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Pulleys, vintage race MGA

Posted by malcox

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Pulleys, vintage race MGA #1
malcox Malcolm Cox Napa, California, USA	Posted: June 02, 2012 12:59PM Registered: 2 years ago Posts: 68

I recently blew up a second alternator (those lawn tractor alternators don't like 9000 rpm !), so clearly I have to do something about the pulley(s) ratio.

Does anyone supply a smaller crank pulley for a B series motor?
( second topic is a torsional damper necessary ?)

Is there available a larger water pump pulley?
(I hear that water pump cavitation may be an issue >6000 rpm)

Does anyone know the pitch diameter of the standard crank and water pump pulleys?

Any ideas on sourcing a larger pulley for a Nippon Denso alternator?

Malcolm and Diane Cox
Napa, CA
1960 MGA, #80

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Re: Pulleys, vintage race MGA #2
blackmgb Fred McConnell Hollidaysburg, Pennsylvania, USA 1992 Mazda Miata NA "MAC"	Posted: June 02, 2012 09:25PM Registered: 6 years ago Posts: 5,193

Why not lose the alternator? This is exactly why I've always ran a total loss system. One less thing to break and screw up my weekends.

2012 SCCA FP MARRS Champion

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Re: Pulleys, vintage race MGA #3
malcox Malcolm Cox Napa, California, USA	Posted: June 02, 2012 11:22PM Registered: 2 years ago Posts: 68

1 weekend, 1 car, 2 entries, 2 drivers = alternator
I tried total loss but I spent all my time hooking up a charger and back to back races were often marginal.
BTW, I estimate the alternator was actually doing 12,000 rpm!
Malcolm

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Re: Pulleys, vintage race MGA #4
Steve64B Steve Opitz Phoenix, AZ, USA 1966 MG MGB	Posted: June 03, 2012 01:12AM Registered: 6 years ago Posts: 8,339

You can get larger pullyes for the alternator at Summit or Jegs

Edited 1 time(s). Last edit at 06/03/2012 01:13AM by Steve64B.

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Re: Pulleys, vintage race MGA #5
blackmgb Fred McConnell Hollidaysburg, Pennsylvania, USA 1992 Mazda Miata NA "MAC"	Posted: June 03, 2012 07:04AM Registered: 6 years ago Posts: 5,193

I understand Malcolm. I run a yellow top Optima and only put a charger on it once a day for a couple of ours. but, you also have to have power. I didn't test it, but I could probably get a whole weekend without a charge.

While at home the battery remains connected to a trickle charger.

2012 SCCA FP MARRS Champion

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Re: Pulleys, vintage race MGA #6
fast-MG.com Dave Headley Cortez, 4 corners, Colorado, USA	Posted: June 03, 2012 08:59AM Registered: 4 years ago Posts: 3,222

I ran a large orbital battery which also served as ballast. I could and sometimes did change it out in about 10 mins. thumbs up smiley

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Re: Pulleys, vintage race MGA #7
Elva Bob Bob Lembcke Florida, USA	Posted: June 05, 2012 09:25AM Registered: 2 years ago Posts: 114

On the Elva (vintage/1622), I ran a lawn tractor battery for years in a total loss system. Got tired of having to find way to charge, etc., then SVRA put 25# wt. pentalty without chargings system, so found a small, 35A, single wire alternator off some type of Indian (from India) fork truck, with my local alternator rebuilder (now there is a business area that is going away, too). Used the large Moroso pulley from drag race guys, Summit or such. Added holes in pulley to get air into/out of alternator. (drilled on angle...supposed to act as impellor for air.)

Have seen several Jap. Alternators out there, special built for high speeds...(I used to twist the 1622 to 8500+, haven't seen that for last few years...guess down on power or it's different...). If you don't care/want a built in regulator, think the RX7 stuff (external regulator) also did pretty high speed in street trim.

Personally, I'm a firm believer in the crank dampeners. Currently have aftermarket on from APT.

Will try to attach photo of engine with alternator and external oil pump...

Bob L.

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Re: Pulleys, vintage race MGA #8
dickmoritz Dick Moritz Philly 'burbs, PA, USA	Posted: June 05, 2012 01:10PM Registered: 3 years ago Posts: 7,243

Malcolm,

I run a dedicated Bosch 1-wire racing alternator. It is specifically designed for racing, only 55 amp output which is plenty for racing, only achieves significant output at higher rpms, and is designed for very low parasitic drag even at racing rpms. Came with pulley installed, has been problem-free and, IIRC, was not very expensive, at about $175 I think.

Dick

Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

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Re: Pulleys, vintage race MGA #9
bills Bill Spohn W. Vancouver, BC, Canada 1956 MG MGA 1958 MG MGA Twin-Cam 1962 MG MGA MkII Coupe 1965 Jensen CV8 1969 Lamborghini Countach → more	Posted: June 06, 2012 05:50PM Registered: 8 years ago Posts: 9,139

The generators are a waste of time in high RPM applications, not just because they have higher drag than an alternator, but because you will spin the guts out of them. You can get by using a larger pulley (that's what they did on the Twin Cam in stock form), but a lightweight alternator would be my choice.

I refuse to run without one - too damned inconvenient if you spin on the circuit and can't restart because the battery is low - a friend lost a championship that way.

Bill Spohn www.rhodo.citymax.com/carstuff.html
1958 MGA Twincam (race car), 1962 MGA Deluxe Coupe
1969 MGC roadster, 1957 Jamaican MGA
1965 Jensen CV8, 1971 Jensen Interceptor
1969 Lamborghini Islero S, 1988 Fiero GT turbo
2009 Pontiac Solstice GXP Coupe
West Vancouver BC

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