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  #16 (permalink)  
Old 06-11-2013, 01:19 PM
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Quote:
Originally Posted by jtomasik View Post
No sight plugs or external adjustments on either bowl.
So much for "progress" and/or "design improvements".
I understand that Holley may have felt the need to "dumb it down" for some folks ... but it sure makes the whole "tinker and adjust at the track" philosophy difficult.

I'm fairly sure that the old "invert the float bowl, and make the top (now the bottom) edge of the float paralell to the float bowl" rule would still apply.

Can anyone confirm this?

I'd be very tempted to chuck those bowls and convert the carb to adjustable center-hung bowls myself. KNOWING that you have fuel in the rear bowl is important, isn't it fellas?

At this point ... checking the fuel pressure and delivery volume would be a very good idea. (already suggested in post #7) A mechanical pump should fill an old-school coke bottle in about 3 strokes. Those stokes should be steady and strong ... no dribbles or bubbles. Fuel pressure should be 4-6 PSI for a Holley, IIRC.

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  #17 (permalink)  
Old 06-11-2013, 02:03 PM
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Assuming your carb list# to be 80551 ... universal 600 CFM Marine


It should use kit #703-1 and float #216-43

I'm not trying to be a $marta$$ in any way at all, but you DID bend the tang on the float to make the adjustment, right?
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Old 06-11-2013, 02:21 PM
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Yeah, I did. Took me awhile to find out exactly what to do, as the Holley kit was a generic (with parts for numerous carbs), and the illustration of the adjustment to this type of float wasn't very informative. I did several searches online and found the proper info. Didn't have that resource back when I was a motorhead....times have changed! Thankfully, we now have the Internets (as GW said...lol).

Oh, I believe this problem existed before the rebuild, but because of the numerous other running issues, it was buried and reared its ugly head when I was out on the lake two weeks ago, prior to the rebuild. I ran it at my house, and it had this high-rpm issue. I thought it was getting too much fuel, and combined with the starting issues I had, that's when I pulled the carb. My starting issues are gone, but this one issue remains. So, I don't believe it's something I did (although that's not a for-sure).

I should mention that I don't want to put a lot of money into this, since I plan on selling that boat.
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Old 06-12-2013, 08:51 PM
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Did a pressure test....5-7 psi at idle. Also did a flow test....about 4 oz in 3 pumps.


So what's up? Where do I go next? I'd rather not dump coin for a carb. I wanna sell this BreakOutAnotherThousand (BOAT). Besides, you b*st*rds have inspired me to build by dream machine. It's all your fault.


Save me.
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Old 06-12-2013, 10:14 PM
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Those flow test results sound kind of pathetic.
Like I said earlier 3 strokes should have filled a (10 oz?) soda pop bottle.


I just looked up a mechanical fuel pump for a 351W 4-bbl (1984 F150 pickup)

NAPA #60318

Attributes
Fuel Pump Fitting Size[s] : Inlet - 3/8", Outlet - 1/2-20 UNF - 2B
Fuel Pump Fitting Type[s] : Inlet - Tube, Outlet - UNF - 2B Inverted Flare Threaded Fitting
Fuel Pump Gallons Per Hour : 30 GPH @ 1800 RPM
Fuel Pump Pressure Rating : 6 1/2 - 8 PSI
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Old 06-13-2013, 06:07 AM
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I just did the math on this ... and quite frankly I'm surprised.

1 US gal = 128 oz

GPH/60 = GPM

So... plugging in the converted variables...

30 GPH / 60 = 0.5 GPM
(64 oz or 2 qt per min ... which sounds reasonable)
This could also be calculated as (30 x 128)/60 = 3840/60 = 64 ... same result

The fuel pump is driven by the camshaft which runs at 1/2 of crankshaft RPM.
1800 RPM / 2 = 900 strokes per min.

