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Camshaft application id
#802057 03/20/20 7:14 pm
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PEH Offline OP
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Can anyone advise on the suitability of the Race cams on this list for Shorttrack racing on 300yrd Uk speedway tracks with a loose surface, They will be going in a Tr6 Trackmaster maybe with a 750 conversion. 9-1 pistons. Im not terribly good when it comes to numbers, i have had some good tips from Mark and Stein, but im trying to find a combo to give good drive and traction for the loose surfaces i have to run on, Duration, In. 300 degrees Ex, 300. Cam Lift, In 0.348 Ex 0.348
Opens/Closes In,48/72 Ex 70/50 Full lift at Tdc 0.116" Ex 0.109" . I think the numbers are @ 0.20" lift. It is a Newman race cam according to there site. regards, Harry.

Last edited by PEH; 03/21/20 8:55 am.
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Re: Camshaft application id
PEH #802246 03/22/20 2:38 am
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102* LC on the intake is indicated if I did math right which is ok but the duration and timing would indicate a higher power band than I thought you wanted. This cam has similar specs to old H&C #9 Magnum 45/75 75/45 300* duration 105* LC, a hot cam back in the day. This would be a good cam (Newman) if you were mostly 4500 rpm and up and using throttle to stay in the power band to steer with the rear. This is just my take and there are current vintage racers on here that should have a more relevant opinion. Originally I was recommending a less duration/overlap cam for what I was envisaging to be more of a loose scrambles type track but when you say 'speedway' track then maybe we are thinking of a different type racing and cam requirement. If you want more low end drive without as much shifting then I'd probably be going less cam and more compression say 10.5-1, I think whoever recommended the T140 inlet set at 45/69 or 100*LC and the 3134 T120 exhaust or half race NH or Harris was about right. I think a 750 with 10.5-1 and those cams would be a good all around combo, maybe 1 5/8" OD pipes and experiment with length and if you have the room behind the head then straighten out the intake manifold for that single carb. I wouldn't enlarge ports or valves.

Is your speedway track just a short oval, flat corners? Mark

Re: Camshaft application id
PEH #802278 03/22/20 11:37 am
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Yes short Oval, usually 300/350yrds paper clips. Some have a very slight 5 ish degree banking but not much, one nasty little track is actually off camber in turn 1, saw loads go down entering that one, i normally gear for 2nd or 3rd and stay in that gear all race, I was hoping to build a long rod with a 750 kit, but my supplier (that i get a great deal on, and manufactures them) is out of stock at the mo, I do have a couple of short rod engines under the bench if necessary, I was running short on time, but that worry has now gone straight out of the window as our first 2 have been cancelled. i would pics up of the tracks i cannot figure out how to do this Url stuff, late starter on computors!

Last edited by PEH; 03/22/20 11:39 am.
Re: Camshaft application id
PEH #802307 03/22/20 4:30 pm
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I'm with you on the computer, I was avoiding them until one day my wife asked me if I'd seen all the motorcycle parts on eBay...e what ?

Off camber loose dirt short track corner...nice for spectators.

Since you're staying in one gear then you're choice of cam would be for mid to high rpm and on the pipe all the time correct? There are so many similar cams to choose from that would work here even the stock T140 inlet with altered timing of 45/69 to close a little earlier and the same profile on exhaust or the 3134 T120 exhaust. This would be an inexpensive choice since you have T140 inlet cams already right? Cams just a small part of package really, Triumphs like compression, are you running pump gas, race gas or alcohol? Exhaust and intake sized for good mid range, to work with cam, so you'll have nice crisp throttle response. Again I'm no expert or current racer, the military draft ended my short racing career back in the earlier '70's. But a light wt., geared down 750 Trackmaster with moderate cams, good compression, maybe a flat slide Keihin or Mikuni 34-35-36mm? will pull really well and would be a blast. I plan to run a single carb on my C&J street tracker but will be welding up a straighter intake manifold to use on T140 parallel port head which is really just a modified TR7 head with a little more casting material for the steel screw in stubs. I wouldn't personally mess with port or valve size on your TR6 head, my dirt bike (650cc) runs an early 8 bolt small port head and manifold with a 32mm Concentric, 32" long 1 5/8" od side pipes, T120 cams and ran great when last ridden. When I ran dual carbs and 1 3/4" TT pipes it still ran great but was a little softer on bottom but still pulled all the bikes of that era to the first corner. At least that's my story and I'm sticking to it.

Since you have the time now and if you have the money for it, MAP has (or had? check stock) a nice light alloy nikasil plated 750 long rod barrel with light wt. forged pistons, your choice of compression, ARP hardware, 'O' ringed top deck of bores, torque plate honed, alloy push rod tubes etc. . I have yet to put one on a running bike but it's probably the nicest kit I've seen. I'm starting to sound like I work for MAP...I don't but am a customer. I should probably hold my recommendation until I can verify but this kit has been run hard by a forum member on winning 750 vintage road racer and has good things to say about it.

