TO-20 cylinder head torquing

[Northvale PA]

As mentioned below, I am getting my TO-20 overhauled and I am disassembling things and checking them out. So, several years ago I replaced the head gasket. I never did get it to seal correctly so I decided to pull the head and make sure the block isnt cracked. Not, but The new gasket is blown between cylinders 2-3. Same place as last time. So here is the question, do the three studs in the center get torqued too? The front two have copper washers under them so I didnt torque them. Mistake? There is no torque diagram in the service manual. Thanks.

 

[Dieseltech]

They should ALL be torqued, and especially re-torqued after engine is up to temp WHILE HOT. The plug side are not so critical, but all the others are. Sometimes the rocker arms need removed, but it's IMPORTANT to do the hot re-torque if there's any chance the gasket will hold. Applies to all Continental and Perkins diesels too.

 

[Northvale PA]

Thanks. Well I assume someone got in there before me, lost the steel washers and put copper ones on. And silly me didnt know better. Hmmm.

 

[Bruce(OR)]

What I see is a head gasket that did not tear in 1/2 when the head was pulled off.
I did a head job with that style gasket a few years ago and per the service manual coated both sides with a thin layer of cup grease. Put it together and a short time later had to tear it apart for a mistake I made.
the gasket tore in 1/2 upon removal. Very nicely sealed gasket with cup grease.
Copper stuff looks to be good to fill in surface imperfections but apparently not so good without a thin layer of good old fashioned cup grease.
I had to ask John(UK) what cup grease was.
Short fiber wheel bearing grease.

 

[Steve@Advance]

A few things to check:

To do a proper head gasket replacement, the block and head surfaces must be cleaned gown to clean metal, scraped, polished, and all evidence of carbon, rust, and old gasket removed. Much easier done with the studs removed.

With the studs out, the threads can be wire brushed (not chased with a die), and the block threads chased with a bottom tap. When clean and inspected the studs can be reinstalled with sealer on any that go through to the water jacket.

The head surface needs to be checked for flat, or just go ahead and resurface it since it has failed and been off before.

That engine uses wet sleeves that just sit in the block. It is easy for them to ride up and trash get under the stop between the sleeve flange and block. The sleeves are designed to stand about .003 above the block surface. I don't have the exact number here, but it is critical they are the correct height and all the same. If any are held up, the gasket stands zero chance of sealing! If any sleeve rode up, not only will there be debris under the flange, but the oring seal at the bottom will be disturbed and probably leak coolant into the crankcase. If any are standing too tall, they will need to be removed, cleaned and new orings installed. Not an easy job as all the crud in the water jacket will fall into the crankcase when the sleeve is removed!

Torque is also critical. Put light oil on the threads, and start with the center studs, working in a circular pattern. Take them to snug first, then to almost tight, then to final torque, repeat several times until no more movement. You will need a crowfoot socket for the side studs.

Then rough set the valves, set up a nurse tank to feed fuel to the carb, run the engine up to operating temperature, then retorque the nuts again. To properly retorque, back each nut off just enough to feel it move, but not enough to relax the hold, then take them to recommended torque. Finally, do a careful valve adjustment.