440 issue after swapping to aluminum heads, need advice

66Satellite47

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Actually the 440 Source heads have smaller combustion chambers than the Edelbrocks.
All depends on which model you are comparing. My point was the OP was not referring to EDE heads. The Source heads are advertised as 80cc. I do agree the Source heads would be a smaller chamber than most all OEM iron heads.
Edit: And the aluminum head should reduce detonation.
 
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Cheapsunglasses

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That one there looks like it would be good for a return visit or 5...

Just put the wrong address down and It’ll come back:bananadance:
 

moperformance

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If I may be so bold as suggest that it's acting imho like a vacuum leak? At least rule it out first. maybe the new heads and intake aren't sealing properly. What if the old heads and current intake were matched after being cut down, etc? I've seen worse things over the years. Any way take carb cleaner and spray it around where the two surfaces join (with it running of course). Any increase in rpm's ........ 2) swap out the dist first than coil. Problem still there? 3) not knowing where tdc is really isn't an option. granted pulling #1 plug and valve cover is a pain but not near as much as all you've been through. You can stick the marks on hb and timing chain cover where ever it's easy to see. But u gotta know where/when to put them. Change one variable at a time.
Good luck!
 

Cheapsunglasses

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If I may be so bold as suggest that it's acting imho like a vacuum leak? At least rule it out first. maybe the new heads and intake aren't sealing properly. What if the old heads and current intake were matched after being cut down, etc? I've seen worse things over the years. Any way take carb cleaner and spray it around where the two surfaces join (with it running of course). Any increase in rpm's ........ 2) swap out the dist first than coil. Problem still there? 3) not knowing where tdc is really isn't an option. granted pulling #1 plug and valve cover is a pain but not near as much as all you've been through. You can stick the marks on hb and timing chain cover where ever it's easy to see. But u gotta know where/when to put them. Change one variable at a time.
Good luck!
Thank you for the suggestions, however I’ve done that and there’s no apparent vacuum leak. I believe I had 2 issues different issues acting together.

1. I believe there was an issue with my avs, someone pointed out the 1971 variant runs leaner, which makes sense emissions crap and all. So I’m using an afb, that solved that issue of strange afr bounces.

2. The 3k rpm cut out, that seemed ignition related, and a few members pointed out some things, one being to disconnect the vacuum advance and see what happens. I did that, and now it’ll rev to 5k rpm without issues.

Thanks for the reply!
:thumbsup:
 

Moparfever65

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Sounds like you have the vacuum advance connected to the ported vacuum rather than manifold vacuum. You'll find quite a debate online as to which port to connect to, but when connected to manifold vacuum you get easier starting and better fuel economy in part-throttle cruising. When you stomp on it the vacuum advance will drop decreasing the chance for detonation. When you connect to ported vacuum you can get too much advance with rpm, causing the problem you see. Of course it all depends on the mechanical curve and diaphram springs as well.
 

Geoff 2

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Sorry, this ^ is incorrect.
[1] Once cruising, there is no difference between PVA & MVA, as they receive the same vacuum.
[2] Because of [1] the cruise economy is the same for PVA & MVA.
[3] Added ign advance would be the same for PVA & MVA. VA is not rpm sensitive.
[4] PVA or MVA doesn't change how easy [ or hard ] the engine starts.

More on MVA benefits, scroll down to post #6.

www.hotrodders.com/forum/vacuum-advance-hooked-up-directly-manifold-bad-47495.html
 

Nxcoupe

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I'll try to help, but I need answers to some questions first.
What camshaft is in the engine?
How far back, in feet, is your sensor from the manifold flange, or is it headers? And a note, it's mounted upside down. Should always be in the too 180*.
Measure the diameter of your balancer, order a timing tape from Summit, I use them exclusively, wipe balancer surface down with brake clean a couple times and then apply the tape. Line it up with your tdc mark. I usually verify tdc before I do this. I peel the part with tdc mark first, stick that on even with tdc mark and then slowly peel and stick all the way around the balancer, use a breaker bar and socket to rotate the balancer as you apply.
Set your total timing to 32 to start with. This is with the vacuum line off the vac advance port.
Answer tge questions for me first and then we'll talk about your WB readings.
 

