Timing for stock 350

[84GMCSierra]

I have an 84 Sierra 2500 2wd, and I have the timing at 4 degrees before TDC, and the truck is running rough. Feels like its missing when I step on the gas but all the plugs are good as are the wires. complete new distributor, coil has been replaced. I need to know if there is a better timing for it? I have a basic timing light, nothing fancy. I probably need to have someone adjust my carb as I had to mess with it and got it off of it's sweet spot. I've tried to get it back but don't know enough about carbs to get it right. Any help or pointers would be greatly appreciated.
Thanks

 

[bucket]

What you are describing doesn't sound like a timing issue, but 4* should be fine.

What makes you say the plugs and wires are good? Are they new? A compression test may be good for diagnosis as well.

 

[fast 99]

Check manifold vacuum
vacuum leaks
adjust idle mix
EGR stuck open if equipped

Adjust idle mix by backing out the screws until highest RPM is reached then turn in 1/4 turn at a time till RPM drops about 50. That should get it in the ballpark. Assume it is a Q-jet.

 

[75gmck25]

Base timing can usually be set to about 8-12 degrees BTDC and it will work fine. Just make sure you measure it at a low rpm (about 650 rpm ) so you are really measuring base timing.

However, it sounds like you might have other problems. Start out by buying or borrowing a vacuum gauge. Gently turn in the idle mixture screws until they bottom out, and then turn them out about 2 1/2 turns. Start the engine and then slowly turn them out further (about 1/2 turn at a time) until you get highest vacuum at idle. Also look for pulsating vacuum that indicates a cylinder with a valve that is not sealing properly.

 

[DoubleDingo]

My '81 says to set it at 4* btdc, but the engine likes 10*. It runs fines at 4*, but way better at 10*.

 

[84GMCSierra]

What you are describing doesn't sound like a timing issue, but 4* should be fine.

What makes you say the plugs and wires are good? Are they new? A compression test may be good for diagnosis as well.

I replaced the plugs about a year ago, as well as the wires. I'll do a compression test next. I forgot to add that the engine is a crate 350

 

[84GMCSierra]

Check manifold vacuum
vacuum leaks
adjust idle mix
EGR stuck open if equipped

Adjust idle mix by backing out the screws until highest RPM is reached then turn in 1/4 turn at a time till RPM drops about 50. That should get it in the ballpark. Assume it is a Q-jet.

Carb is an Edelbrock 1406, electric choke

 

[fast 99]

Idle adjustment lower front, 2 screws, same procedure.

 

[84GMCSierra]

What plugs are best for it? I believe I have R45TS in it now

 

[84GMCSierra]

What you are describing doesn't sound like a timing issue, but 4* should be fine.

What makes you say the plugs and wires are good? Are they new? A compression test may be good for diagnosis as well. Rest of the plugs aren't too bad but need to be replaced. Cylinder number is on the plugs.

Found this on number 3 today. Plugs have been clean and dry until now.

 

[bucket]

Yeah, I'd do a compression test to verify if there is a dead hole.

A set of plugs will probably help a bunch and if #3 becomes a problem again, you can run an anti-fouler on that plug.

 

[73c20jim]

Add 1 degree of base timing for every 1000 feet of altitude. Also loose 1 inch of vacuum for every 100 feet of altitude. Also need less jet size at higher altitude,

 

[84GMCSierra]

Yeah, I'd do a compression test to verify if there is a dead hole.

A set of plugs will probably help a bunch and if #3 becomes a problem again, you can run an anti-fouler on that plug.

That's what I was thinking too. Seems lie everything is starting to leak or go to pot, lol. Even my master cylinder lid gasket is leaking now.

 

[BadBowtie]

That's what I was thinking too. Seems lie everything is starting to leak or go to pot, lol. Even my master cylinder lid gasket is leaking now.

On a new 350cid crate engine??!!

 

[84GMCSierra]

On a new 350cid crate engine??!!

It's not new. I don't know when it was put in. It was in it when I bought the truck in 2019. I have the block number but no date. Is there a way of finding out what year it was made?