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Dead at 3500 #68545
06/06/08 08:43 AM
06/06/08 08:43 AM
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PA USA
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flatiron Offline OP
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flatiron  Offline OP
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PA USA
I have a real problem and I'm at the end of my rope.
1967 coronet 383bored and stroked to 431 Holley 4160
750cfm vaccum secondaries. 6psi of fuel pressure 5/16 fuel line.
My problem is it just shuts down. 1st gear fine shift at about 4 grand, 2nd gear fine I shift to 3rd/drive at about 5 grand it drops to 3500 when I shift and just dies at around 3800. It actually bogs/sounds like it shuts off pull my foot out of it and it comes back to life around 3000.
What I've tried to do to fix it.
new blaster 2 coil
new plugs
new cap and rotor
replaced rubber fuel line at tank and from hard line to fuel pump.
put a pc of fire blanket between header and fuel line. to divert heat.
Anyone have any Idea's

Re: Dead at 3500 [Re: flatiron] #68546
06/06/08 08:47 AM
06/06/08 08:47 AM
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Posts: 4,084
Indiana
W5Duster436 Offline
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Is the return or vent plugged? Loosen the gas cap and see what happens. I've also seen this happen with too much preload on the lifters but it acts a little different.

Re: Dead at 3500 [Re: flatiron] #68547
06/06/08 08:50 AM
06/06/08 08:50 AM
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New Mexico
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dmerc Offline
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I had to replace my hard line from my tank to the fuel pump. I also upgraded to 3/8 line. You might also have a worn fuel pump pushrod.

Re: Dead at 3500 [Re: flatiron] #68548
06/06/08 08:51 AM
06/06/08 08:51 AM
Joined: Jan 2003
Posts: 4,084
Indiana
W5Duster436 Offline
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When you are checking the 6 psi of pressure are you watching the gauge while you drive or is it under the hood at idle? That is where you'll find your answer. Need to watch it as you're driving.

Re: Dead at 3500 [Re: W5Duster436] #68549
06/06/08 09:04 AM
06/06/08 09:04 AM
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PA USA
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flatiron Offline OP
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I don't have a return line.when I open my gas cap it's under pressure. To check my fuel pressure I hooked a pressure gauge up to a rubber fuel line ran it throught the hoodscoop to carb and watched it under driving conditions held a steady 6 psi and as Far as I know I have astock mechinical fuel pump.

Re: Dead at 3500 [Re: flatiron] #68550
06/06/08 10:26 AM
06/06/08 10:26 AM
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PA USA
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flatiron Offline OP
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Re: Dead at 3500 [Re: flatiron] #68551
06/06/08 10:30 AM
06/06/08 10:30 AM
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chicagoland,usa
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buildanother Offline
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chicagoland,usa
I run elec fuel pumps on everything now to avoid those crappy fuel issues. Some have had luck with certain mechanical pumps, but I have not.

Re: Dead at 3500 [Re: flatiron] #68552
06/06/08 10:34 AM
06/06/08 10:34 AM
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Posts: 1,367
Jersey shore
Gary67 Offline
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Jersey shore
Is this a new build? Has it worked fine in the past and just started giving you problems? What ign box you running? Can you slowly get to speed and that rpm without trouble?

Re: Dead at 3500 [Re: buildanother] #68553
06/06/08 10:39 AM
06/06/08 10:39 AM
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Posts: 36,040
Lincoln Nebraska
RapidRobert Offline
Circle Track
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Lincoln Nebraska
could you rig a plastic overflow bottle or something similar under the hood with a half gallon of gas hooked to pump inlet & go for a quick test drive.


live every 24 hour block of time like it's your last day on earth
Re: Dead at 3500 [Re: RapidRobert] #68554
06/06/08 11:34 AM
06/06/08 11:34 AM
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dogdays Offline
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Sounds like ignition. Electronic or points type distributor? Is the coil hooked up right? Or, pickup coil on the electronic distributor hooked up right? Or if electronic change the box and see what happens.

My guess is that you have a weak spark that'll run to 4K with light load but when you put your foot in it and build maximum cylinder pressure the spark isn't happening.

R.

