TR4/4A Cylinder Head Install - Questions

[RJS]

Hi

Head is successfully off. Will now replace broken head stud. Will check the liner protrusions. Never having done this before, a few questions first:

• Any more prep work to do beside getting face of block and cylinder head clean and spotless? I will carefully use a gasket scrapper and acetone if I have to
• I have 87mm pistons and liners. Any recommendations for a head gasket? I see standard copper ($24), German copper made on Payen tooling ($58), modern composite with silicone sealing rings ($70) or a Cometic Gasket $79). Any advantage or experience with any of these?
• Copper Coat gasket sealer?
• Any special tips, tricks or things to look for to ensure a successful install?
• When torquing the first time, will go in order but, what increments should I take each step at?
• When to re-torque? After first heat cycle, after 100 miles or after 500 miles?

Thanks

Bob

 

[TR3driver]

Wow, no responses. I wonder why?

Anyway, IMO, just clean up the surfaces to take the liner measurement. Be sure to check on both sides, they may not be the same.

I have no suggestion for head gasket or coating. I've had a lot of trouble in the past, tried several different gaskets and coatings with pretty much the same results. Using a regular copper clad composite gasket combined with soldering a "fire ring" to it is what works for me. It's my belief that the liner protrusion being low on one side is my problem (I never had problems with several previous engines using just a cheap gasket from JCW and no coating); the fire ring is a workaround for that. But given how well it has worked out, I may do that next time as well, even with the correct protrusion.

I don't know if it's "best", but what I do is 60 ftlb the first time, then 80, 90 and 102. I know the book says "100-105", but torque wrenches are never perfectly accurate (when is the last time you had yours calibrated?) so I shoot for a reading in the middle of the given range. ISOA ran an article some years ago where they compared several torque wrenches against a "digital" torque sensor and found that both the overall accuracy and the deviation from one reading to the next were fairly large. For example, in 5 trials, the Snap-on dial type torque wrench gave actual values (as indicated by the torque sensor) from 49.9 all the way up to 53 ftlb for a wrench reading of 50.

Workshop manual says to retorque after 500 miles, not just head nuts but manifolds and so on. But it certainly will not hurt to retorque multiple times, both sooner and later. I generally check after the first heat cycle as well. Best practice IMO is to keep track of nut position, and keep retorquing from time to time until they always stop at the same position. My front and rear manifold nuts (the ones without the bridge piece) used to always go some more until I added some heavy flat washers (aka "setup" washers) under the lock washers.

Note that when taking a torque reading, it is important that the nut still be moving when taking the reading. If it stops moving, it will take extra torque to get it moving again (an effect known as "stiction" for static friction). For that reason, when retorquing head nuts, I always loosen the nut a bit first, so I can take the new reading with it moving. Doesn't need to be very far, just a fraction of a turn will do fine. But I don't bother with that (or even using a torque wrench) when doing manifold nuts.

Make sure your head nut washers are in good condition. The factory apparently used relatively soft washers, and they tend to crush in service until sometimes they won't even slide easily over the threads. IMO replacements should be at least Grade 5; the ones I use are harder than that. Of course all the lock washers should be replaced with new as well.

If you are reusing studs, clean the threads with just solvent and a rag, then try spinning a new nut down the threads. If it binds partway down, discard that stud. Chasing threads is fine in other places, but not IMO for high stress applications like head nuts, rod bolts or flywheel bolts.

 

[CJD]

And the most time consuming job is removing the scale from the inside of the block. Just a bit of scale under the liners will mess up the entire job, so it's worth taking lots of time scraping the block walls thouroughly.

 

[TR4nut]

I like the Lucas branded head gasket with the sealing rings.

 

[Tybalt]

For your basic, run of the mill, traditional type head gaskets we always used to give them a thin coat of silver or "aluminum" paint from rattle can prior to installation to help with sealing.

The advent of asbestos free stuff has given rise to all manner of new head gasket materials. I have a feeling from your description that the copper gaskets you reference are different from the old style reusable solid copper gaskets that were typically used by racers and are instead some sort of laminated construction at the prices you mention. Some of these new gasket types require the use of sealers, some do not, so the bottom line is that you follow what the gasket manufacturer's instructions state for that particular gasket. If in doubt, you can always contact them.

 

[TR3driver]

And the most time consuming job is removing the scale from the inside of the block. Just a bit of scale under the liners will mess up the entire job, so it's worth taking lots of time scraping the block walls thouroughly.

I used a cup type wire brush in a drill motor for the liner seats and most of the walls. Since very little cooling happens through the cylinder block, it doesn't have to be extremely clean other than the liner seats. So I cleaned the corners and water pump passage a bit with a wire "toothbrush" and let it go at that.

 

[RJS]

Thanks Everyone,

For your input. I've ordered the composite gasket with the silicone sealing rings (supposedly made by Lucas UK). I'll see what instructions come with it. I tried to measure the liner protrusion unsuccessfully. I tried a straight edge across the top of the liners and could hardly slip a 0.003" feeler gauge under the edge. I could catch the edge of a finger nail on it. But, I may well add a fire ring to the new head gasket using 26 AWG copper wire for good measure. I assume the fire ring is supposed to line-up on the top edge of the cylinder liner, correct?

