440 Help Needed

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Rat Bastid said:
If we are talking about the Holley then drill some holes in the throttle blades. Start at about .080ish and see what you get. If you don’t have 4 corner idle just do the primaries.

You need to get the throttle shut. Otherwise nothing you do will fix it.
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I wouldn't be drilling any holes in the carb plates until I was 100% sure that nothing else was causing the need to open them that wide..
Even then , there are other ways to bypass air on a Holley 4BBL, that won't limit its use after you drill holes in the blades.
I had an engine exhibit some of the same characteristics as the one above.. Turned out to be a mechanical issue.
 
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Bakerlite said:
I wouldn't be drilling any holes in the carb plates until I was 100% sure that nothing else was causing the need to open them that wide..
Even then , there are other ways to bypass air on a Holley 4BBL, that won't limit its use after you drill holes in the blades.
I had an engine exhibit some of the same characteristics as the one above.. Turned out to be a mechanical issue.
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Throttle blades are cheap. Are you suggesting he doesn’t now how to close the throttle? Or maybe he has the throttle cable adjusted wrong?
 
PRH said:
What’s the carb part number, and how many turns out are the mixture screws?

My experience has been that the “wandering” idle speed can indicate a lean condition.

If you look down into the primary barrels while it’s idling, is there fuel dribbling out from the boosters?

Float levels have been set/checked?
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So the part number for the carb is 0-80459SA. Its their classic series carb. 750CFM, 4160, 64 jets, 8.5PV, vacuum secondaries, electric choke.

The idle screws have been turned out one full turn from fully seated. But with as far as the throttle blades are opened, I dont believe the idle screws would add a significant amount of fuel as compared to the overly exposed transfer slots...? correct?

I dont believe there is fuel dripping from the primaries when idling. But I will check again.

Yes the float levels have been set, I set them so there was minimal spillage coming from the ports while idling.

OldmanRick said:
I just have a hard time believing this is carb related. Even if the AVS took a dump, that new 750VS should have been able to bolt on and clean it up at idle. With 72ish jets and even a 10.5PV it should idle with the vacuum he has 10/15.

Maybe it's ignition related, who knows? I know the heat riser is gone, but still seams to me like it's acting like a restriction somewhere. Any chance a baffle in one of the mufflers broke loose? Run it up to 2500 r's or so and see if you have even flow out of both tailpipes?

Ok, that's all i got...:lol:
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Yes there is even flow from both tail pipes. Exhaust is new, with new mufflers. Car only has about 1200-1700 miles on it since restoration.

Bewy said:
I agree that the engine should idle with less than 25* at idle......but it will certainly idle a whole lot better with 25*....& possibly more. Are any of the lifters bottomed out, which would hold the valve open?
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Yea that is my thought exactly, it should idle with less timing at idle, but it doesnt and I am banging my head against the wall ready to send this car over a cliff!! that may be a little dramatic but it is very frustrating.

I did not visually check to see if a lifter was holding a valve opened, or if a lifter collapsed, but when driving the engine is smooth, there doesnt seem to be a miss or anything like that.

Rat Bastid said:
Throttle blades are cheap. Are you suggesting he doesn’t now how to close the throttle? Or maybe he has the throttle cable adjusted wrong?
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There is enough room in the throttle cable to have the throttle blades closed. Getting it to close isnt the problem, the idle speed screw controls that just fine, its just that when I close the throttle blades the whole engine starts to shake and then just stalls.

I dont think I quoted someone who mentioned a vacuum leak, but by damn I looked!! I sprayed the carb base with carb cleaner, Sprayed where the intake mates to the cylinder heads and nothing! I even tried that with running propane from a propane torch over it and nothing!! :BangHead:


The guy I am working with mentioned rotor phasing to the cap. That appears to be easy enough to inspect, so Ill give that a go next time I am in. I can AGAIN look for a blasted vacuum leak. Ill check to see if there is a hang up somewhere in the throttle cable, but like OldManRick said I dont believe this is a carb issue since I am getting the same issue with two very different carbs.

Now, Some history on the engine. The engine was in a fire. It originally came out of a 68 New Yorker that was in a building that was torched. According to the information we found the fire didnt get hot enough to destroy the engine. Everything on the engine is the same as was in the fire with the exception of the pistons, piston rings, seals, oil pump, carb, cam, lifters. I know the engine block was magnafluxed. The heads also go machine work done, I can only ASSUME they were magnafluxed as well. However the cast iron intake did not go to the machine shop so it was not magnafluxed. Spit balling here, could the intake of developed a crack due to the fire that would allow a vacuum leak?
 
How was it determined that one turn from seated was the proper adjustment for the mixture screws?
Have you tried adjusting them?

My presumption going into it would be that a [email protected] cam and exhaust manifolds would be a challenge for many 2 corner idle carbs, and that they’d be lean at idle.
I’ve had to run the mixture screws out 2-3 turns in similar combos.

