[rocks66ss]

I don't don't recall ever seeing a factory distributor with less than 18º advance and most had more than that. Also, most Delco distributors werent' all in until around 4k, many closer to 5k. The only exception I know of was the 365/375 327s, which had 24º mechanical all in at 2350. In contrast, the `65 L-78 had 28º @ 4600. All of the MSD distributors I've had came out of the box with 21º @ about 4,100.

The point I'm trying to make is don't assume anything. The only way to know how much initial a particular distributor should have is to know how much mechanical is in that particular distributor. The only reason the factory could specify an initial setting is because they knew how much mechanical was in the distributor used for a particular application (and they varied a bunch from one application to another).

The distributor I'm currently using is 1112113 2G3 I have my original on the bench and going to rebuild this winter.

I can only get 15* mechanical out of this distributor. I suppose I could remove the rubber bushing off of the pin but I don't know how much more that would get me. i have a B1 vacuum can that give me 16*

To run 36 total, my initial lands at 21. all in with vacuum I run at 52. My car runs very well here except when i run thru the gears just normal driving on the street and just before it's time to shift i get a little rattle that sounds exactly like a rocker arm clattering.

So as to make sure it really wasn't a rocker arm, I redid valve lash and it was still there, so i assumed I was getting a little ping, so I spent last night playing with springs and settings to a point where this ping went away.

So I ended up bringing my total down to 31, and makes my initial land at 16, all in with vacuum is 47 The car runs great, as far as seat of the pants I cant tell an difference from where it was.

I will be able next weekend to check mileage, as i will be going on whats called the fall color tour and i will be driving all over the state of Missouri.

But like i said this is a delco distributor and 15 mechanical is all it's got which from what every one is saying is not the norm for a stock distributor.


Rocky

 

[SWHEATON]

The subject of timing and the theory behind all this on what and where to set your engine for peak performance is all very fascinating, and I have received quite an education this last year with the knowledge I've gained from everyone here and by hands on tinkering with my car, which brings me to my question.

It seem like an average stock distributor has aprox 14 degrees of timing, an average vacuum can has aprox 14-16 degrees in it so why did the stock book setting say for a 66 BB show anywhere from 4 to 10 BTDC?

Lets say you went with book 10 initial, that gives you 24 total and a w/vacuum advance 38.

The general consensuses today is your total should be 34-36, and with vacuum advance, that would puts you in the 48-50 range. This put everyone's initial on the average in the 18-20 range to acheave these numbers.

So if these figures today that is generally accepted by everyone, why were the stock initial settings so low, or am I missing something here?


Rocky

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The main reason even stock perf gm cams generally ran a lot less initial/base timing then your avg aftermarket perf cam does in for example a 396/350hp motor that had gm's version of what they called a hi perf hi lift ft cam is becuase the aftermarket perf cams even mild ones usually have a lot more duration then stock gm perf cam did (not talking L88 cam here either!) which requires more timing to run efficiently.

But in general for street use many mild aftermarket perf cams run decent with 16-18 deg inital/base & 36-38 total and hotter cams 18-20 deg inital/base 36-38 total and some real hot cams 40 deg total.

Vac adv limited to 10-12 deg max will also compliment many perf cams on the street as long as there's enough vac at idle to keep it fully deployed to maintain a stable idle .

Scott