The old gasket was a copper composite. It didn't look like any sealant had been applied. What was odd though was the whole gasket was wet. Pretty sure it was a very thin film of oil (not sure that was good).

Bob

 

[CJD]

You fix the sleeve height with the figure 8 gaskets under the sleeves...not the head gasket. The FO8's are available in steel and copper, with the copper being thicker.

 

[RJS]

Well, I'm just replacing a head gasket, not rebuilding the motor. So, liners and FO8's are not coming out.

Bob

 

[DanB]

I used the copper spray gasket sealant and it worked pretty good.

 

[JerryVV]

Thanks Everyone,

For your input. I've ordered the composite gasket with the silicone sealing rings (supposedly made by Lucas UK). I'll see what instructions come with it. I tried to measure the liner protrusion unsuccessfully. I tried a straight edge across the top of the liners and could hardly slip a 0.003" feeler gauge under the edge. I could catch the edge of a finger nail on it. But, I may well add a fire ring to the new head gasket using 26 AWG copper wire for good measure. I assume the fire ring is supposed to line-up on the top edge of the cylinder liner, correct?

The old gasket was a copper composite. It didn't look like any sealant had been applied. What was odd though was the whole gasket was wet. Pretty sure it was a very thin film of oil (not sure that was good).

Bob

I believe the Lucas Gasket you mention is like one which Cometic makes for our engine and if so I don't believe the copper fire ring can be used since the gasket is not copper and therefore the fire ring can not be soldered to a copper gasket. Perhaps an epoxy could bond but I wouldn't try it. For what it's worth I installed (and some of my friends have as well) the Cometic head gasket 2 years ago and have zero issues after doing a valve job. Head had not been touched since 1966 when the last valve job was done. The head had been off and on a few times. Doubt that my liners protrude more than yours do and as I recall I measured them and decided like you I was not pulling the liners to replace the figure 8's regardless of the protrusion. As a matter of fact a friend who was blowing head gaskets switched to the Cometic gasket and his problem went away. What's the saying "Your results may differ". I have a milled head and a compression check shows 185 / 190 across all 4 pots so I am generating some pressure. Just my 2 cents worth.

 

[ghawk16]

I'm planning to use the head gasket that came in the cheaper Big Bore (non-Lucas) gasket set from BPN. Looking at the descriptions the only thing that seems to be different between them is the Lucas one has the red silicon sealing beads. I spoke with the guys at BPN and told them everything I was doing to the engine and they said I would be fine with this gasket as they haven't had any issues with them.

 

[sp53]

How difficult was it to get the head off and what method did you use? I used copper coat gasket sealer on a copper gasket that came with the kit. The design of the head surface for my way of thinking is not flat enough for a long enough distance. For example the sleeves stick up and then the lifter bay is very close. I believe over the years the block surface falloffs and gets compromised, so I go with the sealer on the head gasket not for compression, but for seepage. Look at the sleeve protrusion and spray the gasket you should/will be fine.

 

[CJD]

Ive been using Wellseal, like the manual calls for. If it held the Rolls
Merlins together at 3k+ horsepower, then I reckon it'll hold my little tractor motor head on!

 

[RJS]

Right, the Lucas head cylinder gasket arrived and it is not copper. It is some type of composite with a steel ring around each cylinder. So, the copper fire ring (AWG 26) may not work.

Interestingly, these guys make some fancy compression rings to be used with their solid copper gaskets.
https://www.headgasket.com/compresring.html
If I have doubts about my liner protrusion, does anyone see a downside to using these?

I am leaning away from using any gasket dressing and simply installing it dry. FYI, the old copper compression gasket worked just fine until my head bolt cracked. So maybe I am worrying about nothing. And I was running 175psi dry compression in the cylinders.

Removing the head was a piece of cake. I removed the head bolts and studs one weekend and lifted the head right off the next. I was prepared to use an engine hoist but, no need.

Last, I want to chase the head bolt threads in the block. It's 1/2" but what is the correct thread - 13 TPI?

Thanks

Bob

 

[RJS]

Hi Again,

I was cleaning up the cylinder head today and noted that the PO must of had a helicoil installed in one of the manifold stud holes. It is supposed to be 3/8" coarse (16 TPI). It turns out that it is 5/16" fine (24 TPI). What came out was a 5/16" fine machine bolt.

It is the lower rear-most stud hole. I chased the threads and they cleaned up nicely. I found and ordered a stepped stud on ebay (I was skeptical it existed but, I found it!). It is a 2" long stainless stud that is 5/16" fine on one side and 3/8" coarse on the other. Does anyone see a downside to using this stepped stud?

On the flip side,
-can I tap that current hole to 3/8" coarse and/or install an new 3/8" coarse helicoil? And is it really worth it?

Thanks

Bob

 

[TR3driver]

If it really has a helicoil in it, then I think you won't be able to tap 3/8 NC and have it be strong. The 5/16 special tap will have cut away part of the original 3/8 threads due to the difference in pitch. For the same reason, I wouldn't leave it as 5/16.

A 3/8 helicoil might work though. I'm guessing someone was worried about striking coolant, but I think there is plenty of meat around those holes. That said, I've not tried it myself. Maybe someone else has? Even if you do, though, a good sealant like Permatex should stop any weeping once the stud is installed.