If opening the mixture screws increased the idle speed, it would let you close the throttle blades.

As far as carbs are concerned, the main thing advancing the initial timing does is increase the vacuum.......Which helps draw fuel out of an idle circuit.

In any case...... fiddling with the mixture screws is easy and free.
 
Rat Bastid said:
Throttle blades are cheap. Are you suggesting he doesn’t now how to close the throttle? Or maybe he has the throttle cable adjusted wrong?
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So that's what you gleamed from my post.?
Guess I need to say it again.
I wouldn't be drilling any holes in the carb plates until I was 100% sure that nothing else was causing the need to open them that wide..
Example:
ignition issues, mechanical issues, vac leaks etc..
Drilling the plates, just to find you then need to replace them after the real culprit is found, is not the smartest thing to do... no matter how "cheap" they are..
Pretty obvious steps to follow, if your a trained licensed mechanic..
 
Bakerlite said:
So that's what you gleamed from my post.?
Guess I need to say it again.
I wouldn't be drilling any holes in the carb plates until I was 100% sure that nothing else was causing the need to open them that wide..
Example:
ignition issues, mechanical issues, vac leaks etc..
Drilling the plates, just to find you then need to replace them after the real culprit is found, is not the smartest thing to do... no matter how "cheap" they are..
Pretty obvious steps to follow, if your a trained licensed mechanic..
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No ****? Seems like he says he’s done all that. Or going to do it.

Licensed mechanic. That’s a joke.
 
This won’t help a lot of people........... but it’s how I’ve isoltated “carb problems” to being either that....... or something else, for over 30 years.

I’ve had multiple carbs of various sizes for that many years.
The line up of what I’ve had has changed a bit through that time.

The easiest way for me to determine if the carb problem is actually a carb problem is to bolt on a “known good” one.
If the problem goes away....... it’s a carb problem. If it doesn’t...... it’s something else.

All of my Holley style carbs have 4 corner idle.

I just noticed this:
64 jets
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Unless the primary Venturi is the same as a 600, those are really small jets for a 750.
I tried looking it up on the Holley site, but the “specs” tab doesn’t seem to be working for me.
But if the carb really comes with 64 primary jets, it’s an indication to me that the fundamental calibration of the carb is probably not a great match for the combo being discussed here.
 
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PRH said:
This won’t help a lot of people........... but it’s how I’ve isoltated “carb problems” to being either that....... or something else, for over 30 years.

I’ve had multiple carbs of various sizes for that many years.
The line up of what I’ve had has changed a bit through that time.

The easiest way for me to determine if the carb problem is actually a carb problem is to bolt on a “known good” one.
If the problem goes away....... it’s a carb problem. If it doesn’t...... it’s something else.

All of my Holley style carbs have 4 corner idle.

I just noticed this:


Unless the primary Venturi is the same as a 600, those are really small jets for a 750.
I tried looking it up on the Holley site, but the “specs” tab doesn’t seem to be working for me.
But if the carb really comes with 64 primary jets, it’s an indication to me that the fundamental calibration of the carb is probably not a great match for the combo being discussed here.
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Main jet size can be that small IF the calibration uses a really small main air bleed or almost no emulsion or both. Unless you pin one you never know what they are doing.
 
PRH said:
How was it determined that one turn from seated was the proper adjustment for the mixture screws?
Have you tried adjusting them?

My presumption going into it would be that a [email protected] cam and exhaust manifolds would be a challenge for many 2 corner idle carbs, and that they’d be lean at idle.
I’ve had to run the mixture screws out 2-3 turns in similar combos.

If opening the mixture screws increased the idle speed, it would let you close the throttle blades.

As far as carbs are concerned, the main thing advancing the initial timing does is increase the vacuum.......Which helps draw fuel out of an idle circuit.

In any case...... fiddling with the mixture screws is easy and free.
Click to expand...

You bring up a valid point. I can’t remember if I tried messing with mixture screws due to attacking this situation with the mind set being that the car wanted more air, not fuel since it appears to be running rich at idle.

but it’s worth a try.

PRH said:
This won’t help a lot of people........... but it’s how I’ve isoltated “carb problems” to being either that....... or something else, for over 30 years.

I’ve had multiple carbs of various sizes for that many years.
The line up of what I’ve had has changed a bit through that time.

The easiest way for me to determine if the carb problem is actually a carb problem is to bolt on a “known good” one.
If the problem goes away....... it’s a carb problem. If it doesn’t...... it’s something else.

All of my Holley style carbs have 4 corner idle.

