Formula Ford high rpm sputtering

[S351]

Hello ApexSpeed community. I'm pulling my hair out with an engine problem on my 88 VD. I'm using it for AutoX currently. The problem is that when it hits 4000-4500 rpm under driving load, the engine sounds as if it's cutting out or bumping the rev limiter. I have an MSD limiting the rpm to 6000, but the engine is giving me fits in that lower range. I've cleaned and rebuilt the carburetor, bumped both carb main jets to 170's, checked the float level (OK @ 1/2 way up or past the "ramp" at the front of the carb base), and increased the idle jet. I've run with the usual air jets of 165/170 and raised both to 195 but there's little or no change.

The engine idles beautifully and spools up to 6000 out of gear at rest with no hiccup whatsoever. Ignition timing seems proper. The cap, rotor, coil, plugs, and wires are new and all the ancillary ignition wiring appears to be in good shape. It has a Pertronix unit.

Any ideas to fix this anomaly? It's killing my times......

Thanks for your help!

[DanW]

Try disconnecting your MSD rev limiter. Mine failed after one race weekend. They don't like the vibes from our little motors.

It could be battery switch, or a loose ground somewhere as well.

[-pru-]

Have you tried disabling the MSD? My last unit did the same thing when it started to fail; worked when rev'ed at full stop in paddock but cut out under load. Pulled power lead to MSD Limiter which cleared up issue under load.

[Jerry B.]

""The cap, rotor, coil, plugs, and wires are new and all the ancillary""

""It has a Pertronix unit.""

if are using a Pert. module (the Series I) make sure u use the correct coil (3 ohms)
if
your using a Pert. II series module use a .60 Ohm coil.

[R. Pare]

Possible also that the battery is coming apart internally. Very common problem.

[Purple Frog]

Throw the MSD away, use the proper coil with the Pertronix, go have fun.
One time many decades ago I had an inexpensive electronic tach become a rev limiter.

[teamwisconsin]

Check the Pertronix magnet basket. Slide it off the distributor shaft and shake it. If you can hear magnets rattling, throw it out. Also, try to wiggle the pickup; sometimes the cheap rivets used will allow the pickup to vibrate at high rpm causing a misfire.

Good luck!

[Dave Cutchins]

Hello ApexSpeed community. I'm pulling my hair out with an engine problem on my 88 VD. I'm using it for AutoX currently. The problem is that when it hits 4000-4500 rpm under driving load, the engine sounds as if it's cutting out or bumping the rev limiter. I have an MSD limiting the rpm to 6000, but the engine is giving me fits in that lower range. I've cleaned and rebuilt the carburetor, bumped both carb main jets to 170's, checked the float level (OK @ 1/2 way up or past the "ramp" at the front of the carb base), and increased the idle jet. I've run with the usual air jets of 165/170 and raised both to 195 but there's little or no change.

The engine idles beautifully and spools up to 6000 out of gear at rest with no hiccup whatsoever. Ignition timing seems proper. The cap, rotor, coil, plugs, and wires are new and all the ancillary ignition wiring appears to be in good shape. It has a Pertronix unit.

Any ideas to fix this anomaly? It's killing my times......

Thanks for your help!

Your engine symptoms sound exactly like what I experienced several years ago when the EuroSwift FF I owned at the time developed those same problems. The engine ran fine and the suddenly the problem developed.
After spending a lot of money and eventually replacing every fuel and ignition part under the engine cover with new high quality race prepped parts and hours of dyno time we found the problem.
It turned out to be an inexpensive ignition switch on the dash. We came to the conclusion that harmonic vibration at a particular RPM was causing the intermittent loss of power to the coil. We bypassed the switch and the car ran great.
These cars have a lot of vibrations and things do break even a simple on/off switch. Check or replace your ignition switch and/or battery cutoff switch. Good luck.

[BURKY]

Check the Pertronix magnet basket.

Agreed...

This is the first thing I would check.

