Looks Like I'ma gonna be a Caddy Guy - Now What? Stroker L92 LS3 Build

[Slidin Gator]

4 BLADE 76" MAXIMUS I would think could hold it back..... maybe a 3 blade. I only have about 7.5 degrees of pitch in mine.

I talked to Andrew, he said he was making one for some PITA coonass he's sick of doing business with, all Eco this Tech that. He said I could have it at 20% off if I hurry. :stirpot:

I wouldn't hesitate to 2.55 or 2.68 with the right size prop. Less gear is more stress than spinning the motor a little high in the RPM range to me.

Actually, dropping gear ratio has nothing to do with dropping the engine operating range, it has to do with spinning the 76" blades fast enough to absorb the power. This is an oddball setup, so prop choices are limited, here are the options so far:

Carbon Max - I need a 4 blade for this power and the only 4 blade hub they make is a long hub. This put's the Maximus at 80" and the 12" Falcon at 79" (I think). Trimming the Maximus to 76" will require putting too much pitch into it where it is in-efficient and creates too much torque roll. Andrew said it would probably tend to dig the nose, meaning all that power goes to friction and the boat won't run free on ground. This is exactly what I am trying to avoid.

Andrew's recommendation is a 4 blade 12" Falcon trimmed to 76" and a 2.0 to 2.12 ratio gear to keep the blade tip speed up. 5,500 engine RPM and a 2.12 gear puts me at 2,600 prop RPM, 2.00 gear = 2,750.

Patti at Water Walker had a similar recommendation with a 4 blade, Carbon Max 2.0 on a 2.0 gear. This is also a 12" blade but they do offer a 76" hub and blade combination that does not need trimming.

Darrin at Sensenich came up with a 3 blade NGR (13" wide blade) with the winglets cut off on a maximum 2.38 gear (2,310 Blade RPM). This setup is normally 80", so the blades would need a 2" trim.

Even at 2:1 gear ratio I am looking at 1,100+ Ft-lbs of prob torque vs. 600 now. On the plus side, this should improve my chances of finding a used box. The problem with ordering a trimmed blade is there is no return if it doesn't work out. I have time to :scratch: on this for a while.

 

[unforgiven11B]

2:0 and 2:1 seem to always be available so that a plus. I was thinking of this issue when you stated your goals. I have one falcon I’ll send you if you need it damn things been takin up space in the shop for too long.

 

[Slidin Gator]

Welp, I'm a dumba$$, I've been taking all my thinking measurements off my deck over :banghead: :banghead: :banghead:

The deck over measures right at 7' wide and 81" inside to inside on the rigging. The hull this setup is going on is a high sided hull with 5" extensions and 1" of overlap for 4" total increase. The pictures below are from the sister hull. The extension makes it 7' - 3" (87") wide outside of the top lip and the conduit rigging on this hull is 84.5" inside.

My plan is to cut out the transom to build a high sided deck over. The extra height will give me room for more fuel :cherry:

Back to the task at hand, this gives me breathing room. Since I will be pushing close to the rigging, I'm gonna leave room for 1-1/4" aluminum tubing on the main rigging hoops (this is gonna be a 2 seat, aluminum rigging setup). Allowing for some offset from the edge, that put's me at 7' (84") on the inside of the rigging which gives me more room for prop, 79" prop diameter is starting to look reasonable, giving me more options.

A 3 blade is my limit for slithering into the cage for engine work and this will be a full cage setup, 4 blades and 2:1 is another area to avoid (harmonics).

Since I prefer 3x blades I am looking for more than 12" width. I am having a hard time seeing this boat not putting a big smile on my face turning 3x 13" wide blades anywhere north of 2,600 blade RPM (2.11 gear). :cheers:

Reviewing options, the Whirlwind EX (13" blade) comes in 77 or 79" hubs. The Sensenich NGR (13" blade) is 80" minimum, so it would only need a winglet trim to get to 78". Same thing with the Falcon, less of a hair cut and might put me in range of the Maximus.

For now, I'm sticking with the motor plan, over build it with a stroker, tune it down if I have to, keep an eye on the classifieds!

I have one falcon I’ll send you if you need it damn things been takin up space in the shop for too long.

I hear ya, tough to let it go, especially if someone ain't gonna make a buck scrapping it, you will be the first to know if I need a filler for the truck gun rack.

