Triumph TR3 drawing

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Frequently asked Triumph questions

 

QUESTION - I have read that there were several variations of heads available for the Triumph TR2 through 4A. How do I tell one Triumph head from another?

 

ANSWER - The head used on the Triumph TR2 through TR4A underwent a series of improvements over time. All versions can be identified with the head on the engine except for telling the two low port heads apart and for the very first engines that came with 86mm pistons.

If you plan to modify a head for additional power obtain a copy of the Triumph Competition Manual by Kas Kastner and read the section on heads before doing anything.

An unshaved high port Triumph head is 3.330" tall. Measure the height of your head and subtract it from 3.33 to determine how much metal has been previously removed.  When the head casting was changed to include a diagonal flat section on the underside of the lower thermostat housing  the thickness of metal between the bottom of the head and the internal water passages was increased.  This made the head less susceptible to cracking under thermal stress and allows the head to be shaved more for higher compression. Don't forget the thinner you shave the head the more likely it is to crack.

In general, the factory has done a very good job improving the head intake over time. The exhaust is the bottleneck to maximum flow. The valves are close together but there is space to add a slightly larger exhaust valve. If you feel a need to polish head passages and match manifold openings to head openings you can get the best return by doing it to the exhaust side.

Here is what I have identified so far. The bulk of the data in the chart below is a result of me measuring 40+ cylinder heads in  a British car wrecking yard.  There is always the possibility that a head version was not represented in my sample. Do not take the engine number data as absolutes.  The factory used whatever was in the shop.  After purchase, head replacements were made with whatever was available to the mechanic.   If you have any additional information that can help sort and identify the versions of heads used, please .

Model

Engine numbers

Piston dia.

Compression ratio

Intake port dia.

Chamfer*

Exhaust valve

Figure #

TR2

To 9349E

83mm

8.5:1

1-3/8"

No

3 springs

1

"Low Port Head" Most restricted intake air flow

TR2-3

9352E to 13051E

83mm

8.5:1

1-1/2"

No

3 springs

1

"Le Mans" head Low port but with different passage angles for better air flow

TR3-?

13052E to ?

83mm

8.5:1

1-5/8"

No

3 springs

2

First high port head provides better air flow than low port heads. All later heads are variations of this design

TR3A-3B

? to ?

83mm

8.5:1

1-5/8"

No

3 springs

3

Diagonal flat added to underside of lower thermostat housing for more clearance. More metal between bottom of head and water jacket makes this head more resistant to cracking.

TR3A?-4?

? to ?

86mm

9:1

1-5/8"

Yes

3 springs

3

This head is identical to the head above but has chamfers machined into the head for 86mm pistons. These appear to be very rare.  They may be  a short production transition head, or possibly even a case of the reworking 83mm heads from the factory part replacement stocks.

TR3B-4

? to 21470E

86mm

9:1

1-5/8"

Yes

3 springs

4

Chamfer added for better fuel mixing & to keep compression down to 9:1 with larger pistons.

TR4-4A

From 21471E

86mm

9:1

1-1/2

Yes

2 springs, different stem dia.

4

Has best low and mid RPM intake air flow. Exhaust valve design changed to improve exhaust flow. Early versions had steel push rod tubes like all previous head variations. Late version had aluminium push rod tubes for better oil seal.

Reproduction Cylinder heads    Available from early 2000's, made from cast iron or Aluminum.  These appear to be based upon the latest TR4A head.

* Chamfer is located on the bottom of the head at the edge of each combustion chamber opposite the spark plug hole.

Figure 1 - Low port head

Triumph low port head

The low port head is recognizable by it's rectangular or boxy shape. The Le Man's had reportedly has raised bosses around the cylinder head bolt holes.

 

Figure 2 - Early high port head

Triumph early high port head

The intake ports have been moved up and enlarged to 1-1/2 inch diameter for better air flow. A 1-5/8th dia ball mill was inserted into the head intake passages about 1/4" to assure that the production intake manifold ports lined up with the production head intake ports. When you measure the intake passages at the head opening, they measure 1-5/8ths inch diameter.

 

Figure 3 - Late TR3A head

Late Triumph TR3A head

This late head is recognizable by the diagonal slant on the underside of the lower thermostat housing. This eliminated a possible interference fit with the water pump housing after the head was shaved. There is also more metal between the bottom of the head and the water jacket. This made the head less apt to crack and allowed more metal to be removed to raise the compression ratio. NOTE: heads with this casting and chamfers for 86mm pistons are known to exist.  This seems to be a very rare version.

 

Figure 4 - TR4 head

Triumph TR4 head

This head style was used on late TR3A & B cars that came from the factory with with 86mm pistons. It is recognizable by the chamfer on the side of the combustion chamber and by the raised flat surface between the number 1 and number 2 intake ports. There may or may not be a serial number stamped on this surface. There is no correlation between head numbers and engine numbers.

Early heads still had the intake ports ball milled to 1-5/8ths dia for the first 1/4 inch to assure that the production intake manifold ports lined up with the production head intake ports.

The ball mill was eliminated in the last version of the head. This eliminated the slight turbulence at the manifold to head mating area, allowing for a higher velocity of the air fuel mixture at low and mid range. These heads measure 1-1/2 inch diameter at the surface.

