Hey guys. Had someone help me the other day changing spark plug wires on a MSD Ignition system which used a similar cap to OEM. Problem is that the wires were pulled without marking them in relation to cap position. My buddy did mark what he believed was #2 cylinder on the old cap but it appears to be one off in relation to my Chilton's manual. Specifically, looking from the grill to the firewall the #1 wire plug should be just forward of the cap mounting screw on the RS according to Chilton but that is what he marked #2. Effectively, the whole cap would be "one" off if I used the marked#2 cap post vs what Chilton's shows. Might the MSD cap be off one as compared to OEM when referencing its mounting screw? Trying to avoid searching for TDC as battery out of car. Can I find TDC by matching harmonic balancer mark (notch) to 0 on timing plate?
The #1 piston will need to be on the compression stroke instead of the exhaust stroke. The stroke can be verified by either removing the driver's side valve cover and looking at the valve movements or by replacing the #1 spark plug with a clean, lint-free shop rag (on the compression stroke the air will displace the rag). After it's on the compression stroke, something like a non-metallic rod could be inserted through the #1 spark plug hole to find TDC. Rotating the crank is easier if all the spark plugs are removed.
As others have stated. I do it as follows. Use a breaker bar on the crank bolt and locate #1 on TDC of the compression stroke. The crank will turn 2 times, one revolution will bring you to the top but it could be the exhaust stroke or the compression stroke, so with the #1 plug removed, (I pull all of them to make it easier to turn the crank) get it to TDC on the compression (not exhaust) and the balancer index will be on the 0 timing mark. I use "foam" ear plugs, because they make a nice pop when the nearing the top of the compression stroke. Or you can use a small toad, humming bird, or have someone hold a finger against the plug hole. Once #1 TDC on compression stroke is reached, look at the rotor, it will be where the #1 post should be on the cap. The distributor does not care where it is with regard to the cap (per manual), as long as #1 wire and the rest are in correct firing order to operate. It is manly "standardization" so that all distributors for the specific engine are similarly configured as well as having the distributor clocked correctly (and as the manual shows) is to ensure the vacuum advance canister is not hitting anything in the full range of retard/advance range when turning the distributor where it needs to be as well as allowing point dwell to be adjusted with the little access door on points distributors that dwell is adjusted while running being located where it can be accessed. If yours is not having any interference once you get it set to TDC on #1, wired correctly and can set proper "power timing", no need to worry about your distributor matching any image, just mark the number # wire and post on the cap. Otherwise and unless you want it positioned per manual, you will need to get to TDC #1 compression, pull and re-clock the distributor. It's not difficult.
If you leave only number 1 plug in when you bar the motor over you will have no question if your on the compression stroke or not.
Another way is to remove the valve cover and watch the #1 intake valve. It is the second valve from the front of the head. The intake valve will open, and when it closes, the piston will be on it's way up in the cylinder on the compression stroke. After it closes, keep turning the engine until the balancer mark is aligned with the timing scale.
If you didn't pull the distributor, and it's just a mix up of wire position, all you need to do is put the wires in their proper position. The number 1 wire is just clock wise of the point adjustment window. Then just follow the firing order clock wise around the cap. 1-8-4-3-6-5-7-2. That's if they were correct before.
Wires were OK as far as position to start with. Using same cap but new. I just lost track of wire placement after they were removed without labeling. My concern is that on the MSD cap it appears that I am one forward (2 vs 1) compared to what I see in the Chilton diagram.
As has been pointed out, it doesn't really matter where number one wire is, as long as you follow the firing order around clockwise, and, the rotor is correctly clocked to fire the number 1 cylinder in proper time. I would trust a Chassis manual over any Chilton manual. Chances are it won't start with the wires off by one. That is 45* difference in distributor timing, which doubles at the crank. Have you tried to start the engine? This is your Chevelle 454, right?
Either the wires were NOT "OK" to start with, or the distributor shaft is mis-positioned by a tooth or two. If the shaft is mis-positioned, the wire position on the cap can be changed to accommodate the incorrect shaft position...but it looks dumb.
stick a cork in plug hole it will pop like Champagne when ready point balancer to '"0" and it will point to #1 on dist cap #1 wire goes there. boom The rotor will be pointing to you in front of car
Just line up the timing mark and pull the cap off. It's either going to be on #1 or #6. If it looks to be near #1, put #1 there and then follow the firing order. If it starts, great. If it doesn't start and backfires, move the wires clockwise four positions. You have a 50/50 shot of getting the wires on the first time.
MSD non HEI system uses no points so there is no window. Just hold down screws to reference. The old GM Chilton book I have and some other sites show a very different non HEI cap diagram.
The MSD cap is the same even if it doesn't have a points window. You can still use the hold downs for reference. The pictures I posted come from GM. That is the way they came from the factory. Is your engine not running because of this? Does your cap look anything like above?
I have had a MSD 85551 system (distributor and box) with a MSD 84335 cap (no metal window) and rotor. Everything new put back in same manner as taken out and the same MSD product. Wires only issue.