T120 Types of Cylinder Heads

[andyw1260]

Hi  I am after getting a T120 Unit Cylinder head around 1968. Can any body advise if the heads marked with a casting number e3663 are all the same. the push rod tubes seem different for 63-65.      66-68.   69-70. Is it just the tubes that are different or are the heads different.   thanks for your time          andy

[henry_norton]

 1968 heads part number is E5348, the 1969 version is E9418. This change was to do with the change to unified threads. All the unit heads are prety well swappable - you can even fit a 750 head to a pre 70 block if you drill the extra hole (or so I hear....). Triumph were always messing around with different ideas trying to seal their pushrod tubes so it's not surprising they can look a bit different to one another. They should all fit though.

[TBS]

They will all fit however the main differences are the early heads have an 1 1/8" diameter inlet manifold and the later have 1 3/16" however the earlier ones can be bored the same. Also the earlier ones have a different thread inlet stub as Henry has already stated the later changed to unified threads for the rockerboxes.  

[andyw1260]

Hi TBS  
          Thanks for your time  can you say what year the inlet manifold changed from 1 1/8" to 13/16". If it changed in 69  I take it  years 63 to 68 were all the same size 1 1/8".    
 The last of the inlet stub with cycle threads were 68 is that correct.
Thanks again TBS     Andy    

[henry_norton]

The heads changed in 1964, so only the 1963 heads have the 1 1/8 inlets, from '64 on they were all 1 3/16.

[L.A.B.]

The heads changed in 1964, so only the 1963 heads have the 1 1/8 inlets, from '64 on they were all 1 3/16.

Sorry, - but I'll have to disagree with what Henry has said.

Firstly, the 1963 head assembly was part E4928 (first Unit 9-stud) which I believe had 1 1/16" inlets?
I think the previous (Pre-Unit 8-stud) heads were also 1 1/16" inlet (head assembly part E4019).

For 1964 both 1 1/8" (head assembly E5348) and 1 3/16" (head assembly E5727) cylinder heads were introduced, according to the information I have.

The 1 1/8" version was fitted to the T120 and the 1 3/16" fitted to the T120TT model for 1964, and from 1966 it was also fitted to the T120R.

So both heads were available from 1964-68.

As Henry has already mentioned for 1969 the new assembly part number changed to E9418.

All T120 heads (Pre Unit and Unit) up to 1968 (or later?) have the same E3663 casting number, I think, as all variants of head were machined from the same E3663 casting blank.

The T120 pushrod tube assemblies and tappet blocks were changed a few times, so it's important that all the correct parts and seals are used together.  

[andyw1260]

Hello again

                Many thanks for your expert help it`s nice to know there is a place to come for top notch info.  thanks again Mr Henry_Norton and Mr TBS for your time.      Andy

[henry_norton]

For 1964 both 1 1/8" (head assembly E5348) and 1 3/16" (head assembly E5727) cylinder heads were introduced, according to the information I have.

You're absolutely right TBS - the standard T120 kept the 1 1/8 head 'til 1966. But as stated before, you should be able to fit any pre 71 unit head to your 68 without too much trouble.

[L.A.B.]

You're absolutely right TBS - the standard T120 kept the 1 1/8 head 'til 1966.

Actually....I'm not TBS

It was the T120R that had the 1 3/16" head from '66. And the standard model T120 kept the 1 1/8" head up to 1968, I believe.

[andyw1260]

Sorry Mr LAB I can see my mistake, thanks for your help it`s nice of you to come back and clarify the time line on these heads,  really helpful.        Andy

[Goldie]

My pre-unit Triton has a 9-stud Bonnie head. Did'nt the later bonnies have 10 -stud heads?

[L.A.B.]

My pre-unit Triton has a 9-stud Bonnie head. Did'nt the later bonnies have 10 -stud heads?

The nine stud head was introduced for 1963 on the first unit models.

Ten stud head used from 1973-on (750 Bonneville/Tiger).  

[henry_norton]

Sorry L.A.B - I'm getting my T.L.A.s mixed up.

BTW(!), the T120R was the standard (US) road model wasn't it?

[L.A.B.]

BTW(!), the T120R was the standard (US) road model wasn't it?

Originally yes, as I don't think we in the UK got the T120R until the 1971 OIF model.