TM6 or AirGap RPM for 451 stroker???

Posted By: Triggerfish

TM6 or AirGap RPM for 451 stroker??? - 07/22/08 03:56 PM

Just built 451 stroker for my 68 Cuda (4spd, 3.55's), 440 source kit, Eddy large chamber heads, Engle hyd flat tappet cam (special grind K56/K58 on 114 centerline), Approx 10:1 compresson. I've got a TM6 w/ Holley 850 on it now, but would the RPM air gap yield more torque & better performance? I'm also thinking of mililng the heads for more compression or switching to the smaller chamber eddys. Want the Cuda to be a hot street car that won't see the strip too much.

Posted By: moper

Re: TM6 or AirGap RPM for 451 stroker??? - 07/22/08 04:00 PM

I cetainly think so.

Posted By: bigsbigelow

Re: TM6 or AirGap RPM for 451 stroker??? - 07/22/08 04:02 PM

It's my understanding that Eddy has designed the Air Gap to make torque like the dual plan that it is and support high rpm like a single plan.

Posted By: dogdays

Re: TM6 or AirGap RPM for 451 stroker??? - 07/22/08 04:29 PM

With your gearing I'd pick the Air Gap. The TM-6 would respond better and be stronger in the quarter with 4.10s.
It's a good intake don't throw it away!
R.

Posted By: JohnRR

Re: TM6 or AirGap RPM for 451 stroker??? - 07/22/08 04:30 PM

RPM AIR GAP ????

Don't all big block mopar wedge engines have an "AIR GAP" intake by DEFAULT ????

just thinking out loud

Posted By: dogdays

Re: TM6 or AirGap RPM for 451 stroker??? - 07/22/08 04:57 PM

OOPS! RIGHT, NO AIR GAP for 400s. You'll have to block the exhaust crossover to get max benefits but still a great manifold. Air gaps and regular Perf RPMs have AFAIK the same interior configuration as far as ports and plenum.
R.

Posted By: Triggerfish

Re: TM6 or AirGap RPM for 451 stroker??? - 07/22/08 05:04 PM

Imight install 4.10's & Gear Vendor's overdrive next year. Then I could use the TM6. One friend said w/ the TM6 would feed the larger cubes & longer stroke than the 383 RPM air gap. Would the dual plane intke need to be ported?

Posted By: AndyF

Re: TM6 or AirGap RPM for 451 stroker??? - 07/22/08 05:09 PM

Try it and see, I bet you'll like the Performer RPM so much that you won't go back to the single plane. On a street driven car you can really feel the difference the RPM intake will make down around 2000-3000 rpm. At the drag strip the single plane may or may not be faster, a lot depends on the chassis and the gears. But on the street you'll really notice the extra torque down low.

Posted By: Triggerfish

Re: TM6 or AirGap RPM for 451 stroker??? - 07/22/08 05:13 PM

Thanks Andy. I'll order one from Jegs today. Would you recommend I have it ported for the extra cubes & stroke?

Posted By: 383man

Re: TM6 or AirGap RPM for 451 stroker??? - 07/22/08 07:17 PM

My son loves the Performer RPM on his 400 Dart. It ran a tad quicker then the Street Dominator did by about a 1/2 a tenth even though it had less mph then the SD. The 1/8 and 60 ft were much better with the RPM and it was enough to keep the 1/4 et quicker then any single plane he tried and the SD was the best single plane on his Dart. He will never go back to a single plane on his combo he says even though I have out 60 ft him with the SD on my 63.

But honestly Andy is so right as the RPM is great for a mild street/strip car. Ron

Posted By: dogdays

Re: TM6 or AirGap RPM for 451 stroker??? - 07/22/08 07:45 PM

Plus, Andy was in another life known as "451boy"!!! But do a websearch on his real name and look up his dissertation. Not a forged piston in sight in that gem!

R.

Posted By: Triggerfish

Re: TM6 or AirGap RPM for 451 stroker??? - 07/22/08 09:28 PM

Quote:

OOPS! RIGHT, NO AIR GAP for 400s. You'll have to block the exhaust crossover to get max benefits but still a great manifold. Air gaps and regular Perf RPMs have AFAIK the same interior configuration as far as ports and plenum.
R.

I thought the RPM air gap for the 383 would fit w/o any modifications. How do I block off the exhaust crossover?

Posted By: AndyF

Re: TM6 or AirGap RPM for 451 stroker??? - 07/22/08 09:38 PM

You don't need to block off the exhaust gas crossover since you're using Edelbrock heads. The E heads don't have the crossover in them so you're good to go. The Performer RPM intake should drop on there without any issues using a factory bathtub style intake gasket.

There is also the Mopar Peformance version of that intake. The MP intake is exactly the same except it has some cool lettering on the front that says MOPAR WEDGE. It costs a few bucks extra but the lettering was worth it for me. The MP unit doesn't seem to be very popular for some reason. I'll post a picture of the one I have since I think it looks cool.

