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Thread: Performance cam

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    Smile Performance cam

    I am getting ready to rebuild my TR4A motor and this will be new for me. I will be posting some questions related to that soon. In thinking of a rebuild a lot of things go thru your head that maybe you should/could or want to do. So I will start off with this question: Can anybody comment on the "street" cam that is available as to whether it is a worthwhile expenditure? I will mention that I do not intend to do anything else in particular to juice the engine and also mention that I have the HVDA 5-speed conversion. I do not autocross, race or anything but do live in a hilly/mountain area which might benefit from the extra torque that cam is supposed to provide. I have read that the original cam is considered quite good. Opinions please?

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    Great Pumpkin TR3driver's Avatar
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    Re: Performance cam

    In your case, I'd stick with the stock cam.
    While there is more power to be had, you need to make changes in concert. Changing just the cam won't provide much improvement, and may cause other issues (like needing different needles).
    Last edited by TR3driver; 12-20-2019 at 10:03 AM.

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    Re: Performance cam

    Are you intending a complete rebuild of the engine out of the car... and are you desirous of a complete factory look or open to modifications/improvements apart from a different cam?

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    Re: Performance cam

    The car is being rebuilt from the ground up. The engine is stripped and sitting in the frame ready to lift out. I would/will do certain non original things ie: change to Pertronix ignition and a altenator. In addition I am not sure what I am going to do with the carburetors. I did not notice when I bought it that it has SU H6 carbs not HS6. It originally had Stromburgs. Why that was done is a mystery. I will probably buy HS6's to go on it I am not very interested in Webers. In contacting the PO he said the H6's hit the hood with the air cleaners on. What did you have in mind? I was just interested in some enhancements but nothing radical.

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    Re: Performance cam

    Every one has different ideas on engine rebuilds, a lot depends on if you want the stock factory look or not.
    Stock look engine and engine bay was not a consideration for me.
    My rebuild....block stripped and cleaned..mild cam with original cam bearings remetalled and then line bored to suit cam journal size..crank grind, pistons etc.etc...cyl head rebuild including head shaved to up compression..engine fan delete with harmonic balancer fitted and thermo fan..small belt alternator.. six cylinder small belt water pump..stromberg carbs, only because I did not like the untidy SU choke mechanism..engine has basic balance including harmonic balancer and clutch.. flywheel lightened..4A exhaust system modified to single pipe, including match port inlet and exhaust manifolds.

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    Re: Performance cam

    I think that is more than I want. I have considered the small belt conversion because until I was installing the steering rack I did not know that refitting a fan belt was a issue until I saw there was almost no clearance . I think the things for me to consider are alternator conversion, already has a sport coil, electronic ignition, the Viton rear main oil seal conversion and valve conversion for unleaded. The crankshaft was supposedly balanced by the PO but who knows? He also told me it had TR3 racing pistons???? Question; Should I use larger valves since I am there?

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    Re: Performance cam

    Larger valves not necessary.

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    Re: Performance cam

    Do a little research on getting rid of the shape edges in the combustion camber and a bit of a shave of the head.
    I do agree a stock cam does a good job, but a well used one will have worn lobs and not product full life. The front of the cam is a know ware area.
    '37 MG TA, '49 Triumph Roadster, '70 TR6, 2000 Jaguar XK8, '78 Spit6

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    Re: Performance cam

    The cam that is see is listed as a street cam and offers larger amounts of torque an increase of 12-15 hp for $300. That sounds like a bargain to me for a simple replacement piece. Idle and such is not suppossed to be affected. I was hoping to hear from some who have used this cam and their impressions of it. It seems like a lot of people would be using it. Does anybody have such a cam? And what do you think of it?

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    Re: Performance cam

    Actually, the main difference between a street or racing cam is not the amount of the torque...but rather where in the rpm range the max torque is located. The racing cam increases HP by moving the torque band up in rpm. The street cam has generally the same peak torque, but moves it lower in the rpm band, thus decreasing HP. Remember the adage, HP sells cars but torque wins races.

    From your description, you want a low rpm torque band from a street style cam.
    John

    1955 TR2

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    Re: Performance cam

    "That sounds like a bargain to me for a simple replacement piece".........not as simple as some may imagine.

