Don Terrill’s Speed-Talk

sbc summits version of the msd setup about 7 yrs old runs fine
When timing it mark keeps advancing period

had it professionally curved, pulled it otu then checked again on his sun machine (bob Jennings wouldnt doubt him for a min) cant see a problem
Mark dances around also suspicious of the oiil pump or the ign itself. No misfires or other issues
DId the same thing when the motor was a 350 reused the ign system oil pump and timing gear. Engine only ran a handful of times

Leave it be? Hate to just "lock it out" want to figure the problem..if there is one but sure dont want to grenade this thing
After 2 yrs finally in a spot where I can get driving it again

Last time a situation like this came up on S/T, it turned out to be the outer ring of the damper shifting.

Do a temporary lock out with small zip ties in dist weights and recheck it, agree balancer is high on list of culprits.

Yep harmonic balancer would definelty be 1st port if call.
Verify TDC ! Put a paint mark on the balancer inner and outter ring so you know if they move with just quick glance.
OR do you mean that there seems to be no rpm end to the advance curve and that it does consistently come back to the same base timing?

Its a streedampner..on the zip tie thing just tie the weights et all together?
Tempted to lock this thing out period. Nice curve but still needs a lil more advance at at idle I think

cuisinartvette wrote: ↑Thu Nov 09, 2017 11:02 pm Its a streedampner..on the zip tie thing just tie the weights et all together?
Tempted to lock this thing out period. Nice curve but still needs a lil more advance at at idle I think

Yes, use small zip ties to get temporary lock mechanical advance mechanism, try the mark on inner/outer damper sections suggested above.
When you say it keeps advancing are you constantly having to retard the dist position to correct it?

At idle or ver low speed its kinda stable. More rpm the more it bounces.
Temped to just lock the damn thing out but like having a curve not sure if would solve the problem it just never stops advancing period

Any changes to the signal wire routing, ground or any new power wires routed?

It could be the wires from the mag trigger to the ignition box are reversed. At the first connection from the distributor to the extension cord the purple DOES NOT go to the purple. Purple to green, orange to purple. At the connection from the extension cord to the pigtail into the box, purple does go to purple, and green to green.

BOOT wrote: ↑Sun Nov 12, 2017 1:03 am Any changes to the signal wire routing, ground or any new power wires routed?

Good point, i had a BBF in the shop a couple years back with pro billet dissy and 7al ignition box. Timing was good till about 1800/2000 rpm then would dance back and forth , more the harder it was revved. The 7al to dissy wires had been extended with twin core cable with no twist in it. Put a twist, about 360* every 6" along the 4' extension and problem solved.

Illcheck that, tuner bet that is it.

Not sure how that distributor's advance mechanism is set up, but on the cheap hei distributors, like an msd street fire for example, the first thing I do with those is limit the advance mechanism. I go to the hardware store, get a small screw and a nylon lock nut. There is a hole on the base where the weights ride, about a 1/4 over, that I put the screw in, the weight hits that when it starts swinging out, and stops the advance. It limits the mechanical to about 15. The rest is initial. They need that done, otherwise, the weights swing to far and keep advancing. I had an engine once that was going goofy up top. We taped the timing light to the cooling tower, with the trigger locked down, put a white mark on the front of the dampner where the mark was on the tops side, went into the pull, and you could see the line move up and stop when the advance came in, then as rpm went up, so did the line. Say we had it set to have advance all in by 3000, about 4500 it started climbing. We estimated it added about 20 degrees up top. limited the advance mechanism like I described, and it was good to go.