305 V6 Engine question

[Alaska_Ryan]

Driving home with my 69 GMC which has a 305 V6 (yes, it is a 305 V6). The truck starts to shake, shudder and backfire horribly. I felt as though I was on an unbroken horse. I got it home and parked, but now I can't get it started again.

The engine turns over fine, but it will not catch. I have spark and gas going into the carb. I even sprayed starter fluid into the carb and nothing.

The only thing I can think is the timing chain jumped some teeth. Anyone else have any ideas or suggestions?

[slorio]

Alaska:
There is a good chance it is the timing chain. My two quick checks on the chain are:
First, compression test. My compression dropped from 125 lbs/cylinder to about 75 lbs./cylinder when my chain jumped. The jumping of the chain retards cam timing which hurts compression on all of the cylinders.
Second, rotate the engine at the crank back and forth with the distributor cap removed. If you have a chain loose enough to jump, you will have a lot of movement at the crank (quarter turn) before you see corresponding movement at the distributor.

These aren't definitive, but they give you a good indication of what kind of shape the chain is in. One other way if you have the equipment is to put a bore scope in where the fuel pump bolts on and have a peak at the chain. I didn't have such equipment. You can find my discussion on this in the archives at the 6066gmcguy.org website's discussion group.

I hope this is helpful. Changing out the chain is a fairly easy job on these V6's and greatly improves performance if the chain is tired.
Regards,
Steve
New Orleans

[Matt's k5]

you can check yyour firing order put number one cyl on tdc and see were your rotor points too on dist, could be your dist gear, i had this similar happen to me on my blazer but i could get it to restart but barley, found my dist came apart where the points screw on too would only go 10mph and backfiring, i know of 3 305 v6's and a 351 i never had had heard of timing chain problems these motors are ussaly bullet proof but it is possible just check all the basics , matt

[68GMCCustom]

...you should probably start your own... rather then derail this guys thread for your trucks issues.

...just my opinion.

[dbaillargeon]

Sorry to step on toes, new
to
this thought that was how it worked I
will use the thread I start. Once again I apologize to
all here