Chevy 454 Question

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#1
I have a 1988 motor home with a chevy 454. It runs great - or seems to - until I get it under load, and it randomly backfires in a kind of popcorn popping like fashion. It does not always do it, and it seems very random - meaning there is no discernible pattern or symmetry to the popping. There does seem to be some power loss when it is happening. My thoughts for possible causes: water in the fuel, timing advance off or not working, worn valves, worn cam lobes. Anybody with some possible insight as to what might be the problem would be greatly appreciated. Thanks!


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nickb2

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#3
I have a 1988 motor home with a chevy 454. It runs great - or seems to - until I get it under load, and it randomly backfires in a kind of popcorn popping like fashion. It does not always do it, and it seems very random - meaning there is no discernible pattern or symmetry to the popping. There does seem to be some power loss when it is happening. My thoughts for possible causes: water in the fuel, timing advance off or not working, worn valves, worn cam lobes. Anybody with some possible insight as to what might be the problem would be greatly appreciated. Thanks!
All symptoms above indicate pinking and advance timing.
 

nickb2

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#4
On a funny note, a guy came with his family from Alberta to quebec and the 454 split a block.

9000$ later, he was back on the road, just to call me back from manitoba. Split another block. Damn. I must say.

That was all due to bad timing, pre ignition, and one heck of a bill.
 

nickb2

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#6
He did the same going back home, the decompression on the 454 did the same as the acceleration on the way back home.

2 454 split.

Wow, what else can I say.
 
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#7
I would go for this.

On a motorhome such as this, timing is taken from underneath.

Do you know how to time a 454 motorhome?

Yep. That was going to be the next thing I did after making sure the fuel tank was completely dry. Start with the free stuff and work toward more expensive solutions.


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#8
On a funny note, a guy came with his family from Alberta to quebec and the 454 split a block.

9000$ later, he was back on the road, just to call me back from manitoba. Split another block. Damn. I must say.

That was all due to bad timing, pre ignition, and one heck of a bill.

Ouch! That's not funny! Heh heh!


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big al

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#9
Is this a carb, or tbi motor? I agree with nick but also want add i hate these tbi units. They were alot better on the small blocks but still had issues when they aged. Have had to repair many of these tbi units. Check where the wires go into the unit for chaffing, regulater, injector. Not to mention they didnt help produce much power, have even changed some over to better aftermarket units
 

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#11
But since I am soon to be 42yrs old, can't say for sure if the TBI system was a major item back then on the motor homes. I was 13yrs old at that point and my only priority then was my BMX or my dads lawnmower.:D:eek:
 

big al

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#14
Yep, you are correct, they were split but that was the start of tbi. I am 42 also but had to drive older stuff when i could drive. Sometimes took alot to keep that stuff going. Then got into the performance seen. Many people thought the motors were junk, but if eliminated a few problem could get decent power out them. Although not like todays pwer options. Altought i do have a 98 454na motor puts out 515hp easily, also have a built 88 old tbi motor with turbos lays down 943hp. I guess we need to know if its carb or tbi (like you said could go either way) also maybe could have the electrictronic q-jet carb back then. With a few slight mods the q-jet was a excellent carb also.