Ignition timing, idling woes, Opinions of what to trouble shoot?
 

Got 454 mags rebuilt with some really good parts from RMBuilder. Installed Performance Distributors' marine DUI distributors. Had no problem setting the timing on my starboard engine with my dial back timing gun. Simply set my timing gun on 24* and revved the engine to 3000 rpm and moved the distributor until the mark on the balancer matched the timing mark. So starboard engine runs and idles great. Port engine I can't get to idle or start after I supposedly set the timing just like the starboard. I have checked the plug wires, and will again in the morning. Port engine's RPMS want to fluctuate (28-3200) too much around the 3000 rpm I am trying to hold to set the timing (if this helps diagnose). Engine wont idle and it coughs back up thru the carb on the first crank then it will turn over with nothing. I have to go back with the distributor wrench and start all over. Any suggestions to how to trouble shoot my starting and idling problem after I supposedly set the timing correct? Am I setting timing correctly? I got the first one correct, what's wrong with this port engine?

well... for me its always start at the beginning... take number 1 plug out and stick your finger in the hole and have someone bump the starter until you get compression that pops your finger. the confirm that the timing mark on the pulley lines up with the indicator on the front cover ( after you roll it the rest of the way to TDC) then take the cap off and make sure the rotor is pointing at the post that you have as number 1 plug.
then you make sure the firing order is correct... then ( if it was me) i would get a gun without the advance dial and set the timing that way... i have seen lots of those dial guns be wrong by a lot and a little and i never believed in them enough to rely on... and then i would set the timing. if all those things are correct, it has to start and run. the only time i have seen that NOT the case is when someone put the cam in pretty significantly wrong...

is balancer new ? if not ck to see if TDC mark lines up with keyway...seen many slip...double ck firing order seen to many have wires crossed, valves adjusted to tight also cause issues like this

The engines have about 20 hours on them with the stock thunder bolt ignition. So I'm pretty confident the engine builder got the cam correct. Went with the new ignitions to get the revs up over the merc rev limiter. Picking up a timing tape from a speed shop in the morning. Just going to set digital gun on zero and measure with timing tape. If still no good going to go buy a cheap timing light. Both Engines ran flawless till I changed the distributor. Got to be the dial back timing gun?

Balancer not new, can you describe key way and I will check. EZ did you see since your post that everything was fine up till me changing distributors?

well... that settles most of that. if they ran before you screwed with it then nothing fundemental is wrong. it has to be something you did. so go back and start over... tdc/marks/dist pointing to #1 etc... you don't need a timing tape ... dia x 3.1417 / 360 times the number of degrees you want and thats how far the mark should be circumfrentially from the TDC mark...

Lol, yep got to be something I did. Was really looking for assurance nothing else. I was looking up how to make timing tape and it was just as you described. 8" dia balancer and I need 24* advance @ 3000 rpm would be 1-11/16". Going to try this in the morning with the gun set to zero and a scribed mark.

Why would you want only 24* total timing???????????????

Total timing should be set at 32-34*

Griff, I may be setting timing incorrect. Do I find out my total timing and then set it while at 3000 rpm? Does it matter whether you set timing while at idle with base timing or reving with total timing. Think I may have messed up by simply timing what was scribed on the new distributors "24* @ 3000 rpm". Going to give Performance Distributors a call to make sure what I purchased and see if they have a timing chart.

EDIT: update: since 6:45 am this morning.

Made some time marks on my balancer, turned my dial back down to zero degrees and just used like a normal timing light. Set rpms at 3000 and timed for the 24*. Waaa-la, idles smooth. Everything is good and it's on like a chicken bone for the weekend! thanks for help working thru problem guys.

I think the "24* at 3000rpms" scribed on the dist is the advance built into the distributor. That is not where you want total timing set. That is not enough timing and will cause high EGT's.
You want 32-34* total timing, so you have to set timing at idle to 8-10*. That plus the 24* built in to the dist will get you 32-34*.