another fuel pump pushrod question..

[Scott H]

Step 1) did a 'search' and read 2 pages of threads about fuel pump pushrods.

Step 2) still didn't find the answer I was looking for

Step 3) It seemed like there was a oil soaked felt washer under the umbrella part of my pushrod on the '40 v8 I'm working on. It doesn't show in the Green Bible and there isn't one in my complete overhaul gasket kit.

Is there such a thing or was I hallucinating?

 

[BILL WZOREK]

Scott :
Is it possable it was put there by someone that had a oil leak around FP
area and thought it a way to slow down oil to the problem area ??

BILL W

 

[Scott H]

On closer inspection its entirely possibly it is just a huge junk of sludge that was formed around the pushrod under the cap of the umbrella...but that seems unlikely because the rest of the engine has little to no sludge anywhere else.

I put it in a little cup with some laquer thinner and it floats. Its starting to soften up a bit and appears to be a closed-cell foam or perhaps neoprene.

It its not supposed to be there it seems to me like it would limit the stroke on the fuel pump. If the rod can't seat all the way down against the block it won't be moving its full range of travel.

 

[G.M.]

Scott if I recall the push rod has a stroke of .212 from the cam. One problem is the amount of play in the rocker arm of the pump. All of the play has to be taken up by the stroke of the push rod before the pump diaphram starts to pump fuel. The length of the push rod, the thickness of the stand base gasket and wear in the rocker arm all effect when the pump starts pumping. On my39 convertible the push rods length is long enough to take the slop and play out of the rocker arm. With all the slop gone I can adjust the output pressure of the pump by changing the length of the adjustable push rod I made. .008 will change the output of the pump 3/4 of a lb. I adjusted this one 3 or 4 times and it works every time.
Last week I was working on my 39 P/U and wanted to increase the pump pressure about 3/4 of a lb. I welded the top end of the push rod and ground it so it was .008 longer, replaced it and there was no increase in pressure. I figure there is still slop in the rocker arm so the .008 didn't take up enough slop to make any change. I will make another adjustable push rod and get all the slop out so I can get the pressure close to 4 lbs where I want it. Some are going to ask why I want 4 lbs and that is to high. I have done extensive testing on the 39 convertible on the boiling of the new 10% gas and found you need to keep the fuel temp in the pump and carb below 115 degrees. At 125 the gas boils, when the gas in the pump boils the pump starts pumping air. As the gas gets hot the fuel pressure drops, this starts as soon as the fuel in the pump starts to get warm. When the temperature gets in the 125 range the pump pressure gets below 1 1/2 lbs. Above 125 the pressure drops to 3/4 lb and starts jumping up and down and the engine don't get enough fuel. When the fuel in the carb gets to and above 125 the engine won't run right and when shut down the fuel in the carb boiling and flooding the engine, plus the carb fuel bowl empties and is hard to start. In some cases you can see fuel on the top of the carb. These problems will occur over 80 degrees outside and become more severe the hotter the outside temperature and temperature of the air trapped at the rear of the engine get. Crankshaft mounted fan engines do not blow any air over the top of the engine and build up more heat around the pump and fuel lines. Stock aluminum intake manifolds are closer to the fuel pump and heat it up more than steel ones. A vented insulated carb spacer from gadgiteer@aol.com and reduceing the heat riser holes from .625 to .325 greatly reduces the temperature of the gas in the carb and cures the carb boiling. G.M.