Port my current M1 single plane or install the RPM Air Gap?

[rumblefish360]

Nice build. Normally I’d say a cam @238@050 is small for a single plane but up top a 408….. I’m betting the engine will like it.
Most runners on the single planes are undersized and after porting to meet the head, both of which are typically ported to the gasket size, will wake up and make good use of a single plane.

Personally haven’t been there. Hopefully correcting that soon.

 

[Whatsup1962]

M1. What carb?

APD billet 750

 

[Rat Bastid]

APD billet 750

Perfect for 408 inches. M1 and send it.

 

[a-bodyguy]

single plane with a tuned dp with spray
although i saw a dyno test and dual plane made more with spray
you already have plenty of torque
better yet run it with the dp and spray get et and mph
then single plane with a tuned dp and spray and compare
every combo is different
I myself iam partial to single planes

 

[Dezduster]

Are All the M1 intakes Thermoquad type of carb flanges??? I never had ospread bores

I believe all single plane M1 intakes for standard heads non W series heads are spread bore and I've never seen an M1 specific to the W series heads. I'm sure they are out there but I haven't seen them. Every M1 I've seen since looking for info on the M1 leads me to spread bore intakes.

 

[rumblefish360]

I believe all single plane M1 intakes for standard heads non W series heads are spread bore and I've never seen an M1 specific to the W series heads. I'm sure they are out there but I haven't seen them. Every M1 I've seen since looking for info on the M1 leads me to spread bore intakes.

I have never seen or remembered a spreadbore intake for the W2. The W5 is the only W head to have a spreadbore intake and it is almost exactly the same as the LA intake save the relocated bolt holes that are of course, moved out.

All the rest are a square bore.

 

[autoxcuda]

I have never seen or remembered a spreadbore intake for the W2. The W5 is the only W head to have a spreadbore intake and it is almost exactly the same as the LA intake save the relocated bolt holes that are of course, moved out.

All the rest are a square bore.

Here's a NOS W-5 version I have.

 

[bdrut57]

hi i got question, would a anti reversion plate work on m1 intake with a fast ez1 throttle body,

 

[pittsburghracer]

hi i got question, would a anti reversion plate work on m1 intake with a fast ez1 throttle body,

I’m a carb type of guy born in the right generation but I think the only way that you could really test this would be several back to back tests at the drag strip. Or if gas mileage is your thing back to back test on tankfuls of gas. Good luck.

 

[justinp61]

APD billet 750

If it's mostly street driven the 750 will be fine, if it goes to the strip very often, I'd run an older 950HP. Not the new billet ones with the huge venturis. The older ones are pretty much a 750 main body on an 850 base, they work excellent on the street too.

 

[512Stroker]

It's not a drag car although it's been to a few tracks, its not an autocross car however I will do more of them in the future but what it must do more of is highway miles due to my rural location.
The Combo is a 422ci la, 11.2:1, stock RPM eddies, M1 intake, 750 BG, 242/[email protected] 109LS 105IC hyd roller, TTI 1-5/8-1-3/4" step header into 3" tapering to 2.5" on the exit of the X full length mandrel TTI exhaust. Lightweight aluminum flywheel and single disk clutch, manual trans 3.2 gear .068 OD and 3.23 rear gear.
The previous hydraulic flat tappet cam is very similar to the above roller cams specs and the engine idled easily at 800, vacuum was 8" to 10" at idle, at WOT vacuum fluctuated between 1 and 2". The combo had plenty of torque and throttle response was great, mpg a tick over 20 highway cruising with the M1 single plane. The M1 is just damn ugly inside, being a spread bore with the sharp radius into the front intake runners. I cannot stop thinking its killing allot of power, yet I like its exterior look and lower height for hood clearance. How much torque is the M1 down, is the RPM down on HP at 5500 to 6200 and by how much if at all? I don't see M1 dyno results let alone ported results to determine if porting it would be worth the money. I've seen the M1 is mid pack in the Motor Trend LA intake ranking. What are your thoughts and experiences?

