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1990 998 John Cooper Conversion Cylinder Head Query

Started by cooperd70 , Feb 06 2018 08:45 PM

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9 replies to this topic

#1 cooperd70

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Posted 06 February 2018 - 08:45 PM

I have an original JC conversion that has been fitted to the 1990 Flame that I own. It has been on the car since the car was purchase from Rover (Swindon) in Nov 1990. The head is stamped 786_ 0.015 25.5_ _ (I assume cc) with last set of numbers disappearing under the rocker cover starting 7.3_ _ and I can just about see COOPER UNLEADED on it as well: The _ are digits that are hidden by the rocker cover/gasket.

I wondered if anyone has any information on what the inlet port size is on these heads? Or were different heads used for these kits which means the ports vary in size? (sorry I don't have the head number to hand). I believe that they were made by Janspeed for Cooper Cars, but have also heard that companies like MiniSpares were also commissioned to work some of them. I am also led to believe that they were classed as Stage III heads?! Am I wrong?

I know that there is a JC Conversion Facebook page, but I have never been a Facebook member {and never will be}. So can't ask the guys on there, unless anyone on here knows another method on contacting the members on the FB site {maybe one is a member here}!

I'm thinking of fitting the Maniflow inlet manifold in the near future and they supply two different port sizes for twin 1 1/4 SU's and I don't know which one I would require. Unless I strip the head down and measure it prior to purchasing.

Any info/leads would be appreciated.

Cheers.

Edited by cooperd70, 06 February 2018 - 09:05 PM.

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#2 Guest_minidizzy_*

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Posted 07 February 2018 - 12:47 AM

There was only one type of Cooper conversion for the 998cc engine. There may not be any particular significance in the head number. The kit was developed with Jan Odor (Janspeed). It is true that other companies did produce heads for the kits though not MiniSpares. The heads made by others were to the original Cooper/Janspeed specification and not just substitutions of their own.

The inlet valve was 32mm and the exhaust valve 26mm. Compression ratio was 9.8 to 1.

I am not sure about the stage III category. I think it probably is but the term has different meanings to different suppliers.

The conversion was more than just the head. The inlet manifold was an essential part of the kit as developed by Cooper/Janspeed so I would be inclined to keep it as it is if it is still there.

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#3 cooperd70

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Posted 07 February 2018 - 06:13 AM

Thanks Minidizzy.

Thanks for the information. I am specifically looking for the diameter of the inlet port on the back of the head and not the diameter of the inlet valve (unless these dims are the same). Looking to replace it as part of further tuning as have heard the standard item isn't great and had heard of minor improvements over the original when using the Maniflow part.

Can anyone.comment on the Maniflow/have one fitted to their car?

Thanks again.

Edited by cooperd70, 07 February 2018 - 09:08 AM.

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#4 Guest_minidizzy_*

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Posted 07 February 2018 - 12:02 PM

Sorry I hadn't read more carefully what you were asking. I cannot find any information about the inlet port diameter. As far as I can see this is unchanged from the standard 998 head. The Janspeed heads were standard heads polished and ported and suppled on an exchange basis.

I was a bit incorrect about the stamped numbers. While the 1275 conversions only had a four digit serial number and the name Cooper, the 998 heads had more numbers as you quoted, most of which mean nothing to me. I have a photo, which is similar to what you describe but with 0.018 instead of 0.015. The last numbers are the date so 25.5__ is 25th May 89 or 90.

Given the enthusiasm for original Cooper conversions I think it would be a pity to break the integrity of the original set-up. I don't think the inlet manifold was a "standard" item and Janspeed did have a good reputation. But it is your choice.

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#5 cooperd70

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Posted 07 February 2018 - 01:14 PM

Again many thanks Minidizzy. I'm starting to think along the same lines as you to be honest.

Funnily the head on mine isn't the Janspeed blue, but a light greeny yellow colour.

On a side note I am led to believe that it still has its original Janspeed LCB and exhaust system, albeit very rusty (surface rust at present - I hope). It will need replacing sometime and thought of doing the inlet manifold at the same time.

I was hoping that you could still get the Janspeed full system but they are no longer made. I have been told if you have an original full system and you can find another nine people interested Janspeed will remake in either mild steel or stainless. If mine is original is anyone out there interested? I'd not be handing the system over until next winter though as I'm looking forward to some driving this year. If anyone can post this info on the JC Conversion Facebook page it may generate some interest.

Edited by cooperd70, 07 February 2018 - 01:18 PM.

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#6 cooperHH

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Posted 07 February 2018 - 07:29 PM

hi can you send me a pm with photos? thank you

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#7 cooperd70

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Posted 07 February 2018 - 08:26 PM

cooperHH. Sorry pictures of what?

Edited by cooperd70, 07 February 2018 - 08:26 PM.

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#8 Guest_minidizzy_*

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Posted 08 February 2018 - 12:45 PM

Cooperd70 - Not all Cooper cylinder heads were blue. The original brochure for the 998 conversion shows it dark grey. Also some of the early 1275 heads were green and that may have been true for 998s.

You are correct about Janspeed remaking the original exhaust systems to order in batches of 10. It took a bit of persuasion initially but the RSP Cooper Register had 10 sets of the 1275 version made in stainless steel, one of which is on my car. Now Janspeed seem to be more open to the idea and I think they remade some for the injection S conversions.

I haven't heard any discussion on remaking the 998 versions but if I find out I will let you know.