Best cam for 2.5
Discussion
Intake?
Carbs?
Compression?
Distributor mods?
I used
one by Piper,
one by Richard Good,
one by Kent, and
one by an independent cam grinder.
As I recall, the best match with my mods* was one with about 282^ duration, and (I think) .55" lift maybe 110^ separation. I'm fuzzy on it, sorry. Also, all of the feedback was seat of the pants.
I do recall that having an adjustable cam sprocket made timing easy.
* Big port head, opened up per Triumph competition manual, port matched, big SS valves, springs, high ratio roller rockers, 10.5:1 compression, polished combustion chambers, ChroMoly tube pushrods, 3-dual throat 40mm carbs on a TWM intake manifold, 6>2>1 exhaust manifold, recurved distributor w/ electronic ignition.
Best,
B.
Carbs?
Compression?
Distributor mods?
I used
one by Piper,
one by Richard Good,
one by Kent, and
one by an independent cam grinder.
As I recall, the best match with my mods* was one with about 282^ duration, and (I think) .55" lift maybe 110^ separation. I'm fuzzy on it, sorry. Also, all of the feedback was seat of the pants.
I do recall that having an adjustable cam sprocket made timing easy.
* Big port head, opened up per Triumph competition manual, port matched, big SS valves, springs, high ratio roller rockers, 10.5:1 compression, polished combustion chambers, ChroMoly tube pushrods, 3-dual throat 40mm carbs on a TWM intake manifold, 6>2>1 exhaust manifold, recurved distributor w/ electronic ignition.
Best,
B.
From memory, so please correct me if info wrong !
Of the 'standard' manufacture, the TR5 PI cam is the hottest, this cam also was used in early TR6, and I think the odd Mk1 2.5PI saloon. This was the (true) 150bhp spec.
Then for the 2.5PI saloon Triumph softened it a little, and this was the 132bhp spec.
Later, this softer cam also found its way into TR6 models.
I put a Triumphtune fast road cam and flowed head on mine (in a Marlin kit car), with bigger advance springs in dizzy, and 2xHIF6 (1.75") carbs. This worked very well except engine would pink at light throttle around the 2200-2400rpm range once lead got reduced, and I couldn't get rid of it without using 5 star.
I'm surprised you can get 10.5 compression to work without detonation ?
Of the 'standard' manufacture, the TR5 PI cam is the hottest, this cam also was used in early TR6, and I think the odd Mk1 2.5PI saloon. This was the (true) 150bhp spec.
Then for the 2.5PI saloon Triumph softened it a little, and this was the 132bhp spec.
Later, this softer cam also found its way into TR6 models.
I put a Triumphtune fast road cam and flowed head on mine (in a Marlin kit car), with bigger advance springs in dizzy, and 2xHIF6 (1.75") carbs. This worked very well except engine would pink at light throttle around the 2200-2400rpm range once lead got reduced, and I couldn't get rid of it without using 5 star.
I'm surprised you can get 10.5 compression to work without detonation ?
Shiney = but those Phoenix type manifolds really hold the torque (BIG TIME).
Any of the good company fast road cams - but head would a lot of work.
10.5 CR is fine, just need RR session to get it tuned right.
You don't see many 2500M's with the full Monty TR 6 pot lumps which is a pity (better than the Essex IMHO).
Any of the good company fast road cams - but head would a lot of work.
10.5 CR is fine, just need RR session to get it tuned right.
You don't see many 2500M's with the full Monty TR 6 pot lumps which is a pity (better than the Essex IMHO).
That picture (nice bits, by the way) reminded me -add the largest/most effective heat shield you can, between the intake and exhaust.
As for the 10.5:1 CR, It was actually only slightly above 10.3, but I did a lot of work in the combustion chambers. They were CCd to an absurd degree, every edge was radiused, valves unshrouded, and the surfaces mirror polished. No rolling road.
Best,
B
As for the 10.5:1 CR, It was actually only slightly above 10.3, but I did a lot of work in the combustion chambers. They were CCd to an absurd degree, every edge was radiused, valves unshrouded, and the surfaces mirror polished. No rolling road.
Best,
B
Yeah - forgot to say WONDERFUL manifolds !!
10.3 Ah.. right. I made the [probably stupid] mistake of assuming the Triumphtune guys had radiused everything as necessary, and they probably hadn't !!
Big Heat shield - is it that simple ? Damn.... Although the Marlin did have big louvres in the sides, but not the bonnet, and very different to TVRs engine compartment.
10.3 Ah.. right. I made the [probably stupid] mistake of assuming the Triumphtune guys had radiused everything as necessary, and they probably hadn't !!
Big Heat shield - is it that simple ? Damn.... Although the Marlin did have big louvres in the sides, but not the bonnet, and very different to TVRs engine compartment.
RCK974X said:
Yeah - forgot to say WONDERFUL manifolds !!
10.3 Ah.. right. I made the [probably stupid] mistake of assuming the Triumphtune guys had radiused everything as necessary, and they probably hadn't !!
Big Heat shield - is it that simple ? Damn.... Although the Marlin did have big louvres in the sides, but not the bonnet, and very different to TVRs engine compartment.
I bought the valves, guides, roller rockers, springs, and Aluminium retainers from Triumphtune, but did all of the work myself. 10.3 Ah.. right. I made the [probably stupid] mistake of assuming the Triumphtune guys had radiused everything as necessary, and they probably hadn't !!
Big Heat shield - is it that simple ? Damn.... Although the Marlin did have big louvres in the sides, but not the bonnet, and very different to TVRs engine compartment.
The heat shield can be simple. I used a somewhat malleable sheet of Aluminium, and riveted woven heat shield, with reflective metal backing to the bottom, then I crimped the edge around, to lock the mat in place. Next, I added extensions that covered the exhaust header turn-downs. The whole thing bolted to the carb/intake manifold interface.
Best,
B.
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