Not sure whats causing it...fuel pump and fuel cell are only "old" parts, line, filter carb all new and already cleaned out once last week. Problem was gone for a couple days put resurfaced recently and is slowly getting worse. last night I couldnt go more than half throttle without it sputtering. Would it be the carb is too small? Holley 750 DP or something else clogging the lines?? I guess it could also be the electric fuel pump going bad, it does whine pretty loud. I just want to be able to punch the gas when I want/need too, otherwise I may as well be driving a beetle.

 

69 -

With that much displacement, the carb may not be optimal, but most likely not causing the problem either.

From the back forward:
Clog in the fuel cell outlet?
Fuel line clog / inadequate diameter?
Clog/dirt in carb passages? (may need rebuild to determine/fix)
Inadequate carb pump/pump cam, jet size?
Something stopping the throttle from opening fully?
Since we can't hear it from here, could the ignition be breaking up?

Archer

 

This is the cam I have:

http://www.compcams.com/Company/CC/c...?csid=718&sb=2

The fuel pump is a Holley:

http://www.holley.com/12-812-1.asp

Carb is also Holley:

http://www.holley.com/0-76750BK.asp

I cant say what the carbs jets are set at because my shop set everything up for me. There is a new Holley billet regulator as well. As for the ignition the dizz is a ready to run from MSD(new), box looks like it was the one on the car when I bought it though (not orange box). Would revving the motor in neutral to see if it sputters then help determine anything? I mean if it isnt sputtering at half throttle then, what could be causing it to do so under load?

 

By the way my rockers are 1.6 ratio if that means anything to this issue.

 

69 -

The info really doesn't help. You're either getting insufficient or erratic fuel flow or flaky spark. Brand new doesn't rule out faulty.

Vacuum may be different under load than it is in neutral. So yes, a vacuum leak (causing a lean condition) should have been included in my first list.

Total timing may also be off, too much or too little. Don't know if you are running a vac advance or not. Yeah, that should have been on the short list too. Can you check the initial and total timing?

Archer

 

Sounds like the problem I had, do you have headers?

I had to reroute my fuel line as the heat was vaporizing the fuel in the fuel line, I got a steel braided line and went up the front of the engine and across to the carb.

 

I agree with the heat issue. I had this issue with another vehicle, when the fuel gets to hot it would start sputtering. DO you have a return line set up? also, I put on a spacer and it kept the carb off the manifold and helped a little as well. (I apologize if I missed this answer in a previous thread)

Also, I had an issue with a fuel pump once. UNder load the car would sputter like it was missing, but only under a load. When I would rev it, would not replicate. What is your fuel pressure set at - should be set at 6 lbs

Hope this helps a bit

 

Ok gotcha, tested the neutral theory, didnt sputter so maybe a vacuum leak. I set up a time to bring her in, I spent too much time and money to let something go that could really hurt the motor. Thanks for the help though, appreciated.

 

I thought about the vapor lock issue, I dont have steel braided lines and the line from my fuel press reg is laying over my valve cover and almost touching the head. I will zip tie it up just to see if that helps at all, I did notice this morning while it was still pretty cool out that I didnt have the problem as much and that sparked the vapor lock answer as well. I will also check the fuel pressure gauge to see what its set at and call my shop about the fuel return line. Is there any way I can tell if I have it myself?

 

For the second/return line, look at your fuel pressure regulator, there would be two lines there. I have my pressure gauge set up there, lots of people put it on the duel feed if you have a Holley. I will post a few pictures in a minute - mine is a mess and I need to do it right, but you will get the idea.

 

Here it is - This works for my GTX, however, it is not pretty. I need to clean it up but working on the new engine first. Also, here is what I would suspect you have if your shop went with all Holley items. (http://www.holley.com/12-803.asp) also, like your cam selection, put that in a 440 I built for my Demon - basicly stock engine put out 425 on the dyno. I would imagine a 528 will push a bit more, did you dyno it? What heads did you go with and what ignition?

 

As you can see I had heat issues melting the spark plug boots, got better headers and wrapped them in a sleeve, but you can see the new braided line run to the front of the motor.