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    Re: Performance cam

    Ok thanks for the input. I will stay with the original cam unless I find during rebuild that I cannot use it. I was going by the info in the service manual for "C" cam or upgraded street cam. I don't know what the torque range is for the new (BPNW #TR4HR270N cam) is so it is hard to compare. I am not knowledgeable on these things so that's why I was asking. I am not interested in a race engine but if a general improvement in torque and revs could be made by simply adding a cam that is what interested me.

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    Yoda CJD's Avatar
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    Re: Performance cam

    More torque will come chiefly from larger pistons and/or higher compression ratio. If you get any more torque from a cam, it is from higher lift...which opens up an entire other bag of worms. Things like upgraded valve springs, valve guide clearance, spring coil bind, rocker geometry, piston clearance, etc.
    John

    1955 TR2

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    Re: Performance cam

    I redid my tr4 engine a few years ago. Went with the BP270 cam, 89mm pistons, then I got a little crazy and added a set of Carrrillo rods (sorry about the inheritance kids). I used a 4A intake and HS6's. Valve size is stock. Whole different engine, winds quickly, really gets down the road. I had Steve Yott at Silver Lake Triumph Centre build it.
    ex spec5 Mark

    63 TR4 Surrey
    50's Cooper Alfa Sports/Racer

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    Re: Performance cam

    Thanks TRMark, I was hoping to hear from some who had installed this cam and their driving experience. I am holding off thru the holidays to get the block in to the machine shop so I will not know till then whether new liners will be required but if so I will at least go with the 87mm. I had the 89mm's in a TR4A back in the late 70's and I bet with the BP270 it made a good combination. One of the liners has rust damage in it. I had taken the head off several years ago family took priority over the car and it sat with the head sitting on the engine but not torqued down in that time. It actually seemed "wet" in the back cylinder when I lifted the head back off. Where that came from I am not sure. But it sounds like you like the cam and you did not mention any regrets.

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    Re: Performance cam

    I had my cam reground by Ken Gillanders (RIP) from BF&E to what is an Erson 149 grind. Very similar to a Kastner "D" cam. 282 deg, w/0.287" lift. I also have 87mm pistons & liners, a tubular 4-2-1 exhaust header and the head is milled 0.085" from stock. I put "RH" needles in the SUs. It's a little lumpy at idle, and so I keep it at about 1000 rpm. The engine is very strong and doesn't lack any low end torque. I have to be careful though, as it likes to rev. In first and second it'll get to 6000 rpm real quick if I'm not watching. I also have a narrow belt conversion with a harmonic balancer with no engine driven fan. It's a fun car and I have no regrets doing the work that I did.
    Art
    '58 TR3A TS236xxL
    '92 Mazda Miata -- Supercharged
    '07 Mazda RX-8
    '11 Mazda CX-7

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    Jedi Knight TRMark's Avatar
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    Re: Performance cam

    Art, we went similar routes with the head mill, 4-2-1 (love the sound), narrow belt and balancer.
    ex spec5 Mark

    63 TR4 Surrey
    50's Cooper Alfa Sports/Racer

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    Jedi Knight Bob Claffie's Avatar
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    Re: Performance cam

    As CJD alludes to above, a cam usually only redirects hp and torque and does not create it. A look at most dyno curves shows the torque and hp curves don't even start until over 2000 /2500 rpms under which most if our tractor engines function. Cam shaft changes are one of the most overrated changes that can be made to an engine used primarily in a street car. Been there,done that. Bob C
    Thank goodness the MG is finally gone, replaced by another Corvette

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    Re: Performance cam

    Correct, just installing a performance cam without thinking it through will lead to a lot of expensive disappointment. I have the proper geometry with shorter push rods, the valve springs are correct for a higher lift cam. The cam in of itself might not do as much as the light Carrillo rods, lightweight flywheel (not aluminum), 89mm cylinders and improved breathing with the 4A manifold.
    ex spec5 Mark

    63 TR4 Surrey
    50's Cooper Alfa Sports/Racer

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    Yoda CJD's Avatar
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    Re: Performance cam

    One cam change that improves everything...across the board... is a roller lifter cam. Flat tappets are restricted in the rate at which the valves can be opened before the lobe scrapes the edge of the lifter. That is not a factor in roller cams, so the valve can be lifted and lowered much faster...resulting an a very significant increase in flow at all speeds, and therefore torque. I am convinced rollers are the single biggest reason modern engines produce so much power without the "temperament" the older engines had. The next biggest reason is variable valve geometry...but that's definitely beyond our old car's grasp.

    Has any manufacturer ever dabbled in roller cams for TR's?
    John

    1955 TR2

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