engine popping at wot

[DANTIP]

The WOT problem does sound like ignition components. Under low-load conditions the ignition flaw is not apparent however under high-load (WOT) conditions ignition problems become exaggerated.

[drewdude92]

ok yeah ill look into it some more do you think i should replace my distributor cap? ive never replaced it since ive had my truck. ill pull my plugs and replace them tonight

[joedoozer]

I have the manual choke version of the 600 on my truck, with the choke removed. I do need to adjust the mixture screws thru the year, as the season change. When its rich it gets sluggish when its hot. And when its lean it skips and misses under hard acceleration and WOT. I wouldn't buy any parts yet. Pull the plugs so you can see what is going on. I would put my money on the timing being a bit off, and it being to lean.

[piecesparts]

Has anyone discussed the issue of the valves floating in this issue. You are getting backfire condition at WOT. It is very possible that a valve spring is weak and the valve is not seating when you are firing the cylinder. If you are running lean, the detonation would be more noticeable, but that can be evaluated with the color of the plugs and the respnse of the motor using acceleration characteristics as a troubleshooting technique.

Just out of curiosity, did you change out the fuel pump, also. I put an aftermarket pump (Edelbrock pump and solid fuel lines to my engine and I get some vapor binding in my engine and it casues the truck to cough and back fire until I flush the hotter fuel out of the system (on the open road).

I purchased a bunch of needles and seats for my carb and adjusted the transition and WOT conditions until I was happy with that, but the cruising around city streets causes the overheating issues.

[drewdude92]

Originally Posted by joedoozer

I have the manual choke version of the 600 on my truck, with the choke removed. I do need to adjust the mixture screws thru the year, as the season change. When its rich it gets sluggish when its hot. And when its lean it skips and misses under hard acceleration and WOT. I wouldn't buy any parts yet. Pull the plugs so you can see what is going on. I would put my money on the timing being a bit off, and it being to lean.

ok ill pull the plugs and tell you what they look like tonight what color would they be if it is just too lean? or can you even tell a difference

[drewdude92]

Originally Posted by piecesparts

Has anyone discussed the issue of the valves floating in this issue. You are getting backfire condition at WOT. It is very possible that a valve spring is weak and the valve is not seating when you are firing the cylinder. If you are running lean, the detonation would be more noticeable, but that can be evaluated with the color of the plugs and the respnse of the motor using acceleration characteristics as a troubleshooting technique.

Just out of curiosity, did you change out the fuel pump, also. I put an aftermarket pump (Edelbrock pump and solid fuel lines to my engine and I get some vapor binding in my engine and it casues the truck to cough and back fire until I flush the hotter fuel out of the system (on the open road).

I purchased a bunch of needles and seats for my carb and adjusted the transition and WOT conditions until I was happy with that, but the cruising around city streets causes the overheating issues.

It very well could be the valve thing but idk it does smoke a lil bit when i start it up is that a sign?

No i didnt put a new fuel pump on the fuel filter is always full of gas so i dont think that would be the problem

[joedoozer]

Blue smoke on start up is most likely valve seals.

Here is a nice link for plug readings.
http://www.dansmc.com/Spark_Plugs/Sp...s_catalog.html

[drewdude92]

what other color could it be just on start up?

[ChevLoRay]

Old school stuff: Blue smoke on start-up is supposed to indicate worn valve stem seals. Grey smoke is fuel-related. White "smoke" is moisture, either from being cold (condensation in the air) or (if up to proper operating temps) white "smoke" indicates POSSIBLE condition in which coolant is entering the combustion chamber.

A little blue puff on start-up ain't gonna hurt anything. The wifes' Lexus does that and I'm not about to tear into that. It doesn't use even a 1/2 pint in 5K miles......

If you still have a points/condensor distributor, the points could be "popping". This is caused by a defective condensor, which will be indicated by a build-up on one side of the points. By this I mean, when you look at the points, you may see a pointed mound on one side of the points. If you do have the original distributor, you should seriously consider upgrading to an HEI. You could get one from a junk yard, but I would recommend a reman unit. You can pick one up for approx. $100-125. ACCEL has a nice one. When you check NAPA, AutoZone, O'Reilly's, you'll soon learn that they all sell the same remanufactured unit, with a little fluctuation in price. But, they all have the same unit.

[ChevyC102007]

When I pulled my plugs weekend before last the color was normal, no moisture at all from either gas or oil. I just replaced the timing chain last year.

[roughedup72]

I had a 305 with a worn lobe on the cam and it wouldn't do anything except sputter and it ran real rough. good luck, these old trucks can be alot of fun but they can also be a pain in the @ss.

[drewdude92]

Originally Posted by ChevLoRay

Old school stuff: Blue smoke on start-up is supposed to indicate worn valve stem seals. Grey smoke is fuel-related. White "smoke" is moisture, either from being cold (condensation in the air) or (if up to proper operating temps) white "smoke" indicates POSSIBLE condition in which coolant is entering the combustion chamber.

A little blue puff on start-up ain't gonna hurt anything. The wifes' Lexus does that and I'm not about to tear into that. It doesn't use even a 1/2 pint in 5K miles......

If you still have a points/condensor distributor, the points could be "popping". This is caused by a defective condensor, which will be indicated by a build-up on one side of the points. By this I mean, when you look at the points, you may see a pointed mound on one side of the points. If you do have the original distributor, you should seriously consider upgrading to an HEI. You could get one from a junk yard, but I would recommend a reman unit. You can pick one up for approx. $100-125. ACCEL has a nice one. When you check NAPA, AutoZone, O'Reilly's, you'll soon learn that they all sell the same remanufactured unit, with a little fluctuation in price. But, they all have the same unit.

thanks about the whole smoke thing that was a great help.

I have the HEI already

[fun in dirt]

Chunk the Edelbrock carb!

[drewdude92]

Originally Posted by fun in dirt

Chunk the Edelbrock carb!

haha! thats the next solution ima try lol your not the first person to tell me that!

[drewdude92]

yeah but no matter what i always love my truck!! well most of the time unless im stranded somewhere when it breaks down! which was just once lol

[piecesparts]

I imagine that there could be something wrong with the carb, but I have run the AFB design carbs for awhile and they work real well, when you tune them. You might try bolting on another carb for a trial. See if you know someone that has one on their truck or car that you could try out. It still sounds to me that you are in a lop for your valves or ignition causing the back fire issues. Just what is your timing set at?

[drewdude92]

ok ill try my friends carb but it is the same exact model and everything lol but maybe his is just tuned right? he has the same year of truck his is just a gmc so it should work i hope if it does ill just accidently forget which one was mine and switch them!! haha
i think i had it set at like 8? ill check tomorrow at lunch for sure i have my test light in my toolbox lol

[piecesparts]

I suggested the carb swap to alleviate one possible failure point. If the truck still pops at WOT with the new carb, then your problem is outside of the carburetor and is something else on the engine. If it were mine, I would set my timing at 10 degrees BTDC and then adjust the idle for 700 to 900 RPMs in DRIVE. That way you are getting a little advance on the ignition. I am still working the idea of bad ignition or valve spring. When was the last time you put gas in the truck, is it bad?

[drewdude92]

yeah i havent got to try the swapping carb thing yet but ill set my timing at 10 BTDC then do all of that. NO the gas is good i drive this truck everyday =)