Lotus Elan

Stromberg Intake Manifold

PostPost by: dlbarnes1 » Wed May 25, 2005 4:42 am

Refer to Miles Wilkins "Lotus Twin-Cam Engine", page 37, in regard to the fork that divides the flow to the ports on Stromberg heads. He states that it was found that blunting off the razor edge of the fork facilitates flow balance.This infers to me that this was a matter that would have been carried out in production.

However, on my Stromberg head I have observed that there appears to be a razor edge on the fork. I'm preparing to do some rebuild work on the head and I'm wondering if I should take a grinder to that razor edge.

I would appreciate any information or thoughts on this matter.
David 72 Sprint DHC
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PostPost by: miked » Wed May 25, 2005 7:51 am

David,

I read the same thing and blunted mine off when I restored my car. I just used a scraper and took the sharpness off. I dont know the technicalities of air flow division but it sounds right and my Stromy S4 SE standard trim goes like stink.

I used the Wilkins book for the whole engine build and was well pleased. The only thing i thought he should have said a bit more about was the rear main seal housing and centralising it more accuartely to prevet misalignment and leaks. Mind you he probably expecetd a level of skill to rebuild a TWINK.

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PostPost by: steveww » Wed May 25, 2005 5:22 pm

Most heads have been messed with in their 30+ years of life. Perhaps in the past someone did a bit of a head job and thought they were improving things by sharpening up the divide. A bit of work with a burr will soon have it back to shape.
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PostPost by: lotusanglia1965 » Wed May 25, 2005 9:13 pm

All three of the stromberg heads i've had/worked on had the sharp divide. I too blunted it with a die grinder,will blame Miles Wilkins if car now goes slower!Actually i think it has more to do with a smoother idle than ultimate power.
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PostPost by: rgh0 » Thu May 26, 2005 9:35 am

The reason for blunting off the edge is to ensure an even flow split to each cylinder. A sharp edge is very hard to align up precisely with the air flow. As a result the flow will separate on one side and flow smoothly on the other. This will result in unequal flow distribution. A blunt edge ensures flow separation on both sides and even distribution to each cylinder. Total flow is actully less but it is evenly distributed and produces smoother running as a result

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