Very rough running over 3,000rpm

[twobone]

I just finished replacing my battery, checking my timing advance and balancing my carbs on my 89 crossflow kent.

Now my car will not accelerate hard over 3,000. I get a horrible misfire/backfire.

I noticed I now have a fairly significant exhaust leak at the connection between the headers at the join for the 4 into 1 exhaust system.

At high revs will that exhaust leak be the culprit to my poor running?

I will check the venturi screws tonight as well as my float level

[danilo]

Replace the Coil ?? Typical symptom of a crapped one is Not revving past 3k.

[jlumba81]

+1 on the coil. It sounds like an ignition issue, spark not strong enough at higher rpms.

[twobone]

OK, its weird

The Bosch Blue coil is supposed to be ballasted. However, when I turn on my ignition (car not running), the voltage is still 11.67 volts. It does show a 3-4 ohm resistance when I test the primary resistance at rest

Is that a symptom of a busted coil? Perhaps the internal ballast resistor breaks down at high revs.

I will swap in a spare coil (that just so happens to be not ballasted) and go for a short drive. If it can rev properly, then I will get either another ballasted coil or an external ballast (as replacing ballasted coils is expensive).

[danilo]

My direct experiences with Bosch "blue" coils of semi recent manufacture is that they are of abysmal quality.
Perhaps this Info on ballasted vs non ballasted coils may be of use?
http://www.vtr.org/maintain/ballast.shtml

[twobone]

I think there is a lucas sport coil with a similar built in ballast. I think I will try that instead.

[twobone]

Well, I swapped out the coil with no success.

I'm just going to order a new Aldon Distributor with an ignitor installed and new plug and coil lead and start from scratch. I figure the $325 investment will at least rule out ignition problems going forward. It may also provide a better advance curve. Surprisingly Caterham UK had the best price.

[bball7754]

Twobone - You might want to find out which Aldon model they are selling you. The "unleaded" version is notorious for having a poor advance curve.

I sent my Aldon back to them to be recurved. Gave them my basic specs (primarily the cam I have) and they changed the curve. Some searches on Blatchat should give you plenty of info on the issue.

Unfortunately, since it's been back I've had other issues with it, but they were still good to work with.

Steve

[twobone]

Thanks

I have the same concern. I've read the blatchat posts as well.

The guy at caterham told me it is set up for a 234 cam supersprint. I agree...it may have a less than wonderful curve.