Fiat twin cam (124) misfiring after prolonged use

[Chris71]

Hi,

I've recently bought a car with a 1600 Fiat twin cam believed to be taken from a 124 Spider (I'll try and update with an engine number if that helps....) running on twin Delhorto 40 DHLA's and normal distributor igntion.

When cold it starts and runs perfectly, pulling smoothly throught the rev range. After about 10 or 15 minutes of running fine it develops the ocasional misfire, intially just at high rpm and/or on high throttle demand. Ove the course of maybe 5 minutes the engine speed and/or severity of the tip-in needed to cause this goes down. Eventually it's like someone's put a soft-cut rev limiter half way through the rev range.

The only things I done are a quick check of the distributor (for wear in the shaft bearings or any signs of arcing) and changed the HT leads for new items.

Prior to me getting it, it's been about 18 months since the car had any significant use and the misfire has materialised in that time. As far as I'm aware nothing mechanical has been done to it in the meantime to affect the spark timing or carb set up.

Any advice greatfully recieved,

Chris.

[Guy Croft]

For starters change the condenser and points.

May not be the cause but they cost little and I'd change them anyway.

GC

[sumplug]

And the distributor cap as well, as this could be tracking.
And put new H/T leads and plugs in as well. Engine will be much better for it.
These engines do not like slow running for long periods, and can foul the plugs up sometimes.

Andy.

[Chris71]

Hi Andy,

I've tried swapping the HT leads over already and this didn't solve the problem.

Running was about as un-slow as I dared with an unfamiliar car on open roads!

My shopping list currently looks something like,

New set of plugs
Condensor
Points
distributor cap
Throttle cable(s) - does it really need two cables when they both seem
to go onto the same linkage? [this is due to another problem!]
Radiator top hose [also due to another problem!]

[sumplug]

Twin cables used in Motorsport in case one failed!! Yes, one will do.
I have replied on your other thread about parts.
Andy.