Sterling carb (modified Nikki)

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biznatch
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Sterling carb (modified Nikki)

Post by biznatch » Sun Feb 09, 2014 1:29 pm

Has anyone on here modified the Nikki carb to flow more CFM, for street and occasional track day use? I've read about the Sterling carb mods and they seem to be an ideal alternative to a RB Holley kit (@about £950 from RB..)
I have a spare carb at present and I'm considering giving it a go or sending it to someone else to machine and modify the venturies. Alternatively I could source a genuine Sterling carb, but these seem to be scarce. Any thoughts?

Lucky
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Re: Sterling carb (modified Nikki)

Post by Lucky » Sun Feb 09, 2014 2:06 pm

From memory, I believe MR TOOL has modified Nikkis to run on cars with more porting, and IIRC Derek with the WankelPop had one on his bridgeported motor that may have been modified by Era. So it can be done. Whether it can be done without sacrificing idle and low driveability, I'd have my doubts but stand to be corrected by those with greater experience.

I was recently talking to Racing Beat about their Holley upgrade, but they advised it won't fit on a right-hand drive car. The brake servo and master cylinder are massively in the way, to the point it's a major job of work to get clearance. Hence my going down the Weber route after all

TOOL
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Re: Sterling carb (modified Nikki)

Post by TOOL » Sun Feb 09, 2014 4:55 pm

I haven't modified a Nikki, but I'm in discussions to acquire a modified one.
I've got a couple of IDAs so never needed to.

Derek's carb was standard when I rebuilt it for him. Whether Era did anything after that I don't know.

Sterling carbs are not active any more afaik.
Back in sunny France

Lucky
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Re: Sterling carb (modified Nikki)

Post by Lucky » Sun Feb 09, 2014 5:52 pm

Ahhh, my mistake. I was sure that Derek's carb had been opened out at some point, but you clearly know better. Must have been confusing myself. I'm sure I remember having a conversation with Jason at Super 7 about it when we discussed my engine build. As I recall, it went along the lines of he'd done it in the past but it was a lot easier and more efficient to upgrade to a better (more suitable) carb

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spirit r
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Re: Sterling carb (modified Nikki)

Post by spirit r » Sun Feb 09, 2014 6:10 pm

http://m.rx7club.com/showthread.php?t=964025

My Rx 7 full bridge port with modified nikki : primary 1,23mm secondary 1,70mm
viewtopic.php?f=4&t=1118&start=50

Thomas

biznatch
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Re: Sterling carb (modified Nikki)

Post by biznatch » Mon Feb 10, 2014 11:40 am

Thanks guys, I didn't know about the trouble fitting the RB Holley into a RHD, I'll steer clear of that.

Thanks for the links Thomas, I would like to give modifying the Nikki a go as I have a spare now and im confident of doing most of the mods myself, although i might find machining the venturis to be tricky. It proably won't be until next month though as I will make the 12a rebuild the priority.

I'll update on progress at the appropriate time.

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spirit r
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Re: Sterling carb (modified Nikki)

Post by spirit r » Mon Feb 10, 2014 9:05 pm

I could Not See something is tricky if you say you can Do Bridge porting. Take of the venturies and machine them as you can See it in the picture.
Thomas

[:evil:attachment=0]venturi.PNG[/attachment]
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biznatch
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Re: Sterling carb (modified Nikki)

Post by biznatch » Sat Mar 14, 2015 12:23 pm

Here's an update on progress with the modified Nikki. So far i have everything modified and ready to reassemble.
The Venturis have been machined to provide an smoother inlet angle and polished to reduce air resistance. To do this i bought a mini-lathe off the bay of E, it was more of a toy than a proper lathe (as you can see in the pictures) but i got the result i wanted in the end...
I would recommend using a more precise lathe than the one i used.
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biznatch
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Re: Sterling carb (modified Nikki)

Post by biznatch » Sat Mar 14, 2015 12:26 pm

Inlets were roughed out with a cutting tool first , then 400 grit sandpaper, and finally polished with 2000 grit.
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biznatch
Posts: 330
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Re: Sterling carb (modified Nikki)

Post by biznatch » Sat Mar 14, 2015 12:31 pm

I have removed the choke linkage and butterfly, this is a big restriction to airflow so has to go.
The primary and secondary throttle shaft were cut and flied to reduce the restriction and shorted screws used.
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