400 stroker build....for a boat

-
wingrider

wingrider

Active Member
Joined
May 21, 2017
Messages
29
Reaction score
2
Location
St. Michael, MN
Hello All,

Hopefully this is ok to ask here, as I need a little guidance to build an engine for a boat I am building.

Slight bit of background...picked up a 400 block to use as a stroker project. I am in the process of building a wooden boat...27' long is the planned length. Bare hull is going to weigh about 1600-1800 pounds. Looks a bit like an old Chris craft.

I have been told the 400 stroked to a 451 or possibly a 470 will give a lot of torque, and rev more like a small block.

What I am wondering is, which of these combos will give me the best low end torque needed for the boat. I don't need it to turn to 7K, but do need stump pulling power low down.

Which engine size would you all pick for this (451,470)? It was once suggested to me to use the old 516 heads with a bigger exhaust valve, but didn't know of some of the newer, smaller aluminum heads would be a better option.

I am researching various options for what cam to use, and what EFI system I am going to plan to use. I am also going to be using a closed cooling system so that I don't have raw sea water running through the block.

Thanks for any help in this project!
 
wingrider said:
Hello All,

Hopefully this is ok to ask here, as I need a little guidance to build an engine for a boat I am building.

Slight bit of background...picked up a 400 block to use as a stroker project. I am in the process of building a wooden boat...27' long is the planned length. Bare hull is going to weigh about 1600-1800 pounds. Looks a bit like an old Chris craft.

I have been told the 400 stroked to a 451 or possibly a 470 will give a lot of torque, and rev more like a small block.

What I am wondering is, which of these combos will give me the best low end torque needed for the boat. I don't need it to turn to 7K, but do need stump pulling power low down.

Which engine size would you all pick for this (451,470)? It was once suggested to me to use the old 516 heads with a bigger exhaust valve, but didn't know of some of the newer, smaller aluminum heads would be a better option.

I am researching various options for what cam to use, and what EFI system I am going to plan to use. I am also going to be using a closed cooling system so that I don't have raw sea water running through the block.

Thanks for any help in this project!
Click to expand...


I'd stay 451. Reason being is more meat to dissipate heat. You're gonna need one hell of a cooling system. I know my grandfather is having an issue with his boat right now. It's a Merlin inline 6 and it runs very very hot. It's all about air flow. One thing too I'll add is you might consider adding a fuel cooler. We had too and this was a fresh factory boat but it kept vaporlocking. Fuel cooler stopped that.
 
dukeboy_318 said:
I'd stay 451. Reason being is more meat to dissipate heat. You're gonna need one hell of a cooling system. I know my grandfather is having an issue with his boat right now. It's a Merlin inline 6 and it runs very very hot. It's all about air flow. One thing too I'll add is you might consider adding a fuel cooler. We had too and this was a fresh factory boat but it kept vaporlocking. Fuel cooler stopped that.
Click to expand...
Why would the 451 have more"meat" than a 470? The difference is in the stroke.
 
SGBARRACUDA said:
Why would the 451 have more"meat" than a 470? The difference is in the stroke.
Click to expand...
Duh duh I'm dumb. My brain dead moment was thinking bore size not stroke for some stupid reason. Disregard that part.
 
Plenty of BB chryslers went in to boats without issue. I think a lot will depend on whether you're going use closed cooling,wet exhaust or dry exhaust, and/or raw water cooling, etc. Wet exhaust won't tolerate much more then mid 220's @ .050 duration. Heat exchangers can be quite pricey. Headers are usually reserved for opened engine boats
 
Thanks for the replies so far! My build puts the engine "below" deck, so I am slowly putting a list together of everything I need for the closed cooling system. I had planned on running wet exhaust to try and keep the heat down in the engine compartment. Actually am going to make an adapter to be able to use the larger port small block chevy manifolds to be less weight, and not have to worry about the old Chrysler log type manifolds.

Heat exchangers are certainly pricy...but I want to do it right the first time if possible.
 
wingrider said:
Thanks for the replies so far! My build puts the engine "below" deck, so I am slowly putting a list together of everything I need for the closed cooling system. I had planned on running wet exhaust to try and keep the heat down in the engine compartment. Actually am going to make an adapter to be able to use the larger port small block chevy manifolds to be less weight, and not have to worry about the old Chrysler log type manifolds.

Heat exchangers are certainly pricy...but I want to do it right the first time if possible.
Click to expand...
Some of the aftermarket chebbie manifolds have better internal design. Just curious, are you using Glen-L plans or anothers? Some pics would be really cool. lol
 
Yes, Glen-L Monte Carlo. We will see if I can figure out how to post a picture of what it will look like.

IMG_0225.JPG
 
I'd run as much stroke as possible since boats are very tough operating environment, and torque is largely a function of cubic inches. I'd look very hard at inconel exhaust valves and durabond or other hardened valve seat material, regardless of what heads you use. All a function of budget limits.

If you're not starting with any parts yet other than the block, a 512 stroker kit will cost essentially same as a smaller kit, and you'd be ahead on torque. A 512 with some rubbed on Eddie RPM's or Trick Flow 240's will make a metric boatload of torque at an rpm you can keep alive.

