High End Performance

Uhm, how bout this...
A perferated secondary diaphram could at first actuate, but then may slowly bleed down and close on its own.

GottaSki wrote: Uhm, how bout this... A perferated secondary diaphram could at first actuate, but then may slowly bleed down and close on its own.

In that case, would this arm come back down? It stays engaged as long as you stay at WOT, even after the RPM's decrease.



Ken, it doesnt sound like a float adjustment tool would be helpful. We'll raise it in the rear a bit more, and if that doesnt solve it, we'll raise the front as well and see the effect.

Nautique2001 wrote: Tim, does the primary have an external adjustment knob or screw? Brad said something about a primary adjustment. Brad's buddy said something about the primary being out of adjustment can effect the workings of the secondary. Can we confirm this? Ken

Nope, no external adjustment on primaries or secondaries. Chris said that primaries can affect the secondaries as well- so if raising the rear float a bit more doesnt get rid of the problem, we'll raise the front float as well. We'll need a few more tools to get the fuel line off though.

1" and 5/8" line wrenches are what's needed for the front, plus a socket to remove the bowl.

Tim I would leave the secondary float alone and raise the front first if the timing doesn't help, set it at 10 not 8 that's where it needs to be anyway. The more timing the better any desent mechanic will tell you the same thing.

It's going to be sucking just as much gas out of the primaries as it is the secondaries so if the primary bowl isn't full then there is no way in hell the secondary bowl is going to be full either and raising the float more will not make any change what so ever.

This might sound kinda dumb but have you cleaned the screen filter at the inlet of the carb? In fact, I even cut that filter right out of my 4160. You already have the fuel filter to keep the gas clean. That inlet filter is very fine and could be restricting flow even if it's a tiny bit dirty. Just a thought.

Something about the float is not making a lot of sense. Granted the float must be set at the proper height for starters. My concern is something that Chris started to touch on earlier. There is a tube connecting the primary and the secondary bowls in the 4160. If the secondary is emptying faster than it can fill, it will be taking fuel from the primary bowl through that tube wouldn't it? The fuel pump should be filling those bowls more than fast enough to prevent this. That makes me think that the flow into the carb is being restricted (like the inlet filter). It's getting enough fuel to run it at 4800 until the floats drop and then the fuel pump can only keep enough gas in the bowls to run it at 4200.

backfoot100 wrote: This might sound kinda dumb but have you cleaned the screen filter at the inlet of the carb? In fact, I even cut that filter right out of my 4160. You already have the fuel filter to keep the gas clean. That inlet filter is very fine and could be restricting flow even if it's a tiny bit dirty. Just a thought. Something about the float is not making a lot of sense. Granted the float must be set at the proper height for starters. My concern is something that Chris started to touch on earlier. There is a tube connecting the primary and the secondary bowls in the 4160. If the secondary is emptying faster than it can fill, it will be taking fuel from the primary bowl through that tube wouldn't it? The fuel pump should be filling those bowls more than fast enough to prevent this. That makes me think that the flow into the carb is being restricted (like the inlet filter). It's getting enough fuel to run it at 4800 until the floats drop and then the fuel pump can only keep enough gas in the bowls to run it at 4200.

Thats not dumb at all- I didnt think of checking that screen. Another good thing to look at.

Im with you on the flow restriction. Our initial assumption was that it was a set-up problem since the carb is only a year old, was never water tested by NECC upon installation, and never ran strong from day one. It could very well be something restricting the flow to or from the fuel pump though.

Sounds logical to work both ends of the carburetor. Just to remind everyone, this carburetor was installed on the rebuild engine July of 2005. It has 23 hours of use on it. I'm comfortable that it's in great shape, but good point on checking the fuel flow through the screen. You never know what the tank will burp up, especially with that corn on the cob fuel mixture.

That little tube that connects the primary to the secondary is clear of turds. I know Tim was looking through it last night. I'm amazed how something minor out of wack can lose 6 MPH. That's about 13% of performance out the window.

Ken

Hey Brad,

Thanks for your assistance last night. I'm up for any ideas. The fuel filter isn't difficult to get to, a tad messy though. I have no problem checking the basics before we tear into the primary.

I'm going to Auto Zone to pick up some fresh oil and a Mobil 1 filter. I'll start by filling it with 4 quarts, then check the level. Tim refreshed me on the thread about the oil capacity. Man, what a debate that was.

Love that video camera. What website did you purchase it on?

Ken

Nautique2001 wrote: Love that video camera. What website did you purchase it on? Ken

Ken- I got it from Adorama.com- they have pretty good prices and are a reputable operation.
btw- that was the Sony DCRSR62- so far, I highly recommend it

Vince at SKIDIM suggests getting a reading on the fuel pressure from the pump. Any idea where to get a device to do this???

Ken

I was just looking at those online. I also found this at NAPA. Is this what I'm looking for? Pressure Tester

Ken

ken that's basicly it but it's missing the rubber connecton that slides over the end of the fuel line.

Nautique2001 wrote: I think we have a lot more to inspect prior to removing any more carburetor parts. We'll have a checklist in place, plus I think the fuel pressure gauge is necessary at this point.

I think thats a good course of action. Verify all your lines, filters and vents are clear and tight between your pump and tank. Then we can move on to the line between the pump and carb, checking the screen as well as the pressure (5 lbs). If that checks out, we'll move back to the float levels, raising the front first.

No need to change the timing until we get this all squared away, but we can advance it to about 10 degrees as well.

79nautique wrote: I would check the other stuff I listed first before worring about the fuel pressure, that would be the last thing to check.

Agreed. If we dont find anything obviously wrong with the lines between the pump and tank, it wouldnt be a bad idea to verify the pump is still good.

Ken, did you check your receipts to see if the pump was replaced when you had the new engine put in?

I might have found it:

Fuel Pressure Gauge. If you confirm that this is the one, I'll buy one tomorrow.

We're looking for 5 Lbs of pressure?

Ken