Tune up tip

[Huck]

With many of us upgrading to HEI, a common problem seems to arise if you try to run at factory specs realtive to timing. Apparently a basic stock 350 likes it's timing to be around 12 degrees advanced with an HEI. Two fairly stock 350 blocks had show a big imrpovement with that little change from the stock settings. So, if your 350 with HEI and a stock carb or even an Edlebrock carb is running kind of punney, try advancing you dist to around 12-14 degrees and see what I mean!!! Huck

[crazy longhorn]

The HEI doesnt have as much mechanical advance as the old points dist, & needs more initial to get the proper total advance. I ran 14 initial , with a 34 total on my HEI...... the dist was very loose, so i swapped to an old points dist with a Pertronix unit & a fast curve. I run the initial @ 8 degrees(after playing a bit), she totals @ 34 @ 2800, & has 16 degrees on the vac can (plugged to manifold vac). Man that sounds like a bunch of timing, but that old" farm truck" has alum heads,a close ratio box & 4.10 gears....I can hear the back tires talkin over the "blowmasters" someday I might grow up, but i doubt that it will be very soon! The biggest drawback on the HEI, is that they arent very adjustable.......without welding ,or filing. Next stop for me will be MSD.......after my wifey stops raisin he!! about the trans crazyL, rowin 6 , & smilin

[GMC Jim]

crazy longhornmail......My understanding is that with the weights and springs available for H.E.I.'s...the mechanical advance can be adjusted to whatever curve is desired... when I bought my rebuilt GM H.E.I unit from a distributor rebuild shop; they asked if I had any special advance curve in mind.....I stated I wished for the stock advance for my '71 402 engine..... This curve also matched the specs as stated in the GM '71 service manual. Installed this unit about 10 years ago.... with no problems whatever ( I also installed a new vacuum advance module at the same time...


Your comments ????

[crazy longhorn]

I wont say all, but most of the HEI dist that I have been into have approx 20 degrees of mechanical advance in the dist, & the springs are very stiff bringing the advance "all in " rather high in the rpm range. They also have way too much vac advance for a perf engine. As far as adjusting the curve, you can change weights & springs for a faster curve, but adjusting the total amount of advance usually requires welding or filing the slots. I use a crane adjustable vac can, & the springs that come with it to alter the curve. my combo seems to like a 34 degree total(checked with the vac can unhooked & plugged). it also starts quicker @ a 8-10 degree initial setting.......8 initial+26 mechanical gets me to the total. The springs let me run "all in " around 2800 rpms......faster curve, & better responce. This also requires cutting back the vac advance, so she doesnt spark rattle under a low rpm load, such as pulling a hill. the stock settings work well for what the factory designed the truck to do, but high comp, hotter cams, & bigger carbs all affect the timing needs of the engine( intended usage, & driving habits). I honestly dont beleive a factory curve is optimum for any engine, it is very conservative & set up for the worst of conditions on a daily driver/hauler. IMO, a good curve will do wonders for even a "stocker" crazyL