Thread: Decked block: How much timing advance/retard...

Dre, Et Al;

Chime in. Finally got Jensen's block back together, made sure the colored link was on the crank correctly (on the dot), and the motor was at TDC.

Put the head on, torqued it correctly (even used copper spray).

Put the head together, installed the cams (dowel pins at 10 and 12 respectively).

Installed the chain onto the cam gears, and tried to rotate the motor. I get it about a 1/4 turn from the crank, and there's interference. It's ROUGH to turn. Just won't budge. Have a suspicion that the valves are kissing the piston. Look at the lobes, and nothing seems off. Doesn't seem like the piston should be touching the valve.

So I remove the cam gears again, and set the crank to TDC CYL#1. Then I manually set the cams to 10 and 12 o'clock respectively. The chain doesn't match up anymore. It's off 2.5 links on the intake and exhaust cam. IIRC, 2 links on intake and exhaust both being off means 1 tooth on the crank.

With that being said, the pins that hold the timing chain on the timing cover are both still there, so it's not possible for the chain to skip a tooth.

So, with .005" being shaved from the block, and the head POSSIBLY being shaved (unknown to us), how much could the timing be off, mechanically? 2.5 links on each cam is a lot of timing to be off, for only .005". I assume that the timing chain tensioner would have picked up for the slack, since we're talking THOUSANDTHS of an inch shaved.

I know I'm kinda rambling here, but the Jack and Coke made me do it. It's been a ROUGH day.

Thoughts?

you have to shave almost a full 1mm to get 2-2.5 deg off. this was pulled straight from JWT web site.

Ahhh thanks I remember that thread now. I'm going to look at the motor again thurs.

All the slack in the chain must be on the tensioner side. The other side must be tight to get the proper chain position. Since the cams are now closer to the crank, the crank will rotate more for a given cam position. i.e. the cam timing (and ignition timing) will be retarded.
Set the crank at TDC and turn the intake cam backwards to take out all the slack. See where the marks are.

I see what you're saying. So instead of the dowels at 10 and 12, they may be at 9:30ish and 11:30ish. I did the chain install as you suggest, all slack on intake side, exhaust tight and in between int. and exh. tight.

there is suposed to be 20 links inbetween the 2 cams , but I am sure you know that ...dot to dot , or dowel to dowel and set at 10 and 12 , if you really want to see if there is interferance I guess you could bring it to TDC then rotate the cams one by one and see if there is a point where the cam quits roatating , but be careful

Are your bearing in spec. Too tight of tolerances and after torquing down the crank wont budge.

Of course they are

removed the chain fom the cams and she spins just fine. Every turn, we also turned the cams and nothing seized.

I'm curious about this to Cliff... as you know I'm having issues myself. I know I set my cam's at 10 and almost 12 before the lobes started hitting the rockers.

First off what engine is this, VE or DE?