hey there,

some of you guys know me from the Straight 8 forums, well im working on a Nailhead that is in a 55 Ford Truck (dont ask how that got in there) this isnt my truck so i am working with what i got. well, its got a Holley Quick Fuel 4 barrel carb. the motor has great compression 150 psi on all 8 pistons. there is a valve knock (im sure it needs some adjustment, not stressing that).

the problem here is mostly in the carb for now... it is only opening the 2 main barrels. the other 2 are not opening up ever. the motor runs / revs great till about half throttle, then it loses power and studders badly. i think if the other 2 barrels would come on with its added air & fuel then the motor would rev right on up.

well, i thought i would run this buy you guys that are in the know and hopefully walk away with something to go on.

thanks,

http://i10.photobucket.com/albums/a104/tylordurben/DSCF4073Medium.jpg

this would be at idle:
http://i10.photobucket.com/albums/a104/tylordurben/DSCF4090Medium.jpg

this would be at full throttle (notice the back butterfly is in the same position):
http://i10.photobucket.com/albums/a104/tylordurben/DSCF4091Medium.jpg

http://i10.photobucket.com/albums/a104/tylordurben/DSCF4093Medium.jpg

any help or leads would be great!

It does not look like your electric choke is hooked up. The carb will not allow the back butterfly to open unless the choke is all the way open. Try to hold the choke arm open and see if that allows the rear butterfly to open.

It is also a vacuum secondary carb. The secondary butterfly is held closed until there is a lack or lowering of vacuum pressure (as is the case in wide open throttle). You can change the vacuum level where they open by changing the spring in the diaphram.

tried the first option. the choke butterfly is fully open. i live in Miami, Fl it dont take long for the choke to open up, but regardless i did try it manually. didnt work.

ill have to look into the diaphragm. when i hit full throttle it wants to shut off, or anything more than half throttle.

been a while since i logged in. the secondary is still not working. i am almost certain it is what Dr. Frankenbuick said about the diaphragm spring. just havent gotten there.

on another note. the condenser was loose inside the distributor, as in no bracket at all just bouncing in there! so i got new points and condenser and properly installed that, what a difference that made!!! sounds like a new motor.

can somebody tell me what timing these motors are happy at? 12 degrees?

2.5* at idle in gear with the vacuum line off the distributor. #1 is the front cylinder om the passenger side.

wow! thanks. ill get my friend and set it up like that. :hurray:

Here is a Holley link as well: http://www.holley.com/data/Products/Technical/199R10487.pdf. Page 12 describes vacuum secondary tuning.

:wavey:

ok. more problems :clonk:

wanted to set the timing, so i figured heck lets get it around the block. it kinda left me stranded half way around. no biggy got it back on and made it home. thought it ran out of gas. so 2 gallons later it starts right up.

so today i say well, lets get to the gas station and top it off. didnt make it to the end of the block! it wouldnt start up. waited on help, when my pops got there it actually cranked up enough to get to the front of the house. now it wont crank back up. im sure if i wait an hour it will turn on again.

What gives?

could the "MSD Coil" be too much for the stock points / condensor? therefore blowing the spark when hot?

what should i be looking for here?

hope to hear back from yall :wavey:

That sounds like a fuel filter problem.

To check the pump use a pressure tester then do a flow test next hook the tester to the line at the tank and make sure your getting proper vacuum.

The same thing happened on my 1955 Buick Special and I found the line was plugged.

yeah, fuel sounds like its the problem i was throwing out a different consern.

there is an inline fuel pressure gauge (mechanical) and at times it reads over 7psi while other times its down under 5psi. could definitely be something in the line huh. ill inspect and test that later today.

Just an observation and not really related to your issue but you might want to have your friend fix that radiator hose as well....might lead to a slight overheating issue later

haha, yeah that hose. its going to get changed for a regular hose as soon as i get the radiator fixed. funny thing is that hose expands to normal size once the pressure starts to build up. still not a good choice to keep that thing.

Is the fuel cap vented?

ah, good one. i think its not. its got a very tight rubber seal on it. unfortunately the truck did run well 1 day. just after i had changed the points and condenser i drove it to a buddys house some 10 minutes each way. it even burned rubber.

i am certain its a fuel problem now cause the fuel pressure gauge read about 3psi today while it ran for a minute before cutting off. there was small dirt like stuff in the glass filter. tomorrow morning i am going to check the filter at the entry of the carb (both front and rear).

lesson learned.

so i checked the lines after the electric fuel pump for clogs. nothing there.

so i checked the pump by letting it pump to a bucket. minimal gas pumping.

so i try from a bucket of gas back to a bucket (checking the pump itself). minimal gas pumping.

so i say let me try it without this "glass filter" (i had already removed the screen element inside). bada bin bada boom! we got FLOW.

apparently the glass filter (even without the filter) was too much restriction for the pump to pull through. the pump has an inline filter just at the supply side so 2 filters are not needed. please note, most of this stuff was like this when i got to working on it, so sometimes its best to go down to the basics before getting too complicated.

i gotta say i never had a nailhead, this thing is ballzy!!! :shifter:

tomorrow ill take the radiator to get the leak fixed and replace those hoses!

Thank you all!!!

ahhh more problems!

so the truck has been running and driving great around town. we get on the high way for say 25-30 minutes and it shuts off!? what gives? where do i even begin to look. it cranked right up again ran a few more minutes only to shut off again. so off the highway down to city streets, no more problem made it home.

could the fuel pump not provide enough fuel to the Holley carb at high way rpms?

please help!

Tylerdurben,
When it quits, does it just shut oof, or does it surge? When it first shows any signs of a problem, if you put your foot in it does it just coast to a stop, or surge up and down? This could separate electrical from fuel problems. Doug:confused:

May want to check the pick up tube in the tank, they often have a "sock" filter on the end that can clog up. sometimes i could go 7 or 8 miles before it would die, then when the pressure was drained off the sock would unfold and go o.k. , hard rpm's would cause it to last a shorter distance then at idle or min rpm's down the road.
Also to check if it is electrical, you can run a wire off the hot side of your coil to a 12v light ( i used a marker lite, 1.50 at a parts store)laid on the dash with a wire going to ground. When the car dies see if the light stays on or not, lets you know if there is a loss of power.

excellent. ill go on that. also read through the Holley spec / tech sheet link and there are a few minor things that are not as per the specs. so ill check that too.

thanks, any other ideas?

Photobucket sucks! Go try Image Shack (http://imageshack.us/). From what I know, they don´t have a bandwidth limit.

Good thread though.
Pictures say more than words sometimes.

know its been a while, but got to check on the motor and first test just cause was i checked if the fuel pump was still pumping gas??? well its not as much as it should. i start to tap the metal inline filter to find more gas flows. so that can only mean 1 thing. a dirty clogged up filter. rather than replace it and dirty the next one, i drop the tank. its a custom made aluminum tank and it looks like the guy that made it swept up his shop and put all the dirt in the tank. it is filthy dirty inside. the complete base of the tank is covered in black dirt. the little gas that did pump through during my test also shows this dirt at the base as it settled.

guess sometimes the most basics of things will keep you chasing your tail. tank is going to a radiator shop to get properly cleaned and treated.

will update soon after. also decided to go ahead and purchase a Holley fuel pump to match the Holley carb.