high RPM misfire 340 hp.

[Bruce W.]

Re: high RPM misfire 340 hp.

Mike, here is a question you might know the answer. I took off the shielding and the wires say Packard TVRS radio supressed. Do you think that these are 440 solid core? I have owned the car 25 years and these were the wires on it. Also says 4 qtr 61? Maybe the miss fire is plugs? doesn't say 440 on the wires. thanks for your help.
Bruce

[Tom M.]

Re: high RPM misfire 340 hp.

Packard TVRS is a suppression core wire. TVRS = Television & Radio Suppression. It is not 440 solid core wire. The spec for TVRS is 4000 ohms/foot. I have a 25 year old set of LL wires removed from my '69 this spring. The longest wire is 48" and measures 20k ohms.
My 350/300 developed a terrible miss under load - turned out to be fouled plugs. I did the once-every-quarter-century tune up - points, plugs, wires,condenser, cap, rotor. I replaced the LL wires with a new set.

[David M.]

Re: high RPM misfire 340 hp.

Is your carb a Rochester or Holley? Is it stock or other?
What brand of ignition conversion was installed?
Mechanical valve train? Run the valves again. They need to be dead on.
Stop part-replacing and lets do some basic trouble shooting:

Fuel sys:
1. How do the plugs read? White Brown Black?
2. What’s the plug brand & heat range?
3. What do you have the plug gap set to?
4. Any internal engine modifications, say a larger cam? If yes the carb may still need some tuning. The plugs will tell you if you’re lean.
5. Take a fuel pressure reading at idle and WOT(engine under load goin down the road). You should see little to no delta P. 5-7psi.
6. Inspect the fuel lines. A pinhole will slightly weep and suck air...again lean at peak demand. Pressure will drop off at peak demand.
7. Inspect the fuel filter and its position...flow direction, if it’s in the air horn.
8. What is the engine vacuum reading at idle? Hopefully you dialed in the A/F mix and timing with a vacuum gauge (then verified with a timing light).
9. Verify the float floats and the level and drop settings are in spec.

Ign sys:
1. Inspect the cap and rotor and centrifugal advance mechanism.
2. You installed an electronic conversion. What type? Electronic systems, HEI, MSD Pertronix etc... are much more sensitive to a bad ground than a points system. Verify all engine and charging system grounds are clean to include both ends of both battery cables.
3. Are you getting proper voltage to the distributor per the manufacturer specs? Does the new electronic conversion require a full direct 12 VDC source?
4. Do you know your timing curves? Base, Vac & Centrifugal?
5. Ohm test the secondary (plug) wires, cap, rotor, coil and other primary wires feeding the ign sys.

Record the above data and post it. A lot of info here I know. But its proper trouble shooting vs tail chasing.

I like Taylor Spiral Core 8mm plug wires and plain old Autolite plugs. They may make 7mms? Get the proper hand held tool to crimp the wire ends. Use dielectric grease on the plug boots.

[Frank D.]

Re: high RPM misfire 340 hp.

I don't recall the OP stating what electronic conversion is he is running; the LL Breakerless SE will run fine with all other components being stock (e.g. plug wires); the Pertronix doesn't run well with solid core plug wires; per their web site FAQs. It sounds like the TVR wires should work, but if Bruce changes wires and has a Pertronix, he should take note.

As far as plugs, if you're not into judging then the NGK-B4 is an outstanding plug and crosses over to the ACR45 and 46 and I suspect it runs a tad hotter than the 45.. I've run them in my C1 and C2 for many years.

[William F.]

Re: high RPM misfire 340 hp.

Solid core wires are NOT recommended if you have a Pertronix ignition. Get spiral core wires anyway.

[William F.]

Re: high RPM misfire 340 hp.

May sound dumb but are you SURE you don't have bad gas-that is, water in gas? Had same high rpm miss in '62 340 hp, changed plugs, etc, put in tank of new good quality gas and problem solved. Felt dumb. Common things are common.

[Frank D.]

Re: high RPM misfire 340 hp.

Worth checking - also the dreaded fuel pump actuator pin "walk out" that happens on some pumps...it can cause some zany symptoms:

[Harry S.]

Re: high RPM misfire 340 hp.

I installed the Summit wires I mentioned in post 6. I changed the cap and rotor also. Put the WCFB back on today. It runs like new. I think it was a combination of four parts. I'm just happy it performs again. Now for the brake pull and the throw-out bearing.

[Bruce W.]

Re: high RPM misfire 340 hp.

Harry, Congratulations!! We all feel good when we fix something on our cars. So i pulled all the plugs, none fouled. I took out the wires and found the ohms on the old wires were twice that of new K&B 440 wires. Putting in new plugs anyway sine I had to pull them might as well.
Will let you know if this fixes the problem. looking for a miracle
Bruce

[Bruce W.]

Re: high RPM misfire 340 hp.

Harry,
ok I changed the wires to K&B. Says on the box made with Packard 440 wires? Anyway was a very interesting learning experience. So I pulled all the plugs and found they all looked good except #1 cylinder. Black soot. when I used an ohm meter i Found resistance at 20,000. Which would explain why that plug fouled. I changed the wires and plugs anyway since I had the plugs out. It now runs better than ever. Thanks for you help Harry.
Bruce