67 breaking up @ 4200 ??

[Fred Y.]

I just completed my yearly Spring tune-up of my 67 400HP coupe. For the last 2 years,I've noticed it sometimes breaks up when I "excercise it" at the higher RPM's-----this bugs me as I like everything to work just right.Last yr. I tried a 30K volt coil,( as I figured it might help with the poor gas we have in Ct.) along with the lectic limited ignition I have in it with a 50/50 110 leaded/93 unleaded gas mix.I use A/C R4 platinum plugs.The carbs are tuned right & were rebuilt some 6 yrs ago----they're OK! I did find out that the distributor needed a rebuild & had it COMPLETELY DONE.She has never idled better! I had a friend who is more than capable helping me on this & the next issue we summized was fuel pump-----replaced it!!We next looked around for broken or damaged wires both in the engine compartment & under the dash ---everything looked fine.I replaced the fuel tank some 5 yrs ago----spotless---fuel flows fine!Changed the dist. cap---changed the rotor! It still breaks up at 4200 RPM as if it were going FLAT---it sounds like a tractor with a jake brake applied----driving me nuts! Below 4200 it "SINGS" My only guess is the wires----but they are approx. 6yrs old---look fine---electic limited original Pacard wires----I see no arcing at night!!---

I could sure use some input,because I am stumped!!
Go back & install the original coil & work my way backwards??
Thankyou for your help!

[Clem Z.]

Re: 67 breaking up @ 4200 ??

I just completed my yearly Spring tune-up of my 67 400HP coupe. For the last 2 years,I've noticed it sometimes breaks up when I "excercise it" at the higher RPM's-----this bugs me as I like everything to work just right.Last yr. I tried a 30K volt coil,( as I figured it might help with the poor gas we have in Ct.) along with the lectic limited ignition I have in it with a 50/50 110 leaded/93 unleaded gas mix.I use A/C R4 platinum plugs.The carbs are tuned right & were rebuilt some 6 yrs ago----they're OK! I did find out that the distributor needed a rebuild & had it COMPLETELY DONE.She has never idled better! I had a friend who is more than capable helping me on this & the next issue we summized was fuel pump-----replaced it!!We next looked around for broken or damaged wires both in the engine compartment & under the dash ---everything looked fine.I replaced the fuel tank some 5 yrs ago----spotless---fuel flows fine!Changed the dist. cap---changed the rotor! It still breaks up at 4200 RPM as if it were going FLAT---it sounds like a tractor with a jake brake applied----driving me nuts! Below 4200 it "SINGS" My only guess is the wires----but they are approx. 6yrs old---look fine---electic limited original Pacard wires----I see no arcing at night!!---

I could sure use some input,because I am stumped!!
Go back & install the original coil & work my way backwards??
Thankyou for your help!

take it out and run it hard several times to the problem RPM point. shut of the ignition,coast to the side of the road,pull a spark plug. if the plug is clean and white you have a fuel problem and if it is dark you have ignition problem.

[Thomas H.]

Re: 67 breaking up @ 4200 ??

Fuel filter?

Tom

[Fred Y.]

Re: 67 breaking up @ 4200 ??

Thanks----will try tomorrow !

[Fred Y.]

Re: 67 breaking up @ 4200 ??

Members, this note is long over due , but better late than never.The whole problem with my cars breaking up was the wires! I purchased a 100' spool of 7mm wire along with new clips and now on my 2nd yr. using them. Best yet , I was able to slip the old wires from the braided shielding ( after I cleaned it with a rag & simple green) & slip them back through. The boots were AOK still. She now runs perfect at all RPM ranges.

[Timothy B.]

Re: 67 breaking up @ 4200 ??

Frederick,

If you need to replace them in the future consider the NAPA Belden 7mm premium wire set, it's a very top of the line product and Beldon makes many different wire cable products so they are not new to wires.

I just went through this in July with my 67 it started to hesitate cruising in forth and throttling up. The problem was a dirty #8 spark plug caused by a wire that could not deliver the necessary voltage to lite a lean mixture. I think the wire was approx 30-32" long and it's ohm reading was 11000+- ohms. The new Belden long wires that go to the #1-2 & 3 plugs checked at 11000 ohms for comparision.