 

[OneBFC]

Well, looks like your new build will share some similarities with my current one I run. We finished in 2019 about this time so it's 2 years old with the new mods. Converted my 2003 DB hull to use a cut out transom that mimicked a palm beach style arrangement. I can say definitively now that it worked out great. Totally new boat after we were done with it. Here's a couple pics. If you zoom in on the suspended hull pic you can see the total weight before engine/rigging was 607 lbs with riveted 3/8 UHMW included. Not a feather weight for sure.

However, the Aluminum rigging we used was feather weight. All of the rigging minus the engine stand and cage wire was aluminum. The final weight of the boat, fully rigged and ready to run was 1447 lbs hanging from scales.

Before we made these mods the boat weighed 1760 "ish" lbs. I have a pic of that somewhere but don't have the time to dig it up.






Good luck with your new project!

 

[One Eyed Gator]

Sliding I kind of agree but disagree to me each blade has a tip speed it likes for best all-round performance. 76 vs an 80" prop at the same engine rpm have a very different tip speed. Keeping the engine RPM about the same to get best power out of the engine and using the gearbox ratio to dial in the tip speed while also reducing to load of the engine.
Where I tend to agree is a motor with plenty of torque doesn't seems to feel the prop load as much. Specially a smaller diameter need for a deckover to keep the motor as low as possible
I also know that on a round bottom hull and big prop and low gear has quit the pucker factor of torque roll. lol
Just my thoughts

 

[Slidin Gator]

Good luck with your new project!

Thanks BFC, this boat will be light and I should be well under the 2:1 weight to thrust ratio, don't think I'll get to 1:1 helicopter capability though . I'll be cutting a bit deeper, it's a 17-1/2" transom and I plan to make it 9" high. I'm curious if you ever ran the same engine/prop setup between the open hull and deck over setup to compare performance? My son and I can swap props between my 300 Hp 540 on a deck over and his 250 on the open and we use identical pitch settings for the same RPM. One buddy tried to tell me that the 300 must not be making power, but that is not right, she puts out. It's the cleaner airflow into the prop letting her grab.

I plan to integrate the radiator into the seat rigging with electric fans and ducting to keep airflow clean. This will keep me at lower RPM and should help with torque roll. Other advantages will be lower sound signature, faster warm up/cool down and move weight forward. I have been using electric fans in my buggy for years and have had great success.

... to me each blade has a tip speed it likes for best all-round performance. 76 vs an 80" prop at the same engine rpm have a very different tip speed. Keeping the engine RPM about the same to get best power out of the engine and using the gearbox ratio to dial in the tip speed while also reducing to load of the engine.

Where I tend to agree is a motor with plenty of torque doesn't seems to feel the prop load as much. Specially a smaller diameter need for a deckover to keep the motor as low as possible
I also know that on a round bottom hull and big prop and low gear has quit the pucker factor of torque roll. lol
Just my thoughts

1 Eye, we are on the same page, understand the tip speed issues and variations. Torque roll is my #1 concern here, I don't want to go all stupid on it and end up with a boat that is not easy on the Capt.

My reference point is 14' Palm Beach hulls built for this motor. Those boats are 4-6" wider (7'-6", 90") to run super wides on 2.68 gear. Torque roll is a bit complex. Starting from a stop in water it is strictly a function of flotation. Once the boat is moving, hydro dynamic lift come into play. On ground it's the outer rail pushing the most.

The worst case is pure flotation from a stop. In this case the extra 6" of hull width increases flotation and the moment arm resisting roll. Torque Roll resistance is "roughly" equivalent to width^2. To match torque roll the comparison is (84/90)^2 = 87% maximum torque. Assuming a 600+ motor the maximum gear equates to 2.68 * 87% = 2.33.

So that's where I am, somewhere between 2:1 to 2.38:1 gear and matching prop, somewhere between 76-79".

 

[OneBFC]

I think you will hit 1:1 ratio. We are right at that with ours and the LS makes more power. The 80 inch max i turn put out 1435lbs thrust. The same prop on a 418ls put out 1570lbs. I think the LS needed a 4th blade because we had 15 degrees in the prop and the Max blade has a narrow happy range.

Love the prop though!

 

[Slidin Gator]

1570 is not gonna do it for 1:1, maybe a different baseline.

Below is the weight budget from the boat this is going on based on weighing everything that came off/out of it. Full up O-540 with headers and prop hub is 438 lbs. So I'm adding 100 lbs of motor/gear/radiator. The 340 lbs of seat and cage rigging was outrageous (Includes mufflers), giving me a maybe 100 lbs less total with light rigging, heavier engine/gear combo and 3/8" vs. 1/4" poly.

