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Cobra rep · Joined: 30 May 2013 Posts: 27 Location: Illinois

What the best why to time the motor when using a MSD box triggered straight off the magnetic pickup in the distributer. Motors basically stock with dual Webber's. My thought was setting a total advance of 42 degree's at 3500 RPM with vacume advance disconnected. If there's a better way I"m open to suggestions.

Fifty50Plus · Posted: Fri Oct 25, 2013 9:32 am Post subject:

Multi-Spark-Discharge devices produce two or more sparks per plug below about 3500 RPM. Above that, one spark per plug. It is a hotter spark but the timing should remain per factory specs. The MSD benefit is proper ignition at low and mid range. 42 degrees of advance is probably too much for that RPM range on a street car. We go as much as that and more on the race car but at 6000 RPM and the engine is never below 4500 on the track.
_________________
1979 924 NA race car H-Prod SCCA
1982 924 NA race car - Sold
1981 924 Turbo sold
1982 924 Turbo sold
1972 911 E race car - traded for Cayenne Diesel
1975 914 1.8 Building for H-Prod SCCA

Cobra rep · Joined: 30 May 2013 Posts: 27 Location: Illinois

Its a Lemons Car .Its first race is Nov 2 at Road America

924RACR · Posted: Fri Oct 25, 2013 10:19 pm Post subject:

Then 42 max total should do you well... assuming the inside of the engine is clean (no heavy deposits) and you're running premium, just to be sure.

For us, with mechanical advance only, that usually works out to about 12deg at idle...

Have fun!
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Cobra rep · Joined: 30 May 2013 Posts: 27 Location: Illinois

The motor was real clean when I tore it down to replace the gasket and seals in the motor. Who ever owned it before me had rebuilt it not that long ago. Bearings were new head was rebuilt. Compression was 155 165 165 160 . I think the cam is not stock as valve lift is more than stock at .510 intake .520 exhaust . Thanks for the info on timing that's going to be a big help.I'm going to be running 100 octane VP fuel for the race.

924RACR · Posted: Sat Oct 26, 2013 9:43 pm Post subject:

You may not need the expense of that fuel then; with our IT motors, stock cams, we haven't found it necessary to run more than 93 octane pump gas - big cost savings!

I don't know if the cam changes things, but seems like you don't have enough compression to worry about octane rating...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Cobra rep · Joined: 30 May 2013 Posts: 27 Location: Illinois

924RACR · Posted: Sun Oct 27, 2013 8:46 am Post subject:

Kinda like beer: the best kind of race fuel is FREE!!!

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Cobra rep · Joined: 30 May 2013 Posts: 27 Location: Illinois