M-1 Intake Manifold

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Hello. I just picked up a M1 single plane and don't understand why you are using "adaptors" or modifying the shape when it's drill for a Holley carb anyway?
 
Retroboy said:
Hello. I just picked up a M1 single plane and don't understand why you are using "adaptors" or modifying the shape when it's drill for a Holley carb anyway?
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The smoother the transition is from the carb venturi to the plenum, the better the better the airflow will be. Welding with contouring and adapters in this case can minimize the "ledges" the airlow has to go past. Airflow gets turbulent around sharp corners.
 
Retroboy said:
Hello. I just picked up a M1 single plane and don't understand why you are using "adaptors" or modifying the shape when it's drill for a Holley carb anyway?
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The M1 has that opening designed for spread-bore carburetors, If that was the style carb you’re using you’d just remove the 90 degree edge, round the transition of the sides of the opening, round it over,blend it all with the roofs of each runner. If you’re using a square-bore carb you’d still do the same, or weld and shape it to a square-bore opening (or epoxy and shape like others have done) Some have the will, the tools and time, others maybe the money to have it done, others may just prefer to bolt-on and go. Your choice:)
 
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I'm running a flyweight car with a 360, small solid roller, 5300 converter, 4.3 gears, I run it from 5000 to 6800. For my own reasons I have just taken off a single butterfly injector running methanol and sticking a toe in the water with a petrol carb. I reckon I will just use it as is and if I think it's lacking I might try a tapered 4 hole spacer.
 
im in the same situation. i port matched my M1 to the heads and laid a square bore holley gasket over top of the intake and ground out any thing that was in that opening and going to dyno my engine next week trying the phenolic spacer both open and 4 hole and see what it likes.
 
Locomotion is correct. There is a gain.
I've done this, and it seems there's an average of a 4 cfm gain on each runner. Depending upon how the runner meets under the carb.
They're not all the same.
 
EddieSketti said:
im in the same situation. i port matched my M1 to the heads and laid a square bore holley gasket over top of the intake and ground out any thing that was in that opening and going to dyno my engine next week trying the phenolic spacer both open and 4 hole and see what it likes.
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in my mind i think the fact that you port match your intake and use a phenolic spacer will make up for welding up your intake and all that stuff LOL
 
EddieSketti said:
im in the same situation. i port matched my M1 to the heads and laid a square bore holley gasket over top of the intake and ground out any thing that was in that opening and going to dyno my engine next week trying the phenolic spacer both open and 4 hole and see what it likes.
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in my mind i think the fact that you port match your intake and use a phenolic spacer will make up for welding up your intake and all that stuff LOL
 
EddieSketti said:
in my mind i think the fact that you port match your intake and use a phenolic spacer will make up for welding up your intake and all that stuff LOL
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If you blow the carb Mount out you remove the radius to the runner. Power loser every time, unless you run an anti-reversion plate.
 
K.O. SWINGER said:
I ran a m1 single plane on the street with the hot 340 509 purple shaft and modified TQ over 10 years it was a killer manifold and combined with 391 rear end it didn't seem to lack for anything. I now run a six pack now but I keep my m1 on the shelf so if I ever go back to a single 4 setup just use a adapter some are only a piece of 16 gauge steel.
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Do you have a part number or casting number for that M1 manifold. I'm looking to put an M1 on my 340 LA heads but can't get an accurate part number or casting number. Thanks
 
John K said:
Do you have a part number or casting number for that M1 manifold. I'm looking to put an M1 on my 340 LA heads but can't get an accurate part number or casting number. Thanks
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Yes it's still on the shelf I will get that to you in a little while.
 
Here is a part number of my m1 hope it helps.

IMG_20220910_101619816.jpg
 
Thanks have a 893 M1 & it fits standard heads.
John K said:
Thanks, this is the manifold I see available, but not the 891. According to some on this thread, it's not one of the two that will fit my car. I assume it's because the bolt spacing is different. Thanks for the follow up.
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Since this thread came up, and I haven't installed the engine yet, I will show what I did. I opened the top slightly, and radius the opening. I drilled and tapped for a coolant sensor or nipple for a heater hose. There is a boss in the coolant passage, I drilled through it and installed pipe plugs for now. It will be getting a nitrous plate and a 2" spacer.

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12many said:
Here’s the one I reworked with epoxy. I first straightened the sides of the carb base opening so that there would be one continuous piece of epoxy (instead of the two slivers on the secondary side along with the piece for the primary side) I also drilled a series of holes in the perimeter and drove in thin alloy round stock as “pins” as well as dimpled the surface for better grip so that there would be no way the epoxy could ever break off and be ingested. Haven’t gotten around to trying it out yet.

View attachment 1715637280

View attachment 1715637281
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I’ve done it without the dowel pins…

I broke off one of the 4 moon slices. I shut down immediately and by total luck the pushrod popped out clean when it hung open a valve.

took it off, checked everything, re-lapped valve. Remove ALL the epoxy work….been that way for years.

Would like to get it welded.
 
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Looking for a M1 for la block if anyone has one for sale. I have a airgap to get rid of.
 
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