Anyone running accel distributers

[the fall guy]

Just wondering because ever since I got mine installed it knocks when under load. Especially if I'm on the highway. I have a 305 85 k5 and it is stock. I also back down the adjustable vacuum advance but with the timing dead on (4 degrees btc )and the vacuum advance at 1 turn it still knocks. On the manual it says 4 turns will get you at 12 degrees. The carb is adjusted right and the dist. is also installed correctly. I also put the heavier springs in and still it knocks. Any help would be great.
Thanks
Nick

 

[ntsqd]

If you have one less than ~3-4 years sold what you really have is a Mallory dist. The superior Accel dists ceased to exist when Accel was bought by who ever it is that owns Mallory.

The Mallory type dists use a key that allows you to set the maximum mechanical advance. Might see if you have too much advance in the setting.

 

[PhoenixZorn]

I have the accel... I'm pretty sure it's more than 3 years old... but I've never had a knocking problem as far as I know, just the bogging problem so far at idle when I let the clutch out...

 

[the fall guy]

I think it is a older one. I had it installed last year but it could of been on the shelf for a while. I read the manual and it doesn't make refeance to a key to set the mechanical advance only a allen wrench to set the vacuum advance through the nipple on the vacuum canister. I emailed mr. gasket who now owns the accel name and the tech turned around and said to reduce the timing. I thought that if it calls for 4' btc then it should be 4' btc. I think that response was just to brush me off.

 

[mouse]

I'm running one I bought last year, has the adjustable vacuum advance. I have no problems with knock at all. I have the static timing set to 8 degrees and the vacuum advance at what ever came with the distributor. I guess I could hook up the timing light and see what total timing is, but I have 0 problems.

How long since you've had your heads off? Is there any chance you could have carbon buildup/higher compression causing the knock with poor gas?

 

[the fall guy]

Never had the heads off but the engine is still strong...I ran a can of carb cleaner a month ago to clean out anything in the manifold ,carb and heads. I am just stumped. Could it be the module hook up for the factory dist. is not hooked up...mainly because the accel doesn't have that hook up on it.

 

[sweetk30]

i wont buy accel crap. had 2 new dist and supper coils from them and no worked . but every time i put old shot hei back in fire up no problems. thats when i got full msd stuff. no problems there.

 

[trailblazer86]

One thing you might want to check is the vacuum hose maybe you are still pulling vacuum under load.
Pull the vac hose off and plug it.
Take the truck for a drive like this.
If it still pings then you may have that initial timing too far ahead or the springs are too soft on the mechanical weights.
This truck is pretty heavy and the advance need to be slower than a hot rod.

 

[dyeager535]

Under load there is so little vacuum it doesn't matter where it's hooked up.

Vac advance works by "adding" advance when the engine is NOT under a heavy load. (steady cruise) Once the vacuum disapppears (acceleration) the vac source disappears, and so does the advance.

 

[trailblazer86]

Yes-
At wide open throttle the vacuum will drop to near zero.
But-
If he is just pushing into the throttle to keep his speed up such as up a hill or pulling a big load it will still ping if the vacuum advance is not adjusted properly.
This distributor does have an adjustable vacuum advance, and it may need to be set up.

Also if he is picking the vacuum from the wrong port he could still have some vacuum.
There is still a vacuum signal just under the throttle blades due to the venturi effect.

 

[dyeager535]

It's real easy. If you think you have too much timing, just retard the base timing (say 4* if it will still run) and take it for another run.

If the little bit of vacuum it's seeing under load is enough to advance it into pinging territory, then retarding base 4* should prove thats the problem or not...if 4 turns gets him 12* (supposedly) and he's got it at one turn, his vacuum advance should NOT be giving him very much additional.

Whats the timing look like with a timing light hooked up and vac advance disconnected and connected? Is the vac advance adjustable while the engine is running? Make sure that the adjustment is actually doing something.

Those 305's are VERY borderline when it comes to pinging anyways, which is why GM saw fit to use ESC on every one.

 

[Mad-Dog]

The SBC enjoys around 35 degrees of total advance: 10 degrees initial, 10 degrees vacuum and 15 degrees mechanical = 35 degrees total
4 degrees initial is 6 degrees short of what the engine wants and will cause preignition or (knocking), reset the distibutor for 10 degrees initial and try it again...