Falls on it's Face

[BLUE68RT4ME]

Some of you may have seen my restoration and motor rebuild threads.  I have a 512 CI (440) with 440 Source Heads, custom cam by Mr. Porter out in Vermont, a Street Dominator intake, and a Holley 800 Dbl-Pmpr all in front of a 727.

It didn't seem to have any problems running at any range in RPM after I replaced the power valve that was shot.  I started to notice early this summer that occasionally when I get into the throttle in 1st gear and stay on it through second it falls on its face and pops through the exhaust like it's flooding out or something.  It didn't do it every time but it's now gotten to be every time I drive it and get into it.  It's not only when shifting anymore, even in drive - when I stay deep into the throttle it starts to load up and fall on its face.

Since it's been restored, I've driven it about once or twice a week through the summer and a little in the fall.  Winter and spring I try to start it once every month or so.  The only change I made in anything was throwing a little 110 octane in it here and there.  Otherwise, it's 92-93.

Some of my friends believe the double pumper shouldn't be on my car because it's an auto.  I understand their reasons and I'm not opposed to changing as many times as I've had to mess with it before.  However, I'm not convinced that the problems is having the mechanical secondaries because it didn't do this before.  Others say my floats in the back are set too high and when I get into it the front bowl fills the back and it pours out the secondaries.  Again, unless the floats moved on their own, I never changed any of that.  Still others think that sitting a month or more at a time cause crap to form and get stuck somewhere inside but I don't know if that's it either.  When I start it up it runs like a champ.  Normal driving.... perfect.  As soon as I get into the throttle, it's right there until I'm into it for a significant amount of time.

I used to have a similar issue with it before I rebuilt it, the motor, and the car except that instead of flooding it seemed to run out of gas after about 3500 rpms.  Back then, it would just cut out like there was no gas, then recover a little, and then cut out again.  No popping in the exhaust, no gas smell, nothing.  Now, it pops in my exhaust and I even found gas floating in the top of the crank case when I checked the oil.

I've not had a backfire or anything since I replaced the front power valve last summer (2012).  When that was out it would flood like mad and there would be gas pouring out from everywhere when you shut it off.  Now there is no exterior leaks but do you think the power valve in back could be shot?

I'm very confused.  I'm not a genius when it comes to carbs.  My dad was but all that wisdom was lost when he passed.  Being in engineering, all I know is constants and variables and the only constant that I can focus on in my frustration is the fact that this carb is always been a problem.

I do not have the vacuum advance hooked up and I'm also running the Rev-N-ator with my electronic ignition with a Blaster II coil.  I don't see any of that as a problem.

Any suggestions?

Thanks in advance to anyone taking the time to reply!   

[JB400]

What fuel pump are you running?   What about a regulator (if you have one)?

[BLUE68RT4ME]

It's a brand new Holley pump.  Mechanical at that.  I don't have a regulator on it but I shouldn't need one considering it's not electric.  One thing I didn't put on is a return line but, again, that's been the case since I finished the restoration and this didn't happen at first so I can't see that being the issue either.  I've been wrong before though.

[Lord Warlock]

The double pumper is probably a bit more carb than you need right off the line, the original carb for the 440 was only a 625cfm.  I've got a air vacuum secondary 750 on mine and it runs fine,  but it won't dump the gas in like a holley double pumper will.  I used to have an 800 double pumper back the the 70s, it never did work well on the stock 440, but then i had the stock intake on mine and had to use a spacer to get it to fit.  Ended up taking it off and selling it to someone else for a hundred bucks.  It was great once the rpms were up and it could eat the gas well,but too much too soon didn't work well with the gears i had in the car (3.23)

[Back N Black]

I had similar problem with my car, You mentioned that you are running a holly fuel pump, i had the same pump and it was defective, the spring was too stiff and wore the push rod down to a point where it was causing the same issues you are experiencing. Just something to check, pull the pump and measure the push rod.

[sdconcepts]

there is not enough info posted to help you diagnose your problem.  what cam are you running?  whats the cam timing?  whats the ingition timing set at?  initial?  final, and how soon?  an 800cfm double pumper should be ok, but you may need to jet down.  are you running headers?  what rear gear? 

