365 RUNS BADLY WHEN HOT

Thanks for reminding me to update my profile, now done.

OP could also check choke system is not partly on when hot, which would richen the mixture....

 

Chris, I'm with you, it is for any of the mentioned reasons running rich.

Best,

Jack.

 

On that note - I found the enrichening system on my 330 GTC didn't fully return to the normal position via the lever. I lubed it and worked it a bit but it still doesn't return all the way. It seems it could use stronger springs. I set it back to normal by hand and don't use it at all now. 7 pumps on the accelerator and she fires right up, even in cold weather. And I get fully open venturis when hot

 

I have added an helper spring to the choke cable, you can see here.

john
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Thanks John, I may do the same

 

"Redecking" carburetor bases is a no-no.

 

Hi Aaron

Why is that? The carburettor bodies often warp, both through heat and by overtightening hold down bolts. When they have warped bases they let air in underneath which plays havoc with the mixtures and weakens the vacuum efect. It is very common therefore to "redeck" or flatten the base castings when carrying out carburettor overhauls. Am I missing something?

Happy Christmas

Colin

 

Airleaks at the carb base will have most influence at idle and light load, so I would not suspect an issue there, as the problem is higher up the rev range. I suspect it is ignition related, but to check you can do two things, analyse exhaust gas while the fault occurs (high HC will tell you you have a miss, low HC will tell you there is fuel starvation), and/or have the spark analysed with a scope analyzer. The waveforms at coil and plug sides will tell you whether you are losing spark (and where) or whether the spark is poorly generated. You need to find someone with an engine analyser or oscilloscope with high voltage probe, and knows how to read the waveforms. Sounds more difficult than it is but some experience is essential.

 

I agree, a scope analyzer would be ideal, but if you don't have one readily available you can do a quick check with a strobe light. Hook up the light to a plug wire, then run the engine up to the problem revs. There's a good chance that an electrical problem will affect an entire bank, so at a minimum run the test on one plug wire from the left bank and then one from the right. No guarantees, but there's a good chance you'll be able to see if there is an electrical problem and you'll be able to tell if it's intermittent or completely cutting out.

I agree with those who suggest that new parts don't necessarily mean they aren't a source of the problem. I just had two sets of breaker points on my GTC/4 break a leaf spring after less than 500 miles.

 

A strobe light generally has issues to work on higher revs, and it will be much harder to tell the difference between a high voltage leak, high voltage "jump" (inside the distributor cap) or whether the spark is poorly generated.

The strobe can tell you though whether there is play in the distributor drive and how consistent it fires.

Didn't these engines have issues with timing chain stretch? Is the condition of those known?