Cheapsunglasses

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I'll try to help, but I need answers to some questions first.
What camshaft is in the engine?
How far back, in feet, is your sensor from the manifold flange, or is it headers? And a note, it's mounted upside down. Should always be in the too 180*.
Measure the diameter of your balancer, order a timing tape from Summit, I use them exclusively, wipe balancer surface down with brake clean a couple times and then apply the tape. Line it up with your tdc mark. I usually verify tdc before I do this. I peel the part with tdc mark first, stick that on even with tdc mark and then slowly peel and stick all the way around the balancer, use a breaker bar and socket to rotate the balancer as you apply.
Set your total timing to 32 to start with. This is with the vacuum line off the vac advance port.
Answer tge questions for me first and then we'll talk about your WB readings.
Thank you for offering your help, but I think I have it figured out!
 

Moparfever65

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Ported vacuum is created by the venturi effect of air velocity through the carbs bore. The higher the velocity, the higher the vacuum. It's considerably different than manifold vacuum. Advance connected to manifold vacuum gives you more advance during idle which gives you smoother idle, then retards during cranking making it turn over easier. You would run less initial mechanical in this setup. You still have to run curves that make everything work together. It's easier to just go strictly mechanical on a hot rod.
 

4speed68rt

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So, what was the solution to the problem? Disconnecting the vacuum advance completely? Now you are running without vacuum advance?
Enquiring minds want to know!!
 

Cheapsunglasses

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So, what was the solution to the problem? Disconnecting the vacuum advance completely? Now you are running without vacuum advance?
Enquiring minds want to know!!
Well if you must know enquiring minds, the solution for now is running without vacuum advance. If I need to start a separate thread in the distributor section I will.

Or I’ll ask here, does anyone know how to tune a Mallory unilite?
 

Lefty71

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Or I’ll ask here, does anyone know how to tune a Mallory unilite?
I do not know the specifics... possibly Halifaxhops can shed some light?? He's been very helpful with ignition component related issues.
Typically you have an initial timing setting at startup and low idle, then mechanical advance should kick all in by maybe 1500rpm?? (this is with vacuum advance plugged). And then of course with vacuum advance hooked up you would see further timing advance at higher rpms.

I don't remember seeing your results if you gave them earlier?? Would be a good starting point.... One other thing to bear in mind, if the vacuum pod failed by actually ripping the diaphram, that would become the vacuum leak everyone questioned you about, although I think that situation is quite rare, you may want to check into it. Maybe carefully with a Mity-Vac brake bleeder or similar device....
 

Cheapsunglasses

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I can not stress this enough, I do not have a vacuum leak! Not in the intake, not in the carb. Thanks for the help, but please stop with the vacuum leaks, lol.

As soon as I took the avs off and put a different carb on everything was fine with the AFR. I have a 440 afb on it, it might be a little rich at rpm, but that can be taken care of with a little carb work. That’s over with.

Now I’m dealing with the distributor. Plugged to ported vacuum I can’t rev past 3k rpm without it cutting out. Disconnect it and problem gone. So now I need to dig into that

Thanks again for the advice!
 

Cheapsunglasses

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If I need to I can make a new thread in the ignition section to avoid any further confusion
:thumbsup:
 

69a100

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69a100

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:thankyou:. This is real deal old Mallory, I don’t know the year, one of my cheap swap meet finds. That’s what I like about Carter carburetors and Mallory ignition, you can score them cheap at a swap meet.

What happens at a lot of swap meets is old modified raced parts are sold. Racers do not need a vacuum advance. So many put an aggressive timing curve into them. A lot of them are done with home brewed ideas. The way you were set up for all you know you could of had 50+ degrees of total advance. A decent dial back timing light is a tool you should use. Never forget basic 101. Timing first when tuning. Once you train yourself to be step by step systematic you will diagnose and solve your problem. I am glad you tried my suggestion. To many just ignore whats in your face and keep asking for help. Intakes, carburetors, fuel pumps, ignition boxes would of never helped your issues.

Well if you must know enquiring minds, the solution for now is running without vacuum advance. If I need to start a separate thread in the distributor section I will.

Or I’ll ask here, does anyone know how to tune a Mallory unilite?
After going back a few days and reading, this is what I would do. If you don't know what's been done internally to the dist. being a swap meet unit. I would pull it, strip, clean, and rebuild it back to Mallory's stock spec's and go from there and work any bugs as needed. Which I bet will be that advance. Good Luck
 

4speed68rt

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Thanks for sharing the solution. The distributor that I am running does not have a vacuum advance. I guess you don't need one. Just my opinion.
 

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