Engine riddle

[ironman_gq]

put a few more degrees of base timing in it and see if the vacuum picks up or richen up the idle mix a little and see what happens

[jeepsr4ever]

Could be that you need some spacer shims under your bridges so your valves are slightly open.

[chef]

So with 25-30 degrees base timing, it runs pretty good, so either I am out a tooth on the engine timing or it's a bad timing chain set. Opinions? Or could the curve on the DUI be that off?

[tufcj]

Is that going by the mark on the balancer? Is the rubber ring in the balancer in good shape?

I've seen the outer ring slip as the rubber decays with age. I've also seen an engine that has jumped a tooth on the cam run after the spark timing is adjusted.

The only way to check the balancer is to put some sort of piston stop in the #1 plug hole, then rotate the engine by hand each direction and see if the mark on the balancer stops equal distance from TDC each way.

Bob
tufcj

[chef]

Is that going by the mark on the balancer? Is the rubber ring in the balancer in good shape?

I've seen the outer ring slip as the rubber decays with age. I've also seen an engine that has jumped a tooth on the cam run after the spark timing is adjusted.

The only way to check the balancer is to put some sort of piston stop in the #1 plug hole, then rotate the engine by hand each direction and see if the mark on the balancer stops equal distance from TDC each way.

Bob
tufcj

Ya that is on the balancer, when I rotate the engine to TDC. Pop the cap the rotor is about 3/4 inch past number one, when the balancer is TDC

[tarior]

Just set the timing by ear on a virtually stock motor.
Use your right hand or an assistant to bring the engine up to 2500-3000rpm. Advance the timing until you hear it start to miss, you'll hear it out of the pipes. Back the timing off until it runs smooth again. Lock it down, take it for a spin to make sure it doesn't ping. If it don't, you're done.
PS, make sure you have your vacuum advance hooked up to full manifold vacuum.

[Henry Lavrenz]

'the needle is bouncing on the vac gauge' - focus on that. That means a intake(s) valves are not closing. Are you a tooth off on the timing chain setup? most likely not. The end gaskets on the intake manifold have nothing to do with this issue. incorrect ignition timing will not cause the manifold vacuum to bounce. I feel Matt is correct, in that you may need to shim your rockers or check your pushrod lengths. You milled your heads .027", that isnot very much if they have not been milled before. Consider that you have aftermarket gaskets and valvetrain parts and several things may be adding up in one direction, this can happen very easily. I preload hyd. lifters at least .050 and have gone as far as .090. I suggest to take off the valve covers and loosen each rocker bolt a half a turn, set the covers back in place, and start it up, you will know right away if it helps. Hankrod

[chef]

So finally getting back to the engine prob, took the front cover off today the base timing was bang on. Here is one thing I noticed, with both valves closed on number one, if i loosen the rocker arms and retigned the valves go down slightly? so they are not seated fully at TDC. My question is how close do I have to be on the push rod length? I took 27 though of the heads so is 20 though close enough if I can't get one perfect size?
Thanks again guys

[tufcj]

You may need to go shorter than .020" . If you're holding the valve open, then you're bottoming out the hydraulic lifter. You may need to pull the manifold and see how far the plunger is below the retainer clip when the lifter is on the base circle of the cam. I like to keep the plunger about .030" below the retainer.

Like MC says, you could put shims under the bridges, and see how it runs, then order the shorter pushrods.

Bob
tufcj

[chef]

K hard to get an accurate reading, I loosened the rocker arms, set the dial indicater at 0, timing strait up on number one. Snug up both rocker arm bolts and the indicater reads .075, then in 5 minutes it bleeds off to 0. So from my understanding, if i get a pushrod 20 though less, i should be good, yes?
Thanks