View Full Version : TR6 TR6 Cylinder Head Questions

03-07-2013, 07:57 PM
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.


03-07-2013, 08:36 PM
I think I found part of my answer on the campatability issue, but still interested in any other's thoughts

03-07-2013, 10:24 PM
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.


03-07-2013, 10:45 PM
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

03-08-2013, 12:06 PM
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

03-08-2013, 06:33 PM
My 76 with Pacesetter header and Ted's starter.


03-08-2013, 07:11 PM
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.

03-08-2013, 09:03 PM
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.

03-09-2013, 12:44 AM
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.

03-09-2013, 01:28 AM
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.

03-09-2013, 09:11 AM
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.

03-10-2013, 07:52 PM
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.

03-11-2013, 01:08 PM
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 =)

03-11-2013, 01:23 PM
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.

03-11-2013, 02:21 PM
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.

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.

03-11-2013, 09:31 PM
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)

03-11-2013, 09:47 PM
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

03-11-2013, 11:05 PM
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.

03-12-2013, 10:42 AM
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.

03-13-2013, 06:09 PM
This is an interesting link that may help with your decision.


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.


03-13-2013, 08:45 PM
Is that the same as a 219019?


03-14-2013, 11:21 AM

I found the email from Chris (Feb 2006). This was his response;

"We have 219016 heads used for 60. It would be costly to send to USA because of the weight. If you are lucky, you may find a 219019 head in the USA, which is a lower compression export version of the 219016 Chris"

I also found Chris' reply to my email asking the folowing questions;

1) What is the advantage or disadvantage of the smaller exhaust valve in the later US heads?

2) Same question regarding the "recessed" block.


"The smaller exhaust valve is good for at least 200 bhp, the head is less likely to crack, the smaller exhaust valve alows a larger inlet, there will be less lost of incoming mixture on overlap with the smaller exhaust valve.
The 32mm valve is too big. our flow bench man reckons 31.25mm is optimum for the port, but still no gain for road use over the 30.3 If You have a recessed block, you shoud use the 'AK280' gasket to suit Chris"

On the subject of larger exhaust valves. Back in the day (the early 70s) I owned a 1971 TR6. The head had the old style inlet spacing and the Log type intake referred to earlier in this post. When I removed the head for some work. I found a crack between the intake valve and the exhaust valve on one cylinder. I suppose this head had the larger exhaust valves. I didn't know about the different heads back then. The area between valves was very small. I suspect this is the potential problem Chris referred to in his response to question 1.
Another thing to consider when choosing a head for the project.

In one of his articles Chris mentioned increasing the quench area or maybe he called it Squish area. I believe he was referring to the recessed block. Kas talkes about Zero Decking the block. I think both of them are talking about the same thing. Removing material to allow the piston to come closer to the combustion chamber on the compression stroke. The area of the combustion chamber opposite the valves and the rising piston will squish the mixture and push it into the recess around the valves. This is to get rid of the "pinking".
Decking the block increases the CR. All of the material removed from the block and head need to be considered when calculating the new CR. I seem to remember someone commenting that 9.5:1 is about the highest CR you would want for the street?
Someone else with more experience in this area may want to comment on this.


03-14-2013, 12:06 PM
You can do 10:1 without early detonation if you're using 93 octane pump gas. If you go to zero-deck the block, as my engine is, you also need to shave the pistons too. Modern BMW roadster engines have a 12:1 compression ratio and require you to use 93 octane in the car. I believe they also have knock detectors and other modern conveniences as well to prevent early detonation.

03-14-2013, 05:22 PM
That was the head on the 6 I sold last year.
Got it from Ted and was milled for a 9.5:1

03-14-2013, 09:41 PM
Thanks Bobh, that's the information I was looking for on the valves, so I will go with the newer head, the newer intake manifold, some porting and port matching, and maybe 9.75 or 9.80 to 1 on the compression, and maybe a header as well, as long as I am trying to help the breathing capacity/efficiency.

03-14-2013, 10:06 PM
You might want to wait on the header.
Paul is reinstalling the stock manifold and is going to do some testing to compare

03-15-2013, 02:04 AM
You might want to wait on the header.
Paul is reinstalling the stock manifold and is going to do some testing to compare
Cool, haven't bought one yet, curious about the results of the testing, have also been curious about the early single pipe manifold versus the later dual pipe, I calculated that the later dual outlet manifold has considerably more flow capacity, but don't know if that translates into street horsepower, I know the Kastner book says one big pipe is better than the dual exhaust, at least for racing.

03-15-2013, 09:54 AM
Contact him.
I know it is on his plans for this spring
I sent him a note

03-15-2013, 07:23 PM
Don is correct, it is on my ten item list for spring that keeps growing. Mine started as a restoration project for my website (https://www.74tr6.com/exhaustmanifold.htm) and then it came out so well, that I decided to install it. But just prior to that, I spoke to the owner of the ceramic coating shop that did the manifold for me and he is well know for building Corvette engines as well as doing all of the ceramic coatings on the headers and side pipes of every Factory Five Cobra. We were talking about the manifold and he was admiring the design prior to coating and he asked me what I had on the car. I told him that I had Jet Hot coated headers, which he said was a good product but then he said, with a manifold like this, and all of the mods to your engine, you are foolish to go to headers. This manifold is as well designed as any Corvette manifold out there and Chevy does NOT recommend headers on any of the late model Corvette's unless you are full bore racing.

I also did not like the fact that the only way to remove the stock started was to pull the headers back, so off they will come and I will install the new hi-torque starter that has been on my bench for three years. And I do have it machined and tapped for my O2 sensor so I can keep my wide band Air Fuel Ratio Meter working. Picks are all on the link above.

03-15-2013, 09:02 PM
Paul, late or early manifold? Single pipe or dual pipe?

03-16-2013, 09:35 PM
Late manifold, dual pipe. Pictures are complete from start to finish on this link: https://www.74tr6.com/exhaustmanifold.htm

Simon TR4a
03-18-2013, 06:10 PM
Great looking manifold! I also liked the look of the Pacesetter header.
I used to have a TR6 but about 12 years ago upgraded(?) to a TR4a, so don't claim an intimate knowledge of the TR6 head.

My recollection is that the bridge between the valves is susceptible to cracking and this is a limiting factor in valve size. Because the TR6 is a 2 litre engine with a stroker crank the valves are marginal. Like the TR4 head, I think material can be removed to reduce shrouding, particularly of the intake valves.
I am curious about the idea of putting GT6 heads on a TR6, how do you deal with the 25% greater capacity? This would put an 8:1 head up to 10:1 unless the combustion chamber is carved out or a thicker gasket used.