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RonS1985 · 06-04-2011, 02:50 PM

Today I just replaced a muffler and put new hardware on the exhaust flange at the manifolds. Nice & quiet now. Now I have a new problem...she's sputtering. It almost sounds like a backfire but from the intake. Anyone else have this problem before? The RV hesitates each time and it does more the faster I try to go. My first thought is the timing is off. I never set timing on a 454 before so I don't know where the adjustment is. Does anyone have any other ideas? Hopefully a quick fix? Thanks

Guy an a dog · 06-04-2011, 03:04 PM

Quote:

Originally Posted by RonS1985

Today I just replaced a muffler and put new hardware on the exhaust flange at the manifolds. Nice & quiet now. Now I have a new problem...she's sputtering. It almost sounds like a backfire but from the intake. Anyone else have this problem before? The RV hesitates each time and it does more the faster I try to go. My first thought is the timing is off. I never set timing on a 454 before so I don't know where the adjustment is. Does anyone have any other ideas? Hopefully a quick fix? Thanks

You adjust your timing by twisting the distributor. You'll need a timing light and you'll need to find what it needs to be set to. The timing marks will be on the crankshaft pulley that coincide with some marks on the block. Check the timing first before you mess with the distributor because you might find it is set correctly and have a different problem. Good luck and I hope this helped.

bigskymt · 06-04-2011, 03:59 PM

Plug wires open or the boots near the exhaust flange you replaced are shorting to ground. The more load you put on it the worse it will miss.
Did you remove the distributor to upset the timing?

TXiceman · 06-04-2011, 04:47 PM

The Chevy engine of that vintage was really rough on plug wires. If you want to see the wire "leaking" pull the engine cover and wait utill it is good and dark and start the engine.

Best thing to do is to buy a good set of high dollar ceramic boot plug wires for the engine. Install them one a ta time, following the original wire route and keep them clear of the exhaust manifold.

Ken

RonS1985 · 06-04-2011, 09:59 PM

Thank you. That was very helpful.

BZam · 06-04-2011, 10:14 PM

Quote:

Originally Posted by RonS1985

Today I just replaced a muffler and put new hardware on the exhaust flange at the manifolds. Nice & quiet now. Now I have a new problem...she's sputtering. It almost sounds like a backfire but from the intake. Anyone else have this problem before? The RV hesitates each time and it does more the faster I try to go. My first thought is the timing is off. I never set timing on a 454 before so I don't know where the adjustment is. Does anyone have any other ideas? Hopefully a quick fix? Thanks

I had the same problem in my 1990 454 and you probably need to replace the entire wiring harness. They are a bugger on wiring from engine heat.

Bob

whem2fish · 06-05-2011, 05:14 AM

i also have a 1985 i would first check simple things wires plugs then dist. cap and rotor. to set timing use wire # 5 get under the rv look on harmonic balencer on the drivers side (under motor) you will see the timing mark. that said i will lay money on wires

JimElliott · 06-05-2011, 11:29 AM

Quote:

Originally Posted by whem2fish

i also have a 1985 i would first check simple things wires plugs then dist. cap and rotor. to set timing use wire # 5 get under the rv look on harmonic balencer on the drivers side (under motor) you will see the timing mark. that said i will lay money on wires

Right on Dave

Are the metal shields that surrounds the plugs still in place?

If not get them (salvage yard), Next the only wires I use are the cheap "Pep boys Borg Warner select" straight boots HEIs stuff.....Never had a plug wire failure in many miles of driving and thats without the plug boots covered up with anything.....

All this B.S. about "Bling bling wires" being the best IMHO is simply B.S., Metal plug wire shields and decent wire is good....

Jim

ga traveler · 06-05-2011, 11:54 AM

napa sells a set of ceramic end wires. these are very good wires. a little pricey.(about $100.00, but worth it.) The other thread is right in that you must not check timing from #1 plug but from #5 plug. This is because you use the motorhome timing bracket, on the bottom of the motorhome engine. When installing the wires they MUST be clear of the manifolds.

bigskymt · 06-05-2011, 12:52 PM

If your distributor cap develops a carbon trail between two towers or has moisture inside, the High Voltage can leak to the wrong contact and fire that cylinder. If that cylinder's intake valve were open you would hear a popping or backfire through the carb.
Likewise if you have an open wire and the voltage is unable to reach it's load to be discharged it will bounce around the inside of the cap until it finds the available path with the least resistance and travel down that wire. Again it might fire on a cylinder with an open intake valve.
The wires can be ohmed out. 500 ohms to 1K should be OK for GMs 50K HEI. A bad wire might read 500K to 1 meg..... Not positive on those values, its been a long time since I ohmed wires.

whem2fish · 06-06-2011, 02:35 AM

agree with jim i run cheap auto zone have close to 30,000 miles on them if the get bad get a new set free. hey jim daughter graduated last friday now waiting on attorney general

JimElliott · 06-06-2011, 08:46 AM

Quote:

Originally Posted by whem2fish

agree with jim i run cheap auto zone have close to 30,000 miles on them if the get bad get a new set free. hey jim daughter graduated last friday now waiting on attorney general

Ummm, Dave, What will the "A/G" do for you?

Jim

whem2fish · 06-06-2011, 09:27 AM

$780 a mt then feb truck paid off$460

RonS1985 · 06-07-2011, 06:40 AM

Thanks for all the great advice guys. I did a thorough inspection of the plug wires and found two that had worn against metal tubing down to the center wire thus shorting out against the metal tube. It makes me sick thinking about all the extra fuel I've paid for that wasn't getting burned properly. Thanks again!