swbtm

iTrader: (2)

So i've been messing around with my new sp 12a engine for a little while now. It's been running for maybe an hour (adding up all the times i've had it running for timing and idle adjustments) Up to now I have been unable to get her to idle at anything below 1500-1550 rpm. If you want to see the car and a video of the new engine idling at 1500 click on the thread in my sig. Anywho, here's what i've attempted so far

Adjusting fuel pressure up from 4.5-4.75 psi- I had it at 6 psi during cranking when the engine first went in and now it's back down to 4 ish. odd
Changing back to stock replacement fuel filter- I had a hasting's filter in that claimed to catch more junk.. so i thought that got jammed from my dirty tank
Adding more fuel to the tank... just in case my gauge is off

While it was idling at 1500 it started to miss a little more often and then i noticed the fp gauge was dropping a little.. about half a psi and then it died.

Since then i've tried the things above and nothing has really helped. I'm running pretty rich, so says my o2 sensor and my float bowls.

My main question here is, could this problem be my holley fuel pump not providing enough pressure? Or do these symptoms sound closer to a dirty tank that has jammed up the pick up line?

I'm asking this before I jump in remove my fuel pump and whatnot so I have a better idea of what might be going wrong. I do not know which holley pump I have right now, when i do remove it i'll be sure to post up that information...

Thanks

Also, my return line to the gas tank has been capped since the day i bought it. Should this be open to breath or just leave it capped?

RXnos1200

iTrader: (24)

If you are stilll running the Holley carb; the fuel pressure should be set at 6 psi. Check both float levels at the site screw. Gas should barely trickle out when you shake the car from the site hole.
You may have to adjust the secondary throttle plates to get you idle down more if you have already tried adjusting it with the main idle screw. There is a small screw on the bottom side of the throttle plate that can adjust the secondaries. On the opposite side of the linkage by the secondary shaft. Give that a try.

yetterben

Before you yank the carb eyeball the butterflies and confirm they are all the way closed. Also don't rule out a vacuum leak my man. If yah need some help call me!

swbtm

iTrader: (2)

if you're talking about the butterfly on the top that covers two of the ports... that one is fully open... i was looking at it and it was just flopping around. I couldn't see exactly what it should be hooked up to... the linkages that are there are to the throttle and the electric choke... maybe i'm missing a spring? Or my choke is just dead? Vacuum leak??? I'm not sure what's left on my car for a vacuum to leak from... any suggestions?

I've been adjusting idling screws on both sides of the main metering plate, the one facing the front of the car has the most effect on the idle... i haven't noticed any screws on the secondary plate before, i'll go look again

yetterben

I am referring to the throttle plates you have 4 of them lol. The adjustment is a inset screw on the underside of carb!

RXnos1200

iTrader: (24)

So have you adjusted the main idle screw on the linkage? Not the ones on the metering block.

RXnos1200

iTrader: (24)

The secondary one is hard to see because you need to adjust it from the bottom of the throttle plate.

swbtm

iTrader: (2)

holy crap... i had no idea that there were ones underneath the damn thing...

Here's my understanding of the magical block of metal. Please correct me where i'm wrong

It is taking fuel at 4.5-5 psi (right now) and spitting it through the jets as air gets pulled in from the top

The idle adjustment is done first by the main screw... just to the right of the throttle arm and finer adjustment is done on the metering block with the two screws (front and back)

Then there's the electric choke which would work fine if i didn't have to tap the gas twice to get the engine to catch. When i tap the gas the choke get tossed off.

Where underneath are these throttle plate adjusting screws??? Do i take the carb off to get to and adjust them? Or can this be done with it on?

I'm running that fuel pressure right now because that's the highest i can get my damn fpr up to. I'm not sure what's wrong but my fuel pump should be able to do much more than that! The fuel pump is also making some funky high pitch noises when i first turn it on, then it calms down and goes back to it's normal whirrrrrrrrrrrrrrrrrrrrrrrr.

RXnos1200

iTrader: (24)

There's only one small adjustment screw for the secondary plates. The ones for the primary is adjusted with the main screw by the linkage. Just look at the secondary shaft on the throttle plate. Under that throttle shaft is a screw for the adjustment. Just run your finger on the bottom side of the throttle plate and you will feel a small hole there. It's on the side closer to the alt.

swbtm

iTrader: (2)

nice i'll go try it out.... i also forgot to mention that everytime i shut the engine off i get a nice backfire.

RXnos1200

iTrader: (24)

throttle plate pics

swbtm

iTrader: (2)

success!!! Idling at 1000 rpms... now to put the shifter back together, put the seat in, and i'll be off on my first drive with her...

All I had to do was unscrew that little tiny set screw for the secondary butterflies until those closed, i'm not too sure about adjusting this thing any further than this. Does anyone know where I can go to get this thing dino'd and tuned??? Anywhere between NH and NJ would work

By the way, what in the world do the metering block screws do?

The throttle response did seem a little slow once it was down there... any thoughts on that?

and oh if only my liming light light actually worked!

RXnos1200

iTrader: (24)

the ones on the metering block are for the air / fuel mixture

swbtm

iTrader: (2)

ohh.. that might answer my next problem! I just took it down the driveway and at about 1/5 throttle my a/f gauge leaned completely out so i backed it into the garage thinking that my pick up tube in my gas tank is gummed up. I'll go and try that metering block first before i drop the tank.

Thanks for all the help

swbtm

iTrader: (2)

correction, everytime I go above 2500rpm or anymore than 1/4 throttle my a/f mixture gauge leans completely out and i get a small backfire.

Could this possibly be my metering block just being out of wack, or is this my weak fuel pressure? Any help here would be greatly appreciated.

Thanks

RXnos1200

iTrader: (24)

sounds like your float bowls are running out of fuel. Did you check to see if your floats are set right? If they are then I would check fuel pressure next.

RXnos1200

iTrader: (24)

You sure the timing is set correctly? Check that too.

blackdeath647

iTrader: (2)

if you haven't set the fuel pump back to where it should be set for the holley, then that might be it, just lack of fuel pressure, but i'm not sure just an opinion here.

swbtm

iTrader: (2)

Right now, with the way it is behaving i'm leaning towards weak fuel pressure.

Since I am unable to adjust the pressure to anything above 4.75psi and the lowest fuel pump holley sells goes to 7psi, the stupid pick up line in my tank or some line coming forward is clogged.

On the timing comment, my timing light's bulb must be broken. I hooked it up today and poof nothing! I'll give it another try tomorrow when my i'm less tired.

Unfortunately I just don't have the time right now to drop the tank or troubleshoot the fuel system. I live in NJ and the car is in NH and traveling up every weekend is starting to get a little old, so for this single time i'll be bringing the car to my local mechanic with a very detailed description of what is wrong. Then I should be able to pick it up with a cleaned out fuel system with 6psi of fuel and a tuned carb next friday and pick up my wheels up on saturday. If I had my own garage that I could go to during the week i'm sure I could get this figured out... but working for 10-12 hours during the weekends just doesn't accomplish as much.

Thanks for the help, I'll post up on how it turns out.