View Full Version : TR4/4A TR4A Cylinder Head

08-01-2006, 07:56 PM
How much should the exhaust valve guides protrude into the gas flow on this head? I have received one of these heads to put on my barn find 62 TR4 which was missing this. The exhaust valves were missing from the replacement head so I ordered replacements from Moss. When I try to fit them, all but one of them seems to be bottoming into the end of the valve guide.

Also, what does it take to move the guides if I need to adjust them?

08-01-2006, 08:55 PM
I'm not exactly getting your question but the exhaust valve guides are fixed in the cylinder head to accept the evhaust valve. The guides should bottom to a collar on the valve cover side of the head. The guides should not protrude into the exhaust port of the head out so far as to interfere (sp?) with the proper seating (closing) of the exhaust valve. The exhaust valve guide should fit snugly in the cylinder head and may require some knurling to maintain its position on the combustion side of the head. The exhaust valve stem once installed into the valve guide should have no wiggle to it but slide freely up and down through the guide. I'm sure there are special tools for this but I've used a brass flat headed punch same diameter as guide to remove/install. Sometimes I need a hydraulic press and other times I need to send it to my nearest engine machine shop when my blood pressure reach's critical mass.
I can read the Bently manual on this tomorrow and see what I've forgotton to mention but I'm sure someone will chime in with more.


08-01-2006, 09:23 PM
The valve guide should protrude .780 in. above the top face of the cylinder head. I think I remember seeing the exhaust guide protuding into the port more than the intake guide.
See the Bently manual as Harry said, it has a drawing.


08-01-2006, 11:04 PM

Important note:

Is your car a TR4A or an early ('62) TR4? You mention both.

Earlier TR4s had different size exhaust valve stems and guides to match. The stems are 3/8" in diameter. The guide is also larger outside diameter.

TR4A and later TR4 use a 5/16" stem exhaust valve and guides to match (all the intakes valves on all the 4 cyl. TRs also have 5/16" stems, didn't change like the exhaust valves). Without looking it up, I'm not certain exactly when the exhaust valve change took place.

Usually, besides measuring it, you can also recognize the early exhaust valves by triple springs used on them. Later heads used double springs on all valves. However, there are some aftermarket replacement spring sets for the earlier heads that only use double springs so that's not a guaranteed method of identification. Measuring the stem is still the most certain way.

It's possible to convert the earlier head to use 5/16" stem exh. valves. Special guides are used to do this. Moss, British Frame & Engine and others sell them.

08-02-2006, 08:39 AM
Hi All

Alan - It is an early TR4 to which I will be fitting a later 511695 head complete with the double springs and the 5/16 dia valves.

Harry, Bill - I don't have the Bentley manual as my original english Haynes manual from the 70's has served me well up to now. Would it be possible for you to scan the appropriate page(s) and e-mail them to me. Also, is there much more detail in the Bentley manual?

08-02-2006, 10:13 AM
I'll try scanning or paraphrasing the section tonight and e-mail it to you if I can. If someone can do it before that please let me know. I'm not sure about the Haynes detail (I Don't have one) but if the Haynes manual is of the same informational quality as the one I have for my Silverado and Olds you will definitely need to buy a Bentley manual (JMO).