Author Topic: That pesky first 1500 RPM  (Read 730 times)

Offline Ronno6

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That pesky first 1500 RPM
« on: October 12, 2018, 08:53:58 AM »
Dual plane intake manifold choices tend to be divided into 2 camps:

Idle to 5500RPM, lower HP
1500 to 6500RPM. higher HP
In the testing I have seen, RPM for max HP is not stated.
https://www.hotrod.com/articles/dual-plane-intake-manifold-comparisons/
Maybe this test is outdated??

I really don't think my motor will see 6500rpm.....

In 4 speed applications, how important is that first 1500RPMs ??
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Online zieg85

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Re: That pesky first 1500 RPM
« Reply #1 on: October 12, 2018, 09:01:21 AM »




In 4 speed applications, how important is that first 1500RPMs ??

I would think more important, torque converter has some slippage while the manual is locked in.   
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1985 C20 Scottsdale 7.4L 4 speed 3.21
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Offline Ronno6

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Re: That pesky first 1500 RPM
« Reply #2 on: October 12, 2018, 09:32:34 AM »

In 4 speed applications, how important is that first 1500RPMs ??

I would think more important, torque converter has some slippage while the manual is locked in.

that would be my thinking also, but with 2.52 first gear and 3.73 diff, you would hit 1500 just shy of 14mph.
After that, shift points are adjustable........
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Online zieg85

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Re: That pesky first 1500 RPM
« Reply #3 on: October 12, 2018, 10:08:02 AM »
Probably be fine if your not trying to move a load.  I like all the torque down low for my applications.  Shift early, keep the rpms down and maximize your mpg.
1981 C30 C&C under construction
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 3.21 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Offline Irish_Alley

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Re: That pesky first 1500 RPM
« Reply #4 on: October 12, 2018, 10:25:54 AM »
a little off topic but has the same mentality, when i pulled the 350 tbi out of my 91 and dropped in a 5.9 1st gen cummins i picked up at least 4 mpgs. i think the main thing is like zieg said, the power on the cummins is down low around 1600 rpms where the TQ is around 400. HP is up at 2500 and is around 160.
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Offline ehjorten

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Re: That pesky first 1500 RPM
« Reply #5 on: October 12, 2018, 01:37:52 PM »
You mostly picked-up mileage with the Cummins swap because a diesel is about 30% more efficient than a gasoline engine.
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Offline VileZambonie

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Re: That pesky first 1500 RPM
« Reply #6 on: October 12, 2018, 06:00:42 PM »
In 4 speed applications, how important is that first 1500RPMs ??

I would think more important, torque converter has some slippage while the manual is locked in.

The clutch slips too but the torque converter multiplies torque....

Are you daily driving? Weekend warrior? Hitting the track? Do you drive like a maniac? Do you jump stop light to stop light? What's the rest of the engine setup look like? What final drive ratio do you have? These are the main considerations because the only real difference is the runners and where you hit your power curve.
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Offline Irish_Alley

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Re: That pesky first 1500 RPM
« Reply #7 on: October 12, 2018, 09:46:13 PM »
You mostly picked-up mileage with the Cummins swap because a diesel is about 30% more efficient than a gasoline engine.

could you say the same about the 6.2?
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Offline Ronno6

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Re: That pesky first 1500 RPM
« Reply #8 on: October 13, 2018, 09:45:02 AM »
In 4 speed applications, how important is that first 1500RPMs ??

I would think more important, torque converter has some slippage while the manual is locked in.

The clutch slips too but the torque converter multiplies torque....

Are you daily driving? Weekend warrior? Hitting the track? Do you drive like a maniac? Do you jump stop light to stop light? What's the rest of the engine setup look like? What final drive ratio do you have? These are the main considerations because the only real difference is the runners and where you hit your power curve.

Daily driver, but I like acceleration and shifting.
Looks like I'm heading down the 350 path.
Pro Topline heads 1.94/1.5 64cc chamber    9.6:1 compression ?
Comp Cams XE262-h cam
Intake/carb RBT
1 5/8" long tube headers w/2 1/4" dual exhaust
Walker turbo mufflers

M20 Muncie 2.52:1 first gear
3.73 posi diff
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Offline VileZambonie

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Re: That pesky first 1500 RPM
« Reply #9 on: October 13, 2018, 11:32:01 AM »
With that cam and setup a performer intake is fine.
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Offline Ronno6

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Re: That pesky first 1500 RPM
« Reply #10 on: October 13, 2018, 12:54:45 PM »
With that cam and setup a performer intake is fine.
Straight performer, performer RPM, eps, air gap ?
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Offline Ronno6

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Re: That pesky first 1500 RPM
« Reply #11 on: November 20, 2018, 07:32:46 AM »
I have purchased a Weiand 8150 Speed Warrior Dual Plane intake.
It orta do the job.......
You can lead a man to water, but yoiu can't keep him from pissing in it.

Online 75gmck25

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Re: That pesky first 1500 RPM
« Reply #12 on: November 21, 2018, 09:34:59 AM »
I don't know much about those heads, but the cam should be a good match to the compression ratio and good flowing exhaust.   The Speed Warrior manifold should also work well. It might be a little soft right off the line with 3.73 gears, but with the manual trans you can get RPM up fast enough to compensate.

Bruce

Offline Ronno6

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Re: That pesky first 1500 RPM
« Reply #13 on: November 21, 2018, 09:40:29 PM »
I don't know much about those heads, but the cam should be a good match to the compression ratio and good flowing exhaust.   The Speed Warrior manifold should also work well. It might be a little soft right off the line with 3.73 gears, but with the manual trans you can get RPM up fast enough to compensate.

Bruce

Purchase of that motor did not occur.
I now have a 880 roller block 350 bored +.030, flat top pistons, aluminum heads
65cc chamber 185cc runner and an LT4 Hot cam reground by Willhoite in OK City.
Should be close to 10:1, long 1 5/8" Hedman long tube leaders into 2 1/4" dual exhausts.
The M20 is 2.52 first gear, tires 26 O.D.

Still need rocker arms, head bolts and fuel pump. Most other stuff has been ordered.
Tis all coming together.....
You can lead a man to water, but yoiu can't keep him from pissing in it.