308 missing at over 5000Rpm

My input:
Did you check your timing at the higher rpm? It is very important for the max advance to be correct. If you have too much advance it will cause major misfiring at the higher rpms.

I had this happen to a previously owned Lamborghini after a distributor rebuild. The rubber bushing for the advance weights were accidently left out which caused too much advance.

Could be other things, but this is an easy check.

Richard
Dino246 03510

 

maurice -- What type of ignition system do you have on your 308GT4? Single dist, dual dist, points, something electronic, etc.?

If you're using a point-fired system, I'd reverify the mechanical point spacing (and action) is quasi-reasonable too (either just mechanically/optically or with a dwell meter), but please clarify what type of ignition system.

Dist rotor phasing to the distributor cap(s) might also be something to reverify/confirm.

 

My old carb car did that. It was the distributors outta wack.

 

Could also be fuel delivery. If it misses when driving over 5k RPMs but not at idle there, bingo!

Ken

 

If you have the points and the tuning process included "setting" the points, then you should look to see of the points have arc build up. if this is the case, they are set too wide. this will allow the car to run good at idle, but eventually the bank that goes out first will die off and the car will act like it has a reve limiter. you can set the points with a feeler gage making sure that you do not allow the arc build up spot to be included when gapping them. IF this is your problem, and you want to eliminate the arc build up (which is not required, as long as there is sufficiant room to set them around this build up) you can buy a points file. this is used to file this build up off.

also, if the points are really old you may want to replace them.

I have had this problem when setting a friends points, and it initially did the same thing in his 78 308. I thought they were newer than they turned out to be, and he had some build up. it cut out at around 5000 RPMs. reset them working around the build up spots and the car rev'd and ran great.

Dan

 

whe once had a 308 doing a similar thing and we fixed it by changing the distribuitor caps

 

I'd put my money on it being the ignition system. This exact problem started after I had a semi-major service done on the car (didn't do it before I took it in). I was told that my distributors needed to be rebuilt or needed new points and cap & rotor (can't remember). Long story short, I put on an Electromotive DIS and haven't looked back.

Henry

 

The Bosch GT40R is a good coil to use with points ignition running a ballast resistor, BUT make sure you get the "R" type for Ballast use, NOT a plain GT40... ask me how I know!! The wrong coil will not misfire at high rpm as such, just under extreme use/after a long time like 90minutes+ (it's a heat thing).

But if the car was fine before the rebuild, I'd suspect something has been adjusted incorrectly. First guess would be to double check the points and condensors. Gap should be 013". Condensors can be checked with a capacitor tester, but best to just replace them if in doubt. Maybe a bad plug, possibly a carb thing too, but less likely.

I've got all parts in stock if you get in trouble over the holidays.

Regardless of ignition graph, make sure max advance isn't over 38 BTDC (at ~5500 rpm)

Keep us posted.

 

Thanks for explaining that. I've the same problem at the same RPM. It's also the cold bloodiest car I've ever owned. When it warms up, it's OK except for the miss at 5500 RPM.

Bob Wassam

 

Maurice,

Check the sparkplug leads and the extensions with an ohmmeter. They both should have a small resistance. My 82 European 308 ran OK in normal driving but missed on the track at higher rpm. On cylinders with bad extensions the new plugs still looked new after 400 miles.

Tom

 

had the same once after a spark plug change. Reason was ONE faulty spark plug out of a brandnew set of 8.

Best Regards from Germany

Martin

 

the exact same thing happened to me on a volvo, new spark plugs and one failed after 10 miles, replaced it with new and the costumer was very happy

 

If you have ballast resistors fitted as per normal, re-use them, they protect the points and help them last longer.

If you mean one small noise suppressor capacitor is fitted, then re-use it too

Healthy ignition with points can easily go 3000 miles without adjustment, even in hard use. using Non Ballast will reduce that life by about 50%, but it can give a fatter spark.

What plugs are you using... With high comp engine NGK BP7EY are better than ES, and same price pretty much. Std engines better with BP6EY... one heat range lower than std, but helps with modern fuel tendency to foul in traffic.

I'm not a fan of electronic after market systems. I see nothing wrong with points.... it's part of the "charm".... But there are good systems out there if originality is not of concern to you. I see no benefit in terms of reliability, in fact the opposite can be the case as power supply needs to be established, meaning more wiring which can cause problems in itself, and the heat/vibration of a Ferrari engine bay can be detrimental to electronics.

 

You may want to replace your HT leads

 

Sparks from ignition wires is not normal. You should never have any sparks coming from the leads at all. How old are your ignition wires to the spark plugs, what point gap where the replacement plugs set to, and without a timing light how do you know the timing is correct at idle and at higher rpm?

You should buy a timing light and use it to check the timing. Checking the timing is a must do to find out about rpm related problems. After this is done and all looks good you can discount the problem is timing related.

Merry Christmas,
Richard

 

What you've done, perhaps by accident, is perform the standard test to see if your wires are bad, look under the hood at night and look for crossfire! Get new wires. You can get some pretty cheap on ebay from Kingsborne ($80?), I have some of their wires on my other car and I'm satisfied with them. There are also some threads here and/or on the old Fchat related to using generic wire sets.

 

For std leads, the superformance option is good and reasonably cheap, but they can be done locally too for about $175 engine set inc freight etc. BUT, if you are considering going electronic, decide before you get leads. Induction wound leads may be needed.

Extensions would be a good idea for sure. I have the original bakelite style BERU ones, but also make rubberised non reisistor too.

FWIW, I also have both types of plug hole rubber seals... that front bank getting wet when washing/raining need not be a problem.

 

Kingsborne supplied wires and extenders for my Boxer for $200, with the high temp covering they offer.
Very Nice work.
www.kingsborne.com I think.