Here's the deal. The 340 in my 1970 T/A has a strange timing issue. With #1 cylinder at TDC, the rotor points to the #8 plug wire. When trying to time it (vacuum advance unplugged), the timing mark is way off at about 25 degrees BTDC. Turning the distributor to the correct setting of 5 degrees BTDC and it will not run period. When the distributor is set by ear to where it runs the best, the car idles somewhat roughly and the engine shakes alot. The car runs down the highway pretty good though but seems to lack power. When stopping it dies almost every time. Could this be a jumped or stretched timing chain? I thought it might be a slipped harmonic but this doesn't seem to explain the rough idle and dying. Ideas??

It sounds like your cam gear for the distributor is off a tooth. You may need to pull it out and move it a notch. If this is the case,you should be able to get the timing back within the marks and set it properly. If thats not the case,check the timing chain for play by using a 1 1/4 inch socket on the harmonic balancer bolt.

Two things, are you setting TDC by the balancer or by the piston and have you double and triple checked firing order and rotation? 18436572 clockwise around cap. If you are setting it with the piston up, make sure it's on the compression stroke. Once you have done that and confirmed TDC double check you're rotor position. If it's still the same try and clock you're wires to the proper positions #1 to the 8 position on the cap and follow 18436572 in a clockwise direction and see if the car runs better. If that fixes you're running issue then you will have to check the drive gear or timing chain.

how cam the distribtor gear being off a tooth effective the igntion timing?

Or just move the plug wires until wire 1 is were 8 was.

No such thing as being a tooth off on a mopar..

the intermediate shaft drops in and has a slot.

you can move the intermediate shaft to where ever you want the distributor no. 1 to point to as long as the rotor is pointed to 1 on the cap...

now if your distributor body is giving you a problem as far as the vacuum advance hitting something...move the intermediate shaft and realign the distributor..

get a large screw driver and turn the slot clockwise the gear will go up the cam gear...then move it....it might that a couple of tries since the gear will slide down the cam gear and not point to where you want it to

Thats what I was saying,he may have to reindex the distributor drive gear on the camshaft to get the distributor to point at number 1,with the number 1 cylinder at top dead center on the compression stroke. This should get the timing to be within the 10 degrees plus or minus indicator on the crankshaft. This way he can time the car correctly. Maybe his timing chain jumped a tooth.

That's probably the issue, I just wanted to run through the basics. It could be the balancer is off, it's been known to happen so set the #1 piston at TDC. Pull the #1 plug and have a buddy stick a finger over the hole and slowly turn the engine over until you feel pressure and bring the piston to the top. Pull the dizzy and look in the hole and see if the slot is pointing to the front intake bolt on the driver side. If not insert the screwdriver in the slot and index the gear so it points in that direction. If you're running a new distributor you might need to check the gap between the reluctor and pickup. It should be .008 and be sure and check it with a brass feeler gauge, NOT a metallic gauge that a magnet will stick to.

What Mopar Country said. Pull #1 plug and bump the starter at the starter relay w a screwdriver until w your thumb on the plug hole you feel compression building then w a 1&1/4" socket/breaker bar continue turning it CW by hand until the marks are at 10 BTDC. pull/index the intershaft/gear & mock it up so it locates the rotor forward and slightly to the pass side. W the vac can roughly where you want it (has room to be turned both ways) then turn it slightly more one way or the other so the nearest reluctor tooth is lined up dead on w the magnet. The cap terminal above where the rotor is now is #1 of course and wire it CW from there. I'd have the dist medium snug so you can set the initial where you want it when it fires then lock it down. And for rotor phasing the rotor tip should be fairly close to the underside of the cap terminal that's now #1 and note that vac adv will shift phasing CCW (on a SB) from that point. (it'll move the rotor tip more CCW as eng vacuum increases) so ideally you want the rotor blade slightly CW from dead centered under the cap terminal but that's a seperate issue but might check it while you are on it. EDIT read your post halfway down, You installed a new MP dist & now it's acting up? compare The phasing of the rotor blade to the slot on the other end from the old dist to the new MP one.

yes, it would run, but his timing will either be severely advanced, or retarded, depending on which way it was off. i dont know why he cant find tdc, and just wire the cap to the rotor, starting with wire 1, and work his way around, as mentioned. it should fire right up, never mind what the timing marks say. get the slug up top, find the rotor and wire it.

how many miles ? "Jumping" a tooth on the cam gear would mean a very very worn out timing chain or gear (or installed incorrect) and jumping oil pump/distributor drive would mean catrostophic failure. i think that you need to start from scratch and run up #1 on compression TDC, set drive gear as instructed above(usually slot at #1 cylinder as i recall or toward 1st intake bolt on drivers side), find where rotor is pointed on cap (usually at #1 cylinder as i recall), set firing order, time as desired. but don't always trust the ballancer %100 because it can slip. then checking that is a whole nother process.

Problem solved. I took it to a local repair guy who is knowledgeable in Mopars and he got it running great. He fine tuned the distributor curve, timing, and center carb and it came to life. Now it runs strong and doesn't die. I love it when things turn out to be less serious than expected!