Hey guys, I just upgraded my ignition to a GM style HEI distributor and I'm trying to get my timing dialed back in on my Fairlane, its a mild 302, with a performer 289 intake and a 600 cfm Edlebrock carb, a little bit of cam. I dont have the specks on the cam, though. I have it set right now at 18* advanced at 850 RPM at idle. It runs good but seems like it is missing some power. Any suggestions for a good starting point on the timing?
Try 16 and 31 at 3000, pump in the center slot. If you still can not dial it in check your jets. what's your elevation? New carbs are dialed in at sea level. Whats your vacuum, a stock cam should produce 18 to 20 ish, the bigger the cam the lower the vac it will sustain. Idle screws all in and back out 1 1/2 turns. Also check your choke. remember, this is choke car not a computer like the new junk, it needs 4 or 5 minutes to get to temp before you can pound it. What color are your plugs burning, should look like a perfect marshmallow.
You need to know the amount of advance built into the distributor curve. You can have it checked at a speed shop on a distributor machine. Or if you have access to a timing light with an advance dial, just crank in 36 degrees or so,run it up till it stops and lock it down.
At operating temp at 850 RPM i'm pulling about 16 hg in vacuum of off the vacuum advance port (NOT hooked to the dizzy). And I am right at sea level. I'll try 16 tomorrow, and see how she acts, and ill run it up to 3000 and see what my timing light tells me. and what do you mean by pump in the center slot? Thanks for the input!
I've got a nice timing light with a digital advance and tach readout, so its quite handy. I THINK the GM HEI has a full curve of 20* I'm probably going to retune the advance because if I remeber correctly the full advance doesnt come in until over 4500, which I very rarely ever see in this car, goddamn C4.
20 is a lot that won't give you any initial. Have it re curved to about 12 degrees and bring it all in by 2000 crank RPM. Then 12 degrees initial and you should be pretty good. Depending on fuel you could maybe get a little more.
There should be a an idle pump on the brock with three little holes in it, drivers side front, I like to set it at center so it's not getting to much fuel at idle. If you need info on brocks you can go to their website or google them, they also give great tech. Was your car always at sea level, was it a new carb, maybe it came from inland and has the smaller jets and rods. This can affect throttle response and crispness of recovery, again plug color is a good indicator.
I work for a distributor manufacturer. 20 degrees in the distributor (crank degrees) is about right. On a mild SBF I usually set initial between 12 and 16 degrees depending on cam and compression. If it pings back it off. Have your mechanical advance all come in by about 3200, which will be between 32 and 36 degrees depending on the initial. Hook up your vacuum advance after you have dialed in the initial and mechanical. I use ported vacuum in most cases, if it pings under light load back off the adjuster inside the vacuum can. If you're not coming all in until 4500 that is a big part of sluggish performance, change the springs in the dist to something lighter. And there is nothing inherent about a C4 that will stop your little Ford motor from reving, which they like to do. Sounds like you have a bad vacuum modulator, get a performance one and adjust it accordingly.
Ok, here is what I've got: 14* @ 850, 30* @ 2000, and 32* @ 3000. she seems to like 14* and I'm still getting 16hg om vacuum at 850 idle. Thanks guys! Now I'll take her for a spin and see how she does under a load.
did fantastic. thanks for all of the input, my qualm with the C4 is that it shifts so fast, im in 3rd at about 25 mph.
As mentioned before, you need a new vacuum modulator. There are different ones stock,(the Green stripe seems best) and many are adjustable with a tiny screwdriver or Allen wrench in through the vacuum hose nipple.
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