After all this, I've ALMOST got this 440 dialed in...need advice again!

[moparedtn]

Ok gentlemen, as some of you know, I've been after this a long time now.
Car is a '68 GTX. 440 engine is of unknown build (builder passed away some years ago; was a lifelong Dodge tech at a dealer, so...). 4 speed, 3.55 Sure Grip.
Block is a '75, internals are all transplanted from the original '68 440 magnum as far as I can tell.
Cam is a Comp Cams Magnum, really mild - I'd call it two steps up from stock, but nothing like the 509 purpleshaft or anything.
The engine has those God-awful Hedmans that make plug changing a chore. Plugs are new Champions, RJ12YC.
Ignition is Mopar electronic conversion; I have a MSD Blaster II coil and MSD wires. Ballast recently changed to the MSD 0.8ohm to give me proper voltage to the coil.
Carburetor is a new Edelbrock Thunder AVS 650 #1805. I have installed the jets and rods indicated on the chart to go "2 steps rich" on primaries and secondaries and installed the "pink" springs , as the chart indicates in the manual.
Fuel pump is new from Mancini - the Carter "hemi" one that you can rebuild.
All new 3/8" fuel line from Fine Lines. New gas tank, new 3/8" pickup.

The engine pulls very well all the way up to 5500 rpm sitting still, zero hesitation, no drama, VERY smoothly. It didn't before I finally figured out previous owner had the wrong damn ballast on it.
She sure smells rich at idle, although there's no smoking or anything, even when goosing it.

I've just recently gone through all the compression testing (130 across the board, more or less), found true TDC and installed a new Summit harmonic balancer that is dead on; timing is set to give me 38 degrees total mechanical advance at around 2500.
Works out to about 13BTDC @ idle with this new distributor. I haven't worked on the distributor at all. Stock ECU.

Vacuum advance is disconnected; although I checked it out at about 55 degrees total when hooked up, the car just never has liked it hooked up, especially in high rpm mode. Not worried about it.

Engine was supposedly rebuilt before I bought the car 6 years ago. It might have 250 miles on it now, maybe.

Now, when driving:
Very pleasant, normal driving. Not a hiccup out of anything, takes moderate throttle smoothly. Drinks like a fish, though. No noticeable smoke out of the tailpipes.
When I row it up through the gears in stomp on it mode, the first two gears all the way to my self-imposed 5500 rpm redline are damn near perfect. No hesitation, no bog, pulls like crazy all the way up.
3rd gear - at about 5000 rpm, it stumbles just once or twice but pulls on to 5500.
I grab 4th and floor it - again, pulls great all the way towards the top of the rpms, but there's just a little stumble up towards 4800rpm or so.

It's like it's running out of something up there in the higher gears....
I can't believe it's running out of gas. Good Lord, I'm feeding it like crazy with the fuel system after all. Timing is dead nuts what the factory manual says to set the mechanical advance to and has tons of spark now (I think), so....

QUESTION:
Is it possible I'm simply running out of CFM in the upper RPMs with the 650?
If it's timing, does the stumbling indicate I have too much or too little advance?
How do it finally finish off this tuning exercise?
Thanks!

 

[hangn0ut]

If it had the symptoms that appeared at the same rpm when in neutral or second or even reverse its mechanical,like maybe valvesprings. But yours is load dependant. That points to ignition related problem. Check the basics. Burning that much fuel,plugs can be gas fouled. Cant clean gas fouled plugs. Reset your floats for correct fuel level and for float drop if called for. Make sure the step up rods are perfectly straight and move freely in the bores. Check fuel pressure with a gauge. Then inspect cap rotor and wires carefully and in sunlight for carbon tracks. Tracks can be hard to see,thats why you check in sunlight. Or the other approach is to stare at the motor running in absolute darkness. In gear helps but be careful! 5 minutes for your eyes to adjust. No cheating. And you might see a light show,,,out of the corner of your eye. Blue sparks running along the wires,jumping across the cap. Even grounding across the porceline of the plugs. All this dont cost a thing. Just time.

