# Distributor setup.



## Muttley (Jan 22, 2021)

Hi guys,

Ive read the tuning sticky in regards to tuning timing etc. 

I have one more question though ... My distributor (performance world billet RTR) has options for total advance as well as curve.

The options for total are 18, 21, 25 and 28 degrees. They are bushings that you can change out. 
I know I'm looking for 36 degrees total. so the 21 degree bushing (that's what came in it) would need 15 degrees at idle yes ? Should I change the bushings for any reason that I'm not thinking of ?

Also, which springs should I contemplate using in this distributor? I'm new to the whole distributor timing thing and want to get off on the right foot.

Thanks!


----------



## PontiacJim (Dec 29, 2012)

Muttley said:


> Hi guys,
> 
> Ive read the tuning sticky in regards to tuning timing etc.
> 
> ...


I'll say that seems correct, 21 + 15 + 36 total.

The springs you select is what creates the advance curve, or when total is reached. For example, lighter springs might have the total all in by 2,600 RPM's while heavier springs might have total all in by 3,800 RPM's.

So you may want to experiment with the springs and you can mix/match them to get the curve you want. Just stay away from detonation or you'll damage the engine.


----------



## Muttley (Jan 22, 2021)

Jim,

Any idea where I should start? Should I change the advance bushings or is the 21 degree setting ok as a starting point? 

Also, any recommendations for a timing curve based on a stock 68 428? The distributor I have shares springs etc. with the MSD RTR billet distributor.

Any advice is much appreciated.

Thanks for helping me learn.


----------



## PontiacJim (Dec 29, 2012)

Muttley said:


> Jim,
> 
> Any idea where I should start? Should I change the advance bushings or is the 21 degree setting ok as a starting point?
> 
> ...


It really depends on compression and gas octane. I assume the 428 is stock? 10.5 compression? Needs 98 octane?

Personally, I would install the 18 degree bushing with the 15 degrees initial advance with vacuum advance disconnected - assume you have a vacuum advance? 15 + 18 = 33 total. However, if you do have a vacuum advance, you need to know how much. So once you set initial, hook up vacuum, and see how much it changes. That will tell you how much vacuum advance at idle. Typically, you want around 21-22 degrees with vacuum hooked up, so 15 initial may be too much and you will need to drop it down closer to 12. If so, then I would use the 21 degree bushing stop. The key is to make sure the engine cranks over without much laboring. If it is hard to start, then the initial advance may be too much.

Timing curve in my opinion should be all in around 3,200 RPM's, but you may be able to go as low as 2,800 with a high racing octane gas, but I think a range of 3,000 to 3,500RPM is where you can experiment. Again, engine detonation for extended periods, or if very violent, will break piston ring lands, crack pistons, and beat the rod bearings to destruction. So it is better to go conservative and lose a little HP, then to go to the edge and have the engine on the verge of detonation to maximize HP. Very little loss of power in going a little conservative.

Don't think you can tune out detonation by setting up the distributor and keep the 10.5 compression and run on 93 octane. If factory compression ratio, you will have to step up and buy the higher octane gas or use a quality octane additive. Lowering compression is the only answer in running pump gas. My brother has a '69 Boneville with 428 he recently purchased. He said he could not drive it because it pinged so bad on pump gas. He installed a set of 6X heads to lower compression and said he now has no issues and it still pulls like a freight train.


----------



## Muttley (Jan 22, 2021)

PontiacJim said:


> It really depends on compression and gas octane. I assume the 428 is stock? 10.5 compression? Needs 98 octane?
> 
> Personally, I would install the 18 degree bushing with the 15 degrees initial advance with vacuum advance disconnected - assume you have a vacuum advance? 15 + 18 = 33 total. However, if you do have a vacuum advance, you need to know how much. So once you set initial, hook up vacuum, and see how much it changes. That will tell you how much vacuum advance at idle. Typically, you want around 21-22 degrees with vacuum hooked up, so 15 initial may be too much and you will need to drop it down closer to 12. If so, then I would use the 21 degree bushing stop. The key is to make sure the engine cranks over without much laboring. If it is hard to start, then the initial advance may be too much.
> 
> ...


Jim,

Thanks a lot for all that info. 

AFAIK the 428 is stock (although I didn't build the motor) it's not the HO so it should be the 10.5 motor from a grand prix. I don't know exactly what octane iot's going to need but it currently has some 94 in it and I'm not afraid of running some booster. In fact, I think I'm going to have to with all the reading/learning I've been doing.

I can change the bushings easy enough, so putting the 18 degree in shouldn't be a problem. I do have vacuum advance as well. 

I think I'll start with bringing it all in around 3500 if I can and fine tune from there after driving it and listening for detonation.

Thanks again!


----------



## GTO44 (Apr 11, 2016)

PontiacJim said:


> For example, heavier springs might have the total all in by 2,600 RPM's while lighter springs might have total all in by 3,800 RPM's.


Think you have a typo... Typically the lighter springs will bring in the curve sooner, heavier springs bring it in later.

To the op, typically for heavier automatic cars the heavier springs work better (bring the curve in later). For a lighter manual car the light springs are better (bring the curve in earlier). Usually a good rule of thumb on MSD distributors is to run one light spring and one heavy spring. Obviously all cars are different so experiment. There's nothing wrong with starting at 3,500rpm and start bringing it in sooner like Jim mentioned. You want the timing all in as early as possible without detonation for best performance.


----------



## PontiacJim (Dec 29, 2012)

GTO44 said:


> Think you have a typo... Typically the lighter springs will bring in the curve sooner, heavier springs bring it in later.
> 
> To the op, typically for heavier automatic cars the heavier springs work better (bring the curve in later). For a lighter manual car the light springs are better (bring the curve in earlier). Usually a good rule of thumb on MSD distributors is to run one light spring and one heavy spring. Obviously all cars are different so experiment. There's nothing wrong with starting at 3,500rpm and start bringing it in sooner like Jim mentioned. You want the timing all in as early as possible without detonation for best performance.


Thanks for catching that. 7 hits of mescaline, a toke on the bong, and listening to Metallica at full volume can cause one to reverse "heavy springs" with "light springs." I just edited it so it is now correct if others read this post.


----------



## integrity6987 (May 10, 2017)

PontiacJim said:


> Don't think you can tune out detonation by setting up the distributor and keep the 10.5 compression and run on 93 octane. If factory compression ratio, you will have to step up and buy the higher octane gas or use a quality octane additive


----------

