TVR2500 - Alternative carburettors

[matchless_mike]

I have a 1971 TVR 2500 which is running on its original Stromberg carburettors. The car runs ok but I feel that the carbs are holding the performance back. Plus no one seems to have a good word to say about these Strombergs with their emissions control restrictions etc so I have thought about upgrading to a pair of either SU HS6 or Weber 32/36.

Can someone advise on which may be best ? From a price point of view they are quite similar.

[jellison]

matchless_mike said:

I have a 1971 TVR 2500 which is running on its original Stromberg carburettors. The car runs ok but I feel that the carbs are holding the performance back. Plus no one seems to have a good word to say about these Strombergs with their emissions control restrictions etc so I have thought about upgrading to a pair of either SU HS6 or Weber 32/36.

Can someone advise on which may be best ? From a price point of view they are quite similar.

there was a set of second hand webber 40's and manifold on ebay (uk) last week. Might still be there. Think 40's is best for a road 2500 engine with a moderate cam.

Forget any of these twin carbs on a six pot engine if you want any more performance than standard. They kill the performance even over the UK Spec PI on the TR's.

Twin HS6's no way. Tiny - these are fine on a TR4 as a 4 pot but not a 6 of larger size. (My 4 racer used to have twin HS8's!).

Webbers or Pi (not really an option on thhe TVR though.

[Slow M]

I had a set of SKs that were incredible! Their progression circuitry is an improvement over Weber DCOEs in a road going scenario. Also, Richard Good does a triple manifold that I'd strap SUs to. Strombergs are st smog carbs, kill 'em all.

[jellison]

SK's do ring a bell.

Triple HS6's could be good.

I just like webbers!

http://jrellison.blip.tv/file/3758148/

[itiejim]

PI throttle bodies converted to EFI?

A few folk in the Triumph work have done it successfully.

[Slow M]

SKs also have external float adjustment. Nice to have.

Some people have done Keihins.

For reasonable cost/benefit, good looks, simplicity...I'd do these.
http://www.goodparts.com/shop/index.php?categoryID...

Edited by Slow M on Thursday 19th August 22:21

[jellison]

SLOW - they look good.

[m2500tvr]

I haven't had any problems with the Stromberg CD2SE carbs, but they aren't so exciting (they're VERY easy and reliable, but not exciting) - and neither is the TR6 engine, sadly. It's a long way from an alloy 2L Cosworth BD (or even the Lotus-Ford Twin Cam in my Elan). Is there really anything, quantitative or qualitative, to be gained by just switching carbs on an otherwise stock TR6 engine? I see many claims of performance improvement, but nothing quantitive. I mean, is that stock motor with it's crazy low CR, side flow head, port sizes, inlet and exhaust manifold, cam profile, combustion chamber shape, valve size, etc. gonna see a real hp or torque gain (agreed that you would see less fiddly issues with different carbs, like even a set of SUs ).

I have had some more recent experience fitting an MBE PI system to a Renault engine (GREAT motor) in a Lotus Europa. About 200hp at the flywheel from a very lightweight alloy 1.8L 4 cylinder pushrod motor. Simple'ish stuff, though the tuning was sorted on a dyno, which made things relatively easy, but it could be done without the dyno. The cost wasn't so different from a Weber carburetor setup. I like Webers and their clones just fine, but PI is kinda of a real, doable, even cost-effective option.

Edited by m2500tvr on Friday 17th September 21:32

[Slow M]

m2500tvr said:

I haven't had any problems with the Stromberg CD2SE carbs, but they aren't so exciting (they're VERY easy and reliable, but not exciting) - and neither is the TR6 engine, sadly. It's a long way from an alloy 2L Cosworth BD (or even the Lotus-Ford Twin Cam in my Elan). Is there really anything, quantitative or qualitative, to be gained by just switching carbs on an otherwise stock TR6 engine? I see many claims of performance improvement, but nothing quantitive.

I have had some more recent experience fitting an MBE PI system to a Renault engine (GREAT motor) in a Lotus Europa. About 200hp at the flywheel from a very lightweight alloy 1.8L 4 cylinder pushrod motor. Simple'ish stuff, though the tuning was sorted on a dyno, which made things relatively easy, but it could be done without the dyno. The cost wasn't so different from a Weber carburetor setup. I like Webers and their clones just fine, but PI is kinda of a real, doable, even cost-effective option.

