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Thread: TR 4A cylinder head on TR 3 engine

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    TR 4A cylinder head on TR 3 engine

    Good Morning
    I have a 1957 TR 3 engine (TS 16173E) and I am planning to put a TR 4A cylinder on it.
    From reading so far, this cylinder head should be compatible with this engine.
    Will this work and if so, what problems should I anticipate?
    Any advice is appreciated.
    Thanks, JC

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    Re: TR 4A cylinder head on TR 3 engine

    As long as you had the high port head to begin with, it should be a straight bolt-on.
    John

    1955 TR2

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    Re: TR 4A cylinder head on TR 3 engine

    Thanks for the info.
    This engine has a low port head and I want to switch it to a high port head.
    Is there a problem with changing from a low port to a high port head?

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    Re: TR 4A cylinder head on TR 3 engine

    The head itself is a bolt on, but for the low to high port change you will need a new intake...and Randall will have to confirm...but I think the exhaust manifold is different too. You will also need H6 carbs, if you don't already have them. They are ID'd by the 4 mounting bolts instead of 2.
    John

    1955 TR2

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    Re: TR 4A cylinder head on TR 3 engine

    Gotcha. I have a pair of Weber DCOE's with the manifold. That's why I want a high port head. I had not considered that the exhaust manifold might be different. Thanks for bringing that up. I live at some altitude in the Rocky Mountains and I have never had much luck with tuning SU's even with high altitude jets. I converted my MGB, MG Midget, and Sunbeam Alpine to Webers, the downdraft one on those other cars. As you can see, I'm into this British car thing pretty deep. The Weber DCOE does not have a manifold for a low port Triumph head, as far as I can tell. If and when I switch out this head, I will be replacing all the stud for the head because I understand that the stud lengths are different as well. I just want to make sure that what I have in mind will work and that I have what I need to get it done. I don't like to start a project until I understand what problems can occur so that I can be prepared.

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    Re: TR 4A cylinder head on TR 3 engine

    The exhaust did change, I believe, but ISTR the early manifold will still bolt up to the high port head. Difference might be in the way it bolts to the intake manifold.

    AFAIK only one manifold stud changed, and that was to accommodate the rear "lifting eye". As long as you leave the eye off, the original studs should fit.

    Good luck with the DCOEs. I've heard that they are a lot more finicky about changes in altitude and what not than the SUs, but never tried them myself.
    Last edited by TR3driver; 04-05-2020 at 06:53 PM.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Re: TR 4A cylinder head on TR 3 engine

    I remember hearing from a tr2 guy, and what he told me was the big difference in the tr2 heads was in the casting of the height of the head bolt / block studs. I do not know, but maybe your early block studs might be short. I just do not know for sure; I guess the low port head is cast even down along the bolt pattern.

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    Re: TR 4A cylinder head on TR 3 engine

    Oh yes, that's true. All the head studs on the manifold side got longer for the high port head. The 3 short ones went from 5" to 5-3/8", two long ones from 9" to 9-1/2". Then later on, the rearmost stud was bumped up by another 3/16" (to 5-9/16"), to accommodate the lifting eye.

    The combo intake/exhaust gaskets changed as well.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Re: TR 4A cylinder head on TR 3 engine

    Quote Originally Posted by TR3driver View Post
    The exhaust did change, I believe, but ISTR the early manifold will still bolt up to the high port head. Difference might be in the way it bolts to the intake manifold.
    Oops, my mistake. According to Bill Piggott, the late exhaust manifold will fit the early head without modification, but the early manifold won't fit the late head. I don't recall having to change the exhaust manifold when I dropped a high port engine into a car that originally had a low port, but guess I forgot.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Re: TR 4A cylinder head on TR 3 engine

    My advice about the head change would be not to change. I find the SU finicky until I get them set up then they are very reliable; they are just so simple. Plus they look cool. My 1997 Saab 9000 4 cylinder has like 225 hp from the factory, so the beauty in these cars is in the cars originality.

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    Re: TR 4A cylinder head on TR 3 engine

    I agree with sp53, but have to admit it is more of a do what I say, not do what I do....

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    Re: TR 4A cylinder head on TR 3 engine

    Yeah, the SU's are the smart choice...but in the 60's the Webers were the bomb!
    John

    1955 TR2

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    Re: TR 4A cylinder head on TR 3 engine

    My feeling is: It's your car, it should please you. It's a fun little car, and for some, a little extra grunt makes it more fun. Others just like the bling of that row of intakes under the hood. Yet others want to restore it to "showroom floor" condition and then keep it on a showroom floor.

    There's room in the hobby for all of us.

    It is a little odd that it has a low port head; supposedly they were phased out earlier than that (Piggott gives TS12606E through TS13501E) and my TS13986E has what I believe is it's original high port head. Likely someone already did some parts swapping.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Re: TR 4A cylinder head on TR 3 engine

    That reminds me...Most cars swapped to the high port head, since it was a better head, and the low ports were mostly scrapped. Now that the early cars are being restored, the low port brings more money on Ebay than the high ports. So don't toss the head!
    John

    1955 TR2

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    Re: TR 4A cylinder head on TR 3 engine

    Randall Wrote: "Likely someone already did some parts swapping." As an aside to the conversation, I have to admit my experience is mostly with old British cars, but it is a close run between the Sprite Midget and the early TRs as to "car most likely to have a mash of parts from different years of the same model", most all fit, but there were changes over the years. Friend just bought a 59 TR3 "small mouth" with the long headlight pods.


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    Re: TR 4A cylinder head on TR 3 engine

    If you are really looking to improve things in the grunt department it is worth going to 87mm pistons, the 4A cam, a 4A inlet manifold plus 4 into 1 exhaust and a Petronix ignition. I’ve got this set up on my 3A and it gives about 110 horses at the rear wheels. Called a Fast Road setup on this side of the Atlantic.

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