8 replies to this topic

[Sputnik]

Hi mini(ex)perts

To start with some history. After our last race meeting the car overheated and I cracked tha head. With that, I forgot yo switch the car off and a week thereafter the battery was flat.

I got a new head, charged the battery and all was ok.

Now, at high continuous revs that car start to misfire. It does not happen when I am going trough the gears, only when in 4th on one of the straights. It is if the car does not like it to be kept at max rev for to long. If I tap of a bit at mead revs the car runs fines, but when I keep the accelerator down it start to misfire (that's what I think) and then do so for a long time. I loose all power and can then only limp on the track. Then after about 1/2 a lap, the car just suddenly get all power back and I can race again.

I am suspecting a coil or condenser failing at this high revs. Am in working in the right direction ?

Edited by Sputnik, 28 April 2013 - 11:18 AM.

[Sam Walters]

I`m thinking its relative to vibration perhaps or an overheating issue somewhere in the ignition system. Id replace the condenser and all associated bits as a matter of course and check for play in the distributor. Id also replace the coil.

[iwatkins]

Not enough fuel? I.e. fuel pump cannot keep up with demand?

[Sputnik]

Ok, so I will change the condenser and coil, but one thing about the fuel pressure. I also thought so, got a new fuel pump and even changed the tank, but if is is the fuel, should the car not come right shortly after the revs and speed has dropped, for ex ample just after the turn. The car keeps on doing this misfire for at least 3/4 of the track afterwards. That is about 2.8 kms ? I did reset the float already to allow for more fuel to be in the float bowl.

What pressure file pump do you suggest, I am running a standard facet pump with a 45 weber, the car is a 1330

Edited by Sputnik, 28 April 2013 - 01:49 PM.

[summs116]

im guessing that the head has the same cc's and same spec as the old one.as already said just replace the coil,points,rotor,cap and change the plugs and checking the gap and making sure that the little end cap is tite too.

make sure that the carb is not too tight and has a bit of movement on the o rings as could cause fuel starvation

[Gulfclubby]

Boiling fuel?

[johnnyblaze]

id say youve cooked something in the ignition system when you left it on, change the lot coil , points condenser and plugs

[Alex_B]

I would also look into replacing the ignition components, i had exactly the same issue on the way to uni last year, in 4th on the a27 the car started to misfire, revs dropped right off and ended up limping along at about 30, ended up with changing my points and condenser with a leccy unit and was fine after that

[Sputnik]

Thanks for all the reply's. Armed with every single ignition component availible! I went to the track this afternoon with the idea to swop one item at a time, do some lapse and then if not fixed, swop another.

For some reason I read on this forum about many possible causes and decided to check the valve clearances ! To my suprise they were all over the show. Why the mechanic did not recheck them is above my logically understanding.

I reset the valve clearances as per a 'How To" post on the forum. This was my first point of troubleshooting. Done 5 hard and high revving laps, 15 min from one another session, and guess what !!

No more misfiring !!

Thanks again to the miniperts and the forum to asset me !! Appreciate

Edited by Sputnik, 29 April 2013 - 05:59 PM.