Club Triumph

Hi,

I have a few questions about tuning and would be grateful for any info:

-Does anyone know how I can get hold of the revised Tuning Manual by  Gareth Thomas?

-Does this include info on exhaust manifolds?

-Does the 125 hp TR6 have more torque than the early 150 hp one?

-What are the performance figures for the 125 hp version and what are  the pros and cons compared to the 150 hp version?

Many thanks,

Chris

Chris,

I answered your first question on the Sideways forum.

GTs book does have information about exhaust manifolds, though it is a bit biased.  He does (or has) produced some cracking 6-3-1 manifolds albeit pricey and not readily available.  There is quite a bit of information on manifolds on this and other forums.

The 125hp TR6 engine has more low-end torque than the 150hp but the latter has a higher peak torque further up the rev range.  The 125hp engine has pretty much run out of puff by 4500 rpm.  There are better cams out there now.

What car do you have and what are you trying to achieve (what will it be used for)?

Cheers

Nick

Hi Nick,

Many thanks for your replies. I haven't read your Sideways response yet.

I've got a 1971 TVR (Vixen) 2500. I hope you don't mind me using your forum as a guest. The car has the detoxed US spec TR6 engine. I think it's got 104 or 106 bhp and 117 lbs/ft of torque. It's just for road use and I'm considering the options for getting some more mid range oomph. I don't envisage driving it hard and doubt I'll be taking it beyond 5000 rpm. I don't know if a decent 6-3-1 manifold will fit in the TVR engine bay but if it will and if it frees up some torque it might be worth considering.

Which ever route I take I think the tuning manual would be a good place to start.

Best regards,

Chris

Hi Chris,

Might be worth letting us have the engine number prefix (MG, MM, CR or whatever) along with the head number (stamped on the top right hand side of the head alongside the rocker box) as this may give some more clues as to what you are starting from.

If it really is a US spec engine (and there were some variations on that too I think) it will have a mild cam and low compression.  Some US spec engines also had odd inlet port spacings on the head, which is something to watch out for, but if your car has always been a UK car then I think it is unlikely you'll find that.

A head skim to bring the compression up, perhaps a bit of basic port work in the head and a more interesting cam will work wonders.  I'd stay fairly conservative on the cam though - either a 308778 "132 hp" PI saloon cam or something like a Newman PH1 will give a nice torquey mid-range and good low speed manners.

As regards the exhaust manifold, I'm not familiar with the TVR engine bay but there are 3 main variations of the typical 6-3-1 manifold intended for either GT6/Vitesse, TR5/6 or 2000/2500 saloon - one will probably fit.....  Most if not all of the readily available ones are made by Pheonix in Cullompton though sold by most of the various specialists.  In any case, the exhaust manifold is probably not all that significant at the level of tune you seem to be wanting and you could also consider using the TR5/TR6 twin down-pipe manifold as used on the injection cars which iwill be cheaper and (maybe) easier to fit.

Another, completely different approach is to take advantage of the low compression and mild cam already fitted and fit a supercharger kit.  This is a popular mod for US cars.

Nick

Hi Nick,

Thanks for your reply - you've mentioned some things I'd never thought of.

The engine number is CC75***E. I'll get the head number to you tomorrow hopefully. The car already has the TR5/6 twin down pipe manifold. This was the standard fitting. It's got a single silencer which the previous owner told me is MGB. It has HS6 SUs and K&Ns. I haven't got the mixture right yet. According to the ColourTune plug it's too weak at tickover and too rich at anything above. I have some slightly weaker needles on order from BFS.

Good low speed manners and torquey mid range sounds like what I'm aiming for.

I had chat over the phone with Chris Witor a month or two back. He suggested a 219016 head skimmed to about 9:1 CR and an early PI Saloon cam. The cost of the head fully reconditioned and with Chris' stainless valves shocked me a bit. It was somewhere in the region of £1200 and I can't remember if that included the VAT. I thougt I'b best hold fire and consider my options.

I've just had an email from GT. He says there is a load of hype and BS regarding the 219016 head ??? The plot thickens! He also said he has built a manifod for a TVR last year. I'll need to find out exactly what car it was for. If the scavanging effect gives more mid range I may consider one. They also look nice!

The TVR is a UK car - never been exported according to the DVLA history.

Hopefully I'll get the head number to you tomorrow.

Thanks again for your help and advice.

Best regards,

Chris