There is some weight to take out of the 158 lbs of crap, but it's gonna be around 2,400 lbs or more loaded, no hovering.

 

[Slidin Gator]

Did some searching on part numbers today, this turns out to be the most significant. 19329865 comes right up for a GM crate L92 engine, the 2016 manufacture date confirms I got a real good deal at $2,648 delivered to the house. :cheers:

I felt guilty taking this engine apart, but I got over it and now have a low mileage factory rotating group and 30 lb injectors up for sale.

Dropped off the block and heads at the machine shop today for inspection, it's not gonna take much cleaning.

 

[Slidin Gator]

I changed the title (I Hope) to more accurately reflect what I'm building for future searches.

Picked up a 4.3 short block from my machine shop today for my buggy. This is my #1 project right now, they had to bore it to 0.040", thats all that's left after 0.015 and 0.030 bores, the bearings were worn down to copper. Imagine that, this particular motor was run regularly on oil/water mix from a few engine full floods and a worn out carb throttle body. Nothing money can't fix. :banghead: :banghead:

Back to this thread, wrote another, much larger check at the same time to get this build rolling.

Forged stroker crank and H Rods are already in, more coming. For the numbers, the stock engine runs 4.065" bore x 3.622" stroke for 376 cubic inches (6.2 L) displacement. I am installing a 4" stroke crank and boring 0.005" over, netting 416 in^3 (6.8 L). This is 10% more engine. So when comparing torque/Hp figures from stock setups, I just assume 110% as a baseline. The stock motor is 400+ ft-lbf and 406 Hp on 89 Octane. So, for the stroker, the factory baseline would be 440/450 Tq/Hp. I am planning 93 octane fuel and a conservative 11:1 max compression ratio. Cam and tuning should give me an easy 100 added to each figure.

The main :scratch: at the moment is cam selection. My machine shop gets good pricing from Texas Speed (TSP), so that's the starting point. I told him I wanted maximum torque between 3-4K RPM and max Hp at 5,500 or less. TSP came back with the following recommendations for a custom cam:

231/236
.619/.615
114
+2

I assume (but am confirming) that the duration figures are at 0.050". We are putting in double spring kits (0.660" rated) and a rocker trunion setup, but I am concerned that the lift, coupled with relatively steep profiles (to achieve duration and LSA figures) might be a bit much versus reliability. The fact that they are specifying 2 degrees of advance is a bit of a red flag for me. I am thinking less lift and 0 degrees advance as a baseline. Input Welcome.

I asked the Tech Rep at TSP if he had any torque curves for this grind. He said no, the closest match might be their 220/232 L92 Stage 2 grind where they have a torque curve from a stock displacement 6.2. I believe this cam is a 0.600" lift setup, but working on confirming. The tech made the point that the added duration of the cam specified vs. this particular cam is to increase air flow to make up for the added cubes.

Following is the dyno curve for a TSP 376 with the stage 2 cam described. For simplicity I just add 10% to the curve for the added cubes making it 470 Ft-lbf at 3000 RPM, Peak torque of 550 Ft-Lbf at 5,000 RPM and maybe 575 Hp at 5,500 RPM with Hp running out at 630 Hp around 6,200 RPM. I am aiming for 550 Hp max, so I have Hp to give up to move torque to lower RPM. I plan to keep the stock truck intake and use a stock size 87 mm cable throttle body.

All input welcome, throttle response is the primary goal.

 

[Rick McC.]

Did some searching on part numbers today, this turns out to be the most significant. 19329865 comes right up for a GM crate L92 engine, the 2016 manufacture date confirms I got a real good deal at $2,648 delivered to the house. :cheers:

I felt guilty taking this engine apart, but I got over it and now have a low mileage factory rotating group and 30 lb injectors up for sale.

Dropped off the block and heads at the machine shop today for inspection, it's not gonna take much cleaning.

The part number you note isn’t the part number on the crate…

 

[FISHSTICKER]

What do you estimate you will have $ as far as parts and machining to get the motor running. Motor only, no prop, gear, or anything else.

 

[Slidin Gator]

The part number you note isn’t the part number on the crate…

I'm not sure if you are trying the wrong number or if you have a different Google :dontknow:
GM P/N 19329865

https://googlethatforyou.com?q=gm 19329865

 

[Slidin Gator]

What do you estimate you will have $ as far as parts and machining to get the motor running. Motor only, no prop, gear, or anything else.

