For a little over a week the 350 has been lack power and hard starts after heat soak. So i figured it be a good time for a tune up

ITEMS ADDED:
MSD Cap & Rotor kit
Bosch 8.5 mm wires, fine wire platinum plugs
Edelbrock 14X3" Air Cleaner Assembly
180 thermostat (after not having one at all)
new Vacuum advance canister that will work with high altitudes, old one seized on me
4* BTDC base timing

PREVIOUS MODS:
1406 edelbrock carb (electric choke)
GM spreadbore 4bbl Iron intake (non-egr)
Headman LT's 3' collectors flopro muffler

PROBLEM:
on 87 octane there is a faint ping on quarter to half throttle and with full manifold vacuum advance.

on 89 octane its not as bad but still noticeable

on 89 octane 2* BTDC base timing and ported vacuum pinging is occasional but only on hills.

should my carb be recalibrated for the 350 (Its a stock LO5 from a 1990 short bed 2wd p/u). Drove it straight out the box with the only adjustment made to the idle mixture and speed before and after tune up.

another thing i noticed is a loud whistle sucking sound at part throttle if this helps

 

You may hear that sound with a carb, but are less likely to hear it with an air cleaner installed.

Make sure the "timed" or "ported" vacuum port isn't open/uncapped, or a component that may be hooked to it isn't leaking.

A lean mixture can lead to pinging, but you aren't running that much advance (or so it seems).

It is possible that your timing mark isn't where you think it is. What damper are you using? Is it the same one that went with the timing cover? If not, you may be running a bunch more timing than you think. Also possible the damper ring has slipped on the hub.

 

What do you mean by "a vacuum advance canister that will work at higher altitudes"?

On a street performance engine with a carb and non-computer-controlled distributor you only want or need about 12* of vacuum advance, maximum. Most stock replacement vacuum advance canisters supply 20* or more. Often this resuts in part throttle detonation even though WOT performance is fine, and normal like always.

 

Sounds like you got a different canister than what was on there if it's pinging at the mid range, if it's WOT it could be you have too much mechanical advance coming in. Here are a few things to consider:

-If you are using ported vacuum as mentioned, you won't see any advance from the canister at idle or WOT (well if you have a restrictive carb you may see some but in general not)
-TBI engines are not your usual wedge chamber heads. They don't like nor do they need a ton of advance. You're probably talking 25 degrees total or so based on consensus most people have on it.
-Disconnect your vacuum, bring it up to about 3500 RPM and check it with a dial back timing light or use timing tape (my preference overall) Just to give you an idea of where you stand.
-You may want an HEI tuning kit in the long term. Lighter weights and heavier springs may be a requirement depending
-If you are having pinging at mid throttle you may have too much canister advance. There are LOTS of different ones made. Look inside the vacuum port and see if you can stick an allen key in to adjust it. There's a good chance that's part of your issue if you changed it.
-Hard starting hot is an indication of too much timing while cranking in a lot of cases. Back the timing off some and see if it starts easy after that.

 

[quote=Drac0nic;5682617]Sounds like you got a different canister than what was on there if it's pinging at the mid range, if it's WOT it could be you have too much mechanical advance coming in. Here are a few things to consider:

-If you are using ported vacuum as mentioned, you won't see any advance from the canister at idle or WOT (well if you have a restrictive carb you may see some but in general not)
-TBI engines are not your usual wedge chamber heads. They don't like nor do they need a ton of advance. You're probably talking 25 degrees total or so based on consensus most people have on it.
-Disconnect your vacuum, bring it up to about 3500 RPM and check it with a dial back timing light or use timing tape (my preference overall) Just to give you an idea of where you stand.
-You may want an HEI tuning kit in the long term. Lighter weights and heavier springs may be a requirement depending
-If you are having pinging at mid throttle you may have too much canister advance. There are LOTS of different ones made. Look inside the vacuum port and see if you can stick an allen key in to adjust it. There's a good chance that's part of your issue if you changed it.
-Hard starting hot is an indication of too much timing while cranking in a lot of cases. Back the timing off some and see if it starts easy after that.[/q

well now the pings have stop especially after switching to timed vacuum and 0* btdc timing setting, just wasn't use to the somewhat lopey sounding idle. I'm starting to think it had more to do with the platinum plugs since I couldn't gap them they seem to have broken themselves in. But the other day I had a custom 3" bent glasspack catback installed, single in dual out. Now I'm wondering can I run more base timing with the reduced back pressure?

 

it was a high altitude canister

 

Theres mountains in North Carolina?

 

If the engine has many miles on it, you may want to give it the Sea Foam treatment to get rid of any carbon deposits in the chambers.

 

Good call
Love that stuff. We call it tuneup in a bottle.
And yes excessive carbon buildup in the chamber and on the pistons due to an improperly tuned or high mileage engine can cause detonation.
For $10 its worth a shot. I have personally seen it fix detonation problems.

 

Is seafoam safe for cats? Mine is brand new and im currently not running a smog pump but probably will if it protects my converter in the future.

 

few areas of the blue ridge pkwy get up and over 5000 ft but that's almost 2hrs away from the triad which is only 400-600 ft above sea level