Re: Dead at 3500 [Re: dogdays] #68555
06/06/08 12:09 PM
06/06/08 12:09 PM
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PA USA
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flatiron Offline OP
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No this isn't a fresh build, I have a 6a for a box blaster 2 for a coil champion plugs and accel wires.
Istarted to mess with the secondaries (springs) trying to get them to open and I'm wondering if the secondaries are starving for fuel and when it opens it bogs and dies . Then when I lift my foot they close up and everything is ok

Re: Dead at 3500 [Re: flatiron] #68556
06/06/08 01:13 PM
06/06/08 01:13 PM
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Paul_Fancsali Offline
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First thing disconnect the 6A I had 2 MSD boxes do this on my cars over the years. Have the point dist ? Put it in and give it a try but my money is on the 6A screwing up. Said this before MSDs on cars that race other wise a stock electronic or even points will give you the performance you need on a street car

Re: Dead at 3500 [Re: flatiron] #68557
06/06/08 04:11 PM
06/06/08 04:11 PM
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dogdays Offline
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Well if you have screwed up the vacuum secondaries then you need to get them working right first. Find out what color the stock spring is and put it in. OF COURSE if you have the secondaries opening all the way with no air flowing through your engine will go dead lean and make funny noises.

I don't know why Paul is so dead set against MSD boxes, there must be a reason why all the circle track racers use them and it isn't because they break!

R.

Re: Dead at 3500 [Re: dogdays] #68558
06/06/08 04:56 PM
06/06/08 04:56 PM
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Paul_Fancsali Offline
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Not dead set against them just less moneycan get the same job done and when the weird things do occur there is generally a easier fix. Perhaps the new boxes are better butI had several over the yearsnad now I'm back to pertronix, mopar electronic or yes even the evil points. If I have trouble I know where to go with them. By the way a MSD box caused a .4 loss at the track I tested it before and after using a point ignition Bear in mind this is on a street car and MSD seems to hate long running time just my 10cents

Re: Dead at 3500 [Re: Paul_Fancsali] #68559
06/06/08 07:35 PM
06/06/08 07:35 PM
Joined: Jan 2003
Posts: 4,084
Indiana
W5Duster436 Offline
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Quote:

Not dead set against them just less moneycan get the same job done and when the weird things do occur there is generally a easier fix. Perhaps the new boxes are better butI had several over the yearsnad now I'm back to pertronix, mopar electronic or yes even the evil points. If I have trouble I know where to go with them. By the way a MSD box caused a .4 loss at the track I tested it before and after using a point ignition Bear in mind this is on a street car and MSD seems to hate long running time just my 10cents




Holy smokes. You are saying that a 6al box loses 1/2 a second at the track? There is NO way that can be right. Maybe you have to take out the 3K rev pill?


'70 Duster - SDSS 436 W5 4spd (Gone)
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'70 Dodge W100
Re: Dead at 3500 [Re: W5Duster436] #68560
06/06/08 08:35 PM
06/06/08 08:35 PM
Joined: Mar 2008
Posts: 724
PA USA
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flatiron Offline OP
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I'm wondering even if I have 6 psi of fuel pressure through a 5/16 fuel line could it be such a thing as I'm not getting the volume and maybe I need to go to a 3/8 line and a electric fuel pump. I hope tomarrow to change secondary springs and see if the rpm it shuts off changes. It's just hard to get anything done when working 7 days a week. I'll try to get more info to you guys sure am geting tired of taking shots in the dark

Re: Dead at 3500 [Re: flatiron] #68561
06/06/08 09:08 PM
06/06/08 09:08 PM
Joined: Jan 2003
Posts: 4,084
Indiana
W5Duster436 Offline
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Quote:

I'm wondering even if I have 6 psi of fuel pressure through a 5/16 fuel line could it be such a thing as I'm not getting the volume and maybe I need to go to a 3/8 line and a electric fuel pump. I hope tomarrow to change secondary springs and see if the rpm it shuts off changes. It's just hard to get anything done when working 7 days a week. I'll try to get more info to you guys sure am geting tired of taking shots in the dark




a 5/16 line would still feed 450-500Hp more than likely. That is probably not your problem.

Does this happen when the secondaries open? have you checked the fuel level on the secondary bowl to ensure it has fuel? If not and the secondaries open with all air you will run it so lean it should start popping etc.







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