Timing Question???

[HotRod929]

What should I set my timeing at to get the most power? I have a 350 with a new edelbrock 600 cfm carb and a new HEI unit...I want to get as much power out of my engine as i can...dont really care about gas mileage. Also How much would an electric fan save me on horsepower verses the belt driven one i have now? Thanks

HotRod

[crazy longhorn]

Going to elect fans is said to show approx 12 hp & 15 lbs tork at the rear wheels. on the timing, I would go for a Crane adjustable vac can,& a balancer tape. Just follow crane's instructions to recurve the dist. i like to run 10-12 initial, with 32-34 total @ 2800-3000, & limit the can to 10-12 degrees,& plug to manifold vac source at the carb(driver side on the edelbrock). Good luck,crazyL

[Truckstr]

Is the HEI a stock unit? I'd just make sure that it's in good shape (that the mechanical advance is operating properly, and check the endplay) and put it in with between 8-12 degrees of initial advance (much higher than that and it'll likely ping). If you want more power after that (and who doesn't), then I'd install an adjustable vacuum advance (vacuum adavnce only operates during part throttle conditions) and an aftermarket mechanical advance spring kit. Just play with using different springs until you get the right combination.

Do you have a timing light and tachometer? If so, then install timing tape on the harmonic damper and you'll be able to see the amount of advance at RPM with your timing light.

Good luck,
Jeff

[Fred T]

Here's a link to a good article on performance timing.
http://www.chevyhiperformance.com/howto/97438/

[GMC Jim]

Per GM Service Manual; specs for 1971-350 cu. in, auto trans are... Centrifugal advance (degrees) (RPM) :- 0 @ 865; 2 @ 1335; 11 @ 2400; 18 @ 4200......Vacuum advance :- 0 @ 8" Hg., 15 @ 15.5" Hg.
GM Tune-UP Specs ( Manual SD-100) lists 20 to 27 total spark advance @ 2000 RPM.......
I would suggest gaping the spark plugs to .045........

[mikep]

Your only going to get that supposed 12-15 hp if you are going from the largest available stock rigid fan to an electric. If you are running a flex fan or a viscous clutch fan you will see differences of more like 5hp which could really be considered negligible. Then you have little things like a much greater draw on your alternator and battery . I'm sure this is not always the case but I have used several electric fans in the past and have known a LOT of people who did as well and we all had the same problem. They would do fine for around town driving on cooler days but take them out for a long trip on the highway and then slow down or stop and they overheat like its going out of style . I dont know about the dual fan setups but if you look through the catalogs the makers claim that they are "good up to 250 HP " or "good up to 280 HP" . Well...what if I am a good bit beyond that? I like to size things for a bit of overkill. The cooling being the most important thing I can think of next to oiling.


GM timing specs are not worth the paper they are written on. Shoot for 36-38 total depending on if you can handle that much advance. The more advance the merrier up to 40 degrees or so. After that you may lose some power. I run 38 total with 92 octane gas and 9.5:1 compression. No detonation. That 38 degrees does not count 12 degrees of vacuum advance , Actual total at cruise being more like 50 degrees. Helps out the mileage and the throttle response. Its hooked to manifold vacuum. When I gun it the vacuum goes away and I dont detonate but I still retain enough timing to get the spark fired. Othe things to consider are can your starter handle that much timing? I run a late model big block Permanent magnet gear reduction starter that will turn anything over and do you feel like buying 92 octane ALL THE TIME !