[heater63]

So I am stumped, over the winter I built a 77 TA 400. Not much of a build,

-6X heads
-30 over
-Crank 10/10
-Cast Pistons
-Street strip comp cam (should be able to find card but don't think it would matter)
-HEI distributor
-Comp push rods......

Started up fine broke in fine runs good. Finally have some time to drive it so I put a timing light on the engine. I couldn't get it to idle with any less than 25* advance. I verified it with another timing light.

I switch distributors and same issue.

I took off the timing chain cover and marks on gears are at 12 and 6, no excessive slack in chain and slack is on the passenger side of the motor..

I did use a chain cover off a 69 400.

i used a bump stop to find TDC and with that at 0 on the cover it still ran at 25* advance.

I took it out and it performs well, not hot, and no rattle under load which makes me think it isn't really running at 25* initial.

Is it possible the timing marks are positioned differently on the older chain cover?

Thanks in advance for any ideas
Heath

[tom s]

Is the vac advance hooked up?Tom

[heater63]

Advance is blocked off.

[Geoff]

Street/strip cam cam mean anything....

According to my Motors Manual, the 77 400 had a pathetic 7.6:1 CR. Probably run on kerosene...That very low CR will need a looooooooot of timing, made worse by the poor cam choice.
So I am not surprised it needs 25* of idle to get a decent idle with a 'çam'.
Use a Crane adjustable vac adv connected to MANIFOLD vacuum [ MVA ] adv unit to get the best idle. Example, if you use 12* init & best idle is with 34* at idle, the Crane should add 24*. As a starting point, adjust the Allen key all the way CW.

More on MVA, scroll down to post #6.

http://www.horodders.com/forum/vacuu...bad-47495.html

[heater63]

Thanks for the advice.

[JSPONT]

When you are at TDC did you check to see if the balancer line lined up with the zero on the timing tab? The stock balancer could have slipped.
Did you degree the cam to make sure it was correct? dot to dot does not mean much. Some cams are off, some timing chain keys are off.

[Lee]

"I can't get it to idle with less than 25" - so, does it idle BETTER with even more timing? If so (and I know you said you rechecked the timing gears) you are 1-tooth off with the timing chain. I always check the gears at 12 and 12, laying a straight-edge through the crank and cam centerlines to verify the dots ARE in-line. But I also actually degree the cam as well, to eliminate all the guesswork.