250 engine timing question

[CST10]

I have a 250 engine in a 68 swb stepper.

I have installed a hei conversion distributor, new plugs, wires, etc. I set the initial timing at 10* btc with vacuum advanced plugged. Runs fine there.

Curious what others are running for timing on a similar set up?

Is there any HP gains to be made with more advanced timing?

Anyone pushing 12-14* btc settings. How's it run?

I tried the search feature and really didn't find a good answer.

Thanks in advance (no pun intended)

[Shaky]

I usually bump the spark plug gap up to the HEI specification and then, on a hot day, add more timing little by little until it pings and then back off. If I remember right, it's not a lot more than stock.

I can't remember where I got this, and I haven't tried it, but it sounds like it's worth a try:

[Tony]

You need to consider the total timing as provided by the mechanical advance. A stock 250 needs about 34 degrees of total advance. How much is built into the stock HEI?

[68gmsee]

Once you do the above recommendations, there's no reason you can't go up in small increments and see how the truck runs. I did that with mine.

After originally setting it at 10º BTDC, I went up to 12º and 14º BTDC. I'm now back at 10 since I didn't see any significant difference and it seemed to run smoother at 10 BTDC.

[CST10]

Originally Posted by Tony

You need to consider the total timing as provided by the mechanical advance. A stock 250 needs about 34 degrees of total advance. How much is built into the stock HEI?

It's right at 34* now set with 10* initial.

[CST10]

Originally Posted by Shaky

I usually bump the spark plug gap up to the HEI specification and then, on a hot day, add more timing little by little until it pings and then back off. If I remember right, it's not a lot more than stock.

I can't remember where I got this, and I haven't tried it, but it sounds like it's worth a try:

That's what I e done basically but don't wanna push it to detenotation.

[CST10]

Originally Posted by 68gmsee

Once you do the above recommendations, there's no reason you can't go up in small increments and see how the truck runs. I did that with mine.

After originally setting it at 10º BTDC, I went up to 12º and 14º BTDC. I'm now back at 10 since I didn't see any significant difference and it seemed to run smoother at 10 BTDC.

So this is good info. No real reason to push it past 10* initial then I guess. Might experiment and see how 12* runs just for giggles.

Thanks.

[TJ's Chevy]

Spec settings are 8 degrees advanced no vaccum. 20-25 degrees with vacuum. And no more than 36 degrees total no load. On my old 292 I set mine at 8 degrees and it made it a wee bit sluggish(not enough to care about) but made cold starts super easy. When I set it by ear I ended up having it almost at 14 degrees advance...the motor had such low compression it didn't matter and I ran 92 octane. 8-10 degrees is pretty common.