The late version of this head had aluminium push rod tubes fitted to the head to provide a better oil seal. All previous heads had steel tubes pressed into the head.

 

Limited run Competition head

The Triumph competition department had a small run of special high compression heads made. Here is a description by Kas Kastner "I had a series of cylinder heads made wherein they scrubbed the top of the internal cores about 1/8" so that the stock machining gave a 12.5 to 1 compression ratio. Then with the cutting and grinding I would just mill a little more more to get my 12.25 ( ideal) . This left the total thickness almost stock therefore giving the material needed around the combustion cambers on the squish area side."

From Greg Solo:

I recently acquired what I believe to be one of the 13 heads that Kas told me he had made. At first I noticed that the part number, 511695 that is stamped into the head above the #1 inlet port was upside down and in smaller numbers than any of the other TR heads that I have ever seen. I then noticed some differences in the casting. After some measurement, we found that The head that I have has been milled .200" and the bottom surface of the head is still .250" thick where a normal head would no be less than .200 after this much milling.  The edge of the head under the spark plugs is still nice and thick and "blunt" on the edge, whereas a normal head that had been milled that much would have an edge sharp like a knife.

When I received this head, with a bunch of other parts, it have racing springs and alloy retainers on it and had been ported and polished. There was some damage to the "squish area" of two of the chambers from broken rings or other debris getting crushed between the piston crown and the head. Fortunately, the head is still thick enough that it can be milled to clean it up and it will still be thick enough to hold a gasket.  It uses standard valves, and the ports are all basically just like a standard head from a 1964 TR-4, ie. 1 1/2" dia. intake ports at the manifold flange, with the dowel to line up a later style curved runner intake properly. The port cores were also set up very carefully so the rest of the casting did not have any unexpected "core shifts" that would cause issues after porting the head for better gas flow.  The big difference is the thickness of the bottom of the head. The casting sand cores that determined the water space inside the head were made thinner on the bottom side of the head so the bottom "deck" surface of the head is almost 1/4" thicker than normal.

From kas Kastner:

It is interesting the Greg has one of the heads and states that the edge on the spark plug side is thicker. Terrific Morgan driver, Lew Spencer, is my great friend, and Greg now has his car, so as I had done some engines for Lew, maybe that is the routing of that piece. the thicker edge is true, but on some of them I noted strangely, that the shelf was very thin and actually had a slight curve and you could see the top of the block, just as edge that is, right at the back. So don't use the edge thickness of the push rod shelf as a criteria.

 

Cylinder heads with elongated head bolt holes

In the UK a common trick is to move the cylinder head sideways over on the block by elongating the head bolt holes. This was to move the valves closer to the center of the cylinder and away from the "shrouding" caused by the closeness of the cylinder wall on the spark plug side of the engine.  The sides where the heads are normally "undercut" to give more space around the intake valves.  These heads were sold by Racestorations and possibly other companies.  There is a belief by some racers that this modification introduces unreliability in the head gasket for a pretty small gain.

 

Reproduction cylinder heads

New reproduction cylinder heads have been available since the early 2000's.  There are both cast iron and aluminum ones available.  I have not yet been able to take measurements on any yet but they appear to be based upon the last TR4A design. There was not number stamped on the raised flat area over the number one intake passage on the aluminum head I saw.  A lack of  a number stamped there may be the diagnostic for reproduction cast iron heads.  More later when I get a chance to examine the new heads.

Pictures of the aluminum head:

aluminum TR cylinder head

Right side of aluminum Triumph aluminum head

Detail of aluminum TR cylinder head

 

Standard Vanguard head

Some people who have been looking for low port TR2 cylinder heads have been coming across Standard Vanguard heads.  This head looks very similar to a low port TR2 head and with a little stock work will fit and pass concourse for a factory stock low port TR2 head.  The head studs are 7/16" instead of the Triumph's 1/2" studs so will need to be up sized.   It might help to install TR valves with new seats. It may require different valve guides and a little machine shop cutting for the valves.

A quick way to tell between a TR2 low port head and a Vanguard head is all the TR heads came with rectangular exhaust ports & the vanguard came with round exhaust ports.  The Vanguard engine was 2.1L and used 85mm pistons. It was also a low compression engine. While the engine will be quite drivable for touring don't expect the pep of a genuine TR2 low port head.

Triumph Vangard head
Triumph Vanguard cylinder head.  Except for the flat area between stud holes 2 and 3, assembled looks just like a low port TR2 cylinder head.

Triumph Vangard cylinder head side
The Vanguard exhaust ports are circular, the TR low port exhaust ports are rectangular.

Vangard head botom view
The Vanguard head does not have the shrouding around the spark plug that the TR head has.

 

Triumph Vangard head cylinder

 

TR4 cylinder port cross sections:

Photos by Jim Gray

Triumph TR4 intake passage
Stock TR4 intake passage cross section

 

Triumph TR4 exhaust cross section
Stock TR4 exhaust passage cross section.

I just HAD to add this from an e-mail I received!

"What a fine bit of cylinder head information you have provided the TR people on your site. Congratulations. Kas Kastner"

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