[Dino]

Floats too high or fuel pump not working properly would be the first things I would check.  You say the floats had not been touched so start with the pump.  Hook up a gauge and see what pressure you get.


Also, IF you have the option to simply swap the carb for another for testing purposes, it will make diagnosing this a lot easier.

[MSRacing89]

My friend. Anyone telling you that an 800 DP is not the right carb for that car is insane.  I can understand the need for a vacuum secondary but a 512 CI motor is going to need that and some.  What you are describing is a could be a lean pop.  You mentioned a new fuel pump......have you checked to make sure the pressure is set right?  Is the power valve correct?   

I am betting you are just not jetted right for your application, power valve off, or you have a fuel pressure issue.  That motor will need minimum 3/8" lines feeding it and at least 5 to 5.5 psi minumum at load.  If you have stock 5/16"......problem.

Pull a plug for grins and take a look.  That will tell a story.  I mean if they are not obviously fouled.....I am betting they will look fine though.

Might I suggest you make friends with a carb builder, even someone widely known like BIGS or similar.  These guys will take your specs and get you exactly what you need.  I have several of the BIGS carbs, they run great.  Currently run EFI but it's still all the same when it comes to fuel delivery.    

[Brass]

My friend. Anyone telling you that an 800 DP is not the right carb for that car is insane.  I can understand the need for a vacuum secondary but a 512 CI motor is going to need that and some.  What you are describing is a could be a lean pop.  You mentioned a new fuel pump......have you checked to make sure the pressure is set right?  Is the power valve correct?   

I am betting you are just not jetted right for your application, power valve off, or you have a fuel pressure issue.  That motor will need minimum 3/8" lines feeding it and at least 5 to 5.5 psi minumum at load.  If you have stock 5/16"......problem.

Pull a plug for grins and take a look.  That will tell a story.  I mean if they are not obviously fouled.....I am betting they will look fine though.

Might I suggest you make friends with a carb builder, even someone widely known like BIGS or similar.  These guys will take your specs and get you exactly what you need.  I have several of the BIGS carbs, they run great.  Currently run EFI but it's still all the same when it comes to fuel delivery.   

This is excellent advice!  I’m not a carb wizard whatsoever but I know enough not to swallow that misinformation/fallacy about double-pumpers.  My 700 works perfectly with an auto and 3.23 gears.  (With a little stall.)  If it were me; I’d find a guru, put a wideband o2 sensor on it, or maybe get a chassis dyno tune.  Get it sorted out because there may be untapped power there.

[BLUE68RT4ME]

I had similar problem with my car, You mentioned that you are running a holly fuel pump, i had the same pump and it was defective, the spring was too stiff and wore the push rod down to a point where it was causing the same issues you are experiencing. Just something to check, pull the pump and measure the push rod.

A buddy of mine had the same thing happen to him.  Do you know the measurement the rod should be?  Did you find a good replacement?

I'll pop that off and take a look.  I really don't want to have to buy an electric, add a return line, and put a regulator on.

I did put a 3/8" fuel line in.  Again, this isn't something that happened from the beginning.  It was also dyno'ed with the carb on it so it is set up for this motor.  I don't think I've put more than 1000 miles on it since it got off the dyno (new).  Hard to believe that it could have wore down that much so quickly, if that's the issue.

[MSRacing89]

I would seriously consider getting a fuel pressure gauge on that thing, run it into the car and see what is happening when this situation rears its head.  That is going to tell you if you are going the right direction.  It will be very obvious.

If that looks good, then I would go to putting a friends carb on it, something like a nice built 750 DP just to eliminate that side of things.

If all else fails after that, then you might be a looking at electrical.  But with all the issues in that carb you described in the original post, its most likely in that area of things.

BTW, a nice Mallory 140 with regulator (no return needed) perfect set-up for that.

[RIDGERACER383]

I had the same issue with mine and in my case it was the carb.My carb kept getting worse until it stopped squirting fuel.My accelerator pump was shot and it had a check ball stuck under the fuel squirter.Im not sure how old your carb it,but that's where I would start.If you can borrow another carb put it on and try it and see if you have the same issue.

[firefighter3931]

Hi Mark 

This sounds like a fuel delivery issue. Check the fuel pump pushrod....it should be 3.25in long for proper operation. There was a bad batch of pushrods that were not properly hardened and are prone to rapid weardown. 