 

[HEMI-ITIS]

Sound like a street beast! I might suggest you find an open road where you can run it hard up through high gear. At 5500 flip the key off and glide to the side of the road. Bring some extra spark plugs with you even if they are old used ones.You will have to wait a while to let it cool down some then pull as many spark plugs as you can without melting your fingers off and throw the used ones in. Take pictures of the tip of the plugs and post 'em up.
Plug readings tell a story. Timing,jetting and plug heat range can be seen.You can google spark plug reading and get an idea what I'm talking about.I recently installed a data logger but I'm still reading plugs until I get comfy with the logger.

 

[hangn0ut]

Sound like a street beast! I might suggest you find an open road where you can run it hard up through high gear. At 5500 flip the key off and glide to the side of the road. Bring some extra spark plugs with you even if they are old used ones.You will have to wait a while to let it cool down some then pull as many spark plugs as you can without melting your fingers off and throw the used ones in. Take pictures of the tip of the plugs and post 'em up.
Plug readings tell a story. Timing,jetting and plug heat range can be seen.You can google spark plug reading and get an idea what I'm talking about.I recently installed a data logger but I'm still reading plugs until I get comfy with the logger.

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Hey Hemi, you running that 118 fuel? That yellowish color on the ground strap has me asking...

 

[moparedtn]

If it had the symptoms that appeared at the same rpm when in neutral or second or even reverse its mechanical,like maybe valvesprings. But yours is load dependant. That points to ignition related problem. Check the basics. Burning that much fuel,plugs can be gas fouled. Cant clean gas fouled plugs. Reset your floats for correct fuel level and for float drop if called for. Make sure the step up rods are perfectly straight and move freely in the bores. Check fuel pressure with a gauge. Then inspect cap rotor and wires carefully and in sunlight for carbon tracks. Tracks can be hard to see,thats why you check in sunlight. Or the other approach is to stare at the motor running in absolute darkness. In gear helps but be careful! 5 minutes for your eyes to adjust. No cheating. And you might see a light show,,,out of the corner of your eye. Blue sparks running along the wires,jumping across the cap. Even grounding across the porceline of the plugs. All this dont cost a thing. Just time.

Thanks for replying!
Ok, here we go:
1. Plugs are brand new, as I said. Engine used to foul them, but that was because of the wrong ballast severely limiting voltage to coil (2.5V! Sheesh)
2. Carb is brand new, but yes, I've already set float levels and checked drop.
3. Rods are new and perfect. I have the Eddy tuning kit as well, which they came out of when I tuned the carb per the manual.
4. Re: fuel pressure. Checks in at exactly what Mancini says it should (5.5 to 6.5 PSI). As I said, pump is the NEW reissue Carter M6903 "street hemi" fuel pump, 120gph rated. Pump rod is also brandy new.
5. Cap, rotor, wires all brand new as well (Accel still makes the great Tan cap Mopar replacement yay!).
I've stared at it at length in my darkened garage, can't see any arcs.Sorry, but I ain't putting this 4 speed in gear in the garage to check, though.

Thanks much!

 

[moparedtn]

Sound like a street beast! I might suggest you find an open road where you can run it hard up through high gear. At 5500 flip the key off and glide to the side of the road. Bring some extra spark plugs with you even if they are old used ones.You will have to wait a while to let it cool down some then pull as many spark plugs as you can without melting your fingers off and throw the used ones in. Take pictures of the tip of the plugs and post 'em up.
Plug readings tell a story. Timing,jetting and plug heat range can be seen.You can google spark plug reading and get an idea what I'm talking about.I recently installed a data logger but I'm still reading plugs until I get comfy with the logger.

Thanks for replying!
Boy, it'd be a good time to have an O2 reader also, eh?
God yes, it's pure hell getting the plugs out of the damn thing with those Hedmans on there. Awful design, like they didn't bother finishing the engineering or something.
TTI's someday...
*snaps back awake*
I think I could probably get about half of 'em outta there from the side of the road. I'll have to fetch some extra new ones, though. Last set I pulled out before I figured out the problem with the ignition are NOT candidates, however. They're soaked trash.
Thanks again![/QUOTE]

 

[moparedtn]

Hey Hemi, you running that 118 fuel? That yellowish color on the ground strap has me asking...

Oh, that reminds me...
I run non-ethanol "pure" 93 octane pump gas in the critter if that matters.

