webber carb conversion stromberg head

[del@ace]

hi all tried to upload pic but camera has to many pixels , so have found club lotus member that took pics on sunday at knockhill,
email ,. joe [email protected] , joe will gladly email pics , that should sort that , cheers del

[del@ace]

hi all tried to upload pic but camera has to many pixels , so have found club lotus member that took pics on sunday at knockhill,
email ,. [email protected] , joe will gladly email pics , that should sort that , cheers del

[CBUEB1771]

hi all tried to upload pic but camera has to many pixels

Oh deary, deary me, this is always such a bother. Maximum file size here is 768 kb with a further limitation of something like 1024X680 pixel dimensions. It only takes a moment or two to resize the image using the software that came with your camera or is native on your PC. Images come out of my camera in the 5 Mb range so I do this fairly often.

[garyeanderson]

instructions are here on this site
http://www.lotuselan.net/forums/viewtopic.php?t=13052

If you want you can get an account on photobucket.com or one of the other photo hosting site and link with
( [img])%20([/img] )
these tags are above the message body where you type in the text.

baring that mail them to me at [email protected] and I'll resize and post either here or photobucket. I am not trying to be an a$$hole, as I don't really need the practice.
Words just don't explain it properly when photos can.

[types26/36]

For anyone useing M/S XP there s a handy little tool for image resizing on this web page (about halfway down)
http://www.microsoft.com/windowsxp/down ... rtoys.mspx

[mct340]

I just completed a total rebuild on my S4.
Stage 111 engine by Omnitech (John McCoy)
Stromberg to Weber conversion
total drivetrain upgrade to racing spec
you name it I did it
huge $$$$

Result:
engine dyno peak hp 155 @6500rpm
peak torque 148 ft-lbs @4600
chassis dyno max hp 108.6hp@5300rpm
max torque 110.9@4100

[steveww]

Just a carb change should not make that much difference as the Webers flow the same as the Strombergs. The main limitation is the flow of the head. The Weber head flows straight from the carb to the cylinder. The Stromberg head has a kink in this flow not to mention that at certain points in the combustion cycle two cylinders are drawing from one carb. However due to the way CV carbs (Stromberg) work the gas flow is quicker which gives the Stromberg engine better torque. The throttle response of the Weber will be better as it has acceleration jets and the Stromberg does not. However with a little tweaking this difference can be largely overcome.

Still want to see some pictures though

[ppnelan]

BHP = Brochure Horse Power (Graham Arnold)

Matthew

[rgh0]

I
Result:
engine dyno peak hp 155 @6500rpm
peak torque 148 ft-lbs @4600
chassis dyno max hp 108.6hp@5300rpm
max torque 110.9@4100

155 hp on an engine dyno at 6500 rpm from a McCoy stage 3 head is about what I would expect from a 1600cc twin cam with a road fuel compression and suitable cams . The chassis dyno number is a little lower than I would expect as the difference is typically around 30 hp from the egnie dyno 47hp is bigger than normal. However lots of factors can influence this difference so its not impossible.

The chassis dyno peak is always lower than engine dyno as near the peak the frinction losses are increasing faster than the engine output so it starts dropping earlier than on an engine dyno. 1200 rpm lower is again a little bigger than i would expect but not impossible. Tyre pressure can make a big difference on a chassis dyno result and if to low greatley increase the losses

All said though its this sort of data that make me ( and others) question the achievement of 132 bhp (either at wheels or flywheel) by just bolting a new carb and add on manifold onto a stromberg head

cheers
Rohan

[msd1107]

mct340,

What was your engine capacity?

155 hp @ 6500 rpm on a standard 1558 cc TC is a BMEP of 199 psi, 13.7 bar. The torque figure of 148 ft-lbs is a BMEP of 235 psi, 16.2 bar.

These are really surperlative figures. As a point of reference, F1 engines get a little over 200 psi at peak power, 220 at peak torque.

Even a long stroke 1700 cc motor will be at 182/215, still great figures.

David
1968 36/7988

[bcmc33]

I asked Del for a picture - and this is what I received.

[steveww]

Looks interesting. Not sure if the bar just after the carb is a balance tube or not?

Initial thoughts are that there is quite a kink from the carb to the head and this can not help the flow.

IIRC he said he was using a Weber 45 DCOE which about matches the CD175 @ 44.5mm. Can't see that the flow would be much better than a pair of Strombergs. Throttle response may be better due to accelerator pump. However this can be tuned in the Stromberg. Torque may not be as good as the Stromberg due to lower velocity.

Still and interesting solution

[mct340]

David,
Bore : 3.250in Stroke : 3.056in
Cyl Vol : 415.44cc Total vol: 101.4ci
Intake valve 1.562 Exh valve 1.312
comp ratio 10.50
combustion space 43.73cc
cam mccoy440_250

All courtesy John McCoy whom we should be very thankful for and keep
sending him work so he stays in business for ever.
Cheers,
Mike

[msd1107]

Thanks for the info, Mike.

I'm sure John has his reasons, but it is interesting he stays with the 1.562' intakes with a long stroke motor. 6500 rpm is definitely at the upper range for that valve size.

If he had gone to the 1.625" valve size, with his cam, peak power might have gone up 4-500 rpm to give you maybe 165 hp.

But I bet you are quite happy with the performance you have now!

David
1968 36/7988

[del@ace]

so theres nothing to be gained on fitting a webber carb ? i can tell you its like calk and cheese, first of all strombergs are crap, , diaphrams that get pin holes , etc , and whats the point of putting a pic of four motor bike carbs on a webber head , on this topic , your not allowed to run the motor bike carbs in the classic sports and saloon car championship, , and further more i know my adapter manifold works , the end