Timing

289 - 351 cid Small Block Performance

Timing

Postby Rocket989 » Thu May 03, 2018 11:21 pm

Curious what timing folks with aftermarket heads are running. I knew the more efficient the chamber design, the less total timing needed, but I ran across a pretty reputable site that had done a bunch of dyno testing of different SBF heads. The optimal timing for the Edelbrock heads I’ve got was 28 WOT and IIRC 41 cruising.

That works out for me since the distributor I’m using hasn’t been made for awhile & when I bought it the advance springs were included but not the stop bushings. I ordered MSD and Pro Products kits & while the bushing ID is right the OD has been a guessing game.

Only two will really work...using 16-degrees initial I’ve got a choice of 24, 29, or 39 total (the last is with no bushing). Given what I’d read, I went with the one they have 29. There was a noticeable difference from 24 (kinda expected that) so I called it good after getting the right spring combo to have all the advance in by ~2600rpm.

Edelbrock recommends 36 total for these heads though. If I calculated right compression is 10.7:1 so even with 93 octane and a decent amount of cam overlap, I don’t really want to flog it with too much timing. I guess I’m stuck anyway since I don’t have an option between 29 & 39 right now. :D :lol:

I still need to adjust the vacuum advance for part throttle/cruise but the heap runs pretty good so far so I guess I’m just curious! :D
'cause Johno says you gotta have a sig pic! :)
Image
Rocket989
 
Posts: 1643
Joined: Sat Jan 11, 2014 1:53 pm
Location: Kansas City Metro

Re: Timing

Postby vicegrip » Sat May 05, 2018 6:48 am

I would say you probably need to sneak up on the total for optimal but aluminum heads can fool you. The last aluminum headed motor I had on the dyno started at 35,up lost power,finally ended up at 28,29. Hard to go up with the dist and bushings you have. You might try a cheap reman Dura spark where you can modify the slot to get any timing you want and go from there. The 41 cruise is also probably too low but every combo is different.
vicegrip
 
Posts: 228
Joined: Tue Jan 08, 2013 11:12 am

Re: Timing

Postby poboyjo65 » Sat May 05, 2018 11:45 am

I cant remember for sure but mine liked a lot of initial timing, but not over 36 total.it pings if I go over 36. I think I'm running 15-16 initial. I welded up the slots on the dist,then grind the edges back to a certain measurement. I have a chart somewhere for the measurements.I bought a couple sets of springs,,, I'm all in by 2500 I think. (347, edelbrock rpm heads)
Image
347, 4sp, 9''
JOHNO
poboyjo65
 
Posts: 5008
Joined: Thu Oct 20, 2011 7:40 pm
Location: Camden, Tenn.

Re: Timing

Postby Rocket989 » Sat May 05, 2018 12:18 pm

Thanks guys. Yeah, Johno...almost forgot we have the same heads!! Vicegrip, it might have been 51 cruise. I’ll see if I can dig up the link.

Since I’m stuck with either 29 or 39 I’ll likely leave it at 29. The car was never intended to be drag deal but nothing wrong with optimizing what you’ve got! :lol:

I’ll have to find another place that runs occasional specials on dyno time. The only place close turned out to be a turd hole full of arrogant AND incompetent knuckle-heads. They really hosed my brother on a tune after he got the blower installed. That may or may not have gotten a little heated so not probably not wise to go back. :lol: :lol: :mrgreen:
'cause Johno says you gotta have a sig pic! :)
Image
Rocket989
 
Posts: 1643
Joined: Sat Jan 11, 2014 1:53 pm
Location: Kansas City Metro


Return to Small Block V-8 Performance

Who is online

Users browsing this forum: Google [Bot] and 1 guest