350 loss of power - The 1947 - Present Chevrolet & GMC Truck Message Board Network

C101971 · 08-06-2018, 05:26 PM

I have run into an issue today, I was driving my truck, 71 GMC c15, 350 4 speed. When I noticed a loss in power, big time. Thought it was vapour lock but I pulled over, checked the distributor connections, they were all good. Spark plugs seem alright. Bit it was also making this God awful noise coming from the water pump I think. It sounded very different, liquidy sounding. But I had no power, rpm was bouncing everywhere. Timing seemed fine, just did the timing chain last week and it ran fine after, till now, she is acting up all the sudden.

Any ideas?

**Steeveedee** · 08-06-2018, 05:52 PM

It is possible that the bolts holding the gear to the cam came loose. I won't even ask for an audio clip.

C101971 · 08-06-2018, 06:11 PM

Quote:

Originally Posted by Steeveedee

It is possible that the bolts holding the gear to the cam came loose. I won't even ask for an audio clip.

Had to drive her home, she ran very rough then after a few minor highway speed she jerked a bit and was driving like new again. Now I'm thinking the fuel was just too hot maybe? When the problem came it was backfiring Alot when I took off the gas, now it went back to normal, no backfire. I think it might be a fuel issue now, what do you think?

cleszkie · 08-06-2018, 07:18 PM

Backfiring out the exhaust or out of the carb? I would check to see that the distributor hold down bolt is tight and that the distributor is not able to spin. I would also pull the valve covers and check your valve lash, rocker arms and push rods to make sure a rocker didn't partially unseat from a push rod and then fall back into place. The OEM stamped steel rockers have a habit of doing that if they are not adjusted properly, due to the lack of push rod retaining ridges. This usually results in a bent pushrod.

**Steeveedee** · 08-06-2018, 08:02 PM

Quote:

Originally Posted by C101971

Had to drive her home, she ran very rough then after a few minor highway speed she jerked a bit and was driving like new again. Now I'm thinking the fuel was just too hot maybe? When the problem came it was backfiring Alot when I took off the gas, now it went back to normal, no backfire. I think it might be a fuel issue now, what do you think?

If it is running fine now, it's definitely not the cam bolts coming loose. I have no idea what it could be at this point.

Coley · 08-06-2018, 08:26 PM

You did the timing chain....did you replace the original plastic timing sprockets?
These should always go hand in hand.

All Good
Coley

08-06-2018, 05:26 PM	#1
C101971 Registered User Join Date: Jul 2018 Location: Calgary Posts: 53	350 loss of power I have run into an issue today, I was driving my truck, 71 GMC c15, 350 4 speed. When I noticed a loss in power, big time. Thought it was vapour lock but I pulled over, checked the distributor connections, they were all good. Spark plugs seem alright. Bit it was also making this God awful noise coming from the water pump I think. It sounded very different, liquidy sounding. But I had no power, rpm was bouncing everywhere. Timing seemed fine, just did the timing chain last week and it ran fine after, till now, she is acting up all the sudden. Any ideas?

08-06-2018, 05:52 PM	#2
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,181	Re: 350 loss of power It is possible that the bolts holding the gear to the cam came loose. I won't even ask for an audio clip. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

08-06-2018, 07:18 PM	#4
cleszkie Registered User Join Date: Feb 2003 Location: Santa Ana, CA Posts: 2,191	Re: 350 loss of power Backfiring out the exhaust or out of the carb? I would check to see that the distributor hold down bolt is tight and that the distributor is not able to spin. I would also pull the valve covers and check your valve lash, rocker arms and push rods to make sure a rocker didn't partially unseat from a push rod and then fall back into place. The OEM stamped steel rockers have a habit of doing that if they are not adjusted properly, due to the lack of push rod retaining ridges. This usually results in a bent pushrod.

08-06-2018, 08:26 PM	#6
Coley Registered User Join Date: Oct 2011 Location: Victoria, B.C Posts: 3,794	Re: 350 loss of power You did the timing chain....did you replace the original plastic timing sprockets? These should always go hand in hand. All Good Coley __________________ ....for some men, there is experience, skill and effort....for the others...there is visa and UPS LOL 1966 Chevy 1/2 ton (Florida- Red/white) 1972 Chevy 1/2 ton (California- Blue/white) 2005 Chevy Silverado HD2500/Duramax 2000 Dodge Ram 1500



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