71 LA 340 timings moved!! how?? looking for help
How do you know it moved? Are you SURE of what it was ? My 408 runs at about 30 degree advanced. You did not state what you think it should be set at.
I'm afraid not, I don't know what it was set at, I only checked timing after it did the rapid popping when I gave it some, which is not that often so could have been an issue for 100 miles but didn't feel it until I booted it some, I just assumed the timing was high at 32 degs initial and as high as 50 degs fully advanced.
I think it is 32 degs initial after the onset of the issue. How much slop is in the timing chain? I'm not a fan of the tensioners. Mine had broken the guide on the spring side right at the pivot. The flat spring had slid down to the bottom of the cover.
Correct, and checked belt for slack and got none at all..
How about a broken advance spring in the dist?
Have checked and springs are good
With no load on the engine it is common for the engine to want between 50 and 60 degrees of timing at cruise rpm. So you can't hurt it with a true 40/50 after 2500 rpm with no load.
This is also why the Vcan will someday have to be re-connected. The engine wants what it wants, and if you don't give her what she wants,she will complain about it, just not as loudly, or as often, as when it detonates.
I don't know what the big deal is, just put the power-timing back to where it's supposed to be, tighten the clamp and if it idles ok you're done. Then index the D housing to the block with a chisel mark,and keep your eye on it.
I mean 50 less 32 is 18 in the D. If you reset the power-timing to 34 then you will have 16 initial, And that is pretty close to perfect.
Now if it comes in too slow or too fast, well then some springing is in order. But your test shows only 6 degrees added from idle to 2500,and only 10 degrees added by 3500,and only 18* by blipping to guessing 4000; so that looks pretty tame.The curve appears to be pretty safe for the combo.
Thanks for the info, I guessed the vac advance was removed as its been mechanically curved by weights and springs? and I've read a few Mopar posts were they have disconnected there vac, I can only assumed as previous owner is so rude and up himself that if you question anything he did he threw his rattle out the pram!! so just gave up trying when he got mates to also troll me, they even stated that when I do put it up for sale in the future they are going to waste my time by pretending to want to buy etc... we are talking grown men here 40+ years, crazy child like antics or what.. I can only guess he was pissed he had to sell?? but who knows lol!!
So really here on my own and although the net is great it can be wrong and its very hard to explain in a forum sometimes.
The reason didn't just re-time it was I'd rather find out the cause of the sudden advance, or so I thought as it now seems it could well be set at these levels???? hope you understand my ways lol!! I just saw it like seizing a turbo and just putting a new one on without figuring why it seized in the first place, although I know its a bit easier to set timing over replacing a turbo... but anyway its dark now so tomorrow I'm going to drive it and push it some and listen for that popping, which I honestly think has gone now, just by replacing new dist cap and arm with the old ones?? I guess next step is a rolling road while they mess with retarding the timing to a more normal level.
Take a permanent maker and draw a line across the balancer, reset timing to 12 initial for now, tighten distributor and drive it.
Check balancer to see if line is straight across or if it shifted from the center, ring slip.
A distributor with mechanical advane will have some movement , depending on how light the springs are, large the bushing or slot is will determine how much.
It's also possible to reverse the polarity on the pick up wires, and end up changing the timing by a lot.
Key here is...did the idle rpm ever change from what it was before? or was it just performance that went away?.....32 idle would have it well above 1000 rpm at idle.
Hey, checked the balancer already and appears fine, but will do as you outline over the weekend.. the balancer looks like an expensive one although I know that don't mean it can fail.. its a Pro Sport bonded steel high performance application??
Thanks to all for your input and advise hopefully all will be well in due course lol!!
