The M130 has dual Zenith carburetors. The M129 is the straight six cylinder fuel injected engine.

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1962 220Sb ~ The Emerald Bullet http://www.youtube.com/watch?v=hx6tN1W48_o
1957 Ponton 220S
2001 S600 Daily Driver
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Thank you for your suggestion. BTW still haven't checked to see if the flyweights in distributor are sticking.
But I am curious why you believe that fuel pressure and volume may be the problem? Do I need to check it when the car exhibits the symptom? Or can fuel pressure and volume be a little low and it not effect the car until it gets hot? (getting hot occurs after driving the car for say 30 minutes when the ambient temp outside is around 65 F or higher. Indicated engine temp is nominal so this isn't an engine running too hot.)
A thought that was suggested to me in conversation involved the behavior of the injection pump. It probably could use an overhaul and recalibration anyway.
Another thing pertains to the injectors. When I first started driving the car last year and when it got hot it would buck some under heavy throttle with load pulling from 2,000 rpm. If I drove it for an hour at highway speeds the car would barely idle and would buck more at even higher rpms. I used several tanks of gas with B-12 cleaner and it bucked way less, idled better and started easier. Then after another tank or two it began to buck more and it idled poorly. A check of plugs indicated that #3 injector was leaking or stuck open. I replaced the injector and that fixed the rough idle and before things got hot there was very little bucking and it would idle smoothly. But again after driving it say 30 minutes where it gets hot the bucking would come back.
I will check the distributor and fuel system to eliminate those possibilities, then I will send out the injectors to be cleaned and checked. After that I will get the injection pump serviced.
Thanks to everyone posting replies to this thread.
Brad

Fuel needs to circulate in a constant loop from your tank to the injection pump and then back to the tank. Any lessening or obstruction of flow will cause fuel to pick up heat and possibly vapor lock. Engine running temp will affect this to some extent but is secondary to fuel flow.

Both statements are true as they stand; however the M130 was produced in both carbureted and mechanically injected versions; it is a 2.8L engine.


The M129 is mechanically injected; it is a 2.5L engine.

I thought vapor lock was an all or nothing condition, kinda like being a little bit pregnant.
Thanks!

The vaporization of fuel in the fuel supply system can occur when ambient pressure in any portion of the system falls below the vapor pressure of the fuel. That vaporization of the fuel may cause fuel flow to cease ("vapor lock").

When the system is pressurized above the fuel vapor pressure, vaporization of the fuel, and any hazard of "vapor lock" is eliminated.
By locating a fuel pump adjacent to, or within the fuel tank, and below the level of fuel in the tank, the supply system is kept pressurized above the vapor pressure of the fuel, and the conditions for "vapor lock" substantially eliminated.