 

[hangn0ut]

Still using gas like mad. Its going somewhere. I would go back to stock jets and rods. Lean it out. You can smell it you said. 6psi is considered high for that carb. Plugs that hard to get at. Thst means there is a very good chance your cooking your boots. You need heat shield of some kind and probably new boots

 

[moparedtn]

Still using gas like mad. Its going somewhere. I would go back to stock jets and rods. Lean it out. You can smell it you said. 6psi is considered high for that carb. Plugs that hard to get at. Thst means there is a very good chance your cooking your boots. You need heat shield of some kind and probably new boots

I wonder what the stock jets were on the original Carter AVS?
I'd think that would be a great place to start if I could find that out - and believe me, I've tried. Maybe someone has some info on that?
Fuel pressure hovers around 5.5. I see it "spike" to 6 right after I've goosed the throttle, then settle back down. I spoke with both Edelbrock and Mancini before getting that fuel pump; it's actually a pretty good match for the AVS.
Yeah, boots are new - for now. I know their day is coming.
It really would be best to get rid of these headers.
Can't afford the TTI ones right now. Anyone else make a decent set with good plug clearance?
Former owner put 3" duals all the way back on the car. That ain't helping with tuning.

 

[hangn0ut]

Do your research on this site and see what you find out about fuel pressure. Your already at a great place to start with jetting. You know your rich,lean it out before you damage your motor.

 

[BBishere2]

Ok gentlemen, as some of you know, I've been after this a long time now.
Car is a '68 GTX. 440 engine is of unknown build (builder passed away some years ago; was a lifelong Dodge tech at a dealer, so...). 4 speed, 3.55 Sure Grip.
Block is a '75, internals are all transplanted from the original '68 440 magnum as far as I can tell.
Cam is a Comp Cams Magnum, really mild - I'd call it two steps up from stock, but nothing like the 509 purpleshaft or anything.
The engine has those God-awful Hedmans that make plug changing a chore. Plugs are new Champions, RJ12YC.
Ignition is Mopar electronic conversion; I have a MSD Blaster II coil and MSD wires. Ballast recently changed to the MSD 0.8ohm to give me proper voltage to the coil.
Carburetor is a new Edelbrock Thunder AVS 650 #1805. I have installed the jets and rods indicated on the chart to go "2 steps rich" on primaries and secondaries and installed the "pink" springs , as the chart indicates in the manual.
Fuel pump is new from Mancini - the Carter "hemi" one that you can rebuild.
All new 3/8" fuel line from Fine Lines. New gas tank, new 3/8" pickup.

The engine pulls very well all the way up to 5500 rpm sitting still, zero hesitation, no drama, VERY smoothly. It didn't before I finally figured out previous owner had the wrong damn ballast on it.
She sure smells rich at idle, although there's no smoking or anything, even when goosing it.

I've just recently gone through all the compression testing (130 across the board, more or less), found true TDC and installed a new Summit harmonic balancer that is dead on; timing is set to give me 38 degrees total mechanical advance at around 2500.
Works out to about 13BTDC @ idle with this new distributor. I haven't worked on the distributor at all. Stock ECU.

Vacuum advance is disconnected; although I checked it out at about 55 degrees total when hooked up, the car just never has liked it hooked up, especially in high rpm mode. Not worried about it.

Engine was supposedly rebuilt before I bought the car 6 years ago. It might have 250 miles on it now, maybe.

Now, when driving:
Very pleasant, normal driving. Not a hiccup out of anything, takes moderate throttle smoothly. Drinks like a fish, though. No noticeable smoke out of the tailpipes.
When I row it up through the gears in stomp on it mode, the first two gears all the way to my self-imposed 5500 rpm redline are damn near perfect. No hesitation, no bog, pulls like crazy all the way up.
3rd gear - at about 5000 rpm, it stumbles just once or twice but pulls on to 5500.
I grab 4th and floor it - again, pulls great all the way towards the top of the rpms, but there's just a little stumble up towards 4800rpm or so.

It's like it's running out of something up there in the higher gears....
I can't believe it's running out of gas. Good Lord, I'm feeding it like crazy with the fuel system after all. Timing is dead nuts what the factory manual says to set the mechanical advance to and has tons of spark now (I think), so....

QUESTION:
Is it possible I'm simply running out of CFM in the upper RPMs with the 650?
If it's timing, does the stumbling indicate I have too much or too little advance?
How do it finally finish off this tuning exercise?
Thanks!