Posted By: Triggerfish

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 04:17 AM

Andy, thanks for the input. Does MP still make the intake you mentioned? I've never heard of it or seen one before. Its the same inside & out as the Eddy RPM airgap? The TM6 looks pretty cool, but can't put a bigger cam due to smog regs in Reno. Thanks for posting a picture if you have one.

Posted By: AndyF

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 04:48 AM

Sorry, I made a mistake on the intake. MP only sells the RB version of the intake and you have a low deck motor. I'm not sure why MP doesn't sell a low deck version but I guess they decided not to have Edelbrock cast one for them.

Posted By: ZIPPY

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 02:24 PM

I've asked why no low deck mp intake, didn't get an answer

Posted By: AndyF

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 02:30 PM

The MOPAR WEDGE lettering is cool. I hadn't ever seen one before and then I stumbled on one at a swap meet. The picture in the catalog doesn't quite do it justice. I don't understand the lack of the B version either, maybe they just ran out of tooling money for the year or something.

Posted By: AndyF

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 03:07 PM

Here is a picture of the RB version.

Attached picture 4569825-wedge.jpg

Posted By: ZIPPY

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 03:43 PM

Yep, that is part number P5153525.

There is a shot of it on page 62 of the 2007 MP catalog, but I like your picture better!

Oddly, it can actually be bought for less than Summit charges for a regular RPM intake, but you need a good guy parts fella who will sell at a small percentage over dealer net. At retail it's higher priced than Edelbrock...but after a little digging, I found it to be sometimes lower priced, depending on who was selling it.

Personally I would really like a B version for my C body, but there is no such thing

Posted By: AndyF

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 04:18 PM

Yep, intake prices vary quite a bit sometimes. I just bought a Super Victor from Mancini for $290. Summit's price was $360 for the same intake. So it does pay to at least look around a little bit.

That 525 intake in the picture above was purchased at a swap meet for $100. It appears to have been used once and then evidently the guy didn't want it anymore. Nice score for me!

Posted By: AndyF

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 04:22 PM

Quote:

RPM AIR GAP ????

Don't all big block mopar wedge engines have an "AIR GAP" intake by DEFAULT ????

just thinking out loud

At the risk of starting a big brawl I'll say that I do not think the big block Performer RPM intakes are "air gaps". It is true that they have an air space under them, but I think the term "air gap" means that the exhaust gas crossover has been eliminated. The SB "air gap" has an actual air gap on the sides of the intake. The BB intakes have the crossover connected. A Victor, or Super Victor intake for the BB are "air gaps" since the crossover has been eliminated. Anyway, that is my take on the subject. I think that Edelbrock also views the subject this way since they have both a Perf RPM for the SB (#7161) that has the crossover, and they have an Airgap RPM (#7576) without the crossover. The BB version is called an RPM not an airgap since it has the crossover.

Posted By: RTDude

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 04:26 PM

I think I might have to get one.I was going to order up a Performer RPM,but I like the looks of that one much better.Now I just have to get rid of my unused M-1 single plane.

Posted By: JohnRR

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 04:42 PM

Quote:

Quote:

RPM AIR GAP ????

Don't all big block mopar wedge engines have an "AIR GAP" intake by DEFAULT ????

just thinking out loud

At the risk of starting a big brawl I'll say that I do not think the big block Performer RPM intakes are "air gaps". It is true that they have an air space under them, but I think the term "air gap" means that the exhaust gas crossover has been eliminated. The SB "air gap" has an actual air gap on the sides of the intake. The BB intakes have the crossover connected. A Victor, or Super Victor intake for the BB are "air gaps" since the crossover has been eliminated. Anyway, that is my take on the subject. I think that Edelbrock also views the subject this way since they have both a Perf RPM for the SB (#7161) that has the crossover, and they have an Airgap RPM (#7576) without the crossover. The BB version is called an RPM not an airgap since it has the crossover.

Thanks for clearing that up , I didn't know there was such an intake available .

Posted By: firefighter3931

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 07:14 PM

Quote:

RPM AIR GAP ????

Don't all big block mopar wedge engines have an "AIR GAP" intake by DEFAULT ????

just thinking out loud

Yep, that would be correct John. The turkey pan creates the "air gap" between the manifold and the hot engine lube.

The SB mopars don't have a turkey pan and the bottom of the intake itself seals in the oil. The SB airgap design creates the same open space that BB engines have.

The original SB RPM dual plane was a non airgap design and the updated version has the runners raised off of the sealing surface, hence the airgap moniker.

From the Eddy website :

"The air-gap design features an open air space that separates the runners from the hot engine oil resulting in a cooler, denser charge for more power."

http://www.edelbrock.com/automotive_new/mc/manifolds/chrysler/chrysler.shtml

Compare pix of the standard SB RPM to the Airgap RPM and the difference will be obvious.

