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66/67 head on a 70? #693704 05/02/17 2:37 am
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Wally Balden Offline OP
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I am guessing this has been discussed before and I have some information, but wanted to confirm what I have and what I want to use.

The PO put a 71 head and rocker boxes on my 70 TR6C. The 71 set up is different because of the locating pins and rocker boxes. I found the correct rocker boxes and also a head stamped 66. I have read that it was stamped with the year before the bike - meaning the 66 is really for a 67. Correct? Anyway, I also read that 1966-68 (second series) will fit.

Info i have says: The basic idea that all 9 bolt heads will bolt to any 9-bolt cylinder is correct. However, the tappet guide blocks, pushrod tubes and cylinder heads MUST be matched completely.

So, this means I need to replace the current set up with a set from a 70 cylinder head - meaning tappet guide blocks, pushrod tubes? Anything else?

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Re: 66/67 head on a 70? [Re: Wally Balden] #693732 05/02/17 1:04 pm
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Stuart Online Content
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Hi Wally,

Originally Posted by Wally Balden
my 70 TR6C.
I found the correct rocker boxes and also a head stamped 66. I have read that it was stamped with the year before the bike - meaning the 66 is really for a 67. Correct?

Mmmm ... when you say "stamped", you mean the cast date - year ("66") plus up to twelve short radial lines denoting the month(s)? Afaik, this is just a casting date, there isn't any 'rule' about how the raw casting was subsequently machined for a particular 'model year'.

Nevertheless, afaict not a huge problem:-

Originally Posted by Wally Balden
Info i have says: The basic idea that all 9 bolt heads will bolt to any 9-bolt cylinder is correct. However, the tappet guide blocks, pushrod tubes and cylinder heads MUST be matched completely.
So, this means I need to replace the current set up with a set from a 70 cylinder head - meaning tappet guide blocks, pushrod tubes?

Here, no. Having posted you likely have a '66 or '67 head, then "tappet guide blocks, pushrod tubes and cylinder heads MUST be matched completely", why do you want "a set from a 70 cylinder head" ...? confused

If you have a '66 or '67 head, you want '66/'67 tappet blocks and prt (and 70-4746 "Bottom cup")?

If you have a '66 or '67 head, the only other difference is '67 notionally uses a thicker bottom seal (E4752) than '66 (E3547). However, in reality, they're both the same dimensions except E4752 is 1/8" thick while E3547 is only 1/10" thick (both nominal), you'll check the 'crush' and use what's required to get in the 'correct' range?

Hth.

Regards,

Re: 66/67 head on a 70? [Re: Wally Balden] #693736 05/02/17 1:16 pm
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Wally Balden Offline OP
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Thanks for the clarification. I stated it wrong when I made the comment about using the 70 head parts on the 66/67 head. I wanted to make sure if I used the parts on the 66/67 head that there would not be a problem.

Re: 66/67 head on a 70? [Re: Wally Balden] #693745 05/02/17 2:06 pm
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Mike Carter R.I.P. Offline
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Got this from classic bike magazine and actually ran into this problem in shop we wound up machining push rod tube holes deeper on 67 head so we could use 69 cylinder, tappets and tubes as heads on early models are not as deeply cut as newer models and 67 tubes won't fit .

“The basic idea that all 9-bolt heads will bolt to any 9-bolt cylinder is correct. However, the tappet guide blocks, pushrod tubes and cylinder heads MUST be matched completely.

• 1963-1965, first series: Any cylinder head from 1963-1968 is correct because of shallow machining at the upper pushrod tube position.
• 1966-1968 second series: Any cylinder head from 1963-1968 is correct.
• 1969 through last production in 1972, third series: No cylinder head application to earlier series pushrod tubes and tappet blocs. This is because of deeper machining at the upper pushrod tube position to any earlier series of tappet guide blocs and pushrod tubes. If a 1969 or later cylinder head is used, same year pushrod tubes and tappet guide blocs must also be used. All 1963-68 engines must have a thin gasket under the pushrod seal cup at the bottom of the pushrod tube. Rocker boxes interchange to all 650s from 1963 through 1970. 1971-1972 rocker boxes must be used with 1971-1972 cylinder heads because of the locating pins between the cylinder head and rocker boxes. All 650 cylinders have 26 TPI Whitworth threads. All four outer cylinder head bolts interchange with all Triumph 650 engines. Center head bolts are all the same. Inner bolts are all the same from 1963-1970. Inner bolts from 1971-1972 must be used with 1971-1972 rocker boxes.” Kinda mirrors what Stuart said but you can make anything fit all you need is a machine shop smile

Cheers and good information..

Mike Carter

Re: 66/67 head on a 70? [Re: Wally Balden] #693754 05/02/17 3:41 pm
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Wally, If I remember from other postings, you have swapped the '71 two carb head for a single carb head - which is the earlier head you mention.

We are in a similar situation. I have a '72 engine and will be using a single carb head (possibly '66-'68, can't read the stamping well enough). My early head has the shallower machining for the upper push rod tube seat. If I were to use this head, as is, I would have to use the early push rod tubes (70-6000, I think) and tappet blocks (you must use the early tappet blocks - the early tubes won't fit over the later blocks).

I had my head machined with a deeper seat like Mike mentioned. Now I can use the '72 tappet blocks and push rod tubes with their somewhat better sealing. I would have had to buy new tubes and turn the tappet blocks on my lathe to fit the older tube style. I chose to machine the head so I could use the parts on hand, but I have a friend who did the work, probably much more affordably than a shop machinist.

I hope this helps rather than confuses the discussion.
Al



Al Eckstadt
Re: 66/67 head on a 70? [Re: Wally Balden] #693758 05/02/17 4:32 pm
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Wally Balden Offline OP
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Al - the 71 was actually a single carb head. My only issue could be with what was done/used by PO given that he had a 71 head and rocker boxes. I can use the 67/68 head and rocker boxes but did the PO use 70-71 push rods/tubes? Tappet blocks? I don't know the answer to those questions.

Re: 66/67 head on a 70? [Re: Wally Balden] #693766 05/02/17 6:29 pm
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Al Eckstadt Offline
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Do you still have both heads? Look under the heads at the pushrod tube oring seat. If they are the same depth of cut you will have no issues.

I might be interested in the '71 head - let me know.
Al

Last edited by Al Eckstadt; 05/02/17 6:30 pm.

Al Eckstadt
Re: 66/67 head on a 70? [Re: Al Eckstadt] #693767 05/02/17 6:32 pm
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Al Eckstadt Offline
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If you can post a photo of the push rod tubes and tappet blocks we will be able to tell you if they're compatible.


Al Eckstadt
Re: 66/67 head on a 70? [Re: Al Eckstadt] #693805 05/03/17 12:40 am
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Wally Balden Offline OP
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One carb head. It is still on the bike. I will be taking it off next week and replacing with the new one.

Re: 66/67 head on a 70? [Re: Wally Balden] #693812 05/03/17 1:31 am
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Wally Balden Offline OP
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I'll take a pic of the push rod tubes and tappet blocks when I get it off - may be earlier than next week.

Re: 66/67 head on a 70? [Re: Wally Balden] #693813 05/03/17 1:48 am
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wildbill Offline
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To add to the confusion a bit - if the head has been surfaced/milled, the crush will be off and you may have juggle pieces from various years with various o rings and different thickness head gaskets to get the right crush.


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