Convincor LS Swap Project Thread

[corey331]

All aluminum 408, great choice! That's the same direction I went in my Camaro but, I went with 11.5:1 compression

How high do you plan on spinning the motor? My car makes peak power around 6800 and holds power to 7200 before it starts to tapper off.

Are you going with LS7 lifters? Did you just port the stock LS6 heads?

As of now, I plan on spinning it up to about 6500. I don't think the stock bravo will like any more than that. Hell, it might not like the 6500, but we will see. That's another reason I went with the increased displacement, hopefully get more low end to mid range grunt out of it since I'm not going to spin it to the moon. I was originally going to run the motor up around 11.5:1 compression, but with talking to my builder and Bob Madera, running that high in a marine motor, and what I wanted out of that motor, wasn't going to be the best idea. So we ordered a set of -8cc pistons, and brought it down to 10.5:1. The heads are actually 317 (6.0L) truck heads that have had PRC's (Texas Speed) Stage 2.5 CNC port job on them. The chambers were opened up to 70cc's as well. Should be perfect for what I am going to be running.

 

[corey331]

That means I get a full season of being able to outrun you on the lake.

Pretty much everybody out runs me now, lol. But I don't care, I still have fun. And honestly, I'm not sure how the boat will perform once I get the new motor in there. I just have always liked stuff that is different, so that's what I'm doing here. I think I will get just as big of a kick lifting the hatch at the dock and watching people try to figure out what they are looking at, as I will running it across the lake.

 

[Rcenter1]

She will run I wouldn't worry about that, bravo 1 should be just fine as long as you don't throw the torque at her coming out of the hole. Can't wait to see pictures of her coming together

 

[linn]

As of now, I plan on spinning it up to about 6500. I don't think the stock bravo will like any more than that. Hell, it might not like the 6500, but we will see. That's another reason I went with the increased displacement, hopefully get more low end to mid range grunt out of it since I'm not going to spin it to the moon. I was originally going to run the motor up around 11.5:1 compression, but with talking to my builder and Bob Madera, running that high in a marine motor, and what I wanted out of that motor, wasn't going to be the best idea. So we ordered a set of -8cc pistons, and brought it down to 10.5:1. The heads are actually 317 (6.0L) truck heads that have had PRC's (Texas Speed) Stage 2.5 CNC port job on them. The chambers were opened up to 70cc's as well. Should be perfect for what I am going to be running.

What is the HP/TQ goal, 550/500+?

 

[corey331]

If I can hit those numbers, I will be very happy. I think a 500hp all aluminum LS motor would push the boat really well with the massive amount of weight savings I will have.

 

[DropTop5.0]

How much weight do you think you'll save? Will that affect your prop selection?

 

[corey331]

How much weight do you think you'll save? Will that affect your prop selection?

If my math is correct, I should drop at least 450-500 pounds out of the transom. now that's on the 454 that I have in there that still has the cast iron intake and has the stock cast iron exhaust. So the weight savings is pretty substantial. now I plan on weighing everything that I take out of the boat as well as weighing everything that I put back in so I can come up with a pretty close number, within 10-20 pounds anyway. But I love the fact that I can hug the aluminum LS block and carry it around by myself with no problems, and the LS heads I can carry one in each hand like its nothing. Compared to a few weeks ago when I was helping my buddy Brent pull some Dart iron heads off of his big block in his boat and almost popped a grape lifting one head!!!

As far as prop selection goes, it will greatly effect my selection. This is something else that I have been talking Jason at Kunkel's Marine about. My 253 with a big block really like a 4 blade Bravo cause it gives it a lot of stern lift. Well with that much weight out of the back of the boat, stern lift shouldn't be a problem. So I am probably going to start out trying a 3 blade Mirage Plus which will give me more bow lift. My dad runs a 27p Mirage Plus on his *cough* Baja *cough* so I will probably start off trying that. But it seems like with taking all that weight out of the back and running a bow lift prop, getting the boat up and out of the water shouldn't be a problem!! I know in the long run I will most likely end up having a prop worked by BBlades or somebody like that to really get the boat to handle the way I want. This is part of the fun of going into uncharted territory!!!

