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MG MGB Technical - HIF Improvements

This winter's projects include a rebuild (by Joe Curto) of the HIF4s on my '72B. One of the things I am also doing is installing a set of "GerryBob" K&N filters, eliminating the Coopers cans for better air flow. The last time I tried this, the car sputtered from being too lean, so I replaced the cans. What are the suggested needles with this filter set up? Also, what can I expect to gain by replacing the poppet butterflies with plain butterflies in the SUs? Any other suggested modifications while I have the carbs off? The previous owner had removed any trace of emissions systems. I am also ceramic coating the exhaust manifold, mainly to improve appearance. Have any of you experienced any gains in this?
Joe

Joe, AAA needles worked well for me when I switched to open filters. I removed the poppet valves and soldered the holes closed, I cannot say that made any noticeable performance difference. If you have a poppet valve that leaks, replacing the plates should improve the idle. I have a ceramic coated exhaust manifold and I didn't notice any performance gains, it is a little cooler under the hood and the manifold still looks nice. I'm giving a seat of pants opinion and haven't done any rolling road testing of before and after the modifications.

Clifton
Clifton Gordon

Joe
Same as Clifton, AAA needles, plain butterflies fitted getting rid of the poppet valves.

Colin
C J Bryan

I also went to AAA from the original ABD needles on my 73B - was clearly lean before the change and would hesitate severly when pulling away from standstill. I left the poppet valve as was.

Have a good winter!

Regards,

Barry
B.J. Quartermaine

Went to open element on my HIFs and used Curto AAA and also changed the buttrfly to non poppet. Screw out and screw in, no need to dissassemble carbs to swap the butterfly.
Dennis P

This thread was discussed between 13/11/2005 and 16/11/2005

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.