[MaineHandyman]

can you all please help me, ive been working on my own truck for the 15 years iv'e owned it and im really at my witts end with a timing issue (thats what i belive it to be) It has been running rough and lacking power for some time, and when i have a day to play with it (im always working and this is my p30 stepvan work truck) i have tryed to time it correctly. I have rebuilt the top end a year ago, new heads, intake, holly aftermarket carb, new exuast manifolds, have heat sheild boots on my plug wires because they were always getting brittle from the heat and cracking, i don't have that issue anymore. I have put #1 at TDC and tryed to get it 10 degrees advanced. i have also tryed driving down the road playing with the distributor to see how it affects power. I have an aftermarket HEI distributor. for the last few months its been runing very hot on the highway 210-260 and when i pull over and check radiator is bubling into the overflow bottle. I ran this truck un florida before moving to maine, and always had to run it with no thermostat to keep it cool enough. so when i came to maine i put it back in, was ok for a wile, then when it started runing hot i took it out so it could free flow, didn't help any. Flushed everything and had very good flow put thermostat back in and now just going down the road im at 220 cruising at about 45-50 mph. Now its getting very hot and very sluggish up hills. tryed also adjusting carb mixture screws to see if it would run a little better, no luck. Did i mention that thes 350 has about 600,000 miles on it.........I LOVE CHEVY...lol. So how can i corectly time it? how should i know where to set the carb mixture screws? can all this lead to the excessive heat? checked all the plugs they look good, new about a month ago. Please, any help would be appriciated, seeing how i have tryed a million things and maybe im doing them wrong or out of sequense. i also adjusted my valves the other day thinking that was the cause because i read that if the exuast valve didn't open at the right time or enough the exuast gas would burn hotter. PLEASE HELP...lol thanks to everyone on here for the help you give and opinions or answers you provide to all of us.

 

[DoubleVision]

Have you replaced the timing chain? if not with that kind of mileage it`s likely there isn`t anywhere you can set the timing to make it run correctly. the valve train is doing the boogie and the whole while it`s doing so it`s moving the timing around. Usually here`s how the timing is set on a sbc. Disconnect the vacuum advance and plug it, with the engine at idle set it at 12 degree`s before top dead center, lock the distributor, reconnect the vacuum advance, it should be connected to a full time manifold vacuum source ( a source that pulls vacuum even at idle) recheck the timing, it should have around 20 to 24 degrees before top dead center at idle. It`s also possible the balancer has spun on the outer hub and the timing marks aren`t lining up correctly so no matter where you set it, it`s not correct. If the timing is set too far retarded the result is the engine will run hot and it won`t have any power. But with that kind of miles it`s past rebuild time so for it not to have much power especially when the timing chain hasn`t been replaced it`s no surprise.
What degree thermostat did you install? are you sure the cooling system is up to par? with that kind of miles the radiator is past due for a cleaning.

 

[MaineHandyman]

thanks for the info, the timing was pretty good not to lang ago, i know its way way past rebuild time, just no time to take it out of commission as it is my work truck, im trying to get every last minute out of her. I actually put a new radiator in 2 years ago, seems to be good. I know there may be some slop in my timing chane, but it was runing pretty good until i tryed to time it better, now its worse than where it was before...lol but now i cant seem to find that happy medium where its good enough spot. even though its been doing ok, now up hill sucks, i can hear the 4 barrel kick in but just waisting gas cause it doesn't help, although if i drop the trans down too second it has some pickup. I also forgot to mention that this truck is 13,000 lbs, and its been that heavy for the past 10 years, did swap from a 3 speed to an automatic a couple years ago, that i won't do again.....im thinking of changing it back it had much more power to pull things. just sucks on the highway. thanks

 

[S10 Racer]

can you all please help me, ive been working on my own truck for the 15 years iv'e owned it and im really at my witts end with a timing issue (thats what i belive it to be) It has been running rough and lacking power for some time, and when i have a day to play with it (im always working and this is my p30 stepvan work truck) i have tryed to time it correctly. I have rebuilt the top end a year ago, new heads, intake, holly aftermarket carb, new exuast manifolds, have heat sheild boots on my plug wires because they were always getting brittle from the heat and cracking, i don't have that issue anymore. I have put #1 at TDC and tryed to get it 10 degrees advanced. i have also tryed driving down the road playing with the distributor to see how it affects power. I have an aftermarket HEI distributor. for the last few months its been runing very hot on the highway 210-260 and when i pull over and check radiator is bubling into the overflow bottle. I ran this truck un florida before moving to maine, and always had to run it with no thermostat to keep it cool enough. so when i came to maine i put it back in, was ok for a wile, then when it started runing hot i took it out so it could free flow, didn't help any. Flushed everything and had very good flow put thermostat back in and now just going down the road im at 220 cruising at about 45-50 mph. Now its getting very hot and very sluggish up hills. tryed also adjusting carb mixture screws to see if it would run a little better, no luck. Did i mention that thes 350 has about 600,000 miles on it.........I LOVE CHEVY...lol. So how can i corectly time it? how should i know where to set the carb mixture screws? can all this lead to the excessive heat? checked all the plugs they look good, new about a month ago. Please, any help would be appriciated, seeing how i have tryed a million things and maybe im doing them wrong or out of sequense. i also adjusted my valves the other day thinking that was the cause because i read that if the exuast valve didn't open at the right time or enough the exuast gas would burn hotter. PLEASE HELP...lol thanks to everyone on here for the help you give and opinions or answers you provide to all of us.

I think it may just be wore out. A couple questions for you.
1. Are you using a fan shroud?
2. What type of fan are you running?

As far as the carb adjustment goes, most Holley's have (2) idle mixture adjustments, some have (4). You need to turn these in gently (clockwise) until they stop and then back them out 1-1/2 turns. Whatever you do to one, do to the other. That will usually get you real close for starters. Also, check the float level on the carb using the sight glass (if equipped). Fuel level should be at the bottom edge of the sight glass when adjusted properly.