Just changing to a AirGap isn't going to buy you much if anything that you can feel by the seat of your pants. Now port the heads you have and port match an AirGap to the freshly ported heads now your going places and you will feel the difference.

 

[fishmens67]

Just changing to a AirGap isn't going to buy you much if anything that you can feel by the seat of your pants. Now port the heads you have and port match an AirGap to the freshly ported heads now your going places and you will feel the difference.

That can be said for the single plane as well, the race starts at 3000rpm and above. lol
It's kinda hard to get a dual plane to flow in the 320cfm range.

 

[512Stroker]

That can be said for the single plane as well, the race starts at 3000rpm and above. lol
It's kinda hard to get a dual plane to flow in the 320cfm range.

Granted
This appears to be more of a street application, my thought was that the dual plane AirGap may produce a little bit better driving manners.

 

[mhuppertz]

It's not a drag car although it's been to a few tracks, its not an autocross car however I will do more of them in the future but what it must do more of is highway miles due to my rural location.
The Combo is a 422ci la, 11.2:1, stock RPM eddies, M1 intake, 750 BG, 242/[email protected] 109LS 105IC hyd roller, TTI 1-5/8-1-3/4" step header into 3" tapering to 2.5" on the exit of the X full length mandrel TTI exhaust. Lightweight aluminum flywheel and single disk clutch, manual trans 3.2 gear .068 OD and 3.23 rear gear.
The previous hydraulic flat tappet cam is very similar to the above roller cams specs and the engine idled easily at 800, vacuum was 8" to 10" at idle, at WOT vacuum fluctuated between 1 and 2". The combo had plenty of torque and throttle response was great, mpg a tick over 20 highway cruising with the M1 single plane. The M1 is just damn ugly inside, being a spread bore with the sharp radius into the front intake runners. I cannot stop thinking its killing allot of power, yet I like its exterior look and lower height for hood clearance. How much torque is the M1 down, is the RPM down on HP at 5500 to 6200 and by how much if at all? I don't see M1 dyno results let alone ported results to determine if porting it would be worth the money. I've seen the M1 is mid pack in the Motor Trend LA intake ranking. What are your thoughts and experiences?

My vote is RPM air gap for autocross and drivability.

 

[4mulas]

On a separate note, I have an m1 I may end up running, can someone point me to where I might find some information on porting this intake properly?

I think Dulcich did some porting on one in motor trend with magnum rt heads some where. I’ll see if I can find the article etc…. You’d can google it too and may find it faster than me.

 

[4mulas]

Never touched an M1 so I would need some nice runner and plenum pictures to see if it could be improved.

Best I have right now For pictures. Also including the one showing epoxy as warning to folks with these. This manifold is for my 402 magnum and the factory drilled the inner holes too deep on 3 out of the four holes and they went right through, they will cause a vacuum leak unless those locations are actually being used.

 

[autoxcuda]

Best I have right now For pictures. Also including the one showing epoxy as warning to folks with these. This manifold is for my 402 magnum and the factory drilled the inner holes too deep on 3 out of the four holes and they went right through, they will cause a vacuum leak unless those locations are actually being used.

View attachment 1716034826

View attachment 1716034827

The one with the epoxy that broke is probably mine. We used Moroso AB epoxy. FYI, I also run California blend gas too with alcohol content.

Someone later did one in epoxy with metal dowel on the side to support it. That was a years ago. Never heard anything bad with that.

Buddy did a RB M1 since then... TIG welded that one.
Read here: Looking for opinions on Mopar M1 single plane intake

Mine before a slice of epoxy came off and hung up a valve and pushrod fell off the rocker.

 

[autoxcuda]

Here's a thread showing someone welding up a M1: Fixed my M1 / Strip Dominator

 

[canyncarvr]

View attachment 1716032712

Hello friends, neighbors, and all-round well-balanced peoples:

Seeing as this thread has somewhat to do with the comparison of particular manifolds, it might be a good idea to know/understand/read with comprehension (not that I'm famous for that) what IS being talked about.