64 oz / 900 strokes = 0.071 oz per stroke.
Is it just me, or does that sound awfully low?
Perhaps there's a curve?
(It's early in the morning here, LOL)

Last edited by 66GMC; 06-13-2013 at 06:12 AM.
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Old 06-13-2013, 08:37 AM
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Quote:
Originally Posted by 66GMC View Post
I just did the math on this ... and quite frankly I'm surprised.

1 US gal = 128 oz

GPH/60 = GPM

So... plugging in the converted variables...

30 GPH / 60 = 0.5 GPM
(64 oz or 2 qt per min ... which sounds reasonable)
This could also be calculated as (30 x 128)/60 = 3840/60 = 64 ... same result

The fuel pump is driven by the camshaft which runs at 1/2 of crankshaft RPM.
1800 RPM / 2 = 900 strokes per min.

64 oz / 900 strokes = 0.071 oz per stroke.
Is it just me, or does that sound awfully low?
Perhaps there's a curve?
(It's early in the morning here, LOL)
I believe your final number is correct (I arrived at them differently, though). It could be that the diaphragm doesn't fill fully at that speed. Not sure what cranking rpm is, but when I tested, I did it after disconnecting the coil wire (so the engine wouldn't start). My volume is at cranking rpm, whatever that is.

I'm trying to think of how to 'fatten' up the mixture when the secondaries open, just to see if I can get the popping to go away....just pour gas down the carb?.... LOL. My pump pressure seems ok. How would you hook up to test volume at 1800 r's? Are there cheap in-line flow meters out there? I didn't get the "...3 strokes should fill a 10 oz. pop bottle...", but since it seems that volume is highly fuel dependent, what's the rate of strokes during that test? I feel like I need to test at the 1800 rpm's....
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Old 06-14-2013, 09:28 PM
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I found a post by Cobalt327 that talks about fuel delivery while cranking.

I'm also thinking that a pressure guage teed into the line from the pump to the carb might tell you something as well, with the engine under load.

If the pressure drops way off, I'm thinking that the volume would as well?

Thinking about it ... a mechanical fuel pump usually sells for about $25.00 at your local parts store. Look for ID numbers (i.e. 60318 or similar) stamped around the mounting flange ... almost everybody uses the same part number or can c/ref it.

Spending that amount of cash for something that sounds a little suspect anyway *might* be a lot easier and less expensive that buying diagnostic fuel flow meters, etc.?
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Old 06-14-2013, 09:58 PM
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Repeat the test I suggest but make sure the secondaries are wire shut. If they open during the test we're still in guessing mode. Even if the fuel pump is not up to snuff it should run for a few seconds at wide open before the problem shows up. If the problem is happening the insant the secondaries open either there is no fuel in the float bowl or something is prevent fuel from getting to the booster. Having said that has this carb been modified in any way to try to make the secondaries open like a mechanical secondary carb? This often causes problems.
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Old 06-15-2013, 04:19 PM
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Tied off the secondary butterflies. Rapped the throttle, and you could tell the extra fuel wasn't there to really rev the engine (this is no load). The popping would start, but it was barely noticeable, and it didn't start until about 5500 rpm, and only when the engine reached that rpm for a second or two. It wouldn't have the issue as it was revving up. I could understand this, as the primaries can deliver only so much fuel.

I might just replace the fuel pump like one here suggested. Before that, I'm gonna hit the lake tonight and play around with it. Luckily I have a back-up boat for dad's day tomorrow.

Oh, btw, happy father's day to all the dads out there. Have a great weekend!
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Old 06-15-2013, 07:31 PM
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I was reading through this post and nodding my head at Tech Inspectors suggestion of installing an inline fitting to hook up a fuel pressure gauge to know once and for all if its starving for fuel ( a lot of guessing and hair pulling can take place until you know its getting fuel pressure under load with the secondaries open ) . Of course this just reminds me that I should kick my own rear and get some fittings to hook up a gauge for times when I need to diagnose a similar issue. Here's a thought though as more then once I was suspecting a fuel pump but not having the tools to check the pressure, upon closer examination of the rubber line sections on an older truck for example, I discovered a slight dampness ... no dripping though, on the suction side of the mechanical fuel pump line from the tank to the pump. Simply put, it was sucking air through cracked rubber lines so the volume of fuel would be too low at high power with high RPM levels and in addition, it in theory can aerate the fuel with air bubbles which I doubt helps much ether.

