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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: spectreblazer on March 04, 2011, 08:29:08 pm
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allright guys looking for some help cause this has got me stumped. in all the 350s i've seen i have never heard or seen one do this.
in gear 1,2, or drive the truck maxes out foot to the floor at 2500 rpm.
in neutral or park i could during the summer hit 5000 rpm no problem. now it is closer to 3500-4000 in the colder weather.
my setup is a turbo 350 transmission with a np 203. and 35" tires
i believe the gears in the front and rear are 4:10 so i know this truck should scream
my top speed is 67mph with my foot to the floor.
Things i have tried
holding 1st or 2nd to see if any increase in rpm. none
i took the truck mudding and had my foot on it all night. max rpm was 2500 rpm , never got stuck though ;D
as far as i know this engine is stock. my truck had a 6.2L in it from the factory. then the 350 was put in it. i did not put it in.
i checked the kickdown cable and that was fine.
i plan to tear this motors top end down to replace an intake manifold gasket that i believe could be part of the problem but the truck was running the same before this.
my other thought is that i have a few cam lobes wore down and i can't build any power.
what do you guys think and have you ever head anything like this before in a 350? for the most part i've heard these motors are hard to kill
thanks
-dave
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Was that tranny and Torque converter the one from the 6.2L?
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I don't know what you're driving....year? Pre '87 or post '86-- That way we can see if it is a carb or TBI
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its an 82 k5 blazer. the diesel had a 700r4 with it and i don't know what transfer case, but i'm 100% sure it had the 700r4. so the turbo 350 is from something else
according to the block number the block is a middle 70s 350 so it is carbed.
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does it run hot?
I ask because it seems there is a restriction, perhaps, in the exhaust flow. If that is the case, it would run hot since the exhaust will have a hard time leaving the engine. Do you have a catalytic converter on it?
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Check your throttle linkage and make sure your carb is achieving wot, also make sure your choke is fully open after the engine reaches operating temp. Do you see black smoke coming out your exhaust?
At 2500 rpm is the engine missing or bogging? any pinging?
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does it run hot?
I ask because it seems there is a restriction, perhaps, in the exhaust flow. If that is the case, it would run hot since the exhaust will have a hard time leaving the engine. Do you have a catalytic converter on it?
nope doesn't run hot. runs at 180-190
there are 2 cats on it but i believe both have been burned out. it's excempt from emissions
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Check your throttle linkage and make sure your carb is achieving wot, also make sure your choke is fully open after the engine reaches operating temp. Do you see black smoke coming out your exhaust?
At 2500 rpm is the engine missing or bogging? any pinging?
throttle is as WOT, the choke is electric so how would i check that?
no black smoke
at 2500rpm is is running pretty good. it sounds like that is all it has in it.
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the choke is easy to check, if you have no starting prrooblems, then it is closing fine. After about 2-3 minutes of running, you can look at carb and see if choke wing is open all the way.
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To me it sounds like either your timing is way retarded, your exhaust system has a restriction in it or there is a fuel restriction like a kinked line or clogged fuel filter. My $.02
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Put a vacuum gauge on it.
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To me it sounds like either your timing is way retarded, your exhaust system has a restriction in it or there is a fuel restriction like a kinked line or clogged fuel filter. My $.02
timing is 8 degrees advanced right now
it was set at 23 and it ran alot better then it does now at 8.
i'll see if i can get ahold of a vac gauge. where should i hook it up? any vac line?
what should i be reading? 15-20? i know it is measured in (inHG)
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How are you setting your timing
Hook the vacuum gauge to an intake vacuum port and route the gauge up to the windshield. Duct tape it to the windshield and put the truck in gear. Accelerate to WOT and observe the vacuum gauge. It should drop to zero and rise. If it stays at zero suspect a plugged exhaust.
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How are you setting your timing
Hook the vacuum gauge to an intake vacuum port and route the gauge up to the windshield. Duct tape it to the windshield and put the truck in gear. Accelerate to WOT and observe the vacuum gauge. It should drop to zero and rise. If it stays at zero suspect a plugged exhaust.
i set #1 cylinder to TD
then i used a timing light. i took it into my automotive class once and a mechanic i work with helped me the other time.
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How are you setting your timing
Hook the vacuum gauge to an intake vacuum port and route the gauge up to the windshield. Duct tape it to the windshield and put the truck in gear. Accelerate to WOT and observe the vacuum gauge. It should drop to zero and rise. If it stays at zero suspect a plugged exhaust.
Awesome bit of knowledge to lock up in the vault... Hope I can recall it when I need it. Thanks Vile..
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Hook the vacuum gauge to an intake vacuum port and route the gauge up to the windshield. Duct tape it to the windshield and put the truck in gear. Accelerate to WOT and observe the vacuum gauge. It should drop to zero and rise. If it stays at zero suspect a plugged exhaust.
Vile, I have to say I've never heard or seen the "and rise" part. How long are you expecting it to take to start rising? How high would/could it rise? Lorne
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x4 on exhaust restriction.
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x4 on exhaust restriction.
i don't think it is the exhaust. this truck is reallly loud and has a ton of exhaust. it has duals
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I'm with zeig85 on the fuel restriction. I would replace the fuel filter and test fuel pressure. Also check the condition of your spark plugs, black and sooty means your are running rich, clean and dry and white means you have a lean fuel condition. At a minimum check one on each bank and check them all if you want to see if you have a particular problem on one cylinder.
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Just curious, kind of odd question. Where you live? There was a bog event I went to last night
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spark plugs were changed last summer. i will change that fuel filter though if it has one. it was a 6.2L before so it had the water separator/fuel filter in one and it is gone now.
MI
it was mud bogged awhile back. right before winter. so it was in the fall
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spark plugs were changed last summer. i will change that fuel filter though if it has one. it was a 6.2L before so it had the water separator/fuel filter in one and it is gone now.
MI
it was mud bogged awhile back. right before winter. so it was in the fall
You don't need to inspect your spark plugs for wear, you would inspect them for color, this tells you if you are running rich or lean or even a correct a/f mixture, regardless of if they were changed in the summer you should inspect them with your current issue.
white=lean fuel condition
med brown=correct
black=rich fuel condition
an individual plug that is darker than the rest could indicate a problem with that particular cylinder.
report your findings back here and someone here can point you in the right direction.
also you should have a fuel filter in your carb.
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Hook the vacuum gauge to an intake vacuum port and route the gauge up to the windshield. Duct tape it to the windshield and put the truck in gear. Accelerate to WOT and observe the vacuum gauge. It should drop to zero and rise. If it stays at zero suspect a plugged exhaust.
Vile, I have to say I've never heard or seen the "and rise" part. How long are you expecting it to take to start rising? How high would/could it rise? Lorne
Good catch Lorne! I think I was half in the bag when I wrote that. A much needed night of drinking lol - The truck should NOT be in gear it should be in Park or Neutral.
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i'll check the spark plugs out when i get some time on the weekend guys. anyone know where the fuel filter would be on a quadrajet-4 barrel carb?
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yes, it is cylindrical shaped and is located right where the gas line meets the front of the carb.
(http://www.delbridge.net/gasfilter.jpg)
mine is a little different at the front, but, look at this vid, be careful of the spring..
http://www.youtube.com/watch?v=WK0sqMI6mMs
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btw; when you change the filter be sure to check for leaks