Lotus Elan

Stromberg to weber conversion - pictures

PostPost by: promotor » Thu Aug 23, 2012 9:30 am

I'm looking for some pictures of stromberg head's that have been modified for use with weber carbs.

I have looked on Dave Bean and John McCoy's websites and of course they show the finished conversion but not what the head looks like after machining but before the manifold is bolted on.

I have a Stromberg head and am planning on doing something like this but i live in UK and can't afford to send the head to USA and back again while keeping the overall costs down. It'll end up costing more than buying a weber head. Still, with that in mind i want to mod a strommy head - if it costs the same as a weber head then that's fine, but no more.

So, if anyone has one of these heads and has some photo's then i'd be interested to see them. If you don't want to publish them on here and do want to share them with me you can email them.

If no response it looks like i'll be chopping the runners off and going from there!

Cheers.
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PostPost by: garyeanderson » Thu Aug 23, 2012 11:21 am

Some talk
elan-f15/stromberg-webber-head-t15214.html

A couple pictures of Omnitec and [email protected] versions
elan-f14/stromberg-head-conversion-t17640.html

I am sure there are many more but thats on you to take a look.
http://www.lotuselan.net/cgi-bin/search ... oom_sort=0

Gary
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PostPost by: pauljones » Fri Aug 24, 2012 11:40 pm

That sounds like a bit of a project,I thought Stromberg heads made a better spread of torque,zoo would it not be an idea to fuel inject the head instead?

I'm a BIG fan of efi now mines up and running.

Paul
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PostPost by: rgh0 » Sat Aug 25, 2012 4:16 am

A couple of shots showing some of the details of the McCoy conversion. John has done a lot of work to keep the strength in the head with the curved CNC machining of the matching faces and with the substantial base plate and bolting of the manifold to the head. The CNC porting inside the manifold is equally impressive.

None of this is easy to do without access to precision machine tools and a lot of skill. Easier to just send a head to John for conversion I think. However if you have the skills and equipment and a lot of time to generate the needed CNC setups and tooling and jigs it would be an interesting challenge to cast up a manifold and then machine it to match a machined head in this way. The cost in the end would be more and the outcome a lot less certain I think however.... so not for the faint hearted and not because you want to make money

I and a couple of Lotus racing friends have bought close to 10 of Johns head conversions now and never had a problem with the conversion over a lot of track miles in the last 10+ years in big HP and high reving competition engines. John has done (and continues to do) a lot on development work on the porting also and his heads benefit from that in addition to the conversion itself.

cheers
Rohan
McCoy Head (1) 51.jpg and
McCoy Head 51 (2).jpg and
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PostPost by: promotor » Sun Aug 26, 2012 3:02 pm

Thanks for the responses all !

Gary - much help there and some good "discussions" going off!

Paul - I have thought of the fuel injection method - i'm sure the throttle bodies would still need a balance bar between the two inlets to stop "charge robbing" unless injector bosses were welded onto the four individual runners closer to the cylinder head ie direct injection.
Very well worth a look and a lot cheaper than 4 DCOE type throttle bodies. Keep us posted if you go ahead!

Rohan - having now seen the profiling of the manifold that Omnitech do i agree that this is better than anything that i would be able to manage and will have another re-think on whether to send my heads away.

I notice that the weber manifold has a slightly upswept/curved look about it - do the actual inelt ports themselves follow this curve or is it just the outside casting?

Do you now just run a separate collector box for the crankcase fumes/oil or into one central catch tank for all?
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PostPost by: rgh0 » Tue Aug 28, 2012 8:16 am

You can see castings of various port profiles i have posted- search something like weber porting and you should find it. These show the curve of the internal ports for the Omintech heads. The casting posted is for an earlier version of his race porting, I have not yet got one of the latest head i just got from John.

Without the vent chamber in the head I just vent the engine to a catch tank from a connection on the cam cover on the centre front between the cam sprockets. This was the normal vent location use by many race twin cams previously anyhow and you get good oil disengaging in this location so very little carries over into the catch tank


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PostPost by: promotor » Wed Aug 29, 2012 7:31 pm

Thanks Rohan - i'll take a look!
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