Lotus Elan and Lotus Elan Plus 2 Forums

I have been reading about Keith Franck's exploits on improving the tune of the Weber carbs - very impressive.

I also know that for the dear old Stromberg head (count my +2 car in on that) there is a ceiling on the amount of air you can get through the head, so you are effectively limited to about 130 bhp with a following wind and a high compression setup (200psi on the pistons).

My setup with a low compression head (170psi) runs very smoothly, with CLP2 cams and richer needles. Acceleration is also smooth with no hesitation or misfires once warm. My only measure of performance is a 50 to 70 time of 4.5 seconds in 4th gear on a 4 speed - whatever that means.

I think I have gone as far as I can without changing to Webers. I have a small bore manifold but am not sure if going to a larger bore is worthwhile.

I am happy enough, but wondered if there have been any developments or ideas around apart from upping the compression.

Dave Chapman.

Hi Dave - the archives cover a range of discussions on this topic but if I was trying to get the most out of a Stromberg and around 140hp plus at 6500 rpm in a 1600 cc engine should be possible. I would try

1. High lift say .410 to .440 and short duration cam - around 280 degrees seat to seat. If you really want to get fancy talk to the MG racing guys about the scatter timing cams they use to minimise the overlap of 2 valves drawing on the one siamese port and try to get some twink cams made to the same principles
2. Big inlet /exhaust valves and porting to suit
3. Big bore exhaust.
4. 10.5 : 1 comp ratio

regards
Rohan

Thanks Rohan,

There's food for thought - especially the cam idea.

In my zanier moments I have thought about raising the compression ratio by introducing something that intrudes into the combustion space such as a long reach spark plug but I doubt is anything is available (you would file down the protruding thread or you would never get the plug out again as it carbonized).

I will just take a few tablets to calm myself down

So a very rough costing would be (off the top of my head, assuming you do the labour):

1 Cams ?200 each (?400)
2. Large bore manifold ?500?
3. Intruder pistons ?500
3. Head work ?1000 using a contractor?

That comes to roughly ?2400 - an interesting alternative to a weber conversion, which might be:

1. New cams ?200 each (?400)
2. Omnitech or Burton Power to replace or convert the head - say ?2000-3000 - just a stab at this cost
3. Let's say intruder pistons are not needed.
4. Large bore manifold ?500?
5. Two reconditioned Webers ?600 maybe

That comes to ?3500-4500, which could give you 150-160 BHP.

There we go - there may be life in Strombergs yet...

Dave.

At 6500 rpm in a well done Weber head on a 1600 cc motor you will be lucky to get more than 150 hp. The Stromberg will only be a little less if done to an equivalent level. You need a steel bottom end and 8000 rpm to get up around 160 hp plus in a 1600 twink.

The big advantage of a Weber head for a road car is the carbs look more impressive
cheers
Rohan

I have read that the SE Stromb set up was the best set up giving fantastic torque accross the range ref miles wilkins. Makes me wonder about the flat low revs with my webbers.
I ve all ways wanted to post on here the question why does every body go to webbers? Was it a quick fix for more BHP. Little did they know the trade off for the low down torque
I would like to drive a Stromberg car for a comparason as well as a Dellorto setup like on the last of the big valves.
With a lot of traffic on the road speed bumps etc etc its hard work allways driving around at 3000 rpm!! tough on the clutch as well..