 

OK, I clipped my fuel line to the trans dip stick to get it up off the valve cover/head just for the time being to see if that helps. I drove it for about five minutes and so far it seems to help a bit. Still getting some break up though. I also noticed at idle the fuel pressure gauge is at 5psi, not 6 as previously suggested. I also noticed that the passenger side valve breather was somewhat loose, not sure if that is normal. I also have a spark plug boot (in a heat sock) touching my header. It smokes every time I drive it, turned the sock white instead of black but the mech at my shop said that was normal and ok...Would the valve cover breather which also has a hose attaching to the carb be the culpret? If it was too loose then I would assume that vacuum will be lost...like I am right now

 

What shop are you using, that they can't figure out what is going on? You might need to find a better shop. Someplace that can actually diagnose and not just hook up a computer and replace parts hopping to get it right.

 

Valve breather you are talking aboutr does it go to the carb or does it come from the valve covers? If it is to the carb (manifold vaccum) yes, can be a problem, but does not match the symptoms your posting. As for the ones from the valve covers, would be a PCV valve, no issue.

As for the boot touching header - THIS IS AN ISSUE - need to get it away. If you can, pull this plug and compare it to others. If not firing all the time it will be a differnet color, my be a good clue for us.

Also, 5 psi is good, shows you are getting pressure to carb. If possible boost it up to 6 psi. Is there fuel in your cell? Is it low or full? During this trouble shooting process I would try to keep it full.

Is there a spacer between the carb and manifold? if so what type and how much. If not and you have the good clearence, may be a good idea for a 1" preferably and 1/2" if not. Try and find a phenalic (sp) one, non- metal type.

As for the vaccum - can you spray starting fluid around the carb area while the engine is idleing and hear it pick up RPM's - This would rule out a vaccum leak. Please be careful and not turn you or the car into a Roman Candle. If it picks up RPMs, leak is in that area.

 

69 -

If the plug wire is hitting the header, then you have a problem and that can cause a miss. You have to be creative routing the wires and yes, the protective sleeves are necessary - at least on mine.

Archer

 

Question is ?? What is the fuel pressure at WOT If it can't get the fuel it's going to crap out.. Still have points ?? Try a new set of points & condenser...

 

Last night I went for a spin and the car stalled out on me. After trying to start it back up, I mashed the pedal and she started back up with a backfire. After that she was vibrating pretty bad at 2500 rpms and up so I went back home and looked in the valve cover breather hole after I removed it and saw some coolant pooled on top of my heads, right under the roller rockers. Is this normal??? I also found some oil leaking on the k member but it was too dark to find from where. AHHH!! Im worried I may be without a car again for a while....Any ideas?

 

Im running a billet ready to run distrbutor with coil from MSD

 

no fuel retrun line and the boot that touches the headers inside the heat sock looks to be ok, although covered in some oil splatter??

 

Also looked inside the boot, seems to be some clear jelly looking substance covering the contact point inside?? Normal??

 

My guess would be fuel starvation or weak spark !

 

Polara,
I agree with MrecuryDon on the fuel starvation/weak spark. The jelly is probably dialectric grease, what they used to build the plug wires. Oil splatter most likely from the breather. To me the wire looks burnt on one side, as you look at it to the left side. this will cause an arc and drop the cylinder. As for the backfire, seems like timing to me, what is it set at. And agree with TVLynn - what is the pressure at WOT.

Coolant on the head - yes can be issue, are you loosing coolant? is it getting hot? Are you positive, what heads do you have.

 

OK, so should the jelly be cleaned out? It looks to be covering the contact point. I am not sure what the timing is set too, my shop set it. I was loosing a little coolant which was topped off and mentioned last time I was at the garage but they werent sure why or what happened to it. It isn't getting hot, and I'm not positive its just coolant, it could be coolant mixed with oil because it was brownish green. I dropped it off this morning but I really plan on scouting a new place if this car isn't running right after this. I get a lot of the run around there, they did do a good job of putting everything together and it looks real nice but it just hasn't run right since I got her back almost two weeks ago!

 

While not pretty I have seen some use The GM metal spark plug boots

 

Are you saying there is coolant pooled inside the valve cover? That is not good. I dont know if that is your spuddering problem but that is definately bad. Does it smoke at all?