I think you're right on with the carb not flowing enough cfm. One of the online calculators I found showed a 440 at 6k rpm needed almost 800 cfm. The Holley carb finder shows 750 carbs. My builder suggested a Demon 750 over a Holley, so I'm going with a speed demon on mine. We'll see.

 

[WileE]

I'd try a colder plug

 

[HEMI-ITIS]

Hey Hemi, you running that 118 fuel? That yellowish color on the ground strap has me asking...

That's 92 pump junk!!

 

[moparedtn]

Do your research on this site and see what you find out about fuel pressure. Your already at a great place to start with jetting. You know your rich,lean it out before you damage your motor.

I think I might put the jets back in it that came in the carburetor, but only if the "test" results suggested by Hemi-Itis warrant it. I had long forgotten that trick, but it makes perfect sense - seeing the plugs immediately after the issue occurs is logical.
Thanks!

 

[moparedtn]

I think you're right on with the carb not flowing enough cfm. One of the online calculators I found showed a 440 at 6k rpm needed almost 800 cfm. The Holley carb finder shows 750 carbs. My builder suggested a Demon 750 over a Holley, so I'm going with a speed demon on mine. We'll see.

I've had many a 440 in olden days where, back then, I'd just get the Holley 3310 (750cfm vacuum secondary) carb and plunk it on there, set mix and idle and off we'd go. Always worked really well right out of the box - it ought to, since that carb was originally designed by Holley for stock Mopar big blocks.
I did that on this one before the Eddy, too - it just didn't work out and I sold it.
That was probably a mistake. I blamed the carb when it turned out to be something else entirely wrong.
I chose this Eddy 650 because that old carb sizing equation came up just shy of 600cfm (when I input 440 engine and 5500rpm). Of course, that figures a VE of .8 for a mostly stock street engine, which I suppose this one really isn't, given the cam and exhaust.
Long story short - I agree, a 750 would have been the wiser choice.

Question for everyone - how does an engine behave when it runs out of cfm?
Does it just refuse to rev higher, like it hits a wall? Does it start breaking up a bit at higher rpm but will eventually climb higher, like mine is doing?

 

[moparedtn]

I'd try a colder plug

Ok, but why? I'm wanting to learn, not questioning your knowledge, understand.
BTW, the engine runs pretty cool - about 175-180 this time of year.
Of course, new radiator, new shroud, new fan clutch, 7 blade fan, etc.
I went kinda nuts on the cooling system, too. The car originally ran hot 6 years ago.

 

[miller]

Early 440s used 600 cfm AFBs, but as you said, your build is more than stock.

Sounds like too rich, to me. But, reading your plugs can give you direction which way to go.

 

[Hemirunner]

It indicates that you have too much or too little fuel

Ok, but why? I'm wanting to learn, not questioning your knowledge, understand.
BTW, the engine runs pretty cool - about 175-180 this time of year.
Of course, new radiator, new shroud, new fan clutch, 7 blade fan, etc.
I went kinda nuts on the cooling system, too. The car originally ran hot 6 years ago.

Heat range on a spark plug has nothing to do with any of the above. It has to do with how fast heat is transferred from the plug to the head. Those RC12YC plugs are too hot for todays pump gas as far as I'm concerned.

 

[69Runner]

Question for everyone - how does an engine behave when it runs out of cfm?

Generally speaking a carburetor's cfm is rated for 1.5 in.Hg. vacuum at WOT. If you hook a vacuum gauge to either manifold or timed port (run a hose into passenger compartment where you can view the gauge) then what do you get? Higher vacuum indicates restriction, such as at idle when it is the highest.
Another thought - what is the difference between 5500 rpm sitting still (in neutral) compared to going through the gears? Torque at the rear wheels is dropping as you change gears and vehicle drag is increasing as it gains speed. 4800 rpm is probably where your engine torque curve starts to level off. A trip to the dyno might prove or disprove this hypothesis.
Back to the cfm's, try removing the air cleaner to see if that is acting as a restriction. Easy and free. Also, a dual plane intake can tolerate a bigger carb as it divides the carb in half, right? Maybe an open plenum spacer can help a smallish carb to feed a dual-plane intake? Just spitballing here...

 

[moparedtn]

Early 440s used 600 cfm AFBs, but as you said, your build is more than stock.

Sounds like too rich, to me. But, reading your plugs can give you direction which way to go.

Yep, going to try that method this weekend I reckon.