Are you using a zinc additive in your oil ?


Ron

[myk]

Like the others I say fuel pump.  When my e-pump started mucking up I experienced the EXACT same symptoms you were having; I would guess that a mechanical pump could do the same thing...

[cudaken]

Blue said

"Now, it pops in my exhaust and I even found gas floating in the top of the crank case when I checked the oil."

That part has not been addressed and could wash out the cylinders. Have you checked the float level yet?

Do U Tube search if you do not know how. Here is a basic starting point video and go from there.

http://www.youtube.com/watch?v=5_lgTTkXJDM

Good Luck, Cuda Ken

[BLUE68RT4ME]

Sorry for my late reply, just got to diagnosing today.  Push rod is 3.230, seem close enough.  Fuel filter is clear.  Tried to start today and there was no fire.  Then poured gas down the primary and it fired instantly.  I can't believe the pump is bad but it seems the only possibility.  It doesn't have more than 100 hrs on it.  I've not wanted to put an electric pump on it but maybe that's my best choice.  Have I missed something?

[cudaken]

Sorry for my late reply, just got to diagnosing today.  Push rod is 3.230, seem close enough.  Fuel filter is clear.  Tried to start today and there was no fire.  Then poured gas down the primary and it fired instantly.  I can't believe the pump is bad but it seems the only possibility.  It doesn't have more than 100 hrs on it.  I've not wanted to put an electric pump on it but maybe that's my best choice.  Have I missed something?

Mark, if it fires when you dump gas down the carb your Accelerator Pump on the Carb has taken a dump, not the engine fuel pump. Ask me how I know! 

Ken

[69rtse4spd]

How much ethanol is in the gas you are buying, could have eaten the pump or carb diaphragms. .

[BLUE68RT4ME]

The carb only has about a 100 hours on it too, and I replaced the pumps & diaphragms at that time.

I hadn't started the car for a month.  Each time it sits that long everything has drained out of the carb so I have to turn it over a while just to get gas through the fuel pump and up to the carb.  Yesterday, I turned it over for far longer than normal for these types of conditions.  That's when I dropped some gas down the carb because I wanted to make sure I didn't have an issue besides fuel. 

It fired immediately but let me be clear it did not run.  I never got enough gas to the carb to run.  That is why I then went into looking at the pushrod & the filter.

And when it did run, the accelerator pumps were working because when I'd first take off from idle it would tear the pavement off the road but once I was at driving rev's it would cut out when I got into it.

I'll have to look at the floats again to assure myself they're set right but I have to figure out what's wrong now before I even got to that point.

Also, I was wondering if you can buy a check valve for your fuel lines to prevent the fuel from emptying out?   I'm pretty sure a regulator does that so I could probably do that too but again, I still haven't reached my real problem.   

[firefighter3931]

Hey Mark,

It sounds like the fuel pump is toast. You can try filing the holley's float bowls using the vent tubes. I use a small bottle with a squirter to get the bowls filled or you can use a small funnel. With the bowls full you'll be able to fire the engine and run it for about a minute using the fuel in the carb. In that time the fuel pump will have had enough time to prime itself and keep the engine running.....if it's working properly. 

As Marty mentioned above ; get a fuel pressure guage  on it to see what's happening. Use the non-liquid filled gauges because they are more accurate. Most of the Holley dual feed lines will have a 1/8 npt port to install the guage.

http://chucker54.stores.yahoo.net/mrgachgasli1.html

Fuel in the oil pan is certainly possible with a ruptured fuel pump diaphragm.

As for mechanical pumps....I like the 120 gph Carter street pump that is rated at 6 psi discharge pressure 

http://chucker54.stores.yahoo.net/cabheen5psis.html



Ron

[69wannabe]

Like Ron said above your fuel pump has laid down!! It should't take that long for your carb to get fuel even if it has been sitting for a month or so. Mine sit's for weeks at a time and I can pump the pedal to the floor two times and hit the switch and it fires rite up!! (most of the time anyway lol) The carter street pumps are great pumps and for some reason are getting harder to find. Summit and jeg's do not sell them anymore and I had to get one from mancini last year and actually bought two just to have an extra one. I think mancini sells rebuild kits for the carter pumps as well. If your fuel pump is good it will not let the fuel drain back toward the tank. Mine was spraying out of the weep hole like madness so I knew it was bad but sometimes they don't always do the same things. I had a holley pump do the same thing you are describing on a 390 ford engine I had a long time ago. It got a carter fuel pump too!!

