help me with this nailhead...

**tylerdurben** · 01-03-2009, 08:43 AM

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,

this would be at idle:

this would be at full throttle (notice the back butterfly is in the same position):

any help or leads would be great!

**Dr. Frankenbuick** · 01-03-2009, 08:52 AM

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.

**tylerdurben** · 01-03-2009, 03:57 PM

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.

**tylerdurben** · 01-10-2009, 01:39 PM

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?

**Dr. Frankenbuick** · 01-10-2009, 02:37 PM

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

**tylerdurben** · 01-10-2009, 02:45 PM

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

**Dr. Frankenbuick** · 01-10-2009, 02:51 PM

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

**tylerdurben** · 01-16-2009, 08:51 AM

ok. more problems

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

**Jim Carmichael** · 01-16-2009, 09:48 AM

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.

**tylerdurben** · 01-16-2009, 10:00 AM

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.