Combat Head - Wobbly Valves

swooshdave · Mar 3, 2019

I got the head apart, we saw the first step with the oven adventure, and now I got the valves out. The collets did not want to separate and it took some tapping to get them to release.

The valves have been lightly blasted. I'm not sure if they can be saved. Well, at least one of them can't.

The intakes definitely had some play. I'm not sure how you measure the play but I'm guessing these have too much.

The one exhaust valve is a mess. I can't even get the valve back in the guide.

The other exhaust valve is not bad, but it still has some play.

I really don't remember the bike smoking. And it certainly ran good. There is a lot of buildup in the cylinder head. The buildup even prevented the valves from closing, I could see light between the valve and seat.

I don't know if the seats are good or not. Maybe a grinding? I sure hope they don't need to be replaced.

Depending on how much the barrel ends up costing I'll see how much budget I have for this head.

I need to look at the non-Combat head and see if it's any better.

Fast Eddie · Mar 4, 2019

For a 40+ year old bike of unknown history and mileage, I don’t think you’ve found anything bad or unexpected there swoosh.

When you get the head properly cleaned up you should be able to see whether or not the seats have already been heavily cut. If not, they should be fine. If they have already been cut back, sometimes fitting oversized valves can get you a good cut on new seat material.

What are the exhaust stub threads like? That could be a deciding factor in whether or not to send the head to Sir Comnoz...

Time Warp · Mar 4, 2019

swooshdave said:
The intakes definitely had some play. I'm not sure how you measure the play but I'm guessing these have too much.

When the wobble inline with the rocker travel is more than the wobble sideways, the guide bore is starting to go south.
What is to far south is debatable.

Fast Eddie · Mar 4, 2019

Time Warp said:
What is to far south is debatable.

That’s a good point. I once rebuilt a T160 and decided the valves and guides were worn. I sourced and fitted genuine NOS valves and guides. When I’d done, they were not noticeably any better than the ones I’d removed !

sportsroof · Mar 4, 2019

IMHO, too much play there. If it was mine, new guides and valves, no question. HTH
Cheers, Martin

Peter R · Mar 4, 2019

sportsroof said:
IMHO, too much play there. If it was mine, new guides and valves, no question. HTH
Cheers, Martin

I agree,it looks like too much play. Instead of new valve guides, you could consider to have K-liners installed.

marinatlas · Mar 4, 2019

Hi Swoosh, just check too the pushrods lenght , as your C stamped head is combat it has been milled down (as factory done it) by 0.040 ('1mm), and thus if pushrods had not been shorten that will increase the side (fore and aft ) loads on the new guides you will fit......

Tigernut · Mar 4, 2019

Fast Eddie said:
That’s a good point. I once rebuilt a T160 and decided the valves and guides were worn. I sourced and fitted genuine NOS valves and guides. When I’d done, they were not noticeably any better than the ones I’d removed !

Were they Wassell? That would explain it!

Fast Eddie · Mar 4, 2019

No, NOS genuine Triumph.

Which also probably explains it !!

swooshdave · Mar 4, 2019

marinatlas said:
Hi Swoosh, just check too the pushrods lenght , as your C stamped head is combat it has been milled down (as factory done it) by 0.040 ('1mm), and thus if pushrods had not been shorten that will increase the side (fore and aft ) loads on the new guides you will fit......

What is the correct length for the Combat pushrods?

marinatlas · Mar 4, 2019

https://www.oldbritts.com/pushrods.html

this just a quick answer , may be more to come , what cam do you have ?

swooshdave · Mar 4, 2019

marinatlas said:
https://www.oldbritts.com/pushrods.html

this just a quick answer , may be more to come , what cam do you have ?

SS

ILLF8ED · Mar 4, 2019

swooshdave said:
What is the correct length for the Combat pushrods?

