Can't Time Engine Correctly

[Mark A.]

I'm firing up my 71 LT-1 after a rebuild. I think I may know what the trouble is , but want other opinions first. The engine starts and runs, but it reads 65 degrees advance on the light at 800 RPM. I have double checked static distributor placement with #1 on TDC. The pointer is as close to #1 on the cap as I can get it. The engine runs somewhat rough, and only pulls 10" of vacuum. I had the engine align bored when it was rebuilt. The timing chain was somewhat loose when I assembled the engine. I didn't think it was enough to be concerned about, but now I am thinking, the cam must be slightly out of time, and that's why it won't time correctly. I would appreciate some input, before I go through the hideous task of tearing the front off the engine again. Thanks, Mark

[Michael W.]

Re: Can't Time Engine Correctly

An incorrectly aligned cam wouldn't affect timing if you've installed the distributor as described. I doubt the engine would run well at all if you've got the cam off by a tooth or two.

Possibly you've got the timing light connected to the incorrect HT lead and not actually #1. Do you have the vacuum advance disconnected and the vacuum line plugged?

[Mark A.]

Re: Can't Time Engine Correctly

I have the vacuum line plugged. I have the wires all numbered, but will double check them. I know I had the cam timed properly. Mark

[Patrick H.]

Re: Can't Time Engine Correctly

I had the wires off by one position on the cap once.

Oops.

[Mark A.]

Re: Can't Time Engine Correctly

Okay, the wires are correct, I double checked. I had the lead for the timing light on backwards. The timing is actually retarded significantly. I have moved the distributor 1 tooth each way, and moved the wires on the cap, one position each way. I can't get it to be where it needs to be. I cannot get the rotor to point exactly at the correct distributor tower. It is always inbetween somewhere. Ideas? Mark

[Edward J.]

Re: Can't Time Engine Correctly

Mark, I know that sometimes getting everything to line up correctly is a pain in rear , The best advice I can give is to start over fresh.

First look in the AIM and find the picture of the top of dist. cap, it shows you where the NO. 1 Cylinder is located on the cap and the rest of the wires in the correct firing order. Also the orientation of the vaccum advance. I believe cylinder #1 is to the right of the point window looking from the driver side.

Next is to pull Cylinder no 1 plug and put your finger over spark plug hole and bring up on compression. and get the harmonic balancer pointing to zero. Find out where your rotor is pointing.( also the base of dist. has a index mark and the intake also they should be a good starting point)

Remember the vaccum advance should be in its a position, and the tach cable should also be a straight shot to the dist. base so the cable is not kinked.

[Mark A.]

Re: Can't Time Engine Correctly

I have pulled the valve cover 3 times, and put #1 at TDC. I then pull the cap to see where the rotor is pointing. It never lines straight up with a post. I have tried each post closest to it. How much vacuum should the LT-1 pull at idle? Mark

[Michael W.]

Re: Can't Time Engine Correctly

Would this be a new, aftermarket cam by any chance? I've heard that most manufacturers do not index the oil pump/dist drive gear teeth correctly with respect to the alignment pin. As a result the distributor housing ends up at an unusual angle similar to what you have described.

The fix is to remove the distributor gear and rotate it 180 degrees.

[Paul O.]

Re: Can't Time Engine Correctly

Mark 1 question did you have the distributor apart or disassembled if so? You need to look at the distributor gear there is a small dimple just above the gear itself on the gear housing. That dimple should be facing the same direction as the rotor if not you would always have a hard time getting the distributor in the correct position for final timing. You would then need to remove the roll pin move the gear to alignment with rotor and reinstall the roll pin.


Paul 18046

[Edward J.]

Re: Can't Time Engine Correctly

Mark, vaccum at idle may vary a little 14/18 in. all depending of a few factors, timing is one , carb. adjustment .

Is everything indexed correctly Mark? ( vaccum adv. pointing as should be, tach cable )cyl. # 1 located correctly on dist cap. If so, when on TDC can you rotate the dist. to point to the #1 pole on dist. cap. and still keep the geomety of everything correct.

Also did you use a new timing chain and gears, were they the type that will let you advance or retard 4 degrees? Or were they just the normal 6 and 12 marks on the gear set?

[Mark A.]

Re: Can't Time Engine Correctly

I moved the wires clockwise on the cap to index them according to the AIM. Then I moved the rotor 1 tooth, and now I have my 8 degrees at idle. The motor is very sluggish, but I think this is carb related. I will check that later. I thought I had tried every possible wire location, and rotor position. Guess I missed one! Yes I used a new double roller chain, and installed it straight up. I guess you can get shorter chains, for engines that have been align bored. I was not aware of that, when I put it together tho. Mark

[Mark A.]

Re: Can't Time Engine Correctly

Paul and Michael,
Yes I'm aware of the dimple, and it was installed facing the pointer. I double checked that as well. Mark

[Timothy B.]

Re: Can't Time Engine Correctly

Mark,

Is there any chance the valves are adjusted incorrectly?

[Joe C.]

Re: Can't Time Engine Correctly

a correctly built LT1 of 350 inch displacement, whose valves are adjusted per spec and static timing set to 10-12 BTDC should develop about 12 in-hg @ about 850 RPM

i assume you used the fm speed pro cs1145r

the points access door on the cap should be at the base of #1 tower, and nos 1 and 8 should be (more or less) symmetrically pointing toward the front of the engine.

[Dennis O.]

Re: Can't Time Engine Correctly

I had this exact problem on both my '67 350 HP and my '68 300 HP. Both times it turned out to be a "slipped" harmonic balancer. I sent them both out to a guy in Oregon (www.dalemfg.com) and they came back perfect.