 

[linn]

As of now, I plan on spinning it up to about 6500. I don't think the stock bravo will like any more than that. Hell, it might not like the 6500, but we will see. That's another reason I went with the increased displacement, hopefully get more low end to mid range grunt out of it since I'm not going to spin it to the moon. I was originally going to run the motor up around 11.5:1 compression, but with talking to my builder and Bob Madera, running that high in a marine motor, and what I wanted out of that motor, wasn't going to be the best idea. So we ordered a set of -8cc pistons, and brought it down to 10.5:1. The heads are actually 317 (6.0L) truck heads that have had PRC's (Texas Speed) Stage 2.5 CNC port job on them. The chambers were opened up to 70cc's as well. Should be perfect for what I am going to be running.

If I can hit those numbers, I will be very happy. I think a 500hp all aluminum LS motor would push the boat really well with the massive amount of weight savings I will have.

500 should be a walk in the park and will make that boat come alive.

Good luck, let me know if you need any help/info.

 

[ezstriper]

you might try a hydromotive prop, would help with bow lift...keep us posted...

 

[hadleycat]

OK, I decided I would do a little update to this thread. Over the past few months I have done a lot of learning about these motors, and the more I learn, the more excited I am about this swap and more impressed I am with the LS line of motors. And also, as most projects tend to do, this has grown over the past few months.

First thing, I found out that the motor was not an LS3, it is an LS2. Which in the grand scheme of things, doesn't matter much anyways with what the motor is now. Since the rod bearing that spun on the stock crank pretty much wiped it out and I was going to have to buy a new aftermarket crank anyways, it didn't take much convincing from my engine builder to say "Screw it.....go big or go home!". So needless to say the block has been bored .030 and with the help of a Callies compstar forged crank, H-beam rods and a set of Wiseco pistons, the displacement has been upped to 408ci. This is what I mean by the project growing, lol. With the ported heads, my compression ratio will be right at 10.5:1. As far as the heads go, I finally got the flow numbers back and I have to say that I am very impressed with the numbers they get out of a small head. @.500 lift they flow 294cfm, @.600 they flow 316cfm. With those numbers in hand I contacted Bob Madera at Marine Kinetics about a custom ground camshaft. After several phone conversations, we have a good idea of what to do and the cam has been ordered. I will have specs on it early next week. Needless to say Bob is a great guy to work with and he was actually as excited about the project as I am.

My next chore is tackling the cooling system. This is where a lot of the after market parts are scarce, or if they are available, are priced to the moon. The more I thought about it, I just couldn't bring myself to pay almost $1000 for a raw water pump, no matter how pretty it is. So with a lot of help and advice and some parts from Jason Kunkel at Kunkel's Marine, we have come up with a plan on how to make it work saving me about $700 in the process. I'll post up more pics of this stuff as it comes together as well. I'll throw another plug out here, Jason and everybody else at Kunkel's Marine are plain awesome to work with and really know their stuff!!!

As I said, I'll be posting up more pics of stuff as it all comes together. I have a trip up to my engine builder planned later this week, so I will take a bunch of pics and post them up of what's going on.

The guys at Kunkels are awesome for sure!

 

[hotdaddy27]

Great project!

Just out of curiosity, where do you see the budget being on this beast...all in?

Good luck!

HD

 

[corey331]

Great project!

Just out of curiosity, where do you see the budget being on this beast...all in?

Good luck!

HD

Honestly, I have no idea and I really don't want to think about it, lol. So far I have been very lucky in that with everything I have bought, I have been able to sell off what I am not going to use and make some money. Like when I bought that blown up LS1 for $500. I was able to keep the accessories off of it, and sell everything else and ended up making almost $1000 on it. Plus, my plan is to pull the running low hour 454 that's in my boat now and sell it complete, intake to pan with exhaust and all, and get enough money out of it to buy my headers. My guess is that I will have close to $6-8k out of pocket in the build. Now I know that this swap could be done a lot cheaper. However I am not going to "budget" route building a big all aluminum stroker motor, running CNC'd heads, custom grind cam and custom dry headers. I am doing this to be different, and created this thread to show everybody how I did it, what mistakes I made or will make and give a blue print for how to do this swap in the future. The swap can be done on a lot more of a budget than what I am doing. Someone could go buy a $600 junkyard 5.3 or 6.0 truck motor, have it checked out, slap a small cam in it, and buy some exhaust manifolds and have a nice 400hp+ motor to replace their tired old Mercruiser 260hp 350 or even a 310-330hp 454 like mine. Those truck motors in their stock form can easily handle 700hp+ in a car so my guess is 600hp would be no problem in a boat with stock internals and stock heads, just replace the rod bolts with ARP's since that is the weak point in the bottom end.

