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Triumph TR6 - Improving the 2.5?

It's got to be done, well in my mind anyway.
Over the dark winter evenings I'll be rebuilding a 2.5 to go into the TR6 during the spring. The question is what modifications to make? It's a 71 USA spec motor, back in the UK, so there are no emissions regs etc...
What mods have you chaps made?
I've already fitted a pair of HIF44 SUs and a 6-3-1 header with sports exhaust, so what I'm really after is information concerning camshaft specs used and cylinder head mods. The car is only run a few thousand miles per year, but I want it to at least beat up the odd Mk2 Golf GTi.

Alastair

PS. I've done quite a lot of tuning in the past on Buick 215s, so I'm no newbie, but 1st hand TR experiance is like gold dust!
aj mcmurray

Hi Alastair

Gold dust info West Midlands? Geeeeez! Try finding your GGGGGrandfathers Birth/Death/Burial between 1720?/1774? Betley/ Knutton/ Keel. Area West Midlands. The whole bloody place is about the size of a good Saskatchewan grain farm. Thats Goldust.

Anyway I think some of the 6 hotrodders are hibernating after a long winter Christmas party. There are a number of the guys JohnP etc that should be on this shortly.

Can't think of anything to add and late but will keep an eye on the post. Will help all I can.

Bill
Bill Brayford

AJ - Are you a member of the TR Register ? If not, I suggest you join. I've been a member since 1987.

http://www.tr-register.co.uk/

They have the local Stoke Group as well. Call Simon Beresford on 01630 658984. Mention I told you to call.

Also The TR Register has an excellent glossy colour magazine (8 issues per year) with all kinds of info in it. The Tech Editor is Phil Vella who has done to his TR6 what you want to do.

Contact Phil on pvella@vascotrack.com Mention my name.

The TR Register also have at least a hundred race drivers who race about 10 times a year. Many have very potent TR5's and TR6's. I suggest you contact Jon Wood at Classic Racecraft in Maunby, North Yorkshire on 01609 778858. If you talk to Jon, tell him I told you to call. They have done several very fast TR6's. There were two TR6's and 1 TR5 (with triple Webers) from UK at the Triumph races in June, 2002 at Mid-Ohio. The Brits finished 1st through 4th + 6th in the All Triumph Race with 49 Triumph starters at Mid-Ohio. Jon finished 4th about 1/2 a second behind Jon Wolfe (Luton) in his TR7-V8. The winner was Chris Petch from Manchester in his TR5. John Whitley (North of England) finished 6th in his fully mapped PI TR6 with over 200 HP - that's what he told me.

And they are all coming to Mosport Park near Toronto this June 26 to 30th, 2003.

PS, my mother was born in Lancastershire.

Don Elliott, Original Owner, 1958 TR3A
Don Elliott

Mosport will be fun! Sorry to hear about your mom though..
BC
Bryn

A 1971 USA spec car will have the very tame/lame camshaft and the 2.0L Vitesse/GT6 inlet port spacing and the single pipe exhaust manifold. A change in camshaft, exhaust manifold (I personally like the stock PI/later USA spec twin pipe manifold on street cars) and a bit of a bump in compression should be on your list. You can go the Weber route with your head, but will have to change heads to go the PI route. On the cylinder head, try to get hold of the Vizard book or the Kastner USA Competition Preparation Manual. Good info on head modifications in both.

But what cam, what compression ratio to choose. For that I would suggest picking up an engine modeling software package such as Desktop Dyno. You can play with any number of cam profiles, compression ratios, rocker ratios, etc. to help guide you along the path without spending money on parts first. It's not a be all, end all piece of software, but it is great guide. Think about how do you want to use the car. No point in having a street car that makes no power below 3500 rpm. You are basically limited by your imagination and pocket depth.
SteveP

AJ Mccurry,
Don't bother with US specs as they are less horse power than the continent version. If you have a US engine toss the original Carb and intake maniflod and seek an English/eruo PI intake management system.,
Christopher Trace

Hello AJ,

You live in Triumph Country - prolly most of the TR6 racers are in the bar or something. Call Revinton TR.

Anyhow, I'm no expert but I'm hands on and you mentioned "first hand experience" being rare so here's my philosophy...

Spend about $3,000 to get more air and fuel in there to make a bigger bang...do some lightening and balancing as well.

1. My head is shaved 0.160" and I get about 9.7:1 compression. Static is about 175. Do the port work described by Vizard and other sources. That is as far as I went but you could go further such as buy the $350 US valve set with the thin stems. Or further yet - go $1500 US for the exotic head gear from PRI in the US. Main thing is get the six breathing. That is the biggest problem - lack of breathing.

2. I'v got the OEM carb manifold that has long runners and it is ported and gasket matched - nice smooth flow into the head. There is a set of SU HD8 to supply about as much air as the engine can handle.

3. Lighten and balance the rods and pistons. My engine buries the tach with no vibration - nice and silky.

4. Lightened rockers.
5. Free flow exhausts
6. Cold air K&N, electronic ignition etc...

That is the extent of the mods and produced an engine that holds it's own against the Japanese 4 bangers.

The parts I have ready to be installed this winter should help -

7. Kent Fast Road cam
8. 1.55 Roller Rockers
9. 6 into 2 TT Headers
10. Aluminum flywheel
11. Gapless rings
12. Hollow chrom moly push rods

That's about as far as I'm going and should have a six with lots of spirit and a blast to drive. I might look into the supercharger route sometime down the road but just going to enjoy driving the car for a couple years.

Good luck with your Six

Regards,

John Parfitt
Calgary, Canada
1973 Green TR6







John Parfitt

AJ - I have heard that smoothing the intake and exhaust passages can result in a loss of power because the turbulence mixing is no longer as good as with the rough walls.

Tony Lindsay-Dean at Kingston Sportscars have all the air flow equipment and 20 years of experience to do your TR6 head. That is their speciality. I saw the results at the Triumph Races at Mid-Ohio in 1992, where a Vitesse with a TR6 engine and their head won 1st place over all the other TR's. And they don't use a really wild cam. Race cars with their air-flowed heads can idle smoothly.

After that race, I visited them in about 1993 and they took the time to explain it all to me. A wild cam will give more valve lift and a longer open time, but the ports and manifold passages need to be able the let the air get in and let the exhaust get out.

Don Elliott, 1958 TR3A


ll kinds of heads, but one of their specialities is the TR6 head.
Don Elliott

Supercharge it!! Leave the engine as it is- it should have 7.75 compression ratio, which is perfect for supercharging. Buy an Eaton blower, find a good machinist ( no probelm in Midlands!!) and away you go. 50% more torque from 1000rpm upwards will blow away the euroboxes with no trouble and without revving the guts out of the TR engine. It feels like having a V8, and pulls a gear higher than normal. Email me for more info- but correct the deliberate spelling mistake in the address first.
Peter Cobbold

This thread was discussed between 08/12/2002 and 15/12/2002

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