Why do I have high fuel pressure...

steve meltzer · #1 (**permalink**) 03-28-2017, 10:01 AM

Quote:

Originally Posted by patrickt

Alright. There is an old trick that you can use if you really think something is misbehaving between the float mechanism and the N/S valve, but it only does it when you have the bowl screwed on. The only reason I know this factoid is because of the configuration of the secondary side of the 4160. You probably wondered to yourself "why is the float in the secondary side black nitrophyl and the float on the primary side brass?" The reason is not that Holley wanted to cut corners; it is, instead, because a brass float will interfere, sometimes, on the metering plate on the secondary side of the 4160. You can't tell this, of course, when the bowl is off the carb, because there is no interference and everything works perfectly. The way you can check a float in that situation, is with dental floss. You tie the floss around the float and fish it out of one of the top bowl screw holes. You then put the bowl back on with three screws and you can test the operation of the float by pulling the floss. You can also blow in to the fuel line and, if your lungs are strong, you can muster a good 2.5psi to see that the N/S is indeed closing. As I said, this is a rarely used trick, but you now have it in your back pocket just in case you need it.

Actually, I did find it odd that the primary was brass, the secondary, black nitrophyl, thanx for answering that question. So, if the brass is on the primary only, then there would be no need to do the floss test, right? (Can't interfere with the secondary metering plate if it's only the primary side.) Also, if I did the floss test, should I use the wax or unwaxed kind? (only joking!) s

patrickt · #2 (**permalink**) 03-28-2017, 10:11 AM

Quote:

Originally Posted by steve meltzer

Actually, I did find it odd that the primary was brass, the secondary, black nitrophyl, thanx for answering that question. So, if the brass is on the primary only, then there would be no need to do the floss test, right? (Can't interfere with the secondary metering plate if it's only the primary side.) Also, if I did the floss test, should I use the wax or unwaxed kind? (only joking!) s

Right, I don't think you need to floss either side of the carb.

With the primary bowl back on, and the sight plug out, and the electric fuel pump on, if the gas is not pouring out the hole like a river, and you can see the gas level using a little flashlight, then I think all is well with the float and needle/seat. In other words, that's good enough for now and should be good enough to get the car running. The only thing I can come up with that would let you have a "tornado" of gas through the primary is a power valve that was stuck in the open position, so that gas was just pouring by it in gobs. Watching for the accelerator pump arm, and making sure it's not positioned improperly under the pump, is the only other object that's even involved with the bowl -- and I can't think how that would cause the tornado effect, it would just make your squirter not squirt.

steve meltzer · #3 (**permalink**) 03-28-2017, 12:09 PM

I assume that the little black triangular piece is afixed correctly at the top of the bowl, under the gasket, right? s

patrickt · #4 (**permalink**) 03-28-2017, 12:45 PM

Quote:

Originally Posted by steve meltzer

I assume that the little black triangular piece is afixed correctly at the top of the bowl, under the gasket, right? s

Correct.

steve meltzer · #5 (**permalink**) 03-28-2017, 02:10 PM

so far, so good. thanx again. s

steve meltzer · #6 (**permalink**) 03-30-2017, 11:09 PM

Well, it appears that bad teeth have won the battle. Can't get enough starter bite to start the engine, tho' it sounds very promising for a nanosecond. Put a socket on the crank pulley to change the geometery, but, as noted, not enough meshing to get 'er started for more than a second, then the starter won't engage the ring gear any longer. Set the primary float with the e-pump pulling 5 PSI, and the float is unchanged from before, so that's not the issue. Not sure why, but there's clearly a sl. amount of raw gasoline lying atop the secondary butterflies, tho' the car never started. arggggh. s

Gaz64 · #7 (**permalink**) 03-31-2017, 12:13 AM

You can set the float level roughly with the engine off, but the engine needs to running, consuming fuel on the idle circuit to make an accurate level check.

Especially with sight glass bowls.

patrickt · #8 (**permalink**) 03-31-2017, 05:59 AM

Quote:

Originally Posted by steve meltzer

Well, it appears that bad teeth have won the battle
...
Not sure why, but there's clearly a sl. amount of raw gasoline lying atop the secondary butterflies, tho' the car never started. arggggh. s

Well I was afraid of that.

Although, on the bright side, I told my daughter, who is in her second year of dental school, that I was helping a Texas gynecologist with bad teeth, and she was quite interested... for a moment, at least.

OK, if you're going to replace the flywheel, or at least the gear around it, you might as well replace the pressure plate, driven disk, TOB, and pilot bushing, if they all have 15 years on them. Well, bright and early tomorrow, lets start pulling the seats and tunnel.

Did you pull the N/S valve out of the secondary side as well, in order to put a dab of Vaseline on the O-ring? Or did you only do that on the primary side (which now appears to be fixed).