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Hello,

I have a 1970 Triumph Bonneville. The stock 1970 head needs to get sent off or have someone install new valve seats in it. While I figure that out I have a 1964 stamped head which is good to go that I would like to install.

Will the stock 1970 pushrod tubes work? As I understand they may be a bit too long. If the stock pushrod tubes wont work can some point me in the right direction of which ones will work?

Thank you in advance for your response.


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No. You will need 68 on back tubes and tappet guide blocks. You need both. Check push rod length. The early head has a much shallower PRT indent than the 69-70 head. FYI A 71-72 head will work with your current prt’s and blocks. Their easy to find.

Last edited by Roadwarrior; 07/31/22 12:50 am.

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The 71/72 will work, but looks silly with the dowels poking out. It is possible to machine the early head for a deeper indent, but it is at an angle, not one for the faint hearted. Also someone, somewhere, will curse you down the line.

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I had a real PIA trying to put a 71/72 head on my 68 bonnie. I could not get the 72 rocker boxes on over the inner head bolts (motor in frame) and didn't want to have to unbolt the motor any time I wanted to pull the rocker boxes. So I pulled the roll pins and went back to 68 boxes only to find the indents in the head under the head bolts were deep enough to have a gap between the early boxes and the head, this connection is imperative as the 68 head bolts clamp the box to the head as a unit to affect proper torque value and clamping ability. So after a bodge with thinning down washers and three bond I didn't even start it up, still sits in my shop looking pretty with a boogered head fitment. If you're lucky enough to find a 72 head with no indentations it would work with early boxes.


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i mix and match al that stuff. i have a 1973 9 and 1/2-bolt head with early boxes on it right now.

how were you planning on adapting the later head steady to your 68?

Last edited by kevin; 07/31/22 2:58 pm.

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Or use adjustable pushrod tubes

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Of course! It could be done by machining alloy tubes, but in no way reversible!

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i use ^^^daves adjustable tubes. they work fine.


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Where does one source these adjustable push rod tubes from?

Last edited by MaaseyRacer; 07/31/22 10:36 pm.

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DMadigan

See 4 posts above here.


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Originally Posted by slofut
I had a real PIA trying to put a 71/72 head on my 68 bonnie. I could not get the 72 rocker boxes on over the inner head bolts (motor in frame) and didn't want to have to unbolt the motor any time I wanted to pull the rocker boxes. So I pulled the roll pins and went back to 68 boxes only to find the indents in the head under the head bolts were deep enough to have a gap between the early boxes and the head, this connection is imperative as the 68 head bolts clamp the box to the head as a unit to affect proper torque value and clamping ability. So after a bodge with thinning down washers and three bond I didn't even start it up, still sits in my shop looking pretty with a boogered head fitment. If you're lucky enough to find a 72 head with no indentations it would work with early boxes.

my old '70 had a later head and rocker boxes, just used the later two part fixings with
hex's on on the inside and short bolts for the covers. It was tight getting the covers on and off
but was ok. Fabricated a head steady to suit.

Dave Madigan does adjustable pushrod tubes if needed.

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DMadigan, sent you an email.


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The 71-72 head works with a 69-70 motor with the eailier rocker boxes just fine using the earlier rocker box gaskets. Pull the locator pins. The 71-72 head will not work with a 68 or earlier motor unless you also change out the tappet guide blocks and PRT tubes. I’ve done this at least 8 times with complete success.


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Or Dave's adjustable PRT's?

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I ended up checking in with a friend on this issue and he referred me to MAP. I purchased a set of their alloy machineable pushrod tubes, they arrived cross country two days after I ordered them. Installed them on the bike, took my measurements and turned them down for a perfect fit.

I am sure an adjustable tube would be better for exact fitment, but this was a one click purchase solution that does not look completely out of the ordinary.


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