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Thread: Cam choices?

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    Question Cam choices?

    Hello,

    Pursuant to the my thread about the broken bearing cap while I was disassembling the engine to take it for a line bore, I noticed the following:




    cam1.jpg

    The question now is not if I should replace the cam but which one to get. It seems there is a lot of choice out there and they are all a little bit different.

    So, I'd appreciate some recommendations as to which cam to get.

    My use of the car will be as a daily driver, with about 75% city driving. One of the features of the TR6 that I like is the low end torque that the motor has, and that is one thing I'd like to retain. However if I'm paying for a new cam I'd like to up the power a bit (while retaining the torque), but not too much as I still want decent fuel economy. Also I am going to fuel inject it as well.

    Thanks
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    Jedi Trainee Tybalt's Avatar
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    Re: Cam choices?

    Given that you want to retain low end and power up a bit, you don't want anything too radical. The one that first comes to mind is the BPNW BP270, very similar to the Reed XS266 but a new cam instead of a regrind. It's a little "hotter" than your cam but still maintains pretty good low end and hits peak power at a reasonable piston speed. There are number of cams out there that make more power but they make at engine speeds that have higher piston speeds than I would like to see thanks the having the longish stroke of the TR6. It's just a good overall compromise for a street driven car that is warmed over but still easy to live with. Go too hot and too high a compression ratio and you will wind up with something like one of my friends TR250. Loads of power but it doesn't come on until fairly high in the rpm range and nothing down low. Couple that with an aluminum flywheel and front pulley with fan eliminated and it was a difficult car to drive on the street under "normal" conditions.

    One I would definitely not recommend is the Kent cam. When I was building my engine about a dozen different cam grinds were modeled before deciding on the Reed XS266 (the BPNW BP270 wasn't available at the time other wise I would have used it). The Kent cam not only gave up a good deal of low end, but it wasn't that good at the top end either.

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    Re: Cam choices?

    Can't comment on it yet as I haven't installed it or driven it...but for my TR250 project I went with the BPNW PI Cam, 150HP spec. I have some other mods done on the car...it currently has a TSI S2 cam in it.

    Cheers
    Tush
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    Re: Cam choices?

    I haven't found a thing to complain about with this cam:
    https://mossmotors.com/camshaft-stock-grind?assoc=42893
    DRIVE 'EM IF YOU GOT 'EM

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    Re: Cam choices?

    Quote Originally Posted by poolboy View Post
    I haven't found a thing to complain about with this cam:
    https://mossmotors.com/camshaft-stock-grind?assoc=42893
    I had thought about suggesting that one but since I seemed to recall that the OP had a '76 TR6, that's the cam he already has. If he had an early TR6 it would have definitely have gotten a good mention. We had been using Desktop Dyno for building engine models for a GT4 Nissan we were racing at the time and that is what I used for the modeling my TR6 engine with various cams. The downside of Desktop Dyno is that we always thought that it was overly optimistic about the calculated power and torque but we did find that the trends shown in the models held up. So having said that, take the numbers in the attached spreadsheet with a grain of salt but pay attention to the trends. Note that the "stock" TR6 is an early carb model with the mildest of cams fitted to these cars, there is a plot for that cam with the higher compression ratio, head work and triple Webers as well.
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    Re: Cam choices?

    I have looked at the offerings at BPNW, but was leaning towards the 120 or the 150 versions of their cams. Is the BPNW 120 cam the same as stock on the later engine?

    Is there a difference with the stock cam in the earlier and later engine?

    @Tush, what is your overall impressions of the S2 cam?

    Thanks guys!

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    Re: Cam choices?

    How about stock! This is what was designed for a daily driver. No inordinate spring or seat needs, no burns from too short on the seat. What could be better. Ain't gonna get high performance no matter what you do.
    Bob

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    Re: Cam choices?

    Quote Originally Posted by rooster View Post
    I have looked at the offerings at BPNW, but was leaning towards the 120 or the 150 versions of their cams. Is the BPNW 120 cam the same as stock on the later engine?

    Is there a difference with the stock cam in the earlier and later engine?

    @Tush, what is your overall impressions of the S2 cam?

    Thanks guys!
    There were three cams used in the TR250/TR6. The TR250 and the "CC" and earliest of the "CF" engine series TR6s used the 307621, which I believe was also used in the GT6 and the Vitesse. This is the "mildest" of the three cams. The early PI cars (150HP) used the 307689 cam which is the "hottest" of the three cams. The later carb cars and PI cars used the 311399 cam. This third cam is in between the early carb and early PI cam. It was used in the later carb cars to keep horsepower up to the same level that it had been in the earlier cars even with the additional emission requirements tossed at the cars in this market and to address normal traffic driveability complaints about the early PI cars. You sacrificed some power but you had a somewhat more civilized car to live with on a daily driver type basis. This is the one that poolboy talked about in post #4. Since I seem to recall that you have a 1976 TR6, you already have experience with the 311399 and you had indicated that you wanted something just a bit hotter than that. For a factory cam of that era it's really a pretty good stick.

    I cannot speak to direct experience with S2 but was interested in the S2 cam. The models indicated that the 311399 developed more power and torque than the S2 until you got to about 5000 rpm. At 5500 the S2 developed more power and the 311399 trailed off faster than the S2 which climbed in the model until about 6500. The 307689 early PI cam pretty much followed the power trend of the S2, matching the S2 part of the way up the power curve but leveling out and trailing off a bit sooner than the S2. Like you, since I was thinking in terms of a street car the 2500 to 5500 range was where I put the most emphasis. The decision boiled down the 311399 or the Reed XS266 which has very similar specs to the BPNW BP270. I did a quick and dirty modeling of the BP270 when it was introduced for "db" in Huntsville AL comparing it to the XS266 and the numbers almost fell on top of each other. For some reason it was not added to the spreadsheet table and I no longer have a compatible copy of Desktop Dyno to repeat that model. Since the BP270 is a new cam and the XS266 is a regrind, if I were building my engine today, I'd use the BP270.

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    Re: Cam choices?

    I had an S2...if you really want to climb up to 5000 rpms, it'll take you there.
    If you want a smooth idle...you'll need to increase the rpms...1100 did it for me.
    DRIVE 'EM IF YOU GOT 'EM

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    Re: Cam choices?

    I rarely hear of anyone using this company but had a great experience with them. Delta cam shaft. I used them when I built my engine for my TR250. They have many cam profiles to choose from and can adjust them to your needs too. I sent mine to them and they repaired the lobs re-hardend it and it's been great. Around 25k on it. You can also send them your tappets and they can be reground like new. Especially if they are the much better originals. I got their 250 sport grind and a long with 155:1 roller rockers and increased compression to 10:1 this thing is quick. My Triumph mechanic said I have at lease 150hp and if he plays with the weights in the distributor there is more. The specks are in the pictures. I don't think they list their stuff on the web only their phone #. Call them and they will email you the info. It was very reasonable too.
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    Re: Cam choices?

    Years ago I had a cam "built" for my SCCA GP Spitfire. Rather than buying some off the shelf cam I found a small company (in Fla.) who would grind a cam to my specs. Actually they supplied a spec sheet where I filled in my engine modifications and usage and they designed the cam to meet those criteria.

    At the time it would run competitively with the factory/Kastner A7 cam for half the $$. You might look into a cam company who offers that same service.
    Thank goodness the MG is finally gone, replaced by another Corvette

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    Re: Cam choices?

    This is the "mildest" of the three cams. The early PI cars (150HP) used the 307689 cam which is the "hottest" of the three cams. The later carb cars and PI cars used the 311399 cam. This third cam is in between the early carb and early PI cam.
    Thanks Tybalt, that is good information.

    I took a look at the part number on my cam and it is the 11399.

    So about cam regrinding, would it be necessary to get longer push rods or do any other engine mods if I get my existing cam done? There are a number of places local to me that do regrinding, one even features a TR6 on their web site .

    I'm going to take a closer look at the BPNW BP270. It would be nice if they had a chart with HP and torque on it.

    Thanks again guys, all of your input has been informative and helpful, I appreciate it!

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    Re: Cam choices?

    If you haven't seen this you may find some of it interesting.
    http://www.hottr6.com/triumph/tr6cams.html
    DRIVE 'EM IF YOU GOT 'EM

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    Re: Cam choices?

    I saw that , it's the reason for this thread.

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    Re: Cam choices?

    Quote Originally Posted by rooster View Post
    Thanks Tybalt, that is good information.

    I took a look at the part number on my cam and it is the 11399.

    So about cam regrinding, would it be necessary to get longer push rods or do any other engine mods if I get my existing cam done? There are a number of places local to me that do regrinding, one even features a TR6 on their web site .

    I'm going to take a closer look at the BPNW BP270. It would be nice if they had a chart with HP and torque on it.

    Thanks again guys, all of your input has been informative and helpful, I appreciate it!
    The definitive answer to that question is "it depends." The variables in play are the base circle for the lobes and the lift at the lobes along with the deck height of the block and the thickness of the cylinder head. The compressed thickness of the head gasket is also a variable but it's in the noise level of things so not worth worrying about unless you are going with some sort of a custom thickness gasket. Odds are that you would be able to run standard push rods, what you would need to pay attention to is how the cam follower/pushrod/rocker daisy chain sits when the cam is on the base circle of the lobe with adjustment clearance at the valve stem/rocker arm, and how the rocker pad hits the valve stem when the lobe is in play.

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    Re: Cam choices?

    Is is possible to adjust the rockers to make up for the amount of material removed from the cam when it's ground. It looks like there is quite a bit of adjustment room there, or is it not a good idea to do that?

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    Re: Cam choices?

    Quote Originally Posted by rooster View Post
    Is is possible to adjust the rockers to make up for the amount of material removed from the cam when it's ground. It looks like there is quite a bit of adjustment room there, or is it not a good idea to do that?
    It's a matter of how the cam/cam follower/pushrod/rocker arm daisy chain sits when the the cam is on the base circle of the lobe and how the rocker hits the valve stem when the lobe of the cam is in play. You have to take all of the variables that would impact that into account. You want the rocker concentrating its hit on the valve stem about the center of the stem, not biased toward one side of the valve stem or the other. Since other variables come into play for this than just the camshaft itself, the only definitive answer that I can provide is "it depends." I think that odds are that stock pushrods and stock rockers would be fine, but cannot say that with certainty.

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    Re: Cam choices?

    Quote Originally Posted by Tybalt View Post
    It's a matter of how the cam/cam follower/pushrod/rocker arm daisy chain sits when the the cam is on the base circle of the lobe and how the rocker hits the valve stem when the lobe of the cam is in play. You have to take all of the variables that would impact that into account. You want the rocker concentrating its hit on the valve stem about the center of the stem, not biased toward one side of the valve stem or the other. Since other variables come into play for this than just the camshaft itself, the only definitive answer that I can provide is "it depends." I think that odds are that stock pushrods and stock rockers would be fine, but cannot say that with certainty.
    That's good to know. I will definitely pay attention when putting everything back together to make sure the pushrods are properly aligned.

    Thanks for your help!

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    Re: Cam choices?

    Absolutely the stock pushrods will work with a reground camshaft. We're only talking thousandths of inches here. It's not like the regrinder is going to take your old cam down by an quarter of an inch. A 10 or 20 thousandth of an inch misalignment is insignificant. Been there, done that.

    The previous "high point" on the original cam will remain the high point (unless very worn and needing to be recontoured ) only the low point will be a little lower.
    Thank goodness the MG is finally gone, replaced by another Corvette

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    Re: Cam choices?

    Lets not forget Richard Good. Good Parts for Performance TR6. https://www.goodparts.com/ I've driven his car on the cover of his catalog at it was terrific.

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