[kyle_blake]

Hi,

I haven't received an answer on how to get more mechanical advance out of my points distributor so I am taking it to be done professionally.

I have only 16 mechanical and drive around with 12 initial... So 28 total.

What I would like to ask is if you agree:

1) would 20,22 or 24 mechanical advance be a good # to ask for?

2)If I choose 24 mechnical and 12 initial and then engine pings then all I can do is go back to 10 initial and hope it doesn't ping?

3) Would it be safe to say that all advance be in around 2800 or?

Generally when I drive my engine never sees anything below 2700 anywaz with my gearing around town.

I just don't want to over extend myself.

That is why I'm thinking 22.

My combination
is 390 gears
400 pontiac
#64 heads
trw 160 thou domed pistons
comp cam 280H
hooker headers 2 1/2" to 2 1/4"
Guessing stall is around 2600
Static compression is around 180psi
msd blaster 2 coil

[Jack Gifford]

After recently reading articles by some of major companies (Clevite, KB Performance, Total Seal, etc.), they seem to all concur that 34 degrees BTC is a good setting for a fairly "up-to-date" engine- efficient chambers, some amount of squish area, modern quick-lift cam, reasonably good ports, etc.
These articles weren't specific to Pontiac, so you'll probably end up tweaking the timing a little, but I wouldn't think more than a couple degrees. If you know that something about your chambers will be bad for flame travel (squish area thicker than about .050", etc.) then you might want to set 24 degrees into the advance, instead of 22.
I can't comment about your engine having full advance at 2,800 RPM. Someone with a similar combo probably can.
Good luck.
P.S. I don't know what the domes on your pistons look like, but in general a dome creates a worse ratio of chamber volume to area, which is not good from the standpoint of retaining combustion heat through a quick, complete burn.

[kyle_blake]

PJ-> Thats what I hear too, that these domed pistons are 80's technology and aren't very popular right now with new engine rebuilt's.

I dunno runs fine, most people can't tell from sitting next to the engine at the lights.

[Jack Gifford]

There are still plenty of domed pistons being used in various engines. I was just pointing them out in the context of determining maximum spark lead. For example, really old Pontiacs with bathtub chambers and aftermarket domed pistons (and good old high octane leaded gas) wanted ridiculous amounts of advance, as much as 41-42 degrees.

[Sun Tuned]

Kyle,
To increase the centrifugal you need to lengthen the advance slot with a small chainsaw file. Figure about .005 per every extra degree you want to add. That's a little conservative and that's the way I want it, so you don't go to far and have to shorten it back some by brazing the hole smaller.

2800 should work pretty good to start with and you can play with it from there, just be sure it doesn't start to early.

11 works good. That way you can keep the initial a couple degrees higher than if you ran 12 and ended up needing to pull it back some.

Kinda late, but didn't feel you deserved no answer at all, which looks like what you got till now anyway, at least on the question 1 & 2.

[kyle_blake]

P-Jack-> Interesting about the pistons, thanks for clarifying

Sun Tuned-> That slot, ok I'll go have a look for it. Thanks for clarifying!

[cruzn68]

You might want to check into sending your dist. to Larry Rowe (301-739-8320
call between 7-9pm est) He set up my MSD dist. and I couldn't be happier with it.

[kyle_blake]

Hi,

Can one of you verify via the picture that this is indeed the slot for mechanical advance bushing to go?

Also do points generally float around 5600 or higher?

[johnta1]

That's the slot.

I wouldn't mess with it until you have it checked on a distributor machine.
The point distributor should be able to get a lot of mechanical advanceUsually have to bush it to limit it.

The centrifugal springs are probably not letting it get to full advance, unless you run it to 7000 rpm.
Lighter springs will make it work better.

If you're letting a pro shop do it, let them decide what it needs.

[kyle_blake]

Thanks, yup I took it to the shop and they installed new condensor, vac can that adds only 10 or so degrees.

They installed the limiter and put it on the sun tuned machine. Set it all up.

Just have to install it my car.

I'll be taking out my existing distrib which is in the car and ran fine for this one which has been re-curved and the mechnical advance increased.

The total cost in canuck bucks was $135...I phoned around and this seems to be the norm.

Thanks guys for clarifying this.