Depending on how hard it is to access your fuel line or tank fittings as its always possible to have air leaks on steel sections too which includes joint flair points, lets say you do install a gauge and it appears to read marginally ok but its still not working properly. I would be tempted to set up a jerry can of fuel or some smallish boat style fuel tank which is safer and a new section of rubber line to hook it directly to the fuel pump and give that a try to eliminate air entering the fuel. Naturally if the fuel pressure drops way off, given good fuel lines, its the fuel pump at fault.

Something also tells me the ignition system could use a little help too ... such as an upgraded electronic distributor and new wires and knowing for sure that the timing is correct without chasing a harmonic balancer issue etc ( timing fine tuned to your altitude ) but I realize this is a boat which is destined down the road so its a matter of putting as little into it to get it reasonably functional.
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Old 06-19-2013, 08:45 PM
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I tried to eliminate the fuel pump lines to the tank, thinking maybe a line might be collapsing, is old and has an internal flap that restricts at high loads, etc. Put a line from the pump directly to a fuel can. I had to rev the engine close to 6000 rpm before the issue occured (This is with the secondaries hooked up again). I put the normal line back on the fuel pump, and it still runs really smooth until I have the engine screaming. I'm taking it to the lake tomorrow night to see how it behaves under load.

Oh, I ran it numerous times tonight, just playing around with it, and I noticed that after I shut it down and let it sit for a bit, fuel will start dripping out of the primary jets. Stuck float? When I rebuilt the carb, I cleaned everything thoroughly, inspected all contact surfaces (like the float pivot pin, etc.) replaced the float needle and seat, so I'm suspect it isn't a stuck float. Any ideas?
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Old 06-19-2013, 09:12 PM
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At 6,000 RPM ... that would likely be valve float that you're experiencing. The fuel that you see running over when shut down is likely due to thermal expansion of fuel in the bowl, as the fuel pump is no longer pumping, right?
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Old 06-19-2013, 09:39 PM
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I agree with 66GMC's line of thinking, you might be butting up against a points float issue and/or valve float. Do you know what the rated maximum RPM of this engine setup is ?

When you reinstalled the carb, did you make sure to not eliminate a thick gasket or a resin style spacer with two gaskets as it sounds like your carb is getting a certain amount of heat transfer when its shut down and the fuel is expanding/boiling and it wants to find any path it can out of that space. If its bad enough it can flood the engine when you go to restart.

Unfortunately testing it with no load won't tell much in the fuel rate used vs whats being supplied as it takes a fraction of the fuel to rev it out .... its like sitting in your driveway with a pickup that has an almost totally plugged fuel filter, sure it will rev out there, but fall flat on its face when driving it.
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Old 06-20-2013, 05:57 AM
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Thanks for the reply, guys. I'm curious why the valve 'float' or points 'float' would move. That is, when I first started experiencing this problem, it'd hit in the 4000 rpm range consistently, and it would happen ONLY when the secondaries would open. Then, as I tweaked things, that 'float' effect moved into the 5000 rpm range, and last night it's around 6000rpm. It still shows up when the secondaries open, but not immediately anymore. Last night, the secondaries would open about a quarter of the way without the issue, but as I pushed the throttle open more, the issue started.

Not sure if I put a wrong gasket in. I got one of those generic holley rebuild kits. I followed the diagrams and directions closely. And, I took pics of each step when I disassembled the carb, replacing the old gaskets with gaskets that seemed the same as the old stuff.


I'll take it to the lake tonight.
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