Thinking of switching from M1 single plane to LD340 but LD340 would need to be milled to fit. Is it worth it?

-

MobileCustoms

Well-Known Member
Joined
Oct 21, 2013
Messages
1,730
Reaction score
1,916
Location
Rush City, MN
Hi Guys,
So I'm doing a bunch of maintenance stuff on my car and have the drivetrain with front suspension out right now. My car came with an M1 intake on it and that's what I've been running for a few years (street driven) just because it was easiest affordable option at the time of my build. I've been sitting on a LD340 intake for several years and figured now is the time to swap it out, but my J heads were milled down, so the LD340 would have to be milled down too so the bolt holes line up.
My question is: Will I gain enough noticeable improvement by doing the swap to warrant having the intake modified, or should I just stick with the M1 intake for now?

340/416 stroker with mildly ported 2.02 intake valve J heads and no hardened seats, so I know they probably won't last forever.

Thoughts?

EDIT: after further findings, the LD340 does NOT need to be modified to fit. Read through the thread.

Thanks!
-Doug
 
Last edited:
Hi Guys,
So I'm doing a bunch of maintenance stuff on my car and have the drivetrain with front suspension out right now. My car came with an M1 intake on it and that's what I've been running for a few years (street driven) just because it was easiest affordable option at the time of my build. I've been sitting on a LD340 intake for several years and figured now is the time to swap it out, but my J heads were milled down, so the LD340 would have to be milled down too so the bolt holes line up.
My question is: Will I gain enough noticeable improvement by doing the swap to warrant having the intake modified, or should I just stick with the M1 intake for now?

340/416 stroker with mildly ported 1.02 intake valve J heads and no hardened seats, so I know they probably won't last forever.

Thoughts?

Thanks!
-Doug
I really hope you meant 2.02 intake valves in your heads... :lol:
Personally, I would have the heads' manifold surfaces cut instead of cutting the manifold. That way you can run any unmodified manifold you want without having to repeatedly have manifolds remachined.
 
I really hope you meant 2.02 intake valves in your heads... :lol:
Personally, I would have the heads' manifold surfaces cut instead of cutting the manifold. That way you can run any unmodified manifold you want without having to repeatedly have manifolds remachined.
oops, yes, 2.02. My bad! Corrected. I'd rather just keep the current M1 setup that to pull and shave the heads at this point.
 
If your gonna use the ld340 then mill the intake surface on the heads like they should have done originally, but don’t cut the intake. I doubt you’d find any advantage with the dual plane in that combo. I’d keep running the M1 in your shoes.
 
It really depends on the rest of your drivetrain setup, gearing, vehicle weight, and camshaft, but I honestly think the only thing the LD340 would do over an M1 single plane (which is an improved copy of a Holley Srip Dominator) on a 416 stroker is make the car go slower than what it is now, even with unported J heads...
 
Doug, going from an M1 to an LD340 is a major jump. Problem is you have yet to tell us what you plan for the car.
It’s like wood working- cutting plain Jane 2x4 then you use a 24 tooth blade. But cutting 1x6”oak for trim then you want a much finer blade like 80teeth.

It sounds like the M1 did not work well- my question is “why?” Going to an LD 340 (my fav intake) will also give issues. Both have their qualities and low points. Maybe send us some more info like street and full interior. Race only. Street racing or gear ratio and transmission. You get what I mean. The more info you give the better we can weigh in on this properly. Otherwise “opinion” means just that.
Syleng1
 
The fellas are on target there. We are missing a bit of information. Here is what I’m looking for;

Camshaft duration @050
Car Weight
Gear ratio & tire size
 
I appreciate the input, guys.
I decided to get a good night's sleep and look at it again this morning as well as provide some more info. I set the M1 back on it to compare and that was also a challenge to get the bolts started again on both sides. Turns out it was user error. (surprise, surprise!) I think the thin layer of gasket maker was just enough to make it too difficult. My bad. PS, I had not used the end gaskets either. I cleaned the gaskets off completely and did a dry fit. I also discovered that the center 4 ARP bolts had been cut just enough to allow clearance in the M1 intake runners but they had NOT been re-chamfered to a taper. Duh...
Once I gave them a taper, I was able to get them all started and ran in so then I swapped on the LD340 again and was able to get the bolts threaded in that intake as well. You can tell that I don't do this stuff often enough so have a laugh on me for that one.
I ordered a new set of gaskets and will again ditch the end pieces. I had already removed the location pins before as well. (the M1 does have location holes in it though but the LD340 does not)

So now the question is really just which intake to go with, as they both actually fit. I'll plan to also get some Permatex copper spray to hold the gaskets in place this time.

More info on my setup and use:
'67 Notch with full interior, sound deadener, etc. It's not a lightweight car and has US Cartools frame ties. I haven't weighed the car yet.
340/416, 727 reverse manual valve body with 4400 stall converter and currently has 3.73 gears but my plan is to go to 3.91 or 4.10 with the addition of a Gear Vendors overdrive which is on order. I also have a set of 4.56 gears for real fun. Rear tires are 295/55/15
Molnar crank with Autotec dished pistons and 4.080 bore.
Solid roller rockers with the geometry correction kit from B3 Racing
I've attached the cam sheet and engine specs for reference.
Engine Dyno showed peak horsepower of 516 @ 6100 rpm and peak torque of 537.6 @ 4600 rpm.
Mainly street driven but I do want to get it to the track eventually, for fun.
The M1 seemed to work just fine but since I have both options, I figured now is the time to consider a swap, or not.
I think I've covered everyone's questions.
Thanks again!

Cam Card - Specs.jpg

Engine-Specs.jpg

20230602_163811.jpg

20240515_100920.jpg
 
Last edited:
In all honesty, I'd go straight for the M1. Especially with the plans for steeper gears in the future. When you swap in the GV overdrive, go straight for the 4.56 gears.
 
I know a few things from tons of research during my build. The problem is that my memory is real dumb! I'm trying to do better at keeping good records of things for future reference.
That paint looks freakin' awesome, as does the whole car, love that body!!
 
-
Back
Top