Yes, the qualitative gains are that the st Stromberg CD175-2s go where they belong, to the scrap yard. They have circuitry specifically designed for PCV recirculation. They were specifically designed for use in pollution controlled vehicles and made with terrible quality plastic and rubber parts that require constant attention and don't survive long in a hot engine compartment. Either you actually give them the perpetual attention they need or you aren't aware that the diaphragms have torn and the stupid decel valves are constantly open. By comparison, SUs are simply high performance carbs. Sorry if I'm coming off like an asshole here but they relly are st. BTW are there lots of needle options still available for either Strombergs or SUs?

[jellison]

You can get good gains by putting on a set of webber 40's (x3) but you would have to do a few minor tweeks to get any real benifit (skim the head for about 10.5 to one, fast road cam and maybe porting the head if you can stretch), this woul give about 180bhp (up from about 140bhp on a 150 TR6 Pi lump or less than 120bhp from a Strangled US twin carbed 2500.

You can make them go though. COST ALOT though. Webbers! Clicky...

[Slow M]

jellison said:

You can get good gains by putting on a set of webber 40's (x3) but you would have to do a few minor tweeks to get any real benifit (skim the head for about 10.5 to one, fast road cam and maybe porting the head if you can stretch), this woul give about 180bhp (up from about 140bhp on a 150 TR6 Pi lump or less than 120bhp from a Strangled US twin carbed 2500.

You can make them go though. COST ALOT though. Webbers! Clicky...

I still have a head like that. Big stainless valves in bronze guides, ported, polished, port matched, combustion chambers contoured and mirror polished, high rate springs good for high lift cam, with aluminium retainers. It was fun!

[m2500tvr]

Slow M said:

Yes, the qualitative gains are that the st Stromberg CD175-2s go where they belong, to the scrap yard. They have circuitry specifically designed for PCV recirculation. They were specifically designed for use in pollution controlled vehicles and made with terrible quality plastic and rubber parts that require constant attention and don't survive long in a hot engine compartment. Either you actually give them the perpetual attention they need or you aren't aware that the diaphragms have torn and the stupid decel valves are constantly open. By comparison, SUs are simply high performance carbs. Sorry if I'm coming off like an asshole here but they relly are st. BTW are there lots of needle options still available for either Strombergs or SUs?

Danged, Slow, I hear ya I didn't say I was fond of the Strombergs, nor that they're performance carbs, just that I have found them to be easy to service and trouble-free. Rebuild them carefully once every few years, check them at every seasonal tune up, give'em a quick peek whenever you're under the bonnet. This has been the drill for me since I kinda "got them" 25'ish years ago with my M, and other Stromberg-equiped Brit cars. I'm familiar with, understand, and also have hands-on experience with the issues you list, but I haven't seen these things effectively in forever. Most the use my M has seen is on the track, so the car gets used quite hard. No doubt about the SU being as you say. Even a pair of HS6s would be better than the CD2s. Yes, for the SUs there are lots of needle options available, far more than the Strombergs. As I'm sure you know, the SU carbs were/are applied effectively as performance carbs and the tuning options meet the requirement.

A quick additional note on the fuel injection systems... The MBE system fitted to the Lotus Europa I mentioned provides more than just fuel delivery, but a rather complete, flexible, tunable engine management system. Not recommending, just mentioning...

Edited by m2500tvr on Friday 17th September 03:26

Edited by m2500tvr on Friday 17th September 21:34

[jellison]

It is not "Right" for a Six to have a "Pair" of any carb on it. They need three SU's (believe there is a manifold to take 3 HS6's out there), or get some webbers on the thing, Especially if it is mainly used on track and hard. Slows Head sound likes a good addition too.

You only live once.

You can never have enough power under you TVR bonnet.

Slow - my initail dyno numbers have gone UP a good bit - it is in the box, and hopefully on a plane over the weekend

[pumpkin]

If you are going to have to buy new carbs and a manifold why not go straight to a supercharger kit? Good fun, very good torque and no fiddling about trying to balance three carbs!

[Slow M]

pumpkin said:

If you are going to have to buy new carbs and a manifold why not go straight to a supercharger kit? Good fun, very good torque and no fiddling about trying to balance three carbs!

With Weber side draughts that "fiddling" is a one time job; check it every couple of years for insurance. That's why they're are on a common shaft. SUs and Strombergs are always on flex connectors so they need more attention.

Saw a TR6 with 6 Keihins this summer.