Will this be dry sump oiling? I commonly see that on boat engines. Even if not, you should be able to get a nice oil pan and external pickup in there and that will help quite a bit. Consider a crank scraper as mandatory. S/F.....Ken M
 
I have a couple of 470 engines which I use for dyno testing. They are a super nice combination. If you were closer I'd tell you to come over and take a look. Here is an article I did for the Hot Rod website: We Test Intake Manifolds and Carburetors on our 400 Stroker in Search of Ultimate Power - Hot Rod Network

It should give you some details on building a 470. I also wrote a book on big block Mopar engines which you can buy at Amazon: How to Build Max-Performance Mopar Big-Blocks: Andy Finkbeiner, John Baechtel: 9781613250921: Amazon.com: Books

Between the book and the magazine articles you should find all the info you need. By the way, I'd use Trick Flow 240 heads on your engine if the exhaust system will work with angled plugs. If you need straight plugs then the task gets a little harder.

Molnar has the crank and rods that you need, multiple places have the correct piston. Everything else is just standard bolt on stuff. No low deck EFI intakes available so you'll have to roll your own. Wilson Manifolds can do the conversion. I'd recommend starting with a Trick Flow intake manifold.
 
Thanks everyone! So far, just an old block that is going to the machine shop to get cleaned up and tested to be sure that we are starting with good parts. No parts have been purchased, which is one of the reasons for this thread! :)

I do understand that this is a tough environment for an engine. I have read a bit about going with the bigger stroker kits moves the wrist pin to close to the rings...is that something to worry about?

Thanks for the links! I will certainly take a look at it all!

I have looked at the Trick Flow stuff, and it seems like it is pretty good out of the box....
 
You can play with rod length and compression height on the pistons but you will be changing rod ratio. They make bigger engines out of the Low Deck, but I've always been partial to the 451/470 combo.
 
The common 512 combo uses a 1.320 CH piston, same as the common 451 combo. The common 470 combo uses a 1.480 CH. Of those two choices, I'd prefer the 470. More cubes is almost always better.
I work with a lot of sub 1.100CH pistons in NA motors, albeit mostly small blocks and they live fine. Power adders are where you start seeing issues.

What are you planning to use for fuel? Are you doing port injection or something like the Holley/FItech throttle body injection? S/F....Ken M
 
My thoughts were to use something like a throttle body injection, although I would have loved to try the MSD Atomic setup if they made it for the low deck. So, I guess the EFI idea is still up in the air.

EFI is still something I am learning to play with...in the process of converting a couple bikes I have to EFI, and some of it makes my head spin!

I guess as long as we are putting some type of package together, a single plane I take would be better than a dual plane if I am looking for low end torque, correct? Watching the video and reading the article, this seems to be the general consensus? That tunnel ram looks awesome! To bad it probably won't fit under the deck.
 
Last edited:
I forgot to answer the fuel...hoping to get by with pump gas. This boat will be pulled out of the water every night (don't live on the water), so a gas station is cheaper than a marina fill up.

That dry sump oiling system looks like it will be just the ticket!
 
wingrider said:
I forgot to answer the fuel...hoping to get by with pump gas. This boat will be pulled out of the water every night (don't live on the water), so a gas station is cheaper than a marina fill up.

That dry sump oiling system looks like it will be just the ticket!
Click to expand...
 
I would stay with a little taller compression height. Boat engines live at 4-4.5k under full load all the time
 
Not sure what happened with that last post so I'll try again. If you want to go wet sump I have a marine pan that I do not need anymore. It is a cast deep sump pan designed for marine use. I also have the matching pickup assembly which is hinged. Here are a couple of pictures. If you want it just shoot me a PM.

DSC_0646 (Large).JPG


DSC_0647 (Large).JPG
 
Daves69 said:
A thread that may be of interest......
Chrysler crank pump drive drawings 318 to 440
Click to expand...

Thanks for the link! I am a member over there as well, and have scoured the pages looking for info that would help me. The person that originated that thead was actually the one to suggest to me to use a 400 block instead of a 440. He is also the one that suggested using the SB chevy manifolds in place of the old Chrysler ones.

Sadly I have not been able to get a hold of him recently to bounce ideas off of.
 
wingrider said:
Hello All,

Hopefully this is ok to ask here, as I need a little guidance to build an engine for a boat I am building.

Slight bit of background...picked up a 400 block to use as a stroker project. I am in the process of building a wooden boat...27' long is the planned length. Bare hull is going to weigh about 1600-1800 pounds. Looks a bit like an old Chris craft.

I have been told the 400 stroked to a 451 or possibly a 470 will give a lot of torque, and rev more like a small block.

What I am wondering is, which of these combos will give me the best low end torque needed for the boat. I don't need it to turn to 7K, but do need stump pulling power low down.

Which engine size would you all pick for this (451,470)? It was once suggested to me to use the old 516 heads with a bigger exhaust valve, but didn't know of some of the newer, smaller aluminum heads would be a better option.

I am researching various options for what cam to use, and what EFI system I am going to plan to use. I am also going to be using a closed cooling system so that I don't have raw sea water running through the block.

Thanks for any help in this project!
Click to expand...
:popcorn:
 
AndyF said:
If you want to go dry sump then you might want to take a look at this 470 inch dry sump motor that I did for Car Craft. It is a pump gas engine and would work well in a boat. 750 hp would get you across the lake in a hurry!

Dyno Day: Trick Flow 270 Mopar Heads - Hot Rod Network
Click to expand...

Thanks Andy, I found that when I searched for your articles on Hot Rod Network. That engine looked great!
 
You must log in or register to reply here.
-

Back
Top