The OP asked a question about, for one thing, an air gap manifold. The above list does NOT say 'air gap' in the 'E' intake list. I would guess/form an opinion...maybe even understand it to be a true fact then, that the air gap version of the Edelbrock Performer RPM manifold was not tested in the particular dyno runs noted.

Is an 'air gap' manifold different in tune/power/design than the Performer RPM manifold that is NOT an air gap? I don't know that. That they are two rather completely different manifolds suggests to me they are not the same manifold.

A curiosity: If everybody knows that a big hole manifold is the only way to go, why is it that four-hole spacers work so much better than open spacers?

Nah. I didn't ask that. I don't want any boxes of exploding poo in MY inbox!

 

[rumblefish360]

The RPM AG & the RPM are the same intake manifold minus the extra metal and port to allow the intake to be warmed up when it gets cold outside.

As per dyno results, they perform exactly the same. So, if it’s competition, short run use, they’ll perform the same. If it’s auto cross or any long time driving, more than a few minutes, the AG version is what you want.

 

[pittsburghracer]

Best I have right now For pictures. Also including the one showing epoxy as warning to folks with these. This manifold is for my 402 magnum and the factory drilled the inner holes too deep on 3 out of the four holes and they went right through, they will cause a vacuum leak unless those locations are actually being used.

View attachment 1716034826

View attachment 1716034827

A member emailed me some nice pictures and I thought I was going to get a job porting one but so far I haven’t heard back. The RPM is the one that interests me because my son has both a 340 and currently a built 360 in his 1973 Cuda. I’m going to finish up his Speedmaster heads one of these days and I think with the air in Colorado that may be a good intake for him. I did a post on “the ugly” Torquer intake I ported for him and it flowed better than I could get the Speedmaster dual plane to flow.

 

[TT5.9mag]

Hello friends, neighbors, and all-round well-balanced peoples:

Seeing as this thread has somewhat to do with the comparison of particular manifolds, it might be a good idea to know/understand/read with comprehension (not that I'm famous for that) what IS being talked about.

The OP asked a question about, for one thing, an air gap manifold. The above list does NOT say 'air gap' in the 'E' intake list. I would guess/form an opinion...maybe even understand it to be a true fact then, that the air gap version of the Edelbrock Performer RPM manifold was not tested in the particular dyno runs noted.

Is an 'air gap' manifold different in tune/power/design than the Performer RPM manifold that is NOT an air gap? I don't know that. That they are two rather completely different manifolds suggests to me they are not the same manifold.

A curiosity: If everybody knows that a big hole manifold is the only way to go, why is it that four-hole spacers work so much better than open spacers?

Nah. I didn't ask that. I don't want any boxes of exploding poo in MY inbox!

The manifold in the test was in fact an RPM air gap.

 

[12many]

I did the pins with one piece of epoxy. Ended up passing it on to someone with a more appropriate application.
Read here of approx power gains but had no way of verifying.
If I were to consider another M1 for another engine I’d probably just open up the flange like shown in Dykem picture and radius into the runners vs. all that work to epoxy it.

 

[Dezduster]

I think Dulcich did some porting on one in motor trend with magnum rt heads some where. I’ll see if I can find the article etc…. You’d can google it too and may find it faster than me.

Edit! Thank you 4mulas, I'll go look for that article.

 

[Dezduster]

I have never seen or remembered a spreadbore intake for the W2. The W5 is the only W head to have a spreadbore intake and it is almost exactly the same as the LA intake save the relocated bolt holes that are of course, moved out.

All the rest are a square bore.

That's the same intake I have 4452893 it bolted to the RPM heads with enlargement of the bolt holes. The bolt holes in your intake do indeed look spaced wider. Did they use the same casting# and drill the holes spaced wider for the W5? If the ports and volume are the same on the W5 intake and this intake is the same as the W5 intake, I'm certain my combo isn't taxing the intake. I am fairly certain anyone running W5 heads are porting both the heads and the intake though.