[BLUE68RT4ME]

I can't thank everyone who's responded enough for their insight; even the comments I didn't get a chance to respond to earlier.  I tore my gauge cluster out and shipped it off for rebuilding.  I have 6-7 weeks to get this stuff fixed in the meantime.

I am definitely going to follow Ron's advice and get the pressure gauge kit.  I'm on the fence on whether I should go with a mechanical or electric pump this time.  There are a lot of pro's to both sides.  What I've learned is most people are "all or none" on the subject it seems.  Some of my friends swear up and down on electric and others are the same way on mechanical.  I guess if I'm going electric I'm going to need a little push but I'm not opposed.  Is there a measurable amount of power savings by removing the mechanical pump?

While I wait I still have to drop the oil and replace the bad u-joint up front that started howlin' about all the new torque it's dealing with.     And I should really pull the drivers side axle shaft as the seal is leaking.  I have both seals and a new bearing but I'm gonna need to get a torch to get that old bearing off if it's anything like the other side.

Well, if you've got a good sales pitch, let's hear it. 

Thanks again everyone!   

[firefighter3931]

Well, if you've got a good sales pitch, let's hear it. 

Well, that's an easy one because you answered your own question(s) 

Schultzy Quotes :


"It didn't seem to have any problems running at any range in RPM after I replaced the power valve that was shot"

"However, I'm not convinced that the problems is having the mechanical secondaries because it didn't do this before"

"Normal driving.... perfect.  As soon as I get into the throttle, it's right there until I'm into it for a significant amount of time"

"Now, it pops in my exhaust and I even found gas floating in the top of the crank case when I checked the oil"

"Tried to start today and there was no fire.  Then poured gas down the primary and it fired instantly"


So, the progression has been from a good running engine, to a poor running engine and finally an engine that won't even fire. If it ran like a raped ape in the beginning we know that the fuel delivery was adequate. That means that the fuel lines are not a problem unless you somehow kinked one so lets assume that they're OK.

Moving along...the performance begins to deteriate and now it's popping and you discover some fuel in your oilpan. Running out of fuel at high rpm results in a "lean pop" and fuel in the oil can only come two ways : carb is flooding (too much fuel) or the diaphram is ruptured. Since it's running lean indicated by the "pop" that points directly to the diaphram. 

Lastly, the engine will no longer run unless you dump fuel into the carb....so the pump is no longer self priming. I bet if you disassemble that piece you will find a ripped/ruptured diaphram. 

To summarize ; the car admittedly ran great with a mechanical pump so we know that that style pump can deliver enough volume. You just need to get one that's more reliable and all will be well. For a street car making the power you're making the Carter 120 gph street pump is more than adequate using 3/8 fuel line.

Mancini is the only company that carries the Carter 6903 so you'll have to get it from them. Pretty sure they have exclusive distribution rights on that part number and made some kind of arrangement with Carter to be the lone retailer. The 6903 had been discontinued for a few years so it's great to see it available again. 




Ron

[BLUE68RT4ME]

You're right in every area but I will just say one thing, the reason it didn't fire until I poured gas in the carb was because there was absolutely no gas in the carb.  If I am correct in my thought process, if the diaphragm is indeed shot that would allow the gas to flow back to the tank when the car is shut off.  That vacuum would allow the gas to be pulled from the bowls too, correct?

This was why I mentioned a check valve, it seemed to me the gas was flowing back out of the carb.  To further that, and why I think my (accelerator) pumps are fine, is that once I would finally get fuel to the carb it would still have great throttle response until, what I'm assuming is the case, the bowls ran empty.  I realize now, if what I assumed above holds water (or fuel in this case ), is that a good diaphram doesn't allow the fuel to flow backwards through the pump.

Do you follow me?

[68CoronetRT]

If it's still a mechanical fuel pump, why not buy a cheapo pump and see if it works? You had to remove it to get the pushrod out anyway...

Or maybe I didn't read every post thoroughly and I missed something here...