I wish you didn't ask, the best way to stay under budget is to not have one, first 2 rules right?

Like I said, I got lucky, it's very low miles and has the latest internals and parts are in great shape so I can re-use some parts (I even considered re-using the timing chain but that's getting upgraded).

Estimate is:
$2,648 Engine Assy delivered
-$200 Net income from selling rotating group to HotRodPaul in Texas on ebay, cost $75 in shipping, but it's gone!
-$400 Net planned selling oil pan, injectors, cam, 2 pulley balancer, DBW Throttle

$2,050 net on core, re-use oil pump, lifters, intake, heads, coils, water pump
$4,000 check to machine shop to gather parts Liberty (Lunati) crank & H-beams, pistons, cam, Roller chain, sst valves & trunion kits
$1,500 est. for machine work, crank balance, head work (TBD on who assembles short block)
$250 for one of smugglers 8 qt oil pans
$200 gaskets & seals
$250 est balancer
$2,100 ECU & Harness
$300 Cable throttle
$150 pedal cable & brackets
$200 fuel pump & plumbing

$11k complete, I'm sure I'm forgetting $1000 worth of something, starting with a dyno break in and tuning.

 

[FISHSTICKER]

Thats not bad when you consider I know guys paying $18,000 and more for carburated 550 HP motors over here

 

[FISHSTICKER]

And you have some parts listed that is not included in that $18,000.

 

[Slidin Gator]

Already adding on, forgot new injectors, that's another $600 lets say (TBD).

Pretty sure WaterThunder sells a 550 Hp injected 376 for around $14K. If I was smart I would have just written the man a check, but I'm hard headed :banghead: :banghead: I like to start at the beginning, no other way to really know a engine than to put it together.

I am using a local shop just a few block from my home, they have a crank spin balance machine and a dyno, along with a good reputation.

 

[Slidin Gator]

The part number you note isn’t the part number on the crate…

Rick,
I figured out what you are saying and thanks for the input. It's a GM "Service New" long block vs. a fully dressed crate engine. Service New being rebuilt, which matches my initial impression about the rods being numbered. As my shop said when I showed him the oil pump and lifters "Those are the good parts, someone's been in there". Regardless, for my purposes it came dressed, injectors are going away, will test the coils.

 

[Slidin Gator]

I found some good comparison torque curves for 2 cam options on a stroker LS3.

Here is where I am starting.

The main :scratch: at the moment is cam selection. My machine shop gets good pricing from Texas Speed (TSP), so that's the starting point. I told him I wanted maximum torque between 3-4K RPM and max Hp at 5,500 or less. TSP came back with the following recommendations for a custom cam:

231/236
.619/.615
114
+2

The more I read on the LS I am finding duration is more critical than lift for breathing, my shop says I don't want to push duration down or the engine just starts beating up the bearings. With 10% more motor, 10% more duration seems to be in order (vs. 220 duration 376 cams). The further advice is that lift specified is not an issue, the dual springs and trunion upgrades are rated .660 lift to well past 6,000. The TSP cam has less duration, particularly exhaust, than the 2 cams tested below. +2 cam advance is going to move torque down.


In the following article link they compare 2 CompCams cams on a 415 stroker with a factory LS3 intake and the CompCams XFI system.

https://www.cpgnation.com/ls3-stroker-cam-swap/

The baseline is:
.621/.624 lift split, a 235/251-degree duration split, and 113-degree lsa.

The higher RPM cam is:
.623/.596 lift split, a 247/258-degree duration split, and 113-degree lsa.


Using the torque curves from the linked test, my goal is easy to visualize, I want engine max torque at or above 500 ft-lbf from 3000-5500 RPM. On the chart below, this means moving the baseline torque curve 500 RPM lower. I am looking to accomplish this by:
- Using the truck intake
- Smaller throttle (87 mm vs. 92 tested)
- Cam timing advance
- Some reduced duration (vs. curves below)
- Low RPM tuned exhaust, works best with a bit less exhaust duration

I should be able to make a good dent in all this, gonna be hard to overshoot to too low RPM.

 

[CarMotorBarge]

You will want a 223 intake duration for the cam. This is the duration that most airboat engine manufacturers put in their 416 and 418 engines that run at 5600 at WOT. Keep the lift at or below .624 for longevity.