I just noticed this:


Unless the primary Venturi is the same as a 600, those are really small jets for a 750.
I tried looking it up on the Holley site, but the “specs” tab doesn’t seem to be working for me.
But if the carb really comes with 64 primary jets, it’s an indication to me that the fundamental calibration of the carb is probably not a great match for the combo being discussed here.
Click to expand...

the initial carb that was on it was originally on a 70 polara with a 440, 727, 3.23. And it ran okay. That car did not have the same idle issue as this. I don’t know if that means the AVS can be considered a good carb, but it didn’t give me problems on the other car.

holleys site said for the application their 750 carb would work for this. According to the specs I found on their site this carb comes with the 64 jets. What I found in the FSM is that the holleys on 440s also got 64 jets. Now I don’t know what cfm those were rated at, but seeing that both oem and this carb had similar size jets made me think that these okay for the same application
 
Rat Bastid said:
No ****? Seems like he says he’s done all that. Or going to do it.

Licensed mechanic. That’s a joke.
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Seems like?? going too?
Well until he "has" or he's "sure", then he would be wise to heed my advice.. but that's up to him in the end..
Again, this is why I have a license to trade , and you don't..
 
Bakerlite said:
Seems like?? going too?
Well until he "has" or he's "sure", then he would be wise to heed my advice.. but that's up to him in the end..
Again, this is why I have a license to trade , and you don't..
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The difference is I don’t think everyone on here is an idiot. I assume the basics have been done.

WTF?? Your license doesn’t mean ****. Get over yourself.
 
Rat Bastid said:
The difference is I don’t think everyone on here is an idiot. I assume the basics have been done.
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LOL, no, you just think 95% are idiots..you suck up to the rest..Your posts are full of disparaging comments..
And assumptions lead to mistakes..
 
I guess I should have been more specific.
“Known good” for the application at hand.
A known good 1bbl off a slant six might run great on a stock 225, but isn’t going to work on your 440.

Lumpy cams that produce lower vacuum are often problematic for carbs not calibrated for that situation.
Add exhaust manifolds into the mix, and the idle mixture gets diluted with residual exhaust, exasperating the issue.

Part of why I have a variety of carbs is to have something that’s both “known good”, and a good match for the application.

If you have a friend with a similarly set up engine to yours, that’s not having those idle issues........ maybe they’d let you try their carb on your engine.
Or, try you carb on their engine and see if the motor is still happy.
 
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carfreak6970 said:
holleys site said for the application their 750 carb would work for this. According to the specs I found on their site this carb comes with the 64 jets. What I found in the FSM is that the holleys on 440s also got 64 jets. Now I don’t know what cfm those were rated at, but seeing that both oem and this carb had similar size jets made me think that these okay for the same application
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I bought a new Holley "Brawler" that spec-wise is pretty much identical to what you posted above - 750 CFM, vac 2ndary, electric choke, etc. It came with 72 jets. I bolted it straight on and the car fired right up and idles clean. AFAICR all the 750s I've ever owned came with 72 jets in them, 3010s, 80508s, and now this Brawler. But, they were all 4150s (dual inlet) and yours is a 4160. Take that for what it's worth.

If it was me, I would take the carb off, flip it over, and open both the primary and secondary throttles to where the part of the transfer slots you can see are square, and give it another go round. I would also not shy away from giving it all the timing it wants, but would definitely install a mechanical advance limiter plate once I had the initial figured out.
 
But, they were all 4150s (dual inlet) and yours is a 4160.
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Just to clear something up...... 4150/4160 is not determined by single or dual feed bowls.
4150’s have secondary metering blocks, while 4160’s have secondary metering plates.

For example, current 3310’s have secondary metering plates, and even though they are dual feed, they are still 4160’s.
 
Okay, so it appears having that much initial is not as terrible as I thought it was, I just need to find a way to close the throttle blades...

Now should I be concerned with the high compression test numbers? should I remove the head and determine what the actual compression ratio is? Would having over 11:1 compression ratio with iron heads be bad? Why would I need to run race fuel if it is?

Again thank you all for your help
 
Like I said, until you FIX the throttle blade issue anything you do means nothing.

Get the blades closed and then sort out the idle circuit and THEN worry about your initial and total timing.
 
Barry Grant/Demon carbs were a crapshoot at best as to whether or not you got a good one ootb.
However, one thing I think they got right was in how they outlined some criteria for the different carb series.
One of those criteria was camshaft duration @.050.

The milder series were listed as suitable for cams under [email protected].

My take on the OP’s carb is that it probably falls into that catagory.

Imo.......At this point, the carb not being the root cause of the running issues has not been eliminated.
And until it is, you don’t really know if you’re dealing with a carb problem....... or something else.

I’m confident I could get a 440 with an XE274 cam and what I would consider a correct carb(something with 4 corner idle), to idle just fine with 15-20* initial timing at around 850-900rpm in neutral(provided there aren’t other “issues”).
How tight the converter is would play a big part in what you’d have to do for decent “in gear” idle speed and idle quality.

Fundamentally, higher CR will make the idle characteristics “better”.
 
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Realistically, 4 corner idle should just be the norm when you purchase a carb today.
 
After watching the video of this engine idling, I'm curious if the timing is stable. If the distributor has light springs, the advance could be bouncing and that would make the idle hunt up and down. A quick check with a timing light would either prove that condition or rule it out.
 
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