305 chevy to 406 chevy swap, V/P 280

[floater3]

Hi,
I couldn't find this on the forum so forgive me if its been covered over and over. I want to replace the 305 in my 1984 Bayliner Capri with a 406 small block that I built for my car (6000 miles on it now, and I'm selling the car with a different motor). The 406 is a 1976 with two piece rear main seal. My question is, will the flywheel or whatever its called on a boat fit on the 406 and will the starter also fit? Also, any obvious problems with a 406 small block chevy in my boat? Thanks for your help. ALSO, the outdrive is a volvo/penta 280.

 

[cguerrieo]

Re: 305 chevy to 406 chevy swap, V/P 280

I've run into this before when I swapped my 350 mag out for a 383 stroker. the flywheels are different and probably starters too. check the bolt pattern on the starter. the two bolts are either directly side by side, or cris cross from each other. just make sure they are the same on each block. if not, then you'll need to buy a new starter. as for the flywheel. if it's not the same, just go out and purchase an automotive flywheel for a clutch application and paint it with marine grade spray paint....don't be fooled into buying a marine flywheel...they are the same thing, only ad a zero or two on the cost.

 

[Don S]

Re: 305 chevy to 406 chevy swap, V/P 280

Your "406" probably doesn't have a cam or cylinder wall thickness capable of being a marine engine (for very long).
You probably still have a 12" flywheel so that won't be your big problem. Water getting into your engine thru the exhaust due to cam characteristics is going to be your biggest problem.

 

[mtnrat]

Re: 305 chevy to 406 chevy swap, V/P 280

I concur with the possible cam problem. What are the cam specs? I had a custom cam made for my 383 that idles smoothly and designed to match the other components of my build. Best extra $150 I spent to make sure I would get no reversion and have the characteristics I wanted.
BTW what length is your boat

 

[Bondo]

Re: 305 chevy to 406 chevy swap, V/P 280

Ayuh,.....

The 400 Chevy is an Externally Balanced motor...
It takes a Very Different Flywheel.....
Usually a 14", which means your Starter will be Different as well...

 

[EricR]

Re: 305 chevy to 406 chevy swap, V/P 280

Just because it's a 406cid doesn't mean it has some radical cam in it, and for that matter a cam that is "radical" in a smaller cube mill is very mild in a larger cube one.

As far as the flexplate/flywheel situation, find a shop that builds performance marine inboards and ask them.

I am sure this can be done, and want to see the results!

 

[stinger222]

Re: 305 chevy to 406 chevy swap, V/P 280

I had the same motor in my CC Stinger 222 for 6 seasons...until one day I was wide open throttle and #1 cyl wall disintegrated...great motor, make sure you drill the steam holes in the heads and enjoy!!!

 

[Don S]

Re: 305 chevy to 406 chevy swap, V/P 280

Just because it's a 406cid doesn't mean it has some radical cam in it, and for that matter a cam that is "radical" in a smaller cube mill is very mild in a larger cube one

He stated he has a SBC engine, nothing about cam, nothing about bore, nothing about it being a 305, a 350, or a 400. He says it's a 406!
Sorry, but there is no such thing as a 406.
Without some info from the original poster, no one here knows what he has or doesn't have.
He is basically getting a quick education that boat engines, and car engines aren't the same.
And it's best to not assume it will work. Way too many variables

 

[stinger222]

Re: 305 chevy to 406 chevy swap, V/P 280

400 bored 30 over gives you a 406...as long as it is marinized, no reason he can't use it. Big block like torque without the extra weight.

 

[mtnrat]

Re: 305 chevy to 406 chevy swap, V/P 280

That is true, however the 406 is known for possible temp problems (need steam holes for sure), and as DonS alluded to, cylinder wall thickness issues that may rear their head over time in a marine engine. I would like to know a little more about the engine, could be just fine. Give us some build info floater3.
Cheers,

 

[floater3]

Re: 305 chevy to 406 chevy swap, V/P 280

Sorry for the long delay--vacation and non boat issues!

Anyway, the motor is a 400 inch chevy, bored 0.030 to produce 406 cu. The cam is mild-214 intake, 224 exhaust duration @ 0.050" lift. 0.437/0.450" lift, 112 degree intake centerline. The heads have the steam holes drilled in them. They are Chevy Vortec heads with slight bowl porting. The crank and rods are forged. The pistons have around 30 cc dish to keep compression low with Vortec's 64cc (milled and cc'd) head chamber (aprox 9.1:1 with stainless shim head gasket). I've put 6500 miles on the motor in my car. Runs on 87 octane, runs 180 degrees all summer long. The heads/cam won't allow high rpm, but I thought for a marine application below 4800 rpm (volvo-penta 280) it might work, and heck, I already have it sitting in the barn! I've owned/built sbc, bbc, pontiac and cadillac v-8's and a few chevy v-6's, but NEVER anything for a boat so I don't want to march into this as if I know everything. Thanks for any replies.

The current motor in the boat is a 305 chevy, mostly stock.
I understand the wall thickness issue, however, I only used the boat 6 times last season and I'm not doing much better this season. The boat is fresh water only.

 

[mtnrat]

Re: 305 chevy to 406 chevy swap, V/P 280

Heck, throw it in. I am running a 383 on a volvo 280. The only problem I had was with prop torque. When I got over 4000 rpm the boat would want to take a hard right. Solved that by installing a duo prop lower for the 280. With a prop turning each direction , no more prop torque.
Good Luck.

 

[floater3]

Re: 305 chevy to 406 chevy swap, V/P 280

Any thoughts on the cam? This "water in the exhaust" thing is new to me since I have not done marine motors before. What is a good small block chevy marine cam? (capri 1950) Street guys always have a few grinds they swear by.

 

[mthieme]

Re: 305 chevy to 406 chevy swap, V/P 280

Since 350 chevys in boats are as common as rice in Asia and the 400 is a 350 stroked 1/2", doubtful you are going to blow any cylinder walls out. You do need to marinize unless you have fresh water cooling which I've never seen on a Capri but you could add it for around a nickel. Not familiar with the Volvo outdrive, but other brands have different gears for different size engines.
I've never seen a V8 in a Capri. Bayliner isn't the strongest boat on the water structurally and the Capri is the Chevy of boats. I'm not knocking your boat, just want you to think twice about hopping it up.

 

[Eliminator]

Re: 305 chevy to 406 chevy swap, V/P 280

still have your old flywheel or flexplate? With the info you have I would think you would know if the 400 was built internally or externally balanced so proper flexplate would be the main thing. Whole lot more engine than that 305 will ever be!

 