Position of H.E.I. cap in relation to firewall

On my Chev small block (1985) with HEI factory ignition, the HEI cap has a rectangular shape cast into the distributor cap. When looking down onto the cap, assuming that the rotor turns clockwise, the second terminal past the cap is the terminal which I designated as number 1 plug when I reinstalled the distributor. That was based on number one cylinder coming up on compression, and the timing mark on the harmonic balancer lining up with the timing pointer. This should have, in my opinion, meant that that rectangular projection points directly towards the drivers side frame rail, pretty well at 90 degrees to the crankshaft centerline. I have started the car, with vacuum advance disabled and the carb vacuum line plugged. It seems that if I advance the timing by rotating the distributor body counterclockwise untill that rectangular projection almost hits the firewall, that the engine runs very smooth, but the timing marks are way off (showing huge advanced timing using a timing light).----if I retard the timing by turning the distributor body clockwise, I can get the timing marks to line up by the timing light, but the engine runs very rough.-----I assume from all this, that I must be off one tooth on the distributor gear to cam gear mesh. I think that to correct matters, so that the engine runs smoothly with the timing marks correctly aligned, that I have to lift up the distributor and turn it by one tooth . Question is, when viewed from above , do I rotate it clockwise one tooth or counterclockwise one tooth?

Turning the body clockwise is the same as turning the rotor shaft counter-clockwise.

Hey Tech---I know that, but it doesn't answer my question. I don't want to pull this thing apart and turn it the wrong way.

Brian, if you think about it, it DOES answer your question. Lift the dizzy out and move the rotor counter-clockwise one tooth.

Thanks Tech---I'm not being dumb on purpose. Do you know approximately how many degrees the cap would be turned from correct position if the mesh was off by one tooth? It seems there should be a mathematical solution to that, but I don't know how many teeth there are on a distributor gear. If I did, I would think 360 degrees divided by the number of teeth.

It seems to me that if there are no restrictions on how far you can turn the distributor (i.e. hitting firewall), that the engine would run alright even if you were one tooth off, its just that the timing marks wouldn't be correct. Is that a correct assumption?

Brian,

Pull it out and count 'em. :LOL:

Brian, I don't know how many teeth there are and I don't have one here to count, but I really think you're making more out of this than is necessary. Lift the dizzy out and re-align the oil pump drive with a long screwdriver for the new rotor position at one tooth counter-clockwise. Slide the dizzy into position and install the hold-down bolt. Fire it off and see what you have. If it's spot-on, great. If not, it's no big deal to move it one more tooth.

Gee, Thanks Henry. If I got to pull the darn thing out I am just gathering info before I do that. Remember guys, I only do this distributor thing about once every ten years. I have never had an engine act quite like this, but then maybe I always lucked out on my other engine builds/rebuilds and got the gears lined up correctly first go round. It seems strange to me that the engine runs good with the distributor in a position where the timing marks don't line up, but bad when I move the distributor into a position where they do line up.---I think that indicates being off one tooth, and I'm just trying to confirm that, and how I correct it.

Can I throw a couple of points into the fire?

1. IF you are not sure what affect the moving is going to do, just move the plug wires on the cap.....one position....and then you will know if you can time it.

2. If you are trying to get the marks to "line up", arent you trying to time it to 0 degrees? OR is your setup marked with advance?

mike in tucson

Richard,

I liked the old distributors where you could just turn them as much as you wanted to bring the timing in. I was fond of the Malloroy UniLite. Drop it in any old way, take a look at where the rotor was pointing, wire the plugs from there, and turn it until it ran.

Brian,

http://www.clubhotrod.com/forums/sho...threadid=13944

Notice that the rotor is just short of the 2nd terminal. The timing marks are on TDC.

How does this compare to yours?

Of course, I don't know if this works yet. I just put it back where it was when I got the engine out of the crate.

"1. IF you are not sure what affect the moving is going to do, just move the plug wires on the cap.....one position....and then you will know if you can time it."

Well, DUH!!! Thanks mike. Excuse me while I go bang my head on something solid!!!!!:eek:

O.K. Guys---Here's the deal. I was anxious to run the engine to check for oil and coolant leaks, and it did fire and did run, and I did get any leaks buttoned up. I couldn't get it to idle slowly the way I wanted, but it still has the 20 year old quadrajet which has never been rebuilt, leaks, and has been monkeyed with by the previous owner. I had no exhaust system except the manifolds, and it sounded like world war 3 in my garage. I put my timing light on it and discovered the anomaly with the timing mark, as discussed. I was happy to have the engine run, and get the any leaks sorted out. This weekend the car is going to the muffler shop for a complete exhaust system and I am going to buy a rebuilt complete carburater from a shop that specializes in rebuilding carburators. When I get the car back, and the new carb on, I will reexamine this timing issue. It seems to me that I probably am out one tooth on the distributor, but untill I can run the car at a proper idle speed, I am not going to try to reposition the distributor. I am not sure at what speed the centrigugal advance begins to affect things, but it may be that I had the engine running too many rpm's to really check the timing properly. When I get the rebuilt carb on, and things quieted down and slowed down, I will take another shot at the timing.

if you can set you timing with the light thats all you can do to set the timing. if you set your base timing at 10 degrees with a light it is at 10 degrees, if the cap is hitting something so you cant get 10 degrees with it then you would need to change the rotor one way or another, but once you set the time at 10 degrees if you move the rotor 1 notch you would have to move the dist the same amount to get it back to 10 degrees so you didnt do anything. with the timing light on no 1 wire there ant but 1, 10 degrees setting for that cylinder.:HMMM:

Just a thought,,,take your cap off and put a hand vaccume pump on the vac advance module,,,and pump it up,,,look or feel for the movement underneath your vaccume advance module,,the actuating rod should be pulling back,,if not,,the diaphram is probably shot,,,,also,,,check your manual advance weights under the rotor and make sure they are not sticking in an advanced position.

Here is a bit of weird information.---My distributor gear has 13 teeth on it. That means that if you are out one tooth on the mesh with the cam gear, then the distibutor shaft will be 360/13=27.7 degrees out of positon, rotationally. There are 8 terminal lugs on a V8, so there is a terminal lug every360/8=45 degees. So----if you are out of mesh by 1 gear tooth then your cap will be out of position by 27.7/45=0.61, or about 1/2 the distance between 2 terminals. So----it seems to me that you could be out of mesh by one tooth and still be able to adjust the distributor body enough to make the engine run.---this gets into pretty strange science, and I am sure that the engine would run, but not well, and you would never be able to line up the timing marks on the harmonic balancer with the timing pointer. I beleive that is what happened to me. I finally pulled the distributor and re-timed it with number one piston on top dead center (as well as I was able to establish)., and now the engine runs o.k. and the timing mark on the harmonic balancer does line up with the position where it should based on a 305 pointer, not the 350 pointer which I was sold (I was told they were all the same).

dont forget that the distributor turns 1/2 crank speed so
10 deg of crank rotation is 5 deg of distributor rotation!

I have the same issue. Was wondering if you ever got it solved.

Thanks.

[QUOTE]and now the engine runs o.k. and the timing mark on the harmonic balancer does line up with the position where it should based on a 305 pointer, not the 350 pointer which I was sold (I was told they were all the same).

Yes---as I said in the original post, I pulled the distributor and turned the rotor shaft by one tooth to position the cap where it should set in relationship to the firewall, found top dead center on compression stroke on number 1 cylinder, and scribed a new timing mark on my harmonic balancer.

Sorry, missed that earlier statement.

So actually your timing was off because of the balancer mark. Unfortunately mine does read TDC properly. Looks like I have other issues.