After replacing a timing chain and intake gasket my truck starts and idles well. Now I need to set my timing, factory specs is 0 degrees, but anything past about 7 degrees and it dies. I did unplug the EST connector when changing the timing. I took a test drive with it a 8 BTDC and it has a bad off idle hesitation. Does anyone have any suggetions?
Thanks
Jim

 

What happens when you put it at 0 ??

 

I'm not Vader, sorry.

 

When the timing is below 7 it dies. The question was for anyone who can help. I put attn vader because I have already questioned him once and he was very knowledgable. It also seems to lack some power now also. any ideas?

 

Jim,

Make sure the timing mark on the harmonic balancer hasn't slipped. The outer ring can slide on the rubber elastomer and give an incorrect timing indication. The timing mark on MOST SBC engines should be in line with the crankshaft keyway in the balancer hub. You may have to remove the hub bolt and check it with a mirror to get a good viewing angle. If that is correct, your timing shoudl be pretty close.

 

Vader,
The timing mark on my balancer has not moved. It is only about 2 months old and it is in good shape. Before I removed the timing chain and intake I set the timing with no problem. I dont understand what could be wrong here. Any more ideas?
Jim

 

Jim,

Try the factory spec - 0°. Your ECM/EST may be curved by the PROM to load up a lot of advance from the base setting. Most older ECMs will advance the timing to the point of detonation, then step back. Your ECM may be expecting the 0° as a base and stepping ahead from there.

And in case we missed something, what are the specs on the engine? I'm guesing this isn't your 406 build...

 

Vader
It is a stock 350 in a chevy truck. The whole problem I am having is it wont run at 0 degrees. I can get it started at about 7 or 8 but when I try to drop it down to 0 it wont run at all. I did take a test drive with it at 7 and it lacks power and has a bad off idle hesitation to it. Before I replaced the timing chain and intake gaskets it ran good with the stock setting. The truck is used only for towing so I want to make sure it is not advanced to far. What do you think?
Thanks
Jim

 

Jim,

I'm almost afraid to think of what might have happened. If the valve timing is early, the ignition timing would have to be early to make any power at idle/low RPM.

It is POSSIBLE that you got a timing set that was mis-marked. Unfortunately, the only ways to check this are to compare the new parts to the old ones, or degree the cam with an indicator, piston stop, and indicator (to find the LCA of the cam grind).

You may get a good indication by adjusting the timing further. Disregard the marks for now, except as a reference. Advance it to the point where it will start and idle well. Check the intake vacuum if you have a gauge, and set the timing for the highest vacuum at idle, then check the marks to see where you are at (in degrees). Typically it is 7-10° above the ideal timing setting, or in your case the highest vacuum should be at 7-10° BTDC, give or take. Don't be afraid to go to 20° BTC or more. After all, it's just an experiment.

It isn't very likely that the cap is wired wrong, or that you are on the wrong plug wire, since the difference would be more like 90° off the correct marks. Timing differences that small are generally due to the timing set or cam degreeing changes. It is possible that there is some cross-firing happening, but it probably wouldn't idle well at all with severe cross-firing in the cap.

Damn, that bites - on a tow truck you'll need all the torque you can make at the low end.

 

Vader,
I just tried to change the timing again. I dont have a vacuum gauge, but going by ear the highest idle is around 17 degrees. it will run anywhere between about 20 and 6 but it seems the smoothest around 14-17. If a new timing set where mis marked woulndnt I need to move the cam a little in order to install it? I removed the old one and simply reinstalled the new one without having to move anything and the timing marks lined right up. I did have one problem when I reassembled the engine. I installed the distributor 180 degrees out so the engine would not start, however it did build up some fuel in the motor and it eventually backfired. The backfire was severe enough that it blew a valve cover off the engine and the throttle body was on fire. I put the fire out immediatly and there is no visable damage to it so I do not think that is the problem. Could that severe of a backfire caused some kind of internal damage that would cause my timing problems?

 

Jim,

I doubt that the backfire, or in this case, "internal explosion" would have caused any internal damage. The engine is designed to withstand gasoline/air mixture explosions all day long. Even though the case isn't designed to contain them (and obviously didn't) the pistons and crank are designed for those kinds of forces and shouldn't have suffered any damage. It IS possible, however, that the engine was suddenly jerked backward (more on that later).

I went out to the garage for argument's sake and checked out the roller timing set on my current "project" 355. The crank sprocket has 22 teeth and the cam sprocket therefore has 44 (I counted them both just so I would be sure). With that pitch, if the cam sprocket were installed or jumped one tooth off, the timing would be late by 8.18°.

Since your engine is running its best at around 15° by the timing marks, the ignition timing in relation to the valve timing may actually be only 7° advanced, and your chain may have slipped. This possibly could have happened during the "explosion", or not. A sudden jerk in the opposite direction of the chain loading may have slipped/damaged the chain or a sprocket, or possibly even sheared a key.

Unfortunately, my guess is that you'll be removing the timing cover to take a peek. I hope someone else comes up with a better explanation, but I can't think of one at this point.

 

That sucks big time. I am definately tired of taking thing s apart at this point, but I guess I have no choice. Vader, thanks a lot for taking the time to help me with my problems, I really appriciate it, and I am sure that everyone else does too. I'll keep you updated on the situation as soon as I get motivated to take it back apart.
Thanks
Jim