10 Day Magnum Swap - '65 Dart 270

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DionR said:
Here is a link to a post I made about the same issue with a picture. 5.9magnum questions

In the thread I mentioned that I only had the exhuast port issue with the MP R/T heads and not the factory heads my buddy had laying around. My issue was because the material around the port stopped just below the port, but the factory head was cast all the way to the deck surface and then machined. Not sure if this changed, but I assumed it wasn't an issue with any of the factory heads, only the aftermarket R/T head. Not sure what the EQ heads look like, either.
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Okay that is helpful. I have stock heads but plan on going with EQ's. Anyone know if they work with the stock la manifolds?

Thanks again!
 
ValiantOne said:
I have stock heads but plan on going with EQ's. Anyone know if they work with the stock la manifolds?
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Based on the picture shown on Jeg's website, I would say you will have the same issue. JEGS EngineQuest Mopar Magnum Cylinder Heads | JEGS High Performance

I don't think the cast iron HP manifolds have a different exhaust opening than a standard low performance manifold, so I would guess that any A-Body exhaust manifold used on an R/T, EQ or similar head would have this issue. I know there are two LA exhaust gaskets, the pressed metal one and the fiber one, but I don't know if the opening is different between the two. Regardless, I am pretty certain that no matter what manifold is used, if the fiber gasket is used with it, there will be a leak at some point in time.
 
DionR said:
Based on the picture shown on Jeg's website, I would say you will have the same issue. JEGS EngineQuest Mopar Magnum Cylinder Heads | JEGS High Performance

I don't think the cast iron HP manifolds have a different exhaust opening than a standard low performance manifold, so I would guess that any A-Body exhaust manifold used on an R/T, EQ or similar head would have this issue. I know there are two LA exhaust gaskets, the pressed metal one and the fiber one, but I don't know if the opening is different between the two. Regardless, I am pretty certain that no matter what manifold is used, if the fiber gasket is used with it, there will be a leak at some point in time.
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The magnum gaskets are exactly the same as the 318/360 ports with the EXCEPTION of 340 HP. I have downloaded a photo of the 318 drivers side from my 67 GT Vert we just yarded for 5.9 magnum swap. We sell 4-5 pairs of EQ's a week and use them on almost all our cars and they are the same as magnum head with gasket match. we also beat Jegs on price and quality.

318 exhaust.jpg
 
magnummopar said:
The magnum gaskets are exactly the same as the 318/360 ports with the EXCEPTION of 340 HP. I have downloaded a photo of the 318 drivers side from my 67 GT Vert we just yarded for 5.9 magnum swap. We sell 4-5 pairs of EQ's a week and use them on almost all our cars and they are the same as magnum head with gasket match.
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I stand corrected.

Felpro shows a 318 specific gasket for motors '74 and older (MS9939), and a different one for 340/360 motors of the same vintage (MS90460). After '74, all 318/360 motors use the same gasket as the 340/360's did in the prior years (MS90460), until the Magnum motors hit the scene. The magnum motors use a different gasket (MS95480), too.

Based on this, I can see why you would say the 318 and 360 share the same exhaust port, and I would probably agree provided you mean 360's produced after 1974. In '74 and earlier, there was a different gasket, and I would argue that the 340 and 360 are the ones that share an exhaust port. It's possible that Mopar didn't change the port at all after '74 on the 360's, but just used the same gasket on the 318/360 regardless of the port size or mismatch, but I would bet that the port did change and you are right that those year 318 and 360 share the same size exhaust port.

Regardless of the above, if you buy an exhaust gasket for a pre-Magnum smallblock and run it on a non-OEM Magnum head, you will have the issue I ran into. The gasket they sell for the '78 318 is the same one they sell for a '69 340, and is the same one I showed in the picture in my link. That gasket is too long and will not have a surface to seal against on a non-OEM head, regardless of what manifold is used.

But, what you are doing makes sense. If my above extrapolations are correct (a stretch, I know), all 318 manifold and '75 and later 360 manifolds will work well for the swap, regardless of what head is used, with the need to use a magnum gasket being the only real "gotcha".

On a side note, I think the Magnum has proven that the 340 exhaust port isn't necessary to make power. Which makes me think the only real advantage to the driver's side "freeflow" HP manifold is the size of the outlet (2 1/4" vs. 1 7/8" I think?). And I understand that the passenger side freeflow is equaled by a Magnum manifold. So, maybe I could dump the sheetmetal adapters I am running by moving over to a passenger side Jeep manifold (fits better than a Dakota), and opening up the outlet on a 318 driver's side manifold. Then I could sell the expensive HP manifolds and end up with a better package (no adapters) and some cash in my pocket. :D
 
Check this out, just pulled the "fresh" teener out of my 67 Vert and guess what, they used the "big" gasket on it and it was leaking! I also included a magnum manifold just so you can see they are same. The pic of 318 manifold I posted earlier came off this engine, look how it was leaking due to 340 gasket.

gasket leak.jpg


5.2 exhaust.jpg
 
magnummopar said:
Check this out, just pulled the "fresh" teener out of my 67 Vert and guess what, they used the "big" gasket on it and it was leaking! I also included a magnum manifold just so you can see they are same. The pic of 318 manifold I posted earlier came off this engine, look how it was leaking due to 340 gasket.

View attachment 1714952175

View attachment 1714952176
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I'm using large port manifolds on the small port heads and had the same issue with no gaskets, had to go with the small steel mesh I had on hand.... It did stop the leaks though.
 
I have a set of Schumacher headers that they "claim" fit the magnum but they are big port size....$750 for **** that doesnt work is what drove me to make headers for the 67+ A bodies. We will see if I can get them or the early A ones reproduced for a reasonable price....
 
magnummopar said:
Check this out, just pulled the "fresh" teener out of my 67 Vert and guess what, they used the "big" gasket on it and it was leaking! I also included a magnum manifold just so you can see they are same. The pic of 318 manifold I posted earlier came off this engine, look how it was leaking due to 340 gasket.

View attachment 1714952175

View attachment 1714952176
Click to expand...


So was the 340 head used with the hi-po manifolds a different port size?

I am just trying to figure out if my combo (1968 pass side 340 and 1971 dr side 340 exh mannies) will work on EQ heads? (without some sort of quasi-fix)

If not I am terribly bummed as I went this route now (manifolds, complete exhaust system) on my 273, in anticipation of my eventual 360 mag, EFI upgrade.
 
ValiantOne, I am by no means an expert on old school mopar HiPo parts but the 340 HO manifolds I have seen have a much taller exhaust port and it appears that the height was taken from the floor of the exhaust port. I have lots of gaskets around here from various LA builds, Fel Pro, Mopar, header supplied etc..I only know of two exhaust gaskets, standard and tall port. Just my personal exp and by no means accurate or complete, I am a magnum guy and I know them very well but some of the early stuff eludes me. I have compared 273 and 318 since I have a few of each here and they are as close as a "gasket match" ie not more than about 1/8" all the way around in size difference while the HP 340 are more like 3/8" but mostly on bottom of port, taken from looking at gasket not actual manifold
 
when I die I want to be creamated and put in a bottle of douche so she can run me thru 1 more time LMAO
 
a set of earley A bodie headers at a reasonable price THAT FIT RIGHT ha hahaha ha ha ahhahahahaha get it all together thenI"ll buy your car for 12k 10, 000 is drivetrain 2k is headers the math don't work no more SCREW the body and paint get a strong chassie drop in the drive train and letter buck
 
How is this build coming? Also who built your custom radiator?
 
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