***For purposes of this discussion ; "Air Gap" has nothing to do with heat crossover....at least not in terms of the way that it is referenced by Edelbrock.

Back on topic : I like the Airgap RPM for that build as well. Buzz, are you planning to dyno it ?

Ron

Posted By: JohnRR

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 07:19 PM

Quote:

Quote:

Quote:

RPM AIR GAP ????

Don't all big block mopar wedge engines have an "AIR GAP" intake by DEFAULT ????

just thinking out loud

At the risk of starting a big brawl I'll say that I do not think the big block Performer RPM intakes are "air gaps". It is true that they have an air space under them, but I think the term "air gap" means that the exhaust gas crossover has been eliminated. The SB "air gap" has an actual air gap on the sides of the intake. The BB intakes have the crossover connected. A Victor, or Super Victor intake for the BB are "air gaps" since the crossover has been eliminated. Anyway, that is my take on the subject. I think that Edelbrock also views the subject this way since they have both a Perf RPM for the SB (#7161) that has the crossover, and they have an Airgap RPM (#7576) without the crossover. The BB version is called an RPM not an airgap since it has the crossover.

Thanks for clearing that up , I didn't know there was such an intake available .

whoops , I read your reply wrong Andy , you were talking about the differences in the SMALLBLOCK MANIFOLD , I thought there was such an animal as an AIR GAP RPM for a BIG BLOCK , but there IS NOT according to the link Ron posted ?

back on topic ...

Posted By: AndyF

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 08:00 PM

Actually the deleting of the exhaust gas crossover is what makes the intake an "airgap". Take a look at the pictures on the Edelbrock website and you'll see that is how they define it for the SB intakes. The BB intakes aren't called air gaps by Edelbrock.

Posted By: mopowergtx

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 08:36 PM

Quote:

Actually the deleting of the exhaust gas crossover is what makes the intake an "airgap". Take a look at the pictures on the Edelbrock website and you'll see that is how they define it for the SB intakes. The BB intakes aren't called air gaps by Edelbrock.

DEFINATELY not called Air Gap when its a Big Block manifold. B or RB version. Simply a Performer RPM, period. Small blocks now they make and sell two versions currently. Performer RPM which looks like a LD340 basically and designed like any run of the mill SB intake as far as being one solid piece. And then the Small Block Performer RPM Air Gap which looks like a Big Block intake simply because the runners are raised up away from the solid bottom of the manifold covering the engine creating an "AIR GAP" between them and the rest of the manifold.

RB Performer RPM 7193

B Performer RPM 7186

Small Block Performer RPM 7176

And last but not least the only one called "Air Gap" in a Mopar intake the Small Block Performer RPM Air Gap
7576

They all have heat crossovers except the 7576 but its called an "Air Gap" because of the raised runners. And like John basically said, all single 4 barrel BB wedge manifolds already have this feature from Ma Mopar. So no sense in Edlebrock trying to attach that moniker to them thus they are simply called Performer RPM's. If you want to lose the heat crossover then block it. They just couldnt give you that option on the Small Block 7576 because of the design of the raised runners.

Posted By: MoparforLife

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 08:47 PM

The eliminated exhaust crossover is a result of not the reason for the Airgap. The reason for the Airgap is to get and 'cooling' wall of air under between floor of the intake and the engine valley.

Posted By: AndyF

Re: TM6 or AirGap RPM for 451 stroker??? - 07/23/08 08:59 PM

I'll stick with my original description since that seems to be how Edelbrock uses the term. If you look at any of the manifolds that Edelbrock calls "air gap" they all have the crossover deleted and the runners are fully surrounded by air. The intakes where the valley floor is isolated but the crossover is still in place are called the RPM. So it appears that Edelbrock has defined "air gap" to mean fully isolated runners.

The big block Mopar RPM could be turned into a full "air gap" intake by eliminating the cross over and machining away the webbing on the sides of the plenum. I made one of those intakes a few years ago but it took a lot of work and probably wasn't worth the effort.

Posted By: firefighter3931

Re: TM6 or AirGap RPM for 451 stroker??? - 07/24/08 12:58 AM

Quote:

Actually the deleting of the exhaust gas crossover is what makes the intake an "airgap". Take a look at the pictures on the Edelbrock website and you'll see that is how they define it for the SB intakes. The BB intakes aren't called air gaps by Edelbrock.

Not to get into a pi$$ing match Andy, but read the Edelbrock SB RPM airgap description again (from their website):

"The air-gap design features an open air space that separates the runners from the hot engine oil resulting in a cooler, denser charge for more power."

No mention of the heat crossover at all....they're referring to the runners being isolated from the valley. If isolated runners "define" the airgap terminology/decription then all BB manifolds that run a valley pan intake gasket are "by design" an air gap. Just because Edelbrock doesn't call the BB RPM manifolds airgaps doesn't mean that they aren't.

Sorry if you don't see it that way....

Ron