TR6 TR6 Cylinder Head Questions

[glemon]

I am lookking at fitting a modified head to my TR250, I have the chance to buy either an early motor complete with early head and log manifold, or the later head with the longer manifold. I plan on skimming to head to get the compression ratio in the 9.5/1 range and doing some mild port and polish work.

I have generally read that the later head/manifold is the better bet, there won't be any compatibility issues with the earlier block, didn't the later heads and or block have some sort of lip for each cylinder? Also the earlier head has bigger exhaust valves, does it make sense to do a retrofit?

My goal has always been to increase performance with little or no damage to reliability or drivability, if you want to know where I am going with the motor, already has a very mild cam and slightly lightened flywheel.

Also real technical question, I did get a set of the big Joe Alexander intake trumpets, they stick out slightly under 3.5", it looks like the later intake manifold will space may carbs out a couple inches farther from the head, any known or projected clearance issues, thanks, quick help appreciated, want to snap up the motor this weekend.

Greg

 

[glemon]

I think I found part of my answer on the campatability issue, but still interested in any other's thoughts

 

[trrdster2000]

Greg, I think you will run into a problem with the exhaust system on the newer head. I seem to remember a guy getting a set of headers for a later head and they would not clear the starter on the early one, unless of course you have the new high torque starter then this is for naught. Just something you will have to think about.
Are you going to be able to run a air box, the clearance sounds a little tight.

Wayne

 

[glemon]

Right now I run TR4A stand alone paper filters most of the time, and the big trumpets for speed events and shows. Thanks for the comments on the exhaust, hadn't thought of that. Greg

 

[DNK]

Had a late head from Ted on my 71 with the TT headers and wrapped the starter no problem.
In fact to well.
Eventually went to Ted's starter but that is a different thread

 

[tomshobby]

My 76 with Pacesetter header and Ted's starter.

 

[DougF]

The later head has the lip you refer to. The lip is a nonfactor if you shave the head.
Can't speak of any differences between your early head and the head you plan to use. Though I once tried to put a '75 head on a '74 block and found that the cylinders quickly filled with antifreeze. Each engine ran fine with its original head.

 

[glemon]

Head will be shaved, I was offered one engine for $100 or two for $200. The motors include the carbs etc. I decided at that price I could pick the parts I want and either store the rest as spares or sell at reasonable prices to worthy causes, so I am picking up both of them. Will have plenty of time to pick through the bits, though it appears you want a later head for the better intake ports/manifold, yes it will definitely get skimmed. I may bump up the C.R. to closer to 10/1 instead of 9.5, this is the "special test equipment experimental head" so if something doesn't work well I will just put the old one back on.

 

[DougF]

If you aren't aware, Richard Good's website, goodparts.com, has a chart for determining compression ratio under Technical Docs. and Links.
I also found Kas Kastner's book very helpful when porting the head.

 

[glemon]

Thanks Doug, I have the Williams "restore" and "improve" books, the old Kastner competition preparation manual, and the Vizard book on modifying Triumph motors, I think I have looked at the goodparts site, but had forgotten about that one, will look it up and get it bookmarked.

 

[tomshobby]

When I did mine I wanted to be close to 10:1 but not over. I used RG's chart for a guide and then cc'd the head to get to my target of 9.8:1. I felt more comfortable checking the work and was glad I did. Since then my car has traveled over 45.000 miles and uses no oil. It has been driven from 0 elevation to over 12,000 feet and ran great doing it.

 

[glemon]

Tom, yeah, that is what I am going to shoot for 10.0 to 1 or a little under, I got the motors yesterday, was unseasonably warm, so I pulled the head on the newer motor. Very dirty of course, but looks to be in order, it is the low compression 3.55" later head.

 

[justin_mercier]

The exhaust headders are all the same spacing for all tr6 engines, however the late headers with the exhaust rail will not clear under the early intake manifold. The heads themselves are different spacing between early and late, but they will mount on any engine. You dont really want to go above 10:1 because then you'll start risking early detonation on pump gas without additives. My engine is at 9.98:1 with a GP2 cam and other modifications. I have a early head (71) mounted to a late block. Originally I was using a goodparts triple ZS intake, but when i swapped bodies, the front carb wouldn't clear the fender, so I had to find myself an early intake manifold. This was when I discovered that my late exhaust manifold wouldnt fit with the early intake manifold due to the exhaust recycling rails.

