2011 at the Hammond Barn

[Bob Carriere]

HI Phil

I discovered that process in the 1958 GM shop manual for my Dad. It claims to give more information thanjust a compression test.

Anyways.... we first warmed up his 235 for about 20+ minutes..... I know it is not like a good road run by it had to do.

Did some adjustment on the timing.... newer 235 are recommended to be set at ) TDC but earlier manuals talk about 5 BTDC...... we went with the 5BTDC and seems to run better..... re adjusted the idle speed and mixture..... vacuum was a very steady 20/21 inches. After the adjsutment the engine did not b pop back through the carb anymore but still had a rough/out of balance feel...

Then I tried the balance test... it calls for setting the idle at 1500 rpm and grounding out 4 of the 6 cylinders in a particular paired order.

Goes like this.... firing is 153624 ...
......sliced in half 1 / 6 5 / 2 3 / 4 ...... first 3 numbers over last 3 numbers.

So at 1500 rpm I removed the sparkplug wires from 5 and 2 and 3 and 4 holding them between my fingers so they would not spark all over....th-th-that was f-f-f- fun.....

Well expectedly rpm dropped BUT engine kept running.

Did the same with 5 and 2 and the engine stalled out.

restarted the engine and did 3 and 4 and it ran OK.....

So the unbalanced cylinders were the 5 and 2....

Still not sure what to do with that "information" but it was obvious the 2 and 5 had something wrong.

We changed for new plugs..... engine started better and ran smoother with only a small hint of vibration.....

Lack of time prevented me to repeat the process with the new plugs. Rob was to pick up a new set of universal spark plug wires from the tractor shop for the next adventure.

When we removed the plugs we noticed most had a light black deposit as if too rich a mixture BUT since in the past we had to run the engine with some chole to keep running that partly explains it....... two plugs seemed to be wet or wetter..... can't remember which tonite. We did a compression test and got between 135 on the low side and lots of 145/150 .... which greatly relieved us.....

On the spray bottle approach..... I always verify sparks by sticking a screw driver in the wire cap and hold it bare hands.... very stimulating.... how deep you bite your tongue indicates the K voltage.

However, on my engine it's a different story... I installed the Pertronix with a 40k coil ...... which is border line painful.... in fact I have to refrain from pulling sparkplug wires, when running, even with leather gloves as the spark is strong enough to be felt ......

I understand Rob has jumped on a Pertronix system for his engine so we will be setting that up soon.

The Pertronix made a big difference on my engine.... ease of starting... no points to set and reset and then burn..... no need for a ballast resistor.

One caution on the Pertronix..... to run good you have to regap your plugs to 45 T or it will run rough.

Next opportunity we will redo the balance test with the new plugs and wires then repeat the process on my engine.

I will be redoing the valve adjustment on mine as I suspect the small intermittent popping in the exhaust is sign of a miss adjusted valve. It still runs very good and can idle at 450 / 475 easily.... but you the hear this faint clicking noise..... vacuum is good at 22 inches at 600 rpm. I had ti out of the box this past weekend....started first spin.... ran it for about 2 hours at 600 rpm to boil off any humidity it may have accumulated.

Well enough for now.... I have caught up with my need to replenish my MLU fix.......

At time like this I appreciate MLU running well......

Bob