Mike, got a question

[bigd65]

what springs do you have in your MSD distributor. i just got MSD catalog and was looking at the HEI and it showed and also stated that it came stock with the silver (heavy springs) , what i called hood springs awile back. anyway, the MSD springs are the one i ordered awile back and i put the 2 silver springs (HEAVY) and that was what it took to get rid of the spark knock. it is even timed at 12* intial.

now my next project is to play with the vacuum advance can. i can understand now the initial and centrifical advance part od the timing but now i wanna understand more about the vacuum advance. why is so much locked out and why turn the inside screw 9 turns out. i just wanna understand that aspect of it and what to look for.

[swervin ervin]

Jeff,

I used the MSD springs that came with the distributor. It does come with the heavy silver springs installed. On mine, I run a light silver and a blue. My advance starts right at 1000 rpm and is full in by right 3200. I tried the 2 light silver and it was too much. It would be full in by 2500 rpm.

According the catalog that came with my MSD distributor, the springs from latest advance to earliest is: 2 heavy silver, 1 heavy silver and 1 blue, 1 heavy silver and 1 light silver, 2 blue, 1 light silver and 1 blue, 2 light silver. The 2 heavy silver springs starts at 1500 and is full in at 5600, what yours will be close to. This is bad for performance as you can see. Of course this is what it says for my MSD and it may be different for a GM HEI.

If you read the little pamphlet that comes with the Crane advance can, it will explain it a little. First, to limit the amount of vacuum advance, you use the plate which is fastened inside the distributor. This limits how far the can arm can go. The screw is how you adjust when the advance starts. The farther out you go with the screw, the later the vacuum is applied to the can. You can check this with a hand held vacuum tool, like what you can buy to bleed your brakes. I checked mine and at one time I could tell you how much 1 turn would do but it's been so long I've forgot. You can run more vacuum advance if you use a EGR, because the EGR helps cool the combustion chamber somewhat. This is part of the reason you have more locked out than I do.

Best thing I can tell you is, mess with it. No two vehicles are alike. What's best for me, may, as we have seen, be way off for you. There is no one setting for any two of us. We can get close, but the fine tuning is where you make it or break it.

Now, I see you said, you got rid of your spark knock. Good for you. But if you are like me, I wouldn't leave well enough alone. I would try different combos of springs to see if I could get it better. But that's just me.

Good luck with it.

[bigd65]

MIKE we are the same, you know i will be under the hood tomarrow

[swervin ervin]

I thought so.

[bigd65]

Mike, if you still have your stock distributor, would you do me a favor and look at the weights and the center plate and tell me what the numbers are on them. i have a couple differnt factory sets and am wondering if maybe that is where my problem is.
i have the 41 weights in it now and always have, but i have a set of 45. that really aint my cocern but the center plate is. i had one marked 375 in it and you know of all the problems. i put one in marked 452 and the knock was worse so installed one that is marked 368 and the knock was no longer there aint acceleration,i dont know about the WOT yet. i put in one blue heavy spring and one medium siler spring and the knock is gone on acceleration. i dont have time now to get it out on a back road to check it but i will on the way to work and will post it. if it still aint there i am going to try two medium springs.

BTW just a little info. i called the tech line at CRANE and the guy said that the 12* intial and 32*total is a myth and dont work on all motors, that it all depends on cylinder pressure. i just have to keep backing it off till the knock is gone at WOT and then taylor the advance from there.
the stock setting for the 87' surburban that this combo came from is TDC and that is where it has to be for the knock to be gone. what i dont understand is why this motor will not handle the 12* initial that yalls do. one more thing i dont understand is everyone keeps asking what my total timing is. if the stock dist has 20* built in and if the intial is set at 12* then it would be 32*. well then my initial is set at TDC and the dist has 20* then that is my total right. i dont mean to sound rude but this thing is driving me CRAZY. i checked my dist and everything looks great,no wear, no rust, no worn pins nothing. i dont understand why my motor will not handle the 32* total advance.

but if you would and others that read this post please look and see what the numbers are on your weights and center plates.
thanx for yalls time

[swervin ervin]

Nope, don't have it, well at least not to where you can see anything. I made a engine oiler out of mine. You know where you stick it in the hole and use a drill to oil the engine before startup.

Well, as far as I know, all GM HEI's had 10 degrees of of built in mechanical advance. This is 10 degrees at the distributor, but 20 at the crank. You know the drill about how the crank rotates two times for one of the cam because of the difference in the size of the timing gears. My MSD has 10.5 at the distributor and 21 at the crank.

Anyway, the center plate and weights had different rates of advance, hence the different numbers. I don't know a thing about which number is what, but I'm sure Grumpyvette at CT will, or someone over there can help in the Performance forum. When you go messing with the weights and center plates, you are opening up another big can of worms. This is something best left to a shop with a distributor machine to hook it up on.

You say it came from an 87. I thought they all went to the small body distributors and external coils in 87?? I know I drove a 87 cube van at work and it did.

And don't worry about being rude, we all know you are. Kidding. Seriously, I know how nerve racking this stuff is. It will drive you nuts for sure.

Mike

[bigd65]

Mike , this is the motor from an 87 but it was computer controlled so i aced the distributor along with the fuel injection. the guy sold me the motor and tranny combo for 500.00 bucks and said if i wanted the ecu for the F/I and everything that he would throw it in. i know now that i should have taken the whole thing and converted my truck. oh well that is water under the bridge. anyway, at the time i just used my ESC distributor and then i met yall on CT and learned about the ESC system and then aced it and went with a distributor from a 79 truck , well i set the timing at TDC and no knock anywhere, not at WOT throttle nothing. i just advanced it to 6BTDC and am going to try that. i accelerates real good at TDC especially at highway speeds, but there is an irritating vibration, so i figured i would advance it till i start to get the knock back and go from there.

I REALLY DO APPRECIATE ALL YOUR HELP AND PATIENCE. if it wernt for you and all the others that help me understand the distributor , i wouldnt know this much about it. THANX AGAIN and i am sure i will be throwing something else at you. maybe MSD pro billet dist questions,