Ignoring the coolant in the valve cover problem, I would say check your ignition timing at 2000 RPM. I would expect to see something around 30 degrees btdc. Check your fuel pressure at wide open throttle. It should be 4 to 6 psi. If you can have someone power brake it. and watch the fuel pressure guage. If you have a problem, you will see it drop to 0 psi. If it drops to 0 then you have a fuel starvation problem.

 

(Quote)
line, filter carb all new and already cleaned out once last week. Problem was gone for a couple days put resurfaced recently and is slowly getting worse

Looking at your first post again I am guessing this is the sputtering problem. New filter and carb but old fuel cell. You cleaned it up and it worked but started to go bad again. Did you clean it up again? You are probably sucking dirt into your filter and getting it clogged, so it will run good at low rpm but miss when it revs higher.

(Quote)
I couldnt go more than half throttle without it sputtering.

This sound like the choke isn't working. Is the motor hot or cold when this happens? If cold you may just need a good choke.

(Quote)
box looks like it was the one on the car when I bought it though

This looks like someone besides you did the work.

(Quote)
what could be causing it to do so under load?
either poor spark or lean condition. This should not be so hard to figure out. All we can do in an inner net diagnosis is guess.

You have mentioned several times that you had to consult with the machanic (talk to my shop) If you have to tell them what to do, you might want to look for a new shop. Beleive it or not a mechanic might just be taking you for a ride. As long as you keep giving him money he won't care if it is fixed right or not. Not all mechanics, but enough to make me question them. This is why I learned how to fix stuff myself. We could start a thread on poor mechanic horror stories, but there are ones just as good. You have to know what's going on to be sure. I hope I am wrong but...

(Quote)
tested the neutral theory, didnt sputter so maybe a vacuum leak.
Vacuum leak or bad head gasket or cracked head.

Not ignoring the coolant in the heads you probably have a blown head gasket, or cracked head. If it is indeed coolant in there. It lets water out, it might be letting air and or water in. But you need to address this coolant in the heads befor anything else. Don't wanna run it that way. Gonna wanna change the oil if coolant got down in the pan. What color are the plugs when you pull them out? Looking at the pictures it looks kinda like a lot of work has been done recently. Did you buy it this way? If so might be why it was sold. If not, Who did the work?

 

Thanks for the in depth reply, I appreciate the time you all took to try and help me out, thanks. I am no pro mechanic but I can get by, I just don't know anything about carbs really, or older motors in general (learned on sn95 stangs) But I did have a TON of eork done the past two months so I expected a few kinks here and there. Motor as built and installed, along with tranny, driveshaft, fuel and cooling systems. I am and have been afraid my shop has been taking me a little, but I do have to say though, out of the three times I took it back, I havnt paid anything to him again. Anyways I took it to him today and we went for a ride, he quickly said the ignition was breaking up and I told him about the coolant in the heads and he was gonna look into it. So for now I am waiting for a call... I would like to do more work on my own to the car but I am really nervous to dig into this after spending soooo much money on it. I am getting free repairs at the moment and I dont want to F anything up enough to where theyu wont fix it for me. But I do plan on taking it somewhere after my "warranty" is up, for tuning and what not. I need to learn hands on and its hard to find something someone will let me work on, lol. I had a few other mopars before this I would tinker with but nothing major could of been done so...stuck with someone else for th etime being

 

Just got the car back today, I was told that the plugs were fouled because too much gas at idle and not enough rpms. The solution? I was told to put it in neutral and keep it at 2k rpms at all times...around turns, while braking...basically two pedal driving. I was also told that the engine I had built was meant to be driven at high rpm's hence the sputtering...well the problem is it sputters all the time, even in high rpms and then shuts down. We went for a drive and of course no problems for the 5 minutes we drove but on my way home the sputtering and vibrating began. I mean it vibrates so much its undrivable. When I mentioned that I was told that it was because the motor was so "radical", well it just started doing the vibrating a few days ago so its a new issue and vibrates the whole front of the car horrifically. Ive had it with this place so Im going to another shop to spend more money but at least I know this guy does good work since I have had 2 mustangs built and tuned by him. Venting complete

 

Vibration issue answered...drive shaft dropped