Double Plane Intake

[Stroked68Dart]

Got a questions for you guys.

I've got a Mopar 402 crate motor in my '68 Dart. You can see the cam and engine specs here:

402 Magnum : CHICAGO CONNECTION, Your High Performance Parts & Accessory Shop

The motor has a single plane intake and I'd like to make it more streetable. Given the cam and other components do you think bolting a dual plane on it would make it more streetable? I would like more low end torque and better idle, etc...

If you do think a dual plane would help could you recommend a good one that might work with my motor.

As always, thanks for the help and advice!

Bill

 

[yellow rose]

Most of the time it isn't the intake manifold. How much gear and converter do you have.

If you don't have a 3.73 gear and 3500 converter that is the issue.

 

[nm9stheham]

Cam..... 288 advertised on 9:1 CR is gonna be on the rough idle side, and DCR down at high 6's or low 7's so low RPM torque will be not all that hot. (That DCR is like that of a stock 318....)

Gears or TC will not change idle character but will get the motor to rev into an RPM range for better torque when you start out. But then your usable RPM range is not any better on the low end. Wide operating torque band is a good thing on the street.... and that is a cam thing here.

 

[stroked340]

Good luck with that "crate motor" guy I race with bought one had nothing but issues with it..as already mentioned what are you running for converter and gears,as far as dual-plane intakes the Edelbrock "air-gap" is the best out there..

 

[yellow rose]

BTW, what is the ICL right now?

 

[rumblefish360]

To answer your question...

A RPM from Edelbrock is what you want. Now, our question to you is what gears and tires do you have as well as what trans and stall converter are you running. How heavy is the car?
Also what carb & size?

 

[Abodybomber]

Good luck with that "crate motor" guy I race with bought one had nothing but issues with it..as already mentioned what are you running for converter and gears,as far as dual-plane intakes the Edelbrock "air-gap" is the best out there..

1

To answer your question...

A RPM from Edelbrock is what you want. Now, our question to you is what gears and tires do you have as well as what trans and stall converter are you running. How heavy is the car?
Also what carb & size?

Correct answer ,and the win.....Good to see you,Rob......

 

[autoxcuda]

MP put a bunch of cam in those 380 HP and 402 crates. People that bought them that had mouths bigger than their stomachs.

Put a smaller, more modern, better idling cam in it. Something well thought out with realistic expectations might perform just as good as current cam with your gear and converter. Especially on the street.

People try dual planes. Then next would be EFI, and then.... band aid after disappointing band aid.

Troy at Westoaks Mopar Performance saw it many times with those two motors.

 

[Blue Grey Duster]

Bill
Where is your initial timing set? That's where it's at !
What carb. ?
What's your vacuum at idle in park ?
I have good info. on this Motor.

 

[gregsdart]

My 408 with an Airgap dual plane made 504 hp, but we didn't do a low rpm pull so I can't verify the 2,000 rpm and up torque. BUT, a dual plane helps with reversion because it has longer runners, cutting down reversion sooner than a single plane. Try a Duel plane, along with 20 degrees initial timing (cut back the mechanical advance too!) And check the cam installed position. You could go four degrees earlier than the cam maker recommends to see how it works. Leave the gears, but if your converter is tighter than about 2600 to 2800 stall, a move to a 3,000 or so stall minimum will help a great deal. If all this doesn't satisfy you, time for a cam change.

 

[krazykuda]

Got a questions for you guys.

I've got a Mopar 402 crate motor in my '68 Dart. You can see the cam and engine specs here:

402 Magnum : CHICAGO CONNECTION, Your High Performance Parts & Accessory Shop

The motor has a single plane intake and I'd like to make it more streetable. Given the cam and other components do you think bolting a dual plane on it would make it more streetable? I would like more low end torque and better idle, etc...

If you do think a dual plane would help could you recommend a good one that might work with my motor.

As always, thanks for the help and advice!

Bill

Try a set of Rhoades variable duration lifters. they will tame out the cam in the low RPM's without sacrificing top end and mid range...

Rhoads Lifters

 

[273]

I got a 380 hp create 360, same cam and intake but smaller engine. Also running a 2800 rpm stall with 2.96 gears.
It's a little soft under 2000 rpm have to drive in 2nd under 40 mph.

Gears would fix the situation. Also plan on Rhoads lifters to extend the powerband lower and gain some idle quality which is fairly ruff yours should be smoother.
After that I'll decide if I need more bottom and go rpm air gap. Need better tires 1st but if it don't hook no point going with air gap.

 

[rumblefish360]

1st but if it don't hook no point going with air gap

Your right! A look into the suspension is in order!

 

[rumblefish360]

MP put a bunch of cam in those 380 HP and 402 crates. People that bought them that had mouths bigger than their stomachs.

I think MP was banking on people porting the heads. Or use a replacement head well ported. There own Magnum R/T, Edelbrock or EQ. Etc... to the heads available at the time.

 

[Abodybomber]

I think MP was banking on people porting the heads. Or use a replacement head well ported. There own Magnum R/T, Edelbrock or EQ. Etc... to the heads available at the time.

I always figured it ,as a building block.There were not a lot of aftermarket options,in the 90's when this was introduced. I don't have an issue with big cams,as long as they are reliable. Heads being ported, was a given.