Re: Camshaft application id
PEH #802437 03/23/20 9:20 am
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I looked at the Map website but its not showing for sale on there, Thing is, the one i can get is Aerco, and at a price around a 1/4 of an alloy one, its not the same quality but for 6 or 7 meetings a year on pretty short tracks compared to yours, i think its as much as i want to spend for the amount of use its gonna get, I have an account with Harris and can get the nitrided triumph cams at trade as well, so i guess it makes sense to go down that route to start with and see how it performs, I will see how much room there is to extend the carb manifold, It will have to be some sort of pancake filter, which will be of limited choice, We do shut off the throttle on corner entry, then try to balance the throttle to wheel spin / forward motion and usually nail it at about 2/3's of the corner as there isn't much room for error, especially in the early laps, as there would be 12 riders on the grid in 3 or 4 rows. A lot of folks on this site have mentioned the early Bonneville heads where the best 63/64 i think, and the Tr6/7 have the same dimensions, I remember reading a statement by John Healey saying something like "The best british bike he had ridden was a Tr6 with a 750 kit and a Keihin flatslide carb on it", sadly he didn't mention what cams where in it, I had several sets of stainless TT pipes made for T140's, so i shall use those if i can get them to fit without to much alteration. Im also going to try and do as Hillbilly suggested some time ago, and try to get a close squish band with the piston to head clearance, I have a garage near me that has a classic fuel made for customers with old cars that they can buy from a pump, it is 98 octane with lead in it, i mix this with a none ethanol super unleaded 98 octane 50-50, seems to work fine. Lots to do and think about, thanks again for your imput Mark.

Last edited by PEH; 03/23/20 10:47 am.
Re: Camshaft application id
PEH #802526 03/23/20 10:23 pm
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The Newman cam you mentioned should work fine but would be nice to know if it can be used with std. tappets or which tappets 'R' vs. 'std.' those timing figures are based on. With that cam and your fuel, the 10.5-1 cr pistons would be good. The iron Aerco cylinder is fine I"m sure but I'm not sure of their pistons, from what I've seen the dome shape was nothing special. I purchased MAP's forged 9-1 cr (76.25mm) zero deck, tight quench pistons for my Routts kit (iron) with a stock bore of 2.998". These pistons are also 2.998" (238 gr.) for approx. 3.002" bore so I will hone to fit. Look at a picture of MAP's pistons with their very flat low domes and tight chamber fit even in the 10.5-1 cr pistons. These can be set up for real squish and good combustion and would be applicable for your Aerco cylinder with MAP's appropriate rings. Just a thought and these are also the pistons Hillbilly uses to get his squish and performance.

Stick a smaller dia. tube in each intake port and you will see the angle and point of convergenge behind the head. I know the old small dia. backbone Trackmasters had plenty of room behind the head but not sure of the large dia. backbone frames.

Last edited by MarksterTT; 03/23/20 10:32 pm. Reason: mm
Re: Camshaft application id
PEH #803015 03/27/20 11:15 am
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Do you mean making a slightly longer manifold similar to the original but making the 2 ports slightly longer before they join together? A chap (a well known american tuner) did say to me that he felt the main issue with the Tr6/Tr7 is that the intake length was to short. I spoke to Newmans about which Tappets to use and he was unsure which concerns me somewhat, Im going to buy an Aerco one for stock and have a measure up, I looked at the pictures of Map and Aerco and i can see what looks like a slightly higher crown/deck height on the map, would be interesting to no the difference. I can buy the whole kit for trade price at less than cost of the map pistons, I no bargain prices can mean lower quality but these guys have been making these kits a long time, and they are on my doorstep, so any problems and i can be right there, If i was running 1/2 miles i would not hesitate to go with map or similar. If they don't measure up at all close then i will look at some Map pistons a little closer.

Re: Camshaft application id
PEH #803049 03/27/20 5:48 pm
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Kind of weird Newman didn't know which tappet specs were based on, I went to their site and saw the specs for their 3134 cams was not close to what I would have imagined for open/closing and duration so not confident of either cams numbers. Hyde and Harris full race cams are spec'd as Spitfire profiles or T140 intakes, so for economy and testing, just combine a stock T140 intake cam timed as previously recommended and either the full race or half race exhaust from NH or Harris, I would try NH since they're claimed to have same lift as T140 intake.

You have a good deal on Aerco, go with it but with long duration, late closing intake cam I would want 10.5-1 cr.

The TR6/7 port angles forward/outward and is directed right at spark plug, if you extend this port rearward to it's merge with other side you will see how long and straight the runners will be, fabricate and weld up a nice manifold to take a flanged rubber mount (one end) for spigot (other end) type mik/keihin etc. carb.

All I've got, good luck. Mark

Last edited by MarksterTT; 03/27/20 5:49 pm.
Re: Camshaft application id
MarksterTT #803248 03/29/20 10:17 am
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Many thanks for all your input Mark, Hope to figure out how to put up a picture when she's ready to fire up!


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