Timing Position 305 V6

[mookiex4]

My GMC Truck has the 305 V6 and it acts as if it is way out of time. I am atleast down to that. Along with loss of power and backfiring through the Carb, I am assuming the Timing is retarded.

When looking at the Harmonic Balancer the Marks are hard to see. I think it looks like I have listed below but have a hard time telling.

_______________ TDC

_______________

_______________ 10

I am assuming the Line without the Number is 5 degrees. I have had trouble finding what the timing setting is supposed to be. One site mentions it may be 5 degrees of TDC. If this is the case should the 5 degree line be flashing on the TDC stationary pin on the engine?

Thanks for any help you can provide.

Regards,
Mark

[wc63]

I have had a similar issue with my 63 and 66 v6s. they both turned out to be the points. got new plugs and wires along with the points and set the gap at .019 i believe. ran real smooth after that. thats just my suggestion. i havent really messed with the timing much. i have heard some stories of the timing chain jumping and creating a nightmare for the person trying to find the bug, so keep that in mind as well. hope this helps. im sure someone will chime in with some more relavant info. good luck.

[mookiex4]

Thanks for the reply to my post. I actually have done a full tune up with points and am down to the timing. I was just trying to get some timing info. How's Mesa these days. I lived in phoenix for 7 years. As a matter of fact the 65 GMC that I own and am the 3rd owner of is from Phoenix. Have a great evening.
Posted via Mobile Device

[wc63]

its not bad out here. if you dont mind the heat. its still in the 90s, but cooling down. its alot cheaper than cali though. i dont think ill go back unless im making 70grand at least. im far from that...good luck with the timing. try joining jolly's mailing list at 60-66gmcguy.com. i often post there when its a gmc v6 specific question. theres some die hards there. you should be able to an answer

[newbe351]

I'm pretty sure timing is 7.5 degrees. I ran my 351E a 10 degrees and it ran OK but I had some upgrades. Jollie's site can answer your question for sure....

http://www.6066gmcguy.org/

[HEI451]

timing specification for the 305 V6 is such:

Standard transmission: 2.5 degrees BTDC@idle
Automatic transmission: 7.5 degrees BTDC@idle

Both specs are set with the vacuum advance line disconnected from the distributor, and plugged.

So, stick, pointer between center and 0 (TDC) line, auto, pointer between 5 degree and 10 degree line.

[HEI451]

Neglected to add

Point gap from manufacturer should be .016 (.018 works better).

Dwell specification is between 28 and 35 degrees (I shoot for 32 degrees).

[AngryPirate]

yikes!

My 305 v6 will only run reasonably well at 30 degrees from BTDC on my crank pulley. Anything else is a bunch of misfires and stepping on the accelerator pedal pretty much stalls the engine.

I replaced the timing chain a while back when I had the engine out but I marked everything before taking the old one off.

TBH, the engine never has run 'well' just 'well enough', so who knows, perhaps the previous chain had skipped or was set wrong?

The distributor vacuum isn't currently plugged, but I don't imagine that would make a 27.5 degree difference (It's a manual trans).

Thoughts?

[cwcarpenter98]

Originally Posted by AngryPirate

yikes!

My 305 v6 will only run reasonably well at 30 degrees from BTDC on my crank pulley. Anything else is a bunch of misfires and stepping on the accelerator pedal pretty much stalls the engine.

I replaced the timing chain a while back when I had the engine out but I marked everything before taking the old one off.

TBH, the engine never has run 'well' just 'well enough', so who knows, perhaps the previous chain had skipped or was set wrong?

The distributor vacuum isn't currently plugged, but I don't imagine that would make a 27.5 degree difference (It's a manual trans).

Thoughts?

Could be the cam is a tooth off to the crank, or maybe the dizzy is a tooth off? Triple check firing order just in case.
I've crossed plug wires on two separate engines in my truck

[geezer#99]

Distributor vacuum hooked to manifold vacuum port on the carb could easily add 27.5 degrees.
I had one that added 35 degrees.
I assume if you plug off the vac advance then it’ll barely run.
You might need to increase your initial and limit your vac advance.

[AngryPirate]

Originally Posted by geezer#99

Distributor vacuum hooked to manifold vacuum port on the carb could easily add 27.5 degrees.
I had one that added 35 degrees.
I assume if you plug off the vac advance then it’ll barely run.
You might need to increase your initial and limit your vac advance.

None of my vacuum ports on anything are plugged or hooked up to anything.

I suppose I should plug the dist, carb and the one on the intake manifold?

Thanks for letting me know this is a possibility though.

[AngryPirate]

Originally Posted by cwcarpenter98

Could be the cam is a tooth off to the crank, or maybe the dizzy is a tooth off? Triple check firing order just in case.
I've crossed plug wires on two separate engines in my truck

Thanks for the reply.

I'll double check the plug wires.

The other stuff, well, I am not sure of how to easily verify those and I don't think there is one (anyone can feel free to correct me ;-) ).

[geezer#99]

Originally Posted by AngryPirate

None of my vacuum ports on anything are plugged or hooked up to anything.

I suppose I should plug the dist, carb and the one on the intake manifold?

Thanks for letting me know this is a possibility though.

I thought you meant the distributor pot was plugged onto the carb port.

What ports do you have open?
Any on the carb or intake should be plugged off.

[AngryPirate]

They’re all open! :-)

I’ll head to the parts store and get a plug assortment.

Thanks!

[geezer#99]

Can you post a pic of your carb and distributor first?

[Corts60]

Originally Posted by AngryPirate

They’re all open! :-)

I’ll head to the parts store and get a plug assortment.

Thanks!

You have some serious vacuum leaks causing your lean condition my friend. Plug up those holes and you’ll be headed in the right direction.

[slorio]

Mookie:
7.5 degrees and .019 for points according to GMC service manual for 305e v6. See attached.
Regards
Steve
New Orleans

[AngryPirate]

Originally Posted by geezer#99

Can you post a pic of your carb and distributor first?

Here’s the carb, intake and dist

[geezer#99]

Looks like only one uncapped port on the back of the carb. It was likely used for vac advance pot on the distributor.
Is the vacuum pot good ( not ruptured)?
Have you hooked it up?

[AngryPirate]

Originally Posted by geezer#99

Looks like only one uncapped port on the back of the carb. It was likely used for vac advance pot on the distributor.
Is the vacuum pot good ( not ruptured)?
Have you hooked it up?

No idea about the dist pot. I’ll have to look.
I have never hooked them up.
What about the vacuum port on the intake?

Thanks for looking!

[geezer#99]

The one that’s hard to see.
Plug it off.
To check function of vac pot just hook a vac hose to it and apply a little lung power to it and your suction should move the arm forward. Arm is easy to see right on the side of the distributor.