Squarebody Down! HELP - Member Roadside Assistance Volunteer Map

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Skweegle89

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Im brand spankin' new here, but if you want to put me down at 74865, We have a 4 bay truck shop with enough tools to work on everything from a VW to a Kenworth.
 

HotRodPC

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That's awesome. I know where I want to break down now !!!
 

DoubleDingo

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81-C20 Silverado Camper Special-TH400-4.10s; 65-C20 with 4:57 gears and Borg Warner Overdrive
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Carb'ed Vortec 350; 1972 L48 350
Was cruising down the freeway, truck was running strong, and then it started to spit and sputter. There is a ticking sound from the left bank, sounds like a lifter. Could the cam have taken a dump? Rocker loosened up? It starts right up just fine, but has no power now. Any ideas on what it could be? Waiting for a tow truck to haul us back home. Any insight on what to look at would be much appreciated. I won't be able to respond for a while, but don't hold back any suggestions. Thanks guys.
 

BADAZ chevy guy

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Was cruising down the freeway, truck was running strong, and then it started to spit and sputter. There is a ticking sound from the left bank, sounds like a lifter. Could the cam have taken a dump? Rocker loosened up? It starts right up just fine, but has no power now. Any ideas on what it could be? Waiting for a tow truck to haul us back home. Any insight on what to look at would be much appreciated. I won't be able to respond for a while, but don't hold back any suggestions. Thanks guys.

Could be a flat cam lobe, rocker stud pulled lose, broken or bent push rod or a bad lifter.
Lose stud: If you find a lose rocker, lay a straight edge across the rocker stud bolts and see if they're all the same height before you just tighten it back up.
Worn lobe or bad lifter: While having someone crank the engine, look at the lowest part of the push rods as you can (next to where it comes out of the head) and make sure they're all moving about the same distance.
Check the push rod to make sure it's not bent or broken.
That's about all I can think of right now. Keep us posted.
 

HotRodPC

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The thing that bothers me, is, even if only 1 cylinder is affected, it shouldn't lose so much power that it's not driveable. But, yep, all the vavle train possible issues have been mentioned by Doug.

No backfiring at all huh??? Either thru the intake or exhaust? Do you have hardened seats in your heads? Now that, i've seen before become a problem. Usually 3, 4 or 5 seats are actually bad but only 1 be bad enough to be ticking with slop in the rocker/pushrod train. But even then, it's usually gradual, and get worse and worse.

Here's what a head looks like with non hardened seats and unleaded fuel. Ohh ****, and you're in Cali with that high alcohol content fuel too.
 

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raylanr

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Franc
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Your situation sounds like something that happen to us, but we have 2-3 backfires and the truck seem to lose power. After shifted in to park. We were able to drive her home. I'm still trying to learn more about what could have been
 

DoubleDingo

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81-C20 Silverado Camper Special-TH400-4.10s; 65-C20 with 4:57 gears and Borg Warner Overdrive
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Carb'ed Vortec 350; 1972 L48 350
Got towed home, it fires right up, idles smooth, but it feels like it is running on 6 or 7 cylinders. There is a definite rocker slap on the driver's side bank. We were 1 hour into the camping trip when it happened. We were both commenting on how well it was running. It was pulling the grade just fine, didn't get hot, nothing bad and then it made an odd sound and it maintained semi-decent power until the next exit. Just wanted off the freeway as quickly as possible. Pulled off and parked with it running, checked tranny fluid, and listened. To me it sounded valve train related. Was going to limp it home on backroads, but there weren't any that could get all the way home without needing to hit the freeway. Called for a tow. Now regrouping, and contemplating going camping a day later.

The heads are fresh vortecs from GM Performance Parts, barely 1,000 miles on them. Without tearing into it, I suspect a lifter quit, the cam quit, or a push rod got bent.

I have this GM Performance Parts cam and lifter kit laying in my work room, a GM# 12364051, I bought it when I bought the vortec heads. I cannot remember the specs on it, but if my memory hasn't failed me, it is good from idle or 1500 rpm to 4000 rpm. I am thinking if I have to tear into, may as well replace instead of troubleshoot. If a pushrod is bent just get new ones. And I will get fresh cap, rotor, coil, and wires, because I am not sure when the PO replaced it all. Plugs were replaced with the heads, and this engine just passed emissions with flying colors, dang it this sucks.

I do run the crappy Cali fuel but I do splurge and run Chevron 91 octane in all my vehicles.

I have been writing pulling from my memory brain, and sharing stuff from returning home from the tow. I do think it is valve train related, because there is definite slap under the valve cover. I am not tearing into the engine right now, I need to fulfill some plans that ran into a snag.

Thanks for the input, with your input I know where to look when I tear into it.
 

DoubleDingo

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81-C20 Silverado Camper Special-TH400-4.10s; 65-C20 with 4:57 gears and Borg Warner Overdrive
Engine Size
Carb'ed Vortec 350; 1972 L48 350
Forgot to mention there is no backfire, oil pressure is 40 psi at cold idle, and 20 psi at hot idle, but it jumps to 40 psi going down road, and it was 40 psi after getting it home.
 

RetroC10Sport

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Your situation sounds like something that happen to us, but we have 2-3 backfires and the truck seem to lose power. After shifted in to park. We were able to drive her home. I'm still trying to learn more about what could have been

I'm thinking your fuel regulator is bad.
 

RetroC10Sport

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Once you get the rebuild kit, I'll come over and we'll set to rebuilding it.
 

HotRodPC

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85 K20 LWB
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454 - Turbo 400 - 3.73
Got towed home, it fires right up, idles smooth, but it feels like it is running on 6 or 7 cylinders. There is a definite rocker slap on the driver's side bank. We were 1 hour into the camping trip when it happened. We were both commenting on how well it was running. It was pulling the grade just fine, didn't get hot, nothing bad and then it made an odd sound and it maintained semi-decent power until the next exit. Just wanted off the freeway as quickly as possible. Pulled off and parked with it running, checked tranny fluid, and listened. To me it sounded valve train related. Was going to limp it home on backroads, but there weren't any that could get all the way home without needing to hit the freeway. Called for a tow. Now regrouping, and contemplating going camping a day later.

The heads are fresh vortecs from GM Performance Parts, barely 1,000 miles on them. Without tearing into it, I suspect a lifter quit, the cam quit, or a push rod got bent.

I have this GM Performance Parts cam and lifter kit laying in my work room, a GM# 12364051, I bought it when I bought the vortec heads. I cannot remember the specs on it, but if my memory hasn't failed me, it is good from idle or 1500 rpm to 4000 rpm. I am thinking if I have to tear into, may as well replace instead of troubleshoot. If a pushrod is bent just get new ones. And I will get fresh cap, rotor, coil, and wires, because I am not sure when the PO replaced it all. Plugs were replaced with the heads, and this engine just passed emissions with flying colors, dang it this sucks.

I do run the crappy Cali fuel but I do splurge and run Chevron 91 octane in all my vehicles.

I have been writing pulling from my memory brain, and sharing stuff from returning home from the tow. I do think it is valve train related, because there is definite slap under the valve cover. I am not tearing into the engine right now, I need to fulfill some plans that ran into a snag.

Thanks for the input, with your input I know where to look when I tear into it.

Ok, so it's not a recessed valve. I'll make a prediction of 1 of 2 things. 1 you're going to pull the valve cover and the problem is going to be obvious. Rocker Arm gone bad, bent push rod, rocker arm nut loosened up, rocker stud pulling out or something of that nature. If all that is normal looking. Then it's trying to wipe out a cam lobe. You may have done the right thing by getting it towed if that were the case. If it's wiping a cam lobe, it would have completely wiped it out on the drive home and ran all that metal thru your bearings and trashed your motor. Let's hope it's #1 and the problem is obvious as soon as you pull the valve cover. If it's #2, I'd say it might be possible you overtightened a rocker arm when you put the Vortec heads on.
 

DoubleDingo

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Right where I am
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1981, 1965
Truck Model
81-C20 Silverado Camper Special-TH400-4.10s; 65-C20 with 4:57 gears and Borg Warner Overdrive
Engine Size
Carb'ed Vortec 350; 1972 L48 350
Thanks for the input guys. And I apologize for the lengthy response time. It was the day before my birthday when the truck pooped out, and I needed out of this forsaken place to decompress and regroup. 4 nights at 8,000 feet with peace and quiet and awesome sleep, I am back in the smog ridden city.

I may tear into the valve train this week while I am on vacation. I have so much other stuff that needs to get done first. It can't sit for too long though, as it has 2 full tanks to burn.
 

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