[mboone20]

I recently bought a used ‘68 302 after my 289 dropped a valve and ruined the block and head. Because of the differences in the two motors, I swapped the harmonic balancer and water pump to accommodate the inlet and outlet of the radiator in the ‘67. Needless to say, timing this engine has been challenging. I have timed the engine close enough for it to start. Two big problems though, the first is when I try to put it in gear (C4 Auto) the motor dies or backfires and barely has enough power to back out of the driveway, second when it warms up to operating temp I can’t get it started again. I turns over real slow. Is this still a timing issue or something more?

 

[Cracker289]

I recently bought a used ‘68 302 after my 289 dropped a valve and ruined the block and head. Because of the differences in the two motors, I swapped the harmonic balancer and water pump to accommodate the inlet and outlet of the radiator in the ‘67. Needless to say, timing this engine has been challenging. I have timed the engine close enough for it to start. Two big problems though, the first is when I try to put it in gear (C4 Auto) the motor dies or backfires and barely has enough power to back out of the driveway, second when it warms up to operating temp I can’t get it started again. I turns over real slow. Is this still a timing issue or something more?

So you don't have any timing marks to go by? That is a huge challenge then!

I will tell you this about "dying when you put it in gear". I had that problem, and to counteract that I cranked up the idle speed to keep it from dying. Later a friend suggested I adjust the air/fuel ratio using a vacuum gauge, and when I did that I found it was way too lean, and by correcting it the problem of the car wanting to die completely went away.

But I think you need to figure out the timing issue first, and I don't really have any advice about how to do that.

 

[daveboss200]

It is actually quite simple. you will have to mark the balancer manually to find tdc. As long as you have the tab on the engine you are cool. No tab and you will need to find a new one. The easiest way to get TDC is to have the pan or head off so you can see that it is at the top of the cylinder. with the head or pan on, you can put a thin rod inside the spark plug hole and as the piston goes up it will stop. you can turn the crank back and forth as the piston stops movement and find out how much travel there is at the crank while the piston doesn't move. if you locate the place where it stops on each side of TDC, then take it to the middle of that and then mark 0 degrees you should have a pretty good point of reference for TDC.
You can use a degree wheel to help in this. You can make a scribe mark on the balancer and then paint it white or use a white grease pencil.
Now that you have TDC you should be able to figure out the rest for initial advance at 10 degrees and then find what works best for you. Just make sure it is TDC on compression. Good luck
Dave

 

[Cracker289]

It is actually quite simple. you will have to mark the balancer manually to find tdc. As long as you have the tab on the engine you are cool. No tab and you will need to find a new one. The easiest way to get TDC is to have the pan or head off so you can see that it is at the top of the cylinder. with the head or pan on, you can put a thin rod inside the spark plug hole and as the piston goes up it will stop. you can turn the crank back and forth as the piston stops movement and find out how much travel there is at the crank while the piston doesn't move. if you locate the place where it stops on each side of TDC, then take it to the middle of that and then mark 0 degrees you should have a pretty good point of reference for TDC.
You can use a degree wheel to help in this. You can make a scribe mark on the balancer and then paint it white or use a white grease pencil.
Now that you have TDC you should be able to figure out the rest for initial advance at 10 degrees and then find what works best for you. Just make sure it is TDC on compression. Good luck
Dave

That's an excellent suggestion, I would even add, after he has found actual TDC, in order to move the mark to where the pointer is he could get harmonic balancer timing tape to stick on there so he has all the marks, and its bright & clear and easy to read.

Summit Racing SUM-163594 - Summit Racing® Timing Tape - Overview - SummitRacing.com

 

[mboone20]

Good suggestions

I've already established a TDC point and have set the timing about 8 degrees BTDC. May go a little more, based on daveboss200's suggestion. Cracker289 brings up an interesting point, that I may have a vacuum leak somewhere. When our weather warms up, I will try to resolve this issue

 

[Cracker289]

I've already established a TDC point and have set the timing about 8 degrees BTDC. May go a little more, based on daveboss200's suggestion. Cracker289 brings up an interesting point, that I may have a vacuum leak somewhere. When our weather warms up, I will try to resolve this issue

While a vacuum leak is possibly a problem, my point was that the air/fuel mixture could be too lean, and using a vacuum gauge to tune mine showed that, and once I reached the proper setting (which is the point where you get the highest vacuum setting at idle), my problem of the engine dying at every stop sign went away.