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MG MGB GT V8 Factory Originals Technical - distributer curve

When D & D built my 300 Buick I was concerned about the 9.8 compresson ratio & the crappy gas with all the oxygenators & other stuff that gets added in winter, but Dan assured me, "no problem". Well, I had a problem & got the dreaded "ping". A call to D & D & I set the timing back and all was OK, but I felt I was down on power.

Enter a friendly drag car builder who liked my car & listened to my gripe then said bring it by the shop & lets check the timing. By the way, have you had the distributer curved?, he asked. Well, no, not only had I not done it, I had no idea how.

A quick check at the shop showed the dizzy had a total of 51 degrees of advance, while D & D had told me that with the cam & other stuff, the engine should run 28-31 degrees total advance, around 4 degrees initial. My new friend Kevin at Fast Forward, Inc suggested an adjustible vacuum advance as a start & he would dial it in for me.

Yesterday, in about an hour, the Crane adjustible vacuum advance was installed, along with an advance stop that came with the unit, and all was adjusted to perfection. Initial advance was set at 5 degrees, total advance limited to 31 degrees. The rate of advance was adjusted until the timing added in smoothly to the stop. This was accomplished by adjusting the Crane unit & changing springs amoung the ones that came in the Crane package.

Results- easy starting, even when hot, better accelleration, no ping. At 1200 RPM in 5th gear on a slight upgrade, I floored the gas & held it. Smooth increase in speed, no buck or jerk, & NO PING.

So I recommend the adjustible advance kit & someone smarter than me to set it up.. The only test equipment was a timing light with adjustible set back, only tools used were a couple of screw drivers.

And Dan was right. I would have no problems with 9.8 compression & an iron block.
Jim Stuart

Jim - what dizzi r u using ?
Roger
RMW

Dizzy is a Delco, stock for either the 215 or 300 Buick engine, with a Pertronics conversion.
Jim Stuart

Jim if your mileage is not what you think it should be, try to adv the total timming up to 33, thin 36 & if you still get no ping & the mpg goes up, I would run 10btdc at an idle & think nothing of it. You have to play with it, my 4.9 with 12.5-1 comp. I can only run 30deg. total timming or it knocks way to bad BUT I can still get 23-24 mpg on high test only.
Glenn Towery

Jim,

Thanks for the "heads up". IIRC you are also running with a hot wire EFI ?? Do you think the Crane system added to the overall performance ?
Edd Weninger

Sorry if my cars are confusing. The yellow GT runs a Buick 300 & this was the car we curved the dizzy on. It has Dan's favorite Crower hot cam & a bunch of head work & big valves.

The hot wire is on a 215 Buick in my 1966 roadster, a mild motor that gets almost 30 mpg. The other car gets a good bit less in the miliage column.

I think we pulled at least 20 lost HP out of the yellow GT. We did not make any HP, we just recovered what was lost because of poor engine tune.

I did gain a bit of HP by changing to 1 heat range colder plug & using NGK plugs in place of Autolite. That change was made before working on the dizzy
Jim Stuart

This thread was discussed between 04/04/2005 and 06/04/2005

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