Sprint Camshaft - Fast Road

[t+m]

Hi Dale,back in the 80's and early 90's i worked extensively on dolomites and tr7's in a small country garage in berkshire and experimented with tuning them up.We managed to get 160 bhp out of a road used sprint -not a track car- and this is the spec we used (from memory 20+ ago!)A Triumphtune str091 cam and vernier sprocket.standard air filter because its a jag item and can flow enough air for 220bhp,2 very short stub stacks (radius carb intakes between the cabs and filter).standard jets buts the richest needles of the 3 listed for the sprint,i think they were listed for high altitude locations.Standard exh manifold but the 2" 2 box straight through system from Triumphtune.After messing about for ages with a protractor and dial gauge to get the quoted valve timing it was as near as damn it to the standard mark so i think we could have used the standard sprocket and saved ourselves a good few quid.Those cams were ground from standard profiles so the base circle was much smaller and therefore needed thicker shims.i think we used Rover 2.6 SD1 shims which started at 130 thou.The cams have a much harsher opening and closing ramp on the profile and are a lot noisier than standard even with a clearance of only 9 thou.The buckets are also further out of their bores and rock from side to side alarmingly and wear the head much quicker.10 thou oversize buckets were available but needed the head machining to fit.The car was much quicker than standard in every gear from any speed,the standard carbs flow enough air for about 175bhp so the air speed at low revs was high enough to stop it bogging down,(which is a prob with big bore fixed jet carbs)but still allowed enough air for full power.We also chamfered the air side of the carb pistons by a few mill to reduce "eddy currents".I sold the car (GCK586S inca) before we carried out the rest of the planned mods.We were going to take an oil feed from the pressure switch housing and run it to a spray bar across the cam to reduce noise and wear.back with part 2 in a minute.......

[DavePoth]

According to the DVLA that car is still around, and SORNed somewhere...

[t+m]

....part 2.this obviously req the high flow high pressure pump.Iwired in the overdrive to 2nd gear so it would indicate over 70mph flat out in 2nd.Its an easy mod but the o/d unit is the laycock j type and not designed to take that kind of torque.If i remember right the same box was on the big saloons the 2.5pi and Stag and fitted with the de-normanville o/d was ok for 2nd gear.When you fit the cam at 1st start rev up to 2-3k for a couple of mins to bed the lobes,at idle they are under terrrific load. We converted auto's to manual and vice versa.Very easy to do.We fitted sprint engines to tr7's,again very easy and because of the extra space we used Triumphtune 4 branch manifolds in the tr7's and these cars were a lot faster than a standard sprint.If all the parts were to hand we could do a tr7 sprint in a day.1850 into sprint was also done a few times(have to swap the subframe as the eng mounts are at different angles) .Gearbox rebuilds were easy and the overdrive is a very simple attachment in place of the rear g' box extension housing.Auto to manual req the tunnel from the manual car and the spacer on the back of the crank to be removed and a spigot bush pushed in.Looking back now the cars were a pleasure to work on,apart from cutting out the rusty sills/arches/doors bottoms/front panels/etc,and the seized 1850/tr7 head studs but i still tinker about with cars but the modern stuff has no soul or character,they are just efficient modes of transport.Conversion to fuel injection and mappable control of fuel and ignition would be possible now with all the scrap cars to plunder and i dare say that our 160bhp could be easily beaten.Ihope all this waffle is useful to somebody,i,ve still got the BL /Triumph manuals if i can be of assistance to anyone let me know.I,ve just joined the forum so look forward to conversing with you all...Paul in Reading

[triple tango]

all good well proven info.
Welcome to forum.

[xvivalve]

What happened to Ronald's camshaft list?

Does anyone have a copy anywhere?

[tony g]

Half way down the page on Marts post

https://forum.triumphdolomite.co.uk/vie ... hp?t=20629

[TahitiSPRINT]

Original link from post 2 restored now

[xvivalve]

Thanks all, I was trying to refresh my memory regarding 7TY2...but I guess I'll have to measure it.

[xvivalve]

I have three camshafts all marked up as 7TY2

Two are cut from blanks and measure a lift of 383 thou and 387 thou, the third is reprofiled and measures 354 thou which is less lift than a standard cam, but visibly has greater duration and a visibly similar profile to the other two. From Ronald's table, I'm guessing these are STR91 cams, well the first two, at least!

I don't have facility to measure duration here.

Surely there should be greater accuracy between the two than a 4 thou discrepancy, and is this indicative that having a cam reprofiled is less than an accurate science and may not result in the desired effect?