I have a 383 with alum intake large valve heads performance dist and a cam with a bit of duration. I just cant seem to find a sweet spot on timing. I set initial timeng to factory spec but that does not seem right. I read on setting the timing at 2500 RPM to have all mechanical advance in and set it that way but I am not sure what the setting should be. Please any advice can help. FYI I do have a degree timing light vacuum gauge and many other tools of destruction at my disposal.
Joined: Mon Jan 16 2006, 02:52AM
Location: Vantaa,Finland
Posts: 379
A lot of things affect. Combustion chamber style and size, plug location, compression ratio, quench properties.... Usually a factory headed big block likes about 35-38 degrees of total mechanical advance, if the fuel used vs the compression ratio allows that much. You want the maximum advance as soon as the engine allows it without detonation, that depends of the compression ratio. And you don't want to egt the mechanical advance "in" until you are above idle rpm. Ususally it means, that for best results you have to recurve your ditributor. Usually about 15-20 degrees of centrifugal advance, all in at about 2500 rpm works pretty well in all performance big blocks, but like said before there is numerous of things affecting this.
Joined: Mon Oct 10 2005, 01:49PM
Location: Grand Rapids, MI
Posts: 421
Jyrki has it right...I always set mine by total mechanical adv, vaccuum port plugged. Then just double check intial to see where its at.
If you don't have a dial back timing light, 10 to 12 intial should get you close...ideally with a bigger camshaft, the more intial you can run the more responsive the engine is gonna be off idle.
Just for the info the hydraulic cam specs are Gross Valve Lift 0.488 0.491 Duration At 0.006 Tappet Lift 274 286 Compression is approx 10 to 1 the heads are 452 with a slight mill and 214/181 valves. Using an Edel. 750 carb 383 circa late 1965 bored 60 over with aluminum water pump intake radiator and pulleys twin elec fans msd 6a box and Mopar performance elec dist msd wires and 60 amp alternator. gears are 323 ish not for sure. I will set the mech adv and see where it leaves me on initial. Thanks again Brian
Joined: Sun Oct 09 2005, 05:02PM
Location: ALLEN PARK, MI.
Posts: 2007
Full advance above max limit RPM by 300 or so RPM'S with a WELL MARKED dampner will get you there! You must know where your DISTRIBUTOR full advance RPM is at, then take your RPM'S a few hundread above that to insure you have reached max advance. Set timing for a big block between 34 to 38* max. As said by the other gents.....best timing in THAT range will be determined by the quality octane fuel used and such.
This is why I love the MDS PRO BILLET distributor so much! The advance curves as SO EASY to set. Full instructions with color keyed advance springs and stop bushings, along with actual "curves" per set-ups used make it so easy! No speed shop or garage needed!
Example: My MSD curve starts at 1,200 RPM and ramps straight up to 2,400 RPM FULL IN. I set 38* with my engine sitting at 2,800 RPM'S! Cool stuff that MSD! TONYPRO
When you set the timing,try and use a GOOD timing light,the K-MART specials don't cut it,they can be 4 -6 degrees out as i found out on a cheepie that i had.Now i have a Snap On light and it's dead on.Glen