If you chose an early head, they were a slightly higher CR to begin with. Also if you chose an early head and want to go to a triple ZS intake to go with other engine mods... let me know, because i've got the good parts intake manifold sitting in my basement unused now =)

 

[titanic]

I have used a late exhaust manifold with the air injection ports on a early head/intake manifold, but the ports have to be ground slightly to clear the intake manifold. When mixing intake manifolds, heads and blocks, it is important to remember which head&manifold gaskets are needed.
Berry

 

[justin_mercier]

I have used a late exhaust manifold with the air injection ports on a early head/intake manifold, but the ports have to be ground slightly to clear the intake manifold. When mixing intake manifolds, heads and blocks, it is important to remember which head&manifold gaskets are needed.
Berry

That's a good point, always use the gasket that matches the year for the head you are using, the exhaust ports are the same on all of them so it's only the head that matters when getting a new gasket.

 

[MDCanaday]

I am a big fan of Good parts tri-carb setup. If you also get the 1.55 rollers also, you really have a sweet
6. But if you are doing this beast, you may as well start with the crank which sucks in its stock form,needs a lot of lightening.
Then you balance it(all if it passes magging). If you do it right it gets pricey, but think of the smiles per gallon....
MD(mad dog)

 

[justin_mercier]

My engine for example is
-Late block decked .030 (motor numbers milled away) align bored with cylinders bored .030 over
-Crank shaft balanced, polished, and treated oil passages
-lightened and balanced stock flywheel
-Early high compression head milled to .44cc per chamber for 9.98:1 CR with gasket matched and polished parts
-Late stock rods, balanced, ARP rod bolts
-standard vandervell main and rod bearings
-Hepolite pistions .030 milled off top for zero deck height (see first point)
-Deves rings
-Goodparts GP2 cam and dual springs
-1.55:1 aluminum roller rockers
-Tubular chrome moly push rods
-Bronze valve guides with seals
-Custom windage tray inside the stock oil pan
-HD cam sprocket and chain set

 

[glemon]

Justin, just curious, the tri-carb manifolds are for the early head with the tighter intake port spacing? I thought most of the performance goodies were designed for the later head. I am not planning on going to crazy here, the engine is already rebuilt, I am not planning on getting roller rockers or anything exotic like that, but I like the idea. Would like to get the head skimmed to a little higher CR as I have talked about, and do some port an polish work myself, as I understand it the later manifold is a little better too, so will probably go with the later head, but I do have an early and a late to monkey with now.

 

[justin_mercier]

The early and late heads are functionally equivalent. The later heads with their wider port spacing had better 'flow' because the changes made to the intake manifold, not because the head itself was particularly better. (the GP intake manifold flows very differently than the stock intake manifolds, they're a straight shot) The earlier heads had a higher compression ratio from stock, 8.5:1 as opposed to the later heads which were 7.78:1 and then even later only 7.62:1. If I recall the GT6 head was slightly higher than the 8.5:1 head on the 69-71 tr6 and some people would put those on their TR6 engine for a higher CR as well. The spacing on the GT6 heads was the same as the early TR6 heads. (the intake manifolds were different because the stock TR6 manifold wouldn't clear the bonnet on a GT6) Most of the 'performance' differences between late and early heads is dependent on the manifold you use. I'm not aware of any 'performance goodies' designed only for the later head. In fact the port spacing is the only real functional difference so you just need to match your gaskets and your intake manifold (be it a performance intake like a GP tricarb setup, or a stock intake) For someone who doesn't want to send out for machine work, swapping an early head onto an engine is a quick and easy way to raise the CR of the engine.

The tri-carb setup that I have is for the narrower early intake spacing.

 

[bobh]

This is an interesting link that may help with your decision.

https://www.tr6.org/cylheads/index.html

I asked the author about the possibility of buying one of the 219016 heads and having it shipped here. He said no need. The later style TR6 heads used on the US engines is the same head with lower compression. I don't recall if he mentioned the EGR fitting. Based on this article and Kas Kastners writings I think the later head is the way to go.
BTW Kastners Competition Manual has a good section on port matching and cleaning up the insides of the head.

BOBH