Head Gaskets

[Mike Allfrey]

I note a message from Pat Lockyer about cylinder liner sinkage. I agree with Pat on the torque value for the cylinder head nuts. However, I do not agree with the comment that the liner protrusion should be "more". Here in Melbourne (Australia) for nearly fifty years, we have been using solid copper shims for the liners, no gaskets, and a liner protrusion of 0.006" to 0.008". My preference, I have built seven engines, is to opt for 0.006" cylinder liner protrusion.

The most important point is that the cylinder head nuts are re-torqued as soon as the engine has reached normal operating temperature and stabilized for twenty minutes thereafter. If this is carried out, then Jupiter willing, there will be no liner sinkage. If the cylinder heads are not re-torqued, then the car will travel about 600 miles before water enters the cylinders!

I don't think the term 'Monotorque' can be taken literally with respect to the Javelin/Jupiter cylinder head gasket. I think the gaskets are still listed in JBJ as being 'Monotorque'. That term should be deleted.

Recently I built an engine that had 0.002" dip in crankcase surface above one of the water inlets at the rear. The coolant cascaded like Niagra Falls even thought the nuts were re-torqued! It was a case of strip down and start all over again - after welding and local milling.

Kind regards to all,

Mike Allfrey - E0 SA 42R

[Drummond Black]

Like Mike , I always use SOLID copper as liner seats and rigidly work to liner projection of .006 to .008 thous. I check this in the following manner. After settting the liner heights, and most importantly the crankcase halves must be correctly torqued together with the crankshaft fitted and balance pipe sealed and tested, I fit the cylinder heads WITHOUT gaskets and torque to 20 ft lbs. This seats the liners firmly in the block. A feeler gauge can then be inserted between the block face and cylinder head face. A slight variation will always be found but the gap should be between .005 to .009 thou. I then leave the assembly in this condition for a few days and then re-check before final assembly.

The heads are torqued down in stages of 5 ft lbs to a MAX of 40 ft lbs.
The heads are re-torqued at about one hundred miles. I do this with a slightly warm engine.

All through this operation care and attention to detail area must.

Drummond

[Mike Allfrey]

Dear Each,

Firstly, It is nice to see my Jupiter along with Drummond's again!

We need to be careful on this topic. Most of my engines have had the crankcase surfaces skimmed to flatten them after welding. I also know of an engine working really well with only 0.004" liner protrusion on solid shims.

We need to appreciate that the modern head gasket material is not as forgiving as the old copper/asbestos/copper gaskets were. The original Jupiter cylinder head gaskets, steel/asbestos/copper, were not as forgiving in use as the first mentioned copper/asbestos/copper type. I think, and I could be wrong, that the current New Zealand gaskets are even less forgiving than the original Jupiter type. The current NZ gaskets do a marvellous job with liner protrusion at 0.006" to 0.008".

A while ago, many years infact, I did the expansion calculation and I think I found that 0.004" protrusion would just suffice - hence my preferrence of 0.006" protrusion. I have to admit I have never tried the original Jowett Cars Limited specification on solid shims - I just haven'y dared!

In the engine that I built for my Jupiter recently, the crankcase was extensively welded and the joint faces as well as the head gasket faces were skimmed. The liner seats in the crankcase set were corroded, so each set half was set up in a mill and the seats re-machined to provide, with a 0.035" shim spacer each, 0.006" liner protrusion. Each liner has its cylinder number etched into it, making assembly a simple matter.

There have been no problems to date despite running in 40 degrees C plus ambient at 92 degrees temperature indication on the newly repaired temperature gauge, for 400 miles. I think that is a fair test for the NZ gaskets!

Good luck,

Mike Allfrey - E0 SA 42R.

[Forumadmin]

See these links in the old JowettTalk
http://keithclements.co.uk/jowetttalk/% ... 000062.htm
http://keithclements.co.uk/jowetttalk/% ... 0001ac.htm
http://keithclements.co.uk/jowetttalk/% ... 0003de.htm

[Bryan Walker]

You Guys Scare Me!
Does anyone think to ask the people who supply and have the head gaskets made? I am reminded of the definition of an "EXPERT" - Ex is an unknown quantity and SPERT is an Accelerated Drip so we have an unknown drip.....
( I'll email the rest of Neils reply history of the new gaskets etc, when I've got time to type it out -3 pages Bryan).

The below is the instructions Neil Supplies with the gaskets!

FITTING INSTRUCTIONS FOR JAV/JUP HEAD GASKETS

Piston Bore 72.5mm to 75.0mm

1/ Set Liner heights above block 0.006" to 0.008" Use Assorted thickness Copper Shims ONLY to Achieve this.

2/ Smear Thinly Loctite Master Gasket, Silicon Rubber( or similar) to the edge of the gasket and block to assist in sealing water.
(Not on Liner to Head Seal area)

3/ Fit 'O' Ring around stud feeding oil to rockers - push into gasket.

4/ Tighten heads to 37.5 pounds/foot torque.
Say 20x3 times, 30 x2 times 37.5 x2 times.

5/ Run Engine up to 75 degC water Temp.
Leave 15-20 Min's and re torque to 37.5 pounds/foot

6/ Reset tappets.

Jowett Spares (NZ) 2003