I am assembling a 340 engine and have a M-1 intake laying around I was going to install. Is it worth the time to weld up the spread bore flange to a 4150 style ? Have a 700 Holley carb to use
M-1 Intake Manifold
- Thread starter Sterling
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ChargedDart75
Well-Known Member
What about a square to spread bore adapter?
That is possible, but I am not sure how the carburetor to hood clearance might be
ChargedDart75
Well-Known Member
I think they're less than an inch, so you might get away with a drop base air cleaner.
Is it the big single plane? I read a post that welding the pad up makes some flow/hp improvement. I don’t remember but I think it was @pittsburghracer. But I think it more depends on the rest of the engine and car what you’re going to do with it that determines if you need to look into a different intake.
K.O. SWINGER
Meeting in the alley since 1976
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.
It is a street engine, I am putting together with parts I have laying around. .030 over 340, Speed Pro replacement pistons, stock steel crank and rods, a set of X heads, a old Direct Connection solid lift cam and the M-1. Probably not the best intake, but this is a budget build and use some of the parts I have. Thanks for the replies.
K.O. SWINGER
Meeting in the alley since 1976
Don't make the mistake of underestimating an m1 single plane it was the bar that all other small block Mopar manifolds were measured by including a Victor Jr, you would be hard pressed for your combination to beat it with any other manifold especially if you have 391s or steeper rear ratio. And in a combination like yours will make more horsepower and torque above 4600 RPMs just about anything
K.O. SWINGER
Meeting in the alley since 1976
Here is a quick pic of my old setup it all fit under the hood of a 340 swinger. Though I believe dusters don't quite have as much room. Also in the photo is a adapter plate for square bore carburetor.
Locomotion
Well-Known Member
I've run a Holley Strip Dominator, which is very similar overall, including a spreadbore pad. Some say it was basically copied my Mopar Performance. I wouldn't worry about welding it up even though application was race only with a lot more gear. converter, head flow, etc. I also ran a Canton 1" 4-hole tapered spacer. I tested a Weiand Stealth against it and it was about a tenth slower, even after optimizing the jetting. Your milder application may not see as much difference. But the M-1 single plane is a good intake. Focus on tuning the carb and don't use an open spacer. You already have a generous plenum and don't want to give up anything at the bottom.
turboking15
Well-Known Member
Ive converted both of my M1 single plane manifolds to a 4150 flange. I will do it on every single one i run, but i have the ability to do it all myself. If its on a mild street car i dont know if the cost would justify the gains.
Follow the MP books modifications with air/fuel damns placed on the floor of the intake. These mods are to help balance out the intake when used with a Holley carb. Then there should be no problems.
Your overall combo should be considered and that includes the car and it’s weight.
The MP-M1 single plane was a basic copy with improvements over the Holley Strip Dominator. According to MP. So it will perform at least as well in the 3500-7000+ rpm range. It is more so a strip intake manifold than a street unit. If your concerned with around town low rpm driving, sell/trade the M1 for a RPM/LD340 or Stealth/Action Plus. These 4 intakes are excellent power makers that work awesome on the street.
Your overall combo should be considered and that includes the car and it’s weight.
The MP-M1 single plane was a basic copy with improvements over the Holley Strip Dominator. According to MP. So it will perform at least as well in the 3500-7000+ rpm range. It is more so a strip intake manifold than a street unit. If your concerned with around town low rpm driving, sell/trade the M1 for a RPM/LD340 or Stealth/Action Plus. These 4 intakes are excellent power makers that work awesome on the street.
K.O. SWINGER
Meeting in the alley since 1976
My combination was on a 3100 lb swinger 4 speed 340 car I ran gear ratios from 355 to 430. I ran both an ld340 and a stealth manifolds prior to my m1. my car was 100% Street and the m1 was just Superior really didn't care about under 3000 RPM performance ,with the thermaquad combination it never seemed to be an issue. Throttle response on the m1 was beautiful in a whiplash kind of way!
yellow rose
Overnight Sensation
I always weld them up. It’s worth 12-15 HP and it’s a ton of work to do it correctly. The gains come from getting the distribution closer between the cylinders.
Someone...it may have been @12many or maybe it was @MoparSam who modified the top without welding. It turned out very nice.
If you are wanting to pick the fly poop out of the pepper then weld it up. If not...send it.
Someone...it may have been @12many or maybe it was @MoparSam who modified the top without welding. It turned out very nice.
If you are wanting to pick the fly poop out of the pepper then weld it up. If not...send it.
I think it may have been IQ52, but I can't find the thread...
Edit, starting with post #80 in this thread. T.N.A.C.C.B.P.P. EQ360
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QuickDart360
Well-Known Member
I run a Victor 340 intake with and adapter to use my 850 thermoquad and bam it has instant throttle response. It outperformed the airgap that was on my 360 before. It just rocks!!
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.
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IMO, this is how and what that intake should have been. I get the TQ pattern for certain classes, but in racing all other classes, a Holley is going to be used. These are good intakes that can be made better. They can become excellent units. Again, IMO, it’s a shame that MoPar didn’t go there with an updated intake manifold and that they have stopped supporting grass root guys in favor of the modern HEMI engine.
yellow rose
Overnight Sensation
HA!! I did remember it was you. The intake turned out dang nice which is why I remembered it.
EddieSketti
Well-Known Member
i guess I'm lost here can't you just lay a 4150 gasket over top of the intake trace it out and then die grind it and done
Because a M1 single plane is a spreadbore intake designed for use with a TQ carb the secondary side is way wider than the Holley 4bbl. You can grind away what is not there to begin with. Also the quality of aluminum could be of question.
All other intakes for the 4bbl will have the normal square bore for the normal Holley/Carter design.
Is there a big horse power gain by welding this up over using an adapter plate?
I’ve read it’s worth 15 hp or so but can’t say I’ve ever seen reports of gains using an adapter on the spread bore opening on this intake. If it was comparable I’d still rework it to a square bore whether using an adapter (which likely would be even better) or not, especially for those with hood clearance concerns.
I found the adapter plates that I will use with this manifold. Started the engine, but not happy with the piston to cylinder wall clearance.
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