Jim,
The new Iridium's to my mind were too protruded for extensive use with high combustion temperatures and i spent a lot of time chasing NGK Racing for confirmation of suitability...
Eventually after much hard slog between different departments and even countries, and arguing the toss with poxy salesmen, i recieved this from someone who seemed to understand my problem at NGK racing Technical department:
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Stewart
The R7435 type is more projected than the R7235 type, the R7436 type is
less projected and is the best one to use for Cosworth engines and it is
iridium, they do not have a lower limit.
The R7435 has a conventional hook electrode, the R7235 also had a
conventional hook type but not as projected and the R7436 has a small
electrode on the side of the top of the plug, it might be easier to send
you a racing brochure so that you can see the different electrode
configurations.
But for people enquiring about the cosworth plugs we are suggested the new
iridium R7436 type which is the safest.
Regards.
Technical Department
To which i replied:
Dear Sir,
The projection on thje new 7434 to my mind is excessive for use at prolonged periods with in excess of 150bhp per litre where as the old projection (R7234/5-9) should have safely transfered enough heat to the head to deal with in excess of 300bhp per litre safely. Given we have very few sub 150bhp per litre Cosworth YB powered cars in the UK what do you suggest i use as a replacement for the R7234-9 as i still believe your catalogue to be incorrect with its advice for this application. I have been a bulk purchaser of this plug for many years and am now left with a hole in my product range that i would like to correctly fill with another NGK product if possible. Many thanks in advance for any help you can give me on this matter.
Best Regards,
Stewart Sanderson
(Motorsport Developments)
Dear Stewart
On this engine it seems that the projection should be the same as the
older equivalent. The catalogue does indeed suggest a more protruded type and this is indeed incorrect for high powered applications. We have ordered a less projected version of R7435 types which is R7436, but we are not due delivery until the middle of August and we do not have any of the old stock left.
Sorry for any inconvenience and sorry I could not be more helpful.
Regards.
Technical Department
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So there you have it.. keep looking for the R7234/5 - 9 Jim
