Timing on 84 305

[19gmc84]

1984 GMC High Sierra...had 350 engine and head gasket blew. Buddy gave me a 80-84 305 engine...so I put that in.

I'm trying to figure out what I should set timing to for this engine...I find that it would be 6 degrees, but that setting is for a vaccum advanced distributor. The distributor I have is electric...does this make a difference.

Symtoms I have:

When cold, engine starts fine...no problem.
When hot, I turn key and it acts like battery is weak...it drags and then fires up...also...very high idle when warm.

Engine hard to start:

Battery could be bad.
Starter could be bad.
Fuel line could be vapor locked from being warm.

High Idle:

Need to adjust Holley carburator fast and curb idle....

However, before i do all this...I understand an engine not timed properly could cause all this as well...True or False...so with that said...what should I set my timing to...reason I'm asking, every setting I find is normally around 6 degrees, but that's for a vaccum advanced distributor...I have an electric distributor...should I still go with 6 degrees?

 

[Boone83K10]

Why does it not have vacuum advance? You should since it is street driven..

where is your distributor from the 350? Use that one.

you need to get the timing issue resolved first before addressing the carb.

 

[78bigblock]

Sounds too far advanced. Maybe a stuck weight?

 

[19gmc84]

Why does it not have vacuum advance? You should since it is street driven..

where is your distributor from the 350? Use that one.

you need to get the timing issue resolved first before addressing the carb.

Well I just bought the truck a couple months ago...the electric distributor that is in there is the one from the 350. So any clues as to how I should set the timing? If 6 degrees is the recommended setting for vaccum advanced...anybody know what I should set it to with the electric distributor...I hate to have to buy a vaccum advanced.

 

[Boone83K10]

take a pic of this distributor please. I can't picture what you are trying to stab in there.

 

[shortboxchevy77]

take a pic of this distributor please. I can't picture what you are trying to stab in there.

I second that, I've never seen a non vac controlled dizzy unless it was on a fuel injected rig. Sounds like you have too much timing or a weak when hot starter. Confirm your top dead center on the number 1 piston to make sure your balancer hasn't slipped causing false timing readings (a common issue on that era of 305's). I have an 83 chev with a 305 that I have to time by ear because the balancer slipped, if I time it with a light it wont do 25mph

 

[chengny]

When cold, engine starts fine...no problem.
When hot, I turn key and it acts like battery is weak...it drags and then fires up...also...very high idle when warm.

Textbook description of over-advanced ignition timing.

The hard, slow start is the plugs firing too soon - before the piston is close enough to TDC. Tries to force it back down while still coming up.

If way over advanced, the engine can actually rotate backwards for a second - called kickback.

Probably pings severely when a heavy load is applied.

Same thing with the high idle speed - can be caused by overly advanced spark.

Try backing off on the advance a bit. Go CW withthe distributor until you get easy starts. Then bring it back CCW little by little. If you get pinging at WOT or kickback on hot start, retard it a bit.

I wouldn't even think about the OEM timing spec - that is worth zip now - just time it by ear.

 

[19gmc84]

When cold, engine starts fine...no problem.
When hot, I turn key and it acts like battery is weak...it drags and then fires up...also...very high idle when warm.

Textbook description of over-advanced ignition timing.

The hard, slow start is the plugs firing too soon - before the piston is close enough to TDC. Tries to force it back down while still coming up.

If way over advanced, the engine can actually rotate backwards for a second - called kickback.

Probably pings severely when a heavy load is applied.

Same thing with the high idle speed - can be caused by overly advanced spark.

Try backing off on the advance a bit. Go CW withthe distributor until you get easy starts. Then bring it back CCW little by little. If you get pinging at WOT or kickback on hot start, retard it a bit.

I wouldn't even think about the OEM timing spec - that is worth zip now - just time it by ear.

So nutshell...forget about light timing...just move distrib clockwise until I get easy starts when hot and then counter clock wise a tad to advance it as far as I can? So I get engine warm..then tweak distributor and try starting while hot...if it drags...then I tweak it clockwise a tad...then try starting again...again...again and again...until I get easy starts when hot?

 

[Boone83K10]

Pretty much, but I still want to see a pic of this distributor.

 

[chengny]

So nutshell...forget about light timing...just move distrib clockwise until I get easy starts when hot and then counter clock wise a tad to advance it as far as I can? So I get engine warm..then tweak distributor and try starting while hot...if it drags...then I tweak it clockwise a tad...then try starting again...again...again and again...until I get easy starts when hot?


No, no - you can still use your timing light - but disregard the timing tab number marks. Try it like this:

Go out and shoot your timing as it is now. While you are shooting it, make a mental note of exactly where the mark on the balancer displays. You know that mark is too far advanced. Shut down and make a neat mark where the strobe was hitting. Use a sharpened piece of chalk.

Retard the spark a bit, observe how it starts when hot. If it cranks over at normal speed and you get no ping at WOT, shoot it again and mark that spot with chalk like the other one.

You could stop there, but you might want to try to dial it in a little closer to optimal.

Before you started you had a useless set of marks on the timing tab, but now you have two useful reference marks. One is way too early and the other mark is good but might not allow for best performance.

Using those two marks as end points, make several more marks (maybe 3-4) evenly spaced between them. You can assign arbitrary numbers to them if you want or call them A,B,C,D & E. But it doesn't matter what you call them, they will provide reference while you adjust your timing .

You will now have a custom made set of timing marks that you can shoot with your timing light and quickly find the sweet spot.

I keep advancing until I find the earliest timing I can possibly get without ever hearing a ping even under the heaviest load (e.g. WOT, engine hot & while going up a hill with a load in the bed).

Pinging usually happens before kickback, so if you make an adjustment and the engine kicks back when you crank it up - forget about test driving it. You went too far advanced. But just because you don't kick back doesn't mean you won't ping.

 

[1986K5Wa]

Man I'm having just about the same issue with my carb 7.4l when warm. Cold starts fires right. So would these suggestions be the same with mine? I'm guessing they are. So I want to do this with the engine warm, right?

 

[78bigblock]

Yes with the engine warm.

 

[19gmc84]

Thanks to all who replied...I did the TDC...and I was a tooth off on distributor...so it was to far advanced...once I got that straight...I then tweaked cap until I got it where I thougth it should be...and I also adjusted the curb idle on my Holley carburator...after those settings...idle was nice and easy and truck now starts fine when warm.

Thanks to all who replied and thanks to my buds who actually helped me out. Craig and Arnold !!