[roadracer]

The Pertronix magnets are definitely high on the miss-fire list as the plastic ring that holds the magnets in place can separate - just slightly - and cause the magnets to move. It is only 1/16" or so and the miss-fire begins. The only way to check it is to remove the magnet ring and check to see if the two plastic halves can be separated. You can look at it while it is in the car and never see it.
Also, the fuel pump is worth checking as under load the fuel demands are high and if it is getting air in the system or not enough fuel, it will cut out at high revs. It will work fine in the garage but under load it will stumble. A slightly loose fuel line clamp - letting air into the system - can cause the same thing.
It is always 'something simple'. Bets are on the MSD...
Good luck!

[Fred Michael]

Another vote for ditching the MSD and carefully checking the Pertronix. I have had enough failed MSD's to make me never use one again. Ever.
Never had a Pertronix fail, but have seen several on friends cars.

[Albatross]

Is the benefit of the Petronix that much better than what we have all used for years, ie. a set of points and condenser. Petronix costs about $150 as compared to points and condenser being far less expensive. Is the Petronix worth it?

[Hawke]

Also consider getting rid of the ignition switch. You save several lengths and joints of wires and one less component to fail. You have to have battery cut out switch, so use that.

Parts that are not there, cannot fail.

[Ian Lenhart]

Is the benefit of the Petronix that much better than what we have all used for years, ie. a set of points and condenser. Petronix costs about $150 as compared to points and condenser being far less expensive. Is the Petronix worth it?

Points work fine. Never had an issue with points and a condenser.

[Rick Kirchner]

I've had the wiper rapidly wear down on points and reduce the gap to essentially nothing. I've had a condenser gradually fail, producing an ever dropping rev limiter (at load only)

Never had a pertronix fail, and it has the benefit of advance for starting and never having to set dwell....

[Purple Frog]

In all my pintos... pertronix.

[Roland V. Johnson]

Also check to make sure the fuel cell foam is not breaking up and clogging the fuel filter/system.

[CM/FFdriver]

very interesting to here the problems with the MSD, everyone here on the west coast has high Praise for the MSD but I always buy a spare just for this reason. Not a big fan of the pertronix system I'm a big points person mostly because of the cost of the pertronix and if it fails, it's harder to diagnose. Watch the float level very important!

Ben

[Jerry B.]

some good help so far.......

more stuff..........
good spiral core plug wires? Check the resistance of each wire and the coil wire.
While you have the cap and plug wires off the car, again check the resistance from each wire on the plug end to the inside pins inside the cap....same with coil wire.
Check each cap socket hole for corrosion.
Check fuel pressure at idle and mid RPM.

This will keep you occupied...

[S351]

Thank to everyone for all of the expert insight. I have quite a list made of things to look into. Now it's off to the garage and my tools to see what I can find.

I'll let you know what happens.

Thanks

[joefuhring]

I am currently having the exact same problem. I don't use the MSD, could it be the Tachometer causing the problem, as mine starts bouncing around at about 4500 rpm? Before when I had this problem the battery was bad. Now the battery is only about a year and a half old - dry cell; could it be the battery? Fuel level in the Carb is correct, timing is correct, fuel pressure is correct, coil was changed and still did the same thing.
Any way to check the battery to determine if there are any dead cells?

Help!!!

[Hawke]

It could be the condenser. The best and easiest way to fix this is to put an ossissoscope on it. This will pinpoint the cause.

[S351]

Thanks again to everyone who replied with ideas. The problem indeed turned out to be the MSD ignition module. Once unplugged, the engine sang right up to 6k+ while running down the road with no hesitation. The neighbors may not have enjoyed my discovery, but I certainly did. For now, my eyes and the tach. will be the rev limiter.

Once again the ApexSpeed community proves itself a gold mine of expertise!

Take care all!

[rickb99]

If your worried about a rev limiter, call IVEY and get a rev limiting rotor. Very reasonable cost and just as effective as the MSD. If you don't like the RPM it's set at, he will put it on the distributor dyno and set it at any RPM you want.

[beachguy12]

If you find the RPM that the miss occurs is getting lower,6500, then 6400, etc., change the coil.

[mmi16]

Make sure you have good electrical grounds - intermittent grounds can cause all sorts of weird problems that you can spend months if not years chasing. Don't ask how I know!

[Buc01]

Had the same problem on pinto FC. Cure was I ditched the pertronix and went to points. This was after new battery, plugs, wires, caps,,,,,,,,,,,,

Once I switched to points, no more problems. FYI

Aaron