On Fri, 8 Sep 1995, Christopher W. Reichle wrote:
> What year is it? Do you have the vacuum advance hooked up? If you have
> done mods to the engine and it is a late model B (smog), The part
It's a 73, with an original (AFAIK) distributor and a Pirhana system to
replace the points.
> throttle ping is caused by your vacuum advance unit. Later Bs can
> introduce up to 30 deg vacuum advance. When you hit the gas part
> throttle, you are not openning the trottle plates enough to lower the
> vacuum in the manifold enough to lower the amount of vacuum advance
> introduceced at the distributor. Remember that this unit is there to
> acount for changes in charge density. When you floor it, you have almost
> no vacuum in the manifold and the vacuum introduced advance disapears.
> Perhaps the vacuum unit is just sticking. Check for free movement of the
> plate in the distributor.
I think you may have something there. It certainly pings more in a
part-throttle state. I think it just may be a matter of the vacuum
advance pushing it over the edge, though.
My total advance is about 20 degrees more than my idle advance, when
revving the engine in neutral.
Thanks for the reply...
John M. Trindle | jtrindle@tsquare.com | Tidewater Sports Car Club
'73 MGB DSP | '69 Spitfire E Stock | '88 RX-7 C Stock
Home Page: http://www.widomaker.com/~trindle
"Murphy's Second Corollary:
It is impossible to make anything foolproof
because fools are so ingenious"
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