4.5 l head distortion questions

[zooklm]

I have a 1977 450SEL that overheated and blew both head gaskets. I have removed the heads and taken them to a shop to get them checked. They are reporting that the heads have 0.015 inch warp also they are saying that the heads are below minimum thickness. I checked the engine service manual and they allow 0.08 mm of warp. The from "new" head thickness reduction allowed is 0.25 mm. While the manual says that "a slightly distorted parting surface will adapt again to cylinter head when tightened" in section 01-418, I am concerned that the amount of distortion measured is more than "slightly".

Any thoughts or guidance would be appreciated. I really don't want to spend a significant amount on the car due to the body having some corrosion issues.
Thanks,
Lee

[cth350]

First, be careful with the inch/metric conversions. We've lost a few satelites that way.

Second, heads warp. Sounds like these need milling and that will kill them. Complete, used motors are relatively easily available. Finding used heads is also easy, as there are plenty of these cars dead or dying. You can get any 4.5l v8 motor from 1976 and up to switch over with ease. If you get one from an SL, change the oil pan and the oil filter housing.

A 450sel is nothing wonderful to write home about, especially a rusty example. Their principle value is based on that it's your car. If you like it, keep it. If you don't, then either pass it on or part it out.

-CTH

[Tomguy]

Originally Posted by zooklm

I have a 1977 450SEL that overheated and blew both head gaskets. I have removed the heads and taken them to a shop to get them checked. They are reporting that the heads have 0.015 inch warp also they are saying that the heads are below minimum thickness. I checked the engine service manual and they allow 0.08 mm of warp.

0.015" of warp is 0.381mm, which is quite warped.

You either need new heads, or you need to grab a new engine (new to you). Neither is difficult, the first you can probably manage yourself.

That having been said, if you don't want to spend the money on new heads or a new engine and labor, you can always put the old heads back on with new gaskets, and carefully follow the torque pattern and specs, making SURE to loosen and then retorque the head bolts after 200-400 miles when the heads "unwarp". It probably wouldn't hurt the engine, the worst that would happen is you'd blow the head gasket(s) again, and if so, well, you could opt for a new engine at that point. Sadly, there are lots of engines available for these because the overengineered engine far outlasts the rust-prone body.