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timing issue

R

redsnapper386

Regular Contributor
guys i need some instructions on how to reset the timing on my 1987 350 a-1.the motor is not stock.has been rebuilt with -bored 30 over,flat tops,stock crank polished,stock heads shaved .010, cam is stock with a 400 lift.i upgraded to a marine gm hei dist.the hei is tuned with correct springs and wts.i took boat to river for a test run.with timing set at 10 deg the boat simply would not idle.i slowly advanced the timing until all was good,i checked with time light,and the line on harmonic bal was about 2 inches above the timeing tab. i figure the dist is off 1-tooth,or out 180. correct me if im wrong.before i go further,can i get #1 at tdc,and restab the dist with rotor pointing to # 1. or can someone give me better instructions. i even wonder if the balancer is slipping on the hub.the balancer is 1987,and was not replaced.my fault there. thanks in advance.
 
Go to my thread titled "thunder bolt IV timing issue". My setup is different than yours but there are some links in that thread that show the correct procedure for timing the hei system
 
If your ignition distributor has springs/weights, then the advancing mechanism is "Mechanical"... not typical EST!
So any Thunderbolt ignition instructions will be of no value to you..... other than viewing the OEM advance curve, and from the sounds of your build, this is not an OEM build.

With Flat Top pistons, and with the correct 76cc chamber heads (very important), you have a potentially Quench Effect built engine, but only if the correct head q/e gaskets were used.
If these components render a good Marine suitable Q/E, your ignition timing specs can vary some from OEM.
BASE and/or Initial advance are one aspect, and will primarily influence idle RPM ONLY.
However, with Mairne, the more important aspect of ignition timing, will be your TA (total advance) and the RPM at which the system advance will be Full IN!
Too much/Too early, and we have trouble.

Part of my point is, BASE is BASE.... and is BASE all day long, but it is not the more important aspect of ignition timing.
Your curve and limit are much more important.

Marine engine Ignition Induced "Detonation" is nothing to risk, and can be very destructive, so pay particular attention to your TA or TAT.

I'd strongly encourage you to correctly mark off your harmonic balancer up to approx 35*.
Strobe your timing marks at an array of RPM, up to the limit RPM
1k, 1.5K, 2k, 2.5K, 3k and perhaps 3.2k rpm.
Plot these out on paper, and post the results here.

.
 
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thanks rick,this is very helpful.i will post back later as i have other work to do. also,i plan on installing a timing tape on the balancer.
 
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