stromberg head conversion

[del@ace]

have now carried out stromberg head conversion, to fit webbers or delortos, , if any one is interested in this service , the head has been converted and has a removeable inlet manifold , the head i am doing for my own car is at the stage of fitting hardened valve seats , with 42mm inlet valves and 38mm exhaust , , , using serria cosworth valve guides, ,iam more than happy just doing the basic conversion, should anyone want it price would start at ?400 +manifold at ?150. , also do a adapter manifold for a single 45 webber conversion with excellent results at knockhill , cheers

[garyeanderson]

Hi Del

This may or may not be a repeat of your last post on the single weber. You may want to get some photos posted soon as that is what folks are going to want to see.

Gary

p.s. - take a look at
http://www.omnitech-engineering.com/auto/strom.asp

short article from Lotus Limited newsletter
http://www.omnitech-engineering.com/ima ... rque_2.pdf

[del@ace]

here is some pics conversion with removable manifold can be removed complete with carbs attached

[steveww]

Looks like a proper job

[miked]

Del, do you always do the head works or will you supply the manifold for another machine shop to fit?

Mike

[GrUmPyBoDgEr]

I agree with Steve, from your photo's the work looks great.
What do you use for a gasket between the manifold & cylinder head?

Cheers
John

[del@ace]

no problem with the gasket , could use paper or in the middle of getting cometic to make as needed, this is why i have posted this conversion , i know omnitec do a conversion i have changed it only thought it could be improved on , i think what they do is excellent , , any way just trying to workout or gauge interest, turnaround would start at around a week for the basic machinig and fitting adapter plate , then porting would take longer also do a longer inlet manifold for more torque which means carbs are further away from head or the short manifold for high revs, i will be trying both manifold on the rolling road to do a back to back test but i am a few weeks away from that at the moment, but if there is a bit of interest i will press on , thanks for looking

[del@ace]

no problem with the gasket , could use paper or in the middle of getting cometic to make as needed, this is why i have posted this conversion , i know omnitec do a conversion i have changed it only thought it could be improved on , i think what they do is excellent , , any way just trying to workout or gauge interest, turnaround would start at around a week for the basic machinig and fitting adapter plate , then porting would take longer also do a longer inlet manifold for more torque which means carbs are further away from head or the short manifold for high revs, i will be trying both manifold on the rolling road to do a back to back test but i am a few weeks away from that at the moment, but if there is a bit of interest i will press on , thanks for looking

[rgh0]

Hi Del

From the photos it looks like you weld a mounting plate onto the side of the head after machining off the Stromberg inlets. I presume you do this to get sufficient metal in the areas where you have located the manifold mounting studs. Have you had to line bore the cam tunnels and face the head after this welding?

cheers
Rohan

[del@ace]

hi no problem with cam tunnels no need to line bore , yes the head will need refaced but havent shown that because im in the middle of doing valve seat inserts, will put pics up when i feel im happy with it , cheers del

[garyeanderson]

I sent off the link to the topic at hand to John McCoy who has been doing these conversion for a number of years.
http://www.omnitech-engineering.com/auto/strom.asp
I first heard of the project from my Friend Kenny Duclos back in 1996 or so, he had a prototype for fitting and testing I believe. I didn't meet John until last year when I was attending the Monterey Hiistorics in August. John was there Tending to Rawlson Can-Am car that was racing that weekend
http://www.omnitech-engineering.com/aut ... on2001.asp

We had about 20 minutes to talk engines, LoCorts and the like.

So John has done a few Stomberg head conversions and he offered the the following

"Hi Gary;



Well, unfortunately, this fellow is probably in for a tuff, possibly expensive learning curve, depending on how many people bite. My first attempt at this conversion was to do exactly what he has done, however, after several dyno pulls, the manifold loosened, and hair line cracks appeared in stress areas under the cam tappets. If you look at an original Weber head, the inlet ports aid in supporting the heads structure & stiffness, this is derived from the vent box, and some ribs, if you don?t re-establish this support, the head will stress relive under load, and you will have problems.



So, I designed a manifold which mounts on a 3D CNC machined surface, and a mirror of the surface on the manifold, I designed into this mounting plain a large fillet under the tappet intersection, and angle studded the manifold into the fillet, thus establishing support from the side loads from the tappets.



I made the mistake one time to sell a manifold to someone to mount, I amplified the above, however, I think because he was using a manual mill, and wasn?t able to machine the necessary fillet, and mirror fit to the manifold precisely, it also cracked, and the manifold loosened.



There have been those whom have welded on ports, this method creates so much heat, the head is done after the ports are welded.



So, I guess the moral of the story is, there is allot more than meets the eye, tan?t as simple as it looks.



Perhaps, since you?re a neutral party, you might be able to enlighten the readers as to what I discovered in my development, or perhaps, just elude to the point that the conversion is a bit more technical than it appears.



Merry Christmas



John"

Rohan posted these photos a while back on another forum and I guess they might as wall get posted here. Take a look at how John has done it, may save you some time effort and lastly aggrevation.

Gary

[del@ace]

i suppose a new kid on the block is always going to get a hard time , almost treading on toes , cheers del

[Elanintheforest]

Del, Gary has taken the time and trouble to point out , with the help of someone who's been doing this for years, where your ideas may be improved. His words..."Take a look at how John has done it, may save you some time effort and lastly aggrevation".

If you are so arrogant that you think that this is giving you a hard time....you ain't seen nothing yet.

Mark

[rgh0]

Hi Del

The mouniting plate you have welded on the machined face may achieve the needed reinforcement for the cam tunnels and manifold mounting bolts that John describes as critical to avoid problems overtime.

Keep on with the development - love to see the dyno results when you have finished - especially the differences between the short and long inlet runners. Lotus orginally started with signficantly long runners on their first development engines and then shortened the runners for the production engines to enable then to fit in the Lotus Cortina engine bay.

cheers
Rohan

[CBUEB1771]

One "feature" common to both John McCoy's and del@ace's conversions are that the standard crankcase vent with oil drop out box are cut away from the cylinder head. Therefore the crankcase needs to be vented from somewhere else, most commonly the front of the cam cover. Nothing fatal, just another task in completing the conversion. I have to add that nobody is trying to step on del@ace's toes. I applaud his initiative and skill. However John McCoy has learned quite a bit from many, many computer simulations, flow bench and dyno runs. I have to admit some bias here as I have just gotten my original Stromberg head back from John after conversion. I am just starting on the build-up of a 1700cc long stroke engine based on this cylinder head. The goal is lots of torque between 2500 and 5000 rpm to suit my road-use-only +2S. I will start a separate thread to document this project. A final note about inlet tract length. John McCoy deliberately retained the standard inlet tract geometry in hopes to make his conversions acceptable to the FIA for historic racing. I believe he has been successful. Change the geometry and the FIA frowns sternly.