 

[illMATTic]

Do you have any links to other current builds? Everything I am finding seems to be old or just ads for new engines.

 

[corey331]

Do you have any links to other current builds? Everything I am finding seems to be old or just ads for new engines.

I honestly don't know of any other current builds going on right now, and most of the older builds I come across are in jet boats. I do know there is a guy who put twin LS7's in a 32 Skater and it ended up running really well. I know not too many people are doing it because every time I call a vendor about parts and tell them what I am doing, they seem really surprised and say "Well that's a good idea" or "This is the first time I've heard of somebody doing that". So its not too common...yet.

 

[illMATTic]

I honestly don't know of any other current builds going on right now, and most of the older builds I come across are in jet boats. I do know there is a guy who put twin LS7's in a 32 Skater and it ended up running really well. I know not too many people are doing it because every time I call a vendor about parts and tell them what I am doing, they seem really surprised and say "Well that's a good idea" or "This is the first time I've heard of somebody doing that". So its not too common...yet.

I know. It's crazy since there has been so much talk about it for years now. I was hoping to find some info on longevity, durability, etc...

 

[Gimme Fuel]

Jim Stykes (JIMKID on OSO) is the one Corey speaks of with the LS7's in his skater. I saw these engines in person a few years back at his shop and they are impressive for sure!

A lot of New Zealanders/Australians use them in their jet boats as Corey mentioned.
http://www.jetboatbase.co.nz/ecotec/ls-chev-supercharger-kit/

That website is about using repurposed Eaton blowers on LS motors for jet boats. Make some good power. I have done a bunch of reading about "home-made" supercharging using take-off junkyard blowers. Potential is there but it is a lot of fab work.

Bob Madera (Marine Kinetics)seems to know of a few builds going on with Marine LS platforms and is excited people are playing with them.

Here is a good OSO thread about the LS conversion but not a lot of finished examples.
http://www.offshoreonly.com/forums/general-q/301360-whats-truly-needed-swap-ls-engine.html

Michigan Motorz sells drop in LS crate motors that they build as repowering options.

The wakeboard boat market is filled with them. Seems they are quite potent for that purpose but I doubt many want to take off their flat billed Monster hat to hot rod their boats.

I am carefully watching Corey's project and learning as much as I can about the swap. I am interested for another future project.

 

[illMATTic]

The "junkyard truck engine" is appealing. I just wish there was more info on running WOT for extended periods. I am not into throwing money away.

 

[Gimme Fuel]

The "junkyard truck engine" is appealing. I just wish there was more info on running WOT for extended periods. I am not into throwing money away.

I have seen some Chevy truck engines flogged in the mud for minutes on end and towing twice the loads they should uphill at 80 mph with high rpm.

With proper setup and cooling, I don't think there would be an issue. Now just taking one out of a junkyard and slapping it right in, I don't recommend that.

Put it on a stand, open it up, check for issues and proper clearances, re ring/bearing, add proper marine camshaft, then I think they will be just fine for no more effort than a standard rebuild.

 

[corey331]

The "junkyard truck engine" is appealing. I just wish there was more info on running WOT for extended periods. I am not into throwing money away.

The main thing you would need to change is the rod bolts and the oil pan to a larger capacity. I am running a custom 12 quart pan. The problem with oiling over long runs is the oil pump is driven directly off of the crank and is run at a 1:1 ratio, where as old small block pumps were run off the cam at a .5:1 ratio. So these LS motors can literally suck a stock pan dry in a matter of a few minutes as well as foaming the oil. But this is all fixed with a simple deep pan and deep pick up. As far as the internals being able to stand up to it, not a problem!!! If you get a chance, compare the internals of one of these LS motors to the internals of a 350 mag motor. You will see why I say no problem. These motors are beefy!!! Hell, the blocks have 6 bolt mains. Once the rod bolts are addressed and the oiling system, I wouldn't hesitate to hold it wide open for a few miles. Hell, I plan on doing it a time or two with my new one!!!

 

[RNGRDVE]

A friend of mine is in the process of painting this and then it has a pair of LS motahs dropping in.