 

[rumblefish360]

I always figured it ,as a building block.There were not a lot of aftermarket options,in the 90's when this was introduced. I don't have an issue with big cams,as long as they are reliable. Heads being ported, was a given.

I figured the same way. Not that the cam was big IMO, given its 230*@.050 duration. I looked at the set up and thought the cam was a little oversized for the as cast head. Considering how the head is. The good and bad about it. And the rest of the package. I thought the 9.0-1 was a point low & a single plane anbit much. With a cam this big, at least some bowl work like when you were a young guy back in the day! LOL!

 

[nm9stheham]

I think MP was banking on people porting the heads. Or use a replacement head well ported. There own Magnum R/T, Edelbrock or EQ. Etc... to the heads available at the time.

Just my opinion... they put in the larger cam to peak up the numbers and make these look more impressive on paper. I suspect that a lot of crate engine get bought purely on peak HP and torque numbers, with little understanding of what how to look at cams and such a see how that effects other RPM ranges. Use ti for street driving, where the RPM's supported by this cam are rarely seen, and you find that it is not optimum.

Agreed on the the CR being low for this cam size.

 

[autoxcuda]

Just my opinion... they put in the larger cam to peak up the numbers and make these look more impressive on paper. I suspect that a lot of crate engine get bought purely on peak HP and torque numbers, with little understanding of what how to look at cams and such a see how that effects other RPM ranges. Use ti for street driving, where the RPM's supported by this cam are rarely seen, and you find that it is not optimum.

Agreed on the the CR being low for this cam size.

Absolutely.

On the 402 they dyno'd it with a super deep pan tho pull the oil from the crank and get that extra peak numbers. Pan is a PITA in the street.

 

[273]

Yes the create engine is a little bit of a mismatched combo. If you look at the dyno results works quite well. It's actually makes 2 hp per cfm not too many engines accomplish that especially with 9:1 CR.
But a stock long block that makes 400 plus horsepower at 5400 rpm with just a cam 4bbl and headers is amazing. Mine works quite well even being very under geared 2.96. Once I get a set of 3.91-4.10 is gonna wake this beast up.

Personally if I was to put this engine together I'd of went with a smaller cam and air gap.

 

[nm9stheham]

I suspect you mean 1 HP per 2 cfm.... or is this running on a Holley 1920 1-BBL? Took a minute for that to compute LOL

 

[nm9stheham]

Try a set of Rhoades variable duration lifters. they will tame out the cam in the low RPM's without sacrificing top end and mid range...

Rhoads Lifters

I would do that if I wanted to maintain the high end and get a better low end. I'd prefer to go with a different cam but maybe not a bad idea here. They tick at low RPM's, so be ready for that noise.

And DCR will go up and you'll have to watch the total ignition timing as your rev up into the 2000-3500 range, if the ignition timing has been set as far advanced as it can be in the present setup. But so will a lower duration cam.

 

[273]

I suspect you mean 1 HP per 2 cfm.... or is this running on a Holley 1920 1-BBL? Took a minute for that to compute LOL

I'm was talking about the head cfm rule of thumb 2 hp per cfm. The magnum head is supposed to flow around 205 cfm.
You don't see too many street cam and cr hit that rule even a lot of the engines done on engine masters challenge don't even.

 

[rumblefish360]

Well, IMO, for what it is, and let's name what it is, an inexpensive to create crate engine that does indeed perform and perform well for it's intended target audience, street strip hot rodders and mild bracket racing racers.
And reasonably priced.

In the right hands and set up, these have done very well.

Is it as scienced out as much as we can pick it apart? No, but it does t have to be. No , it doesn't have to be and no engine in a box can be. It is designed to fit as many shoes as possible and make as many smiles as possible under one build.

And that's why they offer more than one engine in a box.

 

[autoxcuda]

Yes the create engine is a little bit of a mismatched combo. If you look at the dyno results works quite well. It's actually makes 2 hp per cfm not too many engines accomplish that especially with 9:1 CR.
But a stock long block that makes 400 plus horsepower at 5400 rpm with just a cam 4bbl and headers is amazing. Mine works quite well even being very under geared 2.96. Once I get a set of 3.91-4.10 is gonna wake this beast up.

Personally if I was to put this engine together I'd of went with a smaller cam and air gap.

What about slipping in a comp 274HR-10 in the 360/380: 20-811-9 - Xtreme Energy™ Retro-Fit Hydraulic Roller Camshafts

And the 280HR-10 in the 402 motor:
20-812-9 - Xtreme Energy™ Retro-Fit Hydraulic Roller Camshafts

Those would idle better. Would they get about the same HP and TQ ??

With a comp roller can you reuse his MP/Mopar roller lifters??? And just put in the cam??

 

[nm9stheham]

I'm was talking about the head cfm rule of thumb 2 hp per cfm. The magnum head is supposed to flow around 205 cfm.
You don't see too many street cam and cr hit that rule even a lot of the engines done on engine masters challenge don't even.

OK, I was thinking carb cfm's.....now it makes sense!

Honestly, for the street, I'd let HP number fall where it will and not focus on that... it's where the torque curve falls in the RPM range that is important for that use. When I see an engine test where the torque numbers start at 3000-3500 RPM and go up, that usually is a clue that general driving-around street performance is not what was in mind in the parts selection.