HI Dave,

I used some .060" shorter pushrods on my combat after rebuilding the guides and valves. The left exhaust push rod always rubbed and at the end of last year it finally broke. Not sure if this was due to the shorter length, but I went back to the stock Commando rods and used two copper head gaskets glues together to make us the shave head distance. Seems to run OK, but have not had the chance yet to wring it out after correcting the cam timing. Assembling the timing cover I took a suggestion and bought a neoprene gasket....mistake. I have never had good results with neoprene valve cover and now the same for the timing cover gasket. They leak a lot.

swooshdave · Mar 4, 2019

illf8ed said:
HI Dave,

I used some .060" shorter pushrods on my combat after rebuilding the guides and valves. The left exhaust push rod always rubbed and at the end of last year it finally broke. Not sure if this was due to the shorter length, but I went back to the stock Commando rods and used two copper head gaskets glues together to make us the shave head distance. Seems to run OK, but have not had the chance yet to wring it out after correcting the cam timing. Assembling the timing cover I took a suggestion and bought a neoprene gasket....mistake. I have never had good results with neoprene valve cover and now the same for the timing cover gasket. They leak a lot.

I have the silicone valve cover gaskets and they are quite lovely.

Did they really shave the Combat heads down .060"?

I suspect that .060" short pushrods are not the answer because of geometry. Didn't Combats use the standard length pushrods from the factory?

As posted previously Left Coast Racing has shorter Combat pushrods but only by .036"

https://www.oldbritts.com/pushrods.html

swooshdave · Mar 4, 2019

Fast Eddie said:
For a 40+ year old bike of unknown history and mileage, I don’t think you’ve found anything bad or unexpected there swoosh.

When you get the head properly cleaned up you should be able to see whether or not the seats have already been heavily cut. If not, they should be fine. If they have already been cut back, sometimes fitting oversized valves can get you a good cut on new seat material.

What are the exhaust stub threads like? That could be a deciding factor in whether or not to send the head to Sir Comnoz...

I know it's hard to follow which parts I'm showing at any given point.

The Combat head was the one on the bike that went bang. The history is that it ran just fine, didn't smoke (that I remembered) and has an undetermined amount of miles on it. Threads are great, I tightened down when hot and never had to touch them again. You can see me taking the exhaust off here:

The donor engine I was working on had a Combat cam (SS) but a non-Combat head. That engine I know a lot less about except I don't think it had a lot of miles on it. And I have no idea why it has a Combat cam but a non-Combat head. And certainly why the pistons are missing. But that's the fun of being a Norton archeologist.

baz · Mar 4, 2019

No they took 40 thou off the head of a combat model
But if you are building an engine from different parts you need to check the valve geometry
And adjust the push rods to suit
You may have a lot of valve seat recession etc

ILLF8ED · Mar 5, 2019

swooshdave said:
I have the silicone valve cover gaskets and they are quite lovely.

Did they really shave the Combat heads down .060"?

I suspect that .060" short pushrods are not the answer because of geometry. Didn't Combats use the standard length pushrods from the factory?

As posted previously Left Coast Racing has shorter Combat pushrods but only by .036"

https://www.oldbritts.com/pushrods.html

No the heads were shaved .040”. With the 1.13:1 rocker ratio you need to shorten the push rods more than .040”. I picked these rods advertised as shortened for the combat head and the supplier chose .060”. The problem for a combat head is “the factory use the standard push rods” as you mentioned. It left the angle of the rockers at closed valve not at 90 degrees to the valve stem and causes uneven wear on the valve guides...wobble.

swooshdave · Mar 5, 2019

Good information! Thanks!

dynodave · Mar 5, 2019

How does the fact that the stock cam and the combat have different diameter base circles play into this push rod length engineering exercise.

swooshdave · Mar 5, 2019

dynodave said:
How does the fact that the stock cam and the combat have different diameter base circles play into this push rod length engineering exercise.

I didn't know there was going to be a quiz!

Combat Head - Wobbly Valves

swooshdave

Fast Eddie

Time Warp

.......back to the 70's.

Fast Eddie

sportsroof

Peter R

marinatlas

Tigernut

Fast Eddie

swooshdave

marinatlas

swooshdave

ILLF8ED

swooshdave

swooshdave

baz

ILLF8ED

swooshdave

dynodave

swooshdave

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