ign. timing???

[roadkill]

howdy, i just installed a nh400 bumpstick cam from poston buick in my 65 gs ragtop with a 4 spd.it has a 401 in it ,had to put adjustable pushrods in it because the base diameter of the cam lobes are smaller than the stock ones .....only problem i am having is dialing in the ingition timing .... any specs that you might be aware of??? thank roadkill.

 

[Dr. Frankenbuick]

A good Nailhead curve is 18*-20* of mechanical advance at the crank all in by 2800-3000 rpm. Most good speed shops have a distributor machine that will allow them to curve your distributor to those specifications for $30-$50. Then you would run 12*-14* initial advance for a total of about 32* of advance with the vacuum advance disconnected and the source plugged. Find the initial advance that seems to run best when road tested (no ping- most go). Then reconnect the vacuum advance after you have found the best initial advance setting. Pinging would be the sign of too much advance. If there is too much advance when the vacuum advances is connected after the best initial advance is established, an adjustable vacuum advance may be needed. In the meantime you can run without the vacuum advance, but there will be a loss of 1-3 MPG. I hope that was helpful.

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Steve B.
GSCA #2173 (1986)
67 GS 525 Stg IV
66 GS Convertible
65 GS HT
63 Riv