be machined. Over 0.04" the head is scrap.

If the head has been machined before it can't be machined again.

Bill.

Post by **jimmy57** » 09 Nov 2012, 13:14

If the red pain on block is brown at the top where head meets block then you should walk away. That usually goes with it getting so hot it sticks rings or piston scores cylinders etc,.

lummert · Post by **lummert** » 09 Nov 2012, 14:08

If the rear timing belt cover, where it's attached to the block. has heat damage from overheating it may be wise to pass on it.

e777 · Post by **e777** » 10 Nov 2012, 09:37

Thanks very much to all three of you. I mistyped when I wrote 740; it is a 940. I'll be on the look out for those trouble signs when I look at it today!

Thanks again.

--Eric

e777 · Post by **e777** » 10 Nov 2012, 18:19

So, I looked at engine today and there were no problems with the block or melting of the TB cover. I did notice that there was a 1/2-inch wide band of very superficial rust around the uppermost part of each cylinder. The head has not been off longer than a couple of months. Is this rust a problem? Thanks for any light you can shed on this!

e777 · Post by **e777** » 10 Nov 2012, 18:47

That is, just inside the cylinder itself, the top 1/2 inch.

e777 · Post by **e777** » 11 Nov 2012, 18:03

Ok, here is the final entry. I researched the rust issue a bit and learned that if it is severe rust that has compromised the surface of the cylinder (pitting, etc) then you are in trouble - the cylinders would need to be resurfaced. It seems that even after a short period of time being exposed the inside of cylinders will rust up. If it is only a few weeks, as is the case with this car, then this superficial rust can be easily removed by gently wiping it with WD-40 and a very fine steel wool pad. It came right of after a couple of light wipes, no scrubbing needed. So, after I throw on the extra head I have laying around, I am hoping this well-cared for $800 940 lasts a long time.

Thanks again for the input.

Post by **rgk** » 11 Nov 2012, 20:04

Good luck, and please keep us updated. Some photos of the head replacement job would be great!

e777 · Post by **e777** » 12 Nov 2012, 19:10

will do!