Accel/Summit HEI distributor advance curve

[leftybass209]

I recently purchased the Summit brand HEI distributor, which is the same as the Accel 59107.I'm writing this to explain the advance curve on these distributors ( I replaced my OEM because the bushings and shaft were worn and scored pretty good, and the end play was excessive, giving me 3-4* of inconsistent timing movement)

Everything i'm stating is WITHOUT vacuum advance

This distributor is limited to 11* maximum centrifugal advance with it's weights and center plate. Per the instructions it says
6* @ 900 RPM
8-10* @ 1200 RPM
10-11* @ 1500 RPM

The instructions go on to advice adding about 2-4* initial advance over factory specs, because it will add more performance and better fuel economy.

As a general rule and what most know, SBC's like around 32-36* total advance give or take.

So, that means you'd need around 21* initial timing just to get to 32* total.

This would function great with a high lift cam that needs more initial timing to idle, but not so much for a street engine.

on my 350 crate, it likes between 10 and 12* initial. I couldn't get more than 24-26* total advance at 2000+ RPM's with this distributor. Not nearly enough.

I tore down the weights and springs thinking I could use one of my 2 advance kits, or the OEM weights and center plate, but it looks like the pins are exclusive to Accel and they match what the Accel recurve kit comes with. No bushings or sleeves I have will allow any other weights or center plate to be used.

I just thought this would be good info for anyone that was in the market for a new dizzy, and was looking at this. I read the instructions thinking it was some kind of a misprint at most all factory dizzys have between 18-24* centrifugal advance and that's what I was looking for.

I'm returning this, and going to pick up an MSD Streetfire, which claims 22* centrifugal advance at 4000 RPM (which sounds spot on with late advancing OEM dizzys)

Sorry for the long-winded post, but I thought this could be valuable information for anyone in the market.

[geezer#99]

Your numbers are wacky.
For one simple reason.
Your dizzy is in distributor degrees.

You need to double those numbers to get crankshaft degrees and rpm.
Then your dizzy will be the normal 22 plus your initial of 12 equals 34.

[leftybass209]

Which numbers are you referring to?

[Fitz]

Originally Posted by geezer#99

Your numbers are wacky.
For one simple reason.
Your dizzy is in distributor degrees.

You need to double those numbers to get crankshaft degrees and rpm.
Then your dizzy will be the normal 22 plus your initial of 12 equals 34.

This is that day they told you about in school when arithmetic would save your life......

[leftybass209]

Well, my new distributor is in, and working great. I'm sure something was mechanically wrong with the dizzy I had, because this GMPP distributor I purchased (looked better than the MSD streetfire), has NO problem hitting the button at 34* advance all-in. Vacuum advance is dialed in great as well. Thanks for all the help and comments.

[geezer#99]

This distributor is limited to 11* maximum centrifugal advance with it's weights and center plate. Per the instructions it says
6* @ 900 RPM
8-10* @ 1200 RPM
10-11* @ 1500 RPM


These numbers are in distributor degrees.
To get crankshaft degrees you double them.

[leftybass209]

I'll look into it some more

[geezer#99]

Did you prove your timing tab/balancer is accurate?

[leftybass209]

Timing tab is spot on, balancer is correct and ring hasn't slipped. TDC is nose on at the 0 mark, which was verified using both the old distributor, and the new distributor. Engine can't turn over fast enough and idles smooth as silk around 10-12 degrees initial at 700 rpm

where I don't follow you is, what are distributor degrees, versus crankshaft degress?

I've always heard it put mechanical advance (that of the distributor weights), and initial advance (that of the crankshaft).

If that holds true, this distributor doesn't mechanically advance past 11 degrees, which is what I was experiencing when checking total timing. I had my initial set to 10 degrees advance at first, and I couldn't get over 21-22 degrees total timing (vac ports plugged on advance can and carb). I thought maybe the springs were too heavy not letting it advance within a reasonable RPM (engine is designed for low-end torque, not high rpms), so I used some super light springs, and still couldn't get over 24 degrees total.

I'm not willing to advance my initial timing past 14 degrees. Long story short, after vacuum advance is hooked up, idle rpms set where I want, and my stock stall, the engine isn't happy and wasn't happy with the original distributor if I went over 14 degrees advance.

I suppose it could be a malfunctioning distributor?

[leftybass209]

Okay, after a bit of frustration and some time to cool down, I've found two likely culprits in this distributor for a lack of advance.

The weights are dragging on the metal ridges used to support this distributor, as opposed to the nylon bushings the OEM uses.

The springs were also installed upside down from the factory, so they seem to be blocking the weights from providing whatever advance they should be. Seems I installed my light springs the same way the factory did, and it causes the same issue.

Still unsure of the exact cause, but after having a broken clip, and taking a good look at the inside of this thing, I'm still returning it and purchasing something of better quality.

[67 chevelle]

You need more than that , does it actually say 11 degrees total mechanical advance , most drop in distributors have atleast 20 degrees minimum , that's how msd's are ,,, then by changing bushings you can add 2 degrees per set up to like 26 , with the biggest bushings and 20 dergees total you can have an initail timing of 14 that tops out at 34 , or with the smallest bushing , or none , have an initial of 10 and total of 36

never herd of a dissy with only 11 mechanical , does not make sense

get an MSD dropin , they are worth the cost

[leftybass209]

Originally Posted by 67 chevelle

never herd of a dissy with only 11 mechanical , does not make sense

Neither have I, and I was scratching my head while timing it. the instructions stated exactly as I posted with the "6* at 900rpm...etc". There wasn't anything else in the instructions that stated clearly the total mechanical advance the distributor provides. I tried calling Accel but they were closed.

At this point it doesn't really matter so much, as it's already boxed up ready to be returned, and I've got a new dizzy coming from Summit that will be on the doorstep tomorrow.

It's just irritating as I have an appointment with a BAR station to get my exempt sticker soon, and I have problem after problem.

[geezer#99]

How does the advance slot in the accel compare in length to your stock hei.