Author Topic: ORIGINAL VS MODERN POWERPLANT  (Read 2810 times)

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Offline Plugcheck

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #20 on: March 23, 2023, 01:41:26 PM »
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Offline ccv-19

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #21 on: March 23, 2023, 06:25:08 PM »

 My results on a 455 Olds with log manifolds . 
They are very restrictive .
 Different heads on same motor made no top end speed difference.
 These were the port sizes on the different heads with same valve sizes.

Offline thedeuceman

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #22 on: March 23, 2023, 09:37:16 PM »
I have a set of Nissan manifolds with risers they?re stainless steel. I?ve heard rumors they?re very close.


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Joe
75 GT150 "SeaDeuced"... Its Back !!
92 16CSS "Attitude Adjustment" is for sale
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74 CV-16... its Purple !

Offline rbay

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #23 on: March 24, 2023, 11:13:46 PM »
The key dimension is that the ports are equally spaced, close to 4.4? center to center.

Offline still_fishin

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #24 on: March 25, 2023, 11:46:39 PM »
If those are the ones i gave you they were toyota. If not,  I'll watch my own bobber.
I have a set of Nissan manifolds with risers they?re stainless steel. I?ve heard rumors they?re very close.


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'85 CV23

Offline still_fishin

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #25 on: March 25, 2023, 11:49:30 PM »
One of the ls marine swap pages has a guy posting about some adapters from whatever you have to ls flange.  I'll look for it.
'80 Intimidator
'85 CV23

Offline still_fishin

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'80 Intimidator
'85 CV23

Offline thedeuceman

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #27 on: March 26, 2023, 06:49:49 AM »
Thanks for the correction Tim, yes they are.


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Joe
75 GT150 "SeaDeuced"... Its Back !!
92 16CSS "Attitude Adjustment" is for sale
75 CV-16V8, Project
74 CV-16... its Purple !

Offline rbay

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #28 on: March 26, 2023, 12:19:44 PM »
Great Facebook group tip still_fishin. I?m going to have to join its 6100 members!

Offline still_fishin

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #29 on: March 26, 2023, 01:35:17 PM »
Scroll down that lsx page to August 26 of 2022. Specifically Kyle Frasier, he is the one building the adapters.
'80 Intimidator
'85 CV23

Offline rbay

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #30 on: April 07, 2023, 12:52:51 PM »
Like I tell my daughters when faced with a lot of political mumbo jumbo, show me the data!

For the original powerplant question, "old (big block) vs new (GM LS)", I plotted the horsepower "demand" curve of a Berkeley 12J jet pump against the horsepower "supply" curves of the following engines (by graph color):
ORANGE  - 1969 Olds 455, 310 HP, my CV21 missing engine
 PURPLE  - 1970 Chevy 454, 330 HP
    BLUE   - Chevy 5.7L LS1 (car intake, aluminum block), 350 HP
   GREEN - Chevy 6.0L L96 (truck intake, iron block), 365 HP
      RED  - Chevy 6.0L LS2 (car intake, aluminum block), 400 HP
   BLACK  - Chevy 6.2L L92 (truck intake, aluminum block), 400 HP

Some comments and observations.

1.)  Pardon my squiggles, but the process is to overlay the engine HP graph over the pump graph in .ppt, hand trace the engine HP curve, then delete the engine graph.
2.)  I know all these engines can be modified to make more HP, but I needed to reduce the variables and make an assessment of their starting points.
3.) There's a lot of talk out there about the low rpm torque of the Olds 455 engine.  True, and very important when torque is what's needed to turn a car axle to make it go forward. But a jet boat moves forward when the weight of water (volume x velocity) being thrown backwards creates a forward thrust.....kinetic pumps need power to keep that water moving.  So for a jet boat, the BBO has a lot of unusable torque at the lower RPM, and runs out of HP just when the pump starts needing it.  Yes, it had the lowest HP to start with, but even shifted slightly higher the curves collide. For a propeller-driven boat, it may be back to torque rules.
2.)  Of the two old-school big blocks, the Chevy creates horsepower later and longer, so probably a better inherent match for the needs of a jet pump.
3.)  I'll assume my CV21 has an A-cut aluminum impeller, so for the "A" pump curve:
       - The 5.7L LS1 makes its power too late, it will max out at a lower RPM than the Olds (the BLUE dot)
       - The 6.2L L92 will max out at the highest RPM of all the engines plotted. (the BLACK dot)
4.)  To really optimize the system, going to a cutdown "C", or even a more standard "B" cut, stainless steel impeller is indicated.  Here the L92 and the 6.0L LS2 are about tied.

So my bottom line is that, once I get a good handle on the hull and interior restoration of my CV21, I will start shopping for either:
- A 6.2L L92 engine.  It still has the 100# lighter aluminum block and horsepower of the more expensive LS2 (about avg $2K more on eBay).  For $500 you can swap on the LS3 intake and fuel rails to get the 5" lower intake height and cleaner top of engine appearance.
- A 6.0L LS2 engine, if I want to pay more to be able to show the Corvette LS2 engine covers.

The impeller swap then becomes a stand-alone decision, since either engine would benefit.

I invite comments, or if others want to show their charts using the same process for other engines.

Offline ccv-19

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #31 on: April 13, 2023, 04:07:06 PM »
 You dont need a stainless impeller with your HP.
  They dont flex like a prop does .Alum 500 dollars-1300 stainless

Offline ccv-19

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #32 on: April 13, 2023, 04:12:29 PM »
 
 The last pict. wasnt to show impeller chart but to show how a jet is different from a
   prop tied to a dock reference.

Offline rbay

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Re: ORIGINAL VS MODERN POWERPLANT
« Reply #33 on: April 14, 2023, 08:07:46 AM »
I've seen for an aluminum impeller:
Berkeley chart:    330hp max, 4700 rpm
Websites:    500hp max, 5000+ rpm

Expect to be in the 400-450hp range, will aluminum be OK to 5300-5500 rpm?