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Triumph TR6 - Road Cam
|Does anyone have any experiences with replacing the stock cam with a "road cam" on an otherwise stock engine?|
|Not on a stock engine, truth be known, I don't think that it would be worth fiddling with if that were all you planned on doing. If you are looking to boost performance, the engine must be able to breath and that means some head work and on the US spec cars, the compression ratio should bet a bump up also. Also bear in mind that camshafts can be somewhat tricky. You have to think about where power is made. Go to wild on the camshaft and you have a car that makes lots of horsepoer, but not in an RPM range that you can use. You may want to go back and dig through the archives for some of the camshaft threads.|
|Hi Steve, I searched this BBS and did not find any archives on camshafts. The main reason I am considering a road cam at this point is that we have the head off and I could go ahead with a little shaving. I understand your caution about the RPM range. One of our LBC club members said the TR6 was originally limited a great deal to pass the US emissions requirements and a road cam would make a difference w/o other mods. Any comments on the Performance Camshafts article at www.hottr6.com? Thanks.|
|I've got the GP2 camshaft in and have been quite pleased with it. It's a good "road cam". But you have to ask yourself if that's what you want as there are LOTS of ancillaries involved - milling the head, valves, guides, springs, ect. The final cost will go up.|
Might be time to look into the supercharging options as an alternative. From what I've seen that can get a big bang from an otherwise stock engine. Once you start increasing the compression ratio by milling the head a supercharger is no longer an easy option. I've not heard a single complaint about supercharging a "stock" engine. But search the archives.
|The search engine on the BBS is a little weak and can present problems at times, but here are a few:|
From 21 February 2006 TR6 High Performance Street Cam
From 9 June 2005 Engine rebuild Questions
From 5 May 2005 supercharged TR6 cam
From 26 August 2004 How much HP and Torque
If you have the head off, now is the time to work on it. Get hold of the Kastner books (from Roadster or even directly from Kas hisself) and see what he does to the ports and the combustion chambers on the TR6 motors. Even if you don't take the ports where he took them, at the very least match everything up and that includes the manifold gasket. Properly calculate you compression ratio and determine how much if any you want to take off from the head. It is also time to do the hardened seats, bronze guides and stem seals if you plan on running seals. I know that it will run into some money, but that is part of it.
|Steve, I rebuilt my engine last winter, and replaced the stock worn cam with a non stock "mild street" cam. First let me tell you that I am not an expert on anything to do with the engine! My engine head was shaved, by the PO, and I just had it skimmed on this rebuild. I also have headers, but no porting has been done. The cars performance is substantially improved from before, but because other work was done, I do not know how much, if any improvement is the result of the cam. I can only assume there is a contribution to the overall perfrormance improvement. I purchased the mild cam from BPNW in Oregon, and it's performance improvement range is suposed to be in the 2500-5000 rpm range. I was told by BPNW to expect about a 10% boost in HP???? My engine runs very smooth at idle, (800 rpm)and I am very pleased with results. Let me know if you want the part # or anything else regards my cam.|
How is your Italian?
Contact me off line.
|Pete, I would like the part number for the cam.|
I have dealt with BPNW and was pleased. 95% of engine rebuilt parts came from them and price was less for every item except the VP2 bearings which they seem to have an exclusive on. Maybe MOSS has them too.
Did not change my cam.
|Bob, the camshaft part number is BP270N. If you go on their website, click on TR250/6, then "performance parts", and go to page 2. There are 2 cams with part BP270. One is New the other Reconditioned (I believe) I installed the new one for $280 US.|
Hope this helps.
Pete '74 TR6
|I just ran a quick model with the BPNW cam based upon the limited cam spec sheet info from the website so the model is crude, but can serve as a point of rough comparison for consideration. To refine the model, a full cam spec sheet would be needed with valve opening and closing points, lift at a specified point along the lobe profile while opening and such. I can vary the same duration cam all over the map and generate totally different power curves, so any real comparison needs more than just the duration and lift. Any way, on to the rough comparion using "typical" valve opening and closing points comparison:|
It was almost dead on the Isky Z-19 cam (268 duration inlet, 269 exhaust stick), a minor bit less peaky than the Reed XS-270 cam (another 270 duration stick but more lift) and ever so slightly peakier than the Reed XS-266 but remember the caveat from above. Having said that, I would definitely get a full blown cam sheet and do a better model as it is worthy of consideration when it comes time to do another engine (the TR-250 is waiting on me). It will cost more, but that is because it is available new and not a regrind like the Reed or the Isky. Just from a pure grind standpoint, my favorite of the bunch at this point is still the Reed XS-266. If only that grind was available in a new stick.....
Also available new are the TH56 and the TH26 from APT (aptfast.com). Both are longer duration cams than the BP270, but have different lifts between the two. Using the crude model comparison, the curves are rather similar in shape for TH56 and the BP270, but at any RPM point along curve the power was slightly lower. The TH26 curves came in a bit earlier then those two cams, but the peak power was lower. It's that normal camshft tradeoff. You can come in earlier and have more lower end grunt or you can come in later and make higher peak numbers.
I have have followed your informed commentary on cams and other upgrades and ordered the GP2 cam along with the hardened valves and seats along with Goodparts uprated valve springs and guides. I think I now have the complete package along with the milling and porting of the head, which the machine shop has agreed to do. This should be a nice upgraded engine with a few more HP under the hood. Saving $$ for the Goodparts roller rocker setup to complete the package. Thanks!
1976 - TR6
|I have a set of roller rockers from another source purchased several years ago, but if I were parting with the brass to buy a set today, I would get Richard's. I know someone that runs a set of those on his racer and let me assure you, they are a work of art.|
BP270 is a Piper Cam part number for their nominal 270 degree duration cam (264 degrees actual). If it is the Piper unit, then the overlap is 48 degrees, with a 0.362" cam lift (0.405" at the valve assuming stock rollers). Inlet / exhaust timing is 26-58 / 62-22. As SteveP mentioned this is very similar (but not identical) to the Isky Z19.
If you take a look at CD II, there is a couple of articles under the "Computerized Bench Testing" directory on using computerized simulation to evaluate engine modifications, and the second article includes evaluation of the BP270 cam combined with other modifications.
If you are looking at using either the Piper or the Isky, you might want to look at dialing in a little cam advance to gain a little more low and mid-range torque, at the cost of peak HP. You lose some HP bragging rights for a little more useful torque.
And don't forget the cam bearings (Triumph did)!
|Leonard G Middleton|
|We have been using Desktop Dyno for years now. We first started using it with the GT4 Nissans, but have also used on other projects. I had not dug deep enough into CDII to see those articles, but having now looked them over, I pretty much concur with what was stated. The numbers you get are somewhat optimistic, but in the big scheme of things, they are still a rather useful guide. You can effectively model things before you take the plunge. For my TR6 motor as an example, I played with about half a dozen camshafts, different rocker ratios, different compression ratios, advancing and retarding the various camshafts, etc all before laying out any brass for the various bits. Using it has saved lots of money and effort for us over the years on many engines. If you are going to be building a motor, it is worth the purchase price of Desktop Dyno to include it in the cost of your rebuild and then to use it before you get too far down the trail.|
So to the question at hand, with additional information from the Piper website, what does the refined model say? It is less "peaky" and produces less power than either the Isky Z-19 or the Reed XS-270. It is instead almost dead on the Reed XS-266. For the most part the curves track right on top of one another to peak power then the XS-266 falls off a little quicker than the Piper BP270. And the Piper is available from new....looks like a no-brainer in my book.
On the cam bearing front, definitely a good idea, but unless the block is already worn or you going for the super high ratio rockers and really stiff springs, you should be OK for street use without them. Let your measurements and depth of purse be your guide
|I sent my cam to Shadbolt in Vancouver for a regrind. I told them I wanted to retain the low RPM torque but breathe a little better at the top end. I was sent a "streeter" grind. I can find the numbers if anyone is interested. At the same time I had .055 shaved off the head to give 9.5 to 1 and bored the block 0.060 over due to severe wear. Finally the machine shop dynamically balanced the bottom end. I can "light 'em up" no problem and run to 6000 RPM if I want. It is smooth and beautiful. One thing I recommend is to replace the springs while the head is off. I didn't and lived to regret it, broke two springs and a keeper before I learned. I also kept the single springs and installed valve stem seals, not a problem if I can stay away from the red line. I figured with the seals I could run platinum plugs. Apart from a stubborn leak I am thrilled with this engine. (no headers yet)|
I cannot confirm nor dispute your comment that "the numbers... are somewhat optimistic", although I expect you are right. I just fed the "tool" the data, and that was the results. And as we know in using tools, the results will depend (in various degreees depending upon the tool and the tasks) on the capabilities of the tool and the individual wielding it. Note also in the first article, I did use some disclaimers / "weasel words" that were the automotive industry equivalent to "your mileage may vary".
With respect to numbers, given all the variables (including variations between dynometers), I view comparing the actual numbers as a bit of a mug's game. Order of magnitude / percentage change against a baseline is useful, but really the only real number that counts is the one on a stopwatch (assuming identical conditions).
I agree with your assessment of it as an excellent tool for evaluating various engine modifications, and as you imply a good way to determine where to spend your money. Do you take out the engine and overbore it 0.040" for a modest improvement in torque at a cost of over $500 (pistons, machine work, etc.) and a lot of work; OR shave the head to bump the CR for less money, less work, and a bigger performance increase. All else equal, the answer is obvious.
Good re-direct on the cam bearings. Thanks for your comments.
|Leonard G Middleton|
This thread was discussed between 03/10/2006 and 11/10/2006
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