427/435

[Donald W.]

I've developed a miss at around 3500 rpm and up. The engine has been rebuilt complete and has 4000 miles of use. The ignition is transistor and also has been completely rebuilt with the same miles of use. Let me know where i should be looking to inspect and repair.

Thanks,

Don

[Clem Z.]

Re: 427/435

i would install some AC R-45 XLS plugs gapped at .035 and see what happens because even with TI too cold of a plug will cause this problem as the plugs carbon foul from low speed driving

[Mark #28455]

break it down into systems

First, you have to inspect what you have-

How is the idle? Has it changed at all (slower, rougher, etc.)? There may be a vacuum leak somewhere. Try the engine with the different vacuum hoses disconnected and the ports capped.

Do all the spark plugs have an even tan color? If one is different, that may be your problem cylinder.

Are all of the parts relatively new and in good condition? Check the distributor cap and rotor, check that the mechanical and vacuum advance are working (engine running, watch timing as you slowly rev the motor and also when you disconnect the vacuum advance).

Try it with the radio interference capacitor on the coil disconnected (they can go bad too).

Are you using the original style plug wires with the braided shielding? They can degrade and leak voltage even if the braid looks fine.

Give us more info as you go along to narrow down the problem.

Good luck,
Mark

[Donald W.]

Re: break it down into systems

I have new AC-45 Spark Plugs installed with no change. Replaced the Distributor cap and Rotor with no change. All Vacuum lines are in good shape. The Plug wires were new when i rebuilt the engine, only 4000 miles on them, dont think they are bad, they are the dated type and are expensive. Any other area's i should look.

[Clem Z.]

Re: break it down into systems

several other owners of the repo braid covered wires posted on the vetteheads site they have had trouble like you discribed.

[Mike M.]

Re: break it down into systems

agree with clem. the repo wires are usually good for their initial installation on the spark plugs. pull them off the plugs once or twice and they are history. Long live Packard 440 plug wire. mike

[Myron Sleeva]

Re: 427/435

A good mechanic friend showed me the best and cheapest way to check plug wires.

Have the car running. Simply use a slow stream of water from the garden hose, wetting down each wire, starting around the spark plug. If there is a short, the water will ground out that wire and the engine will develop an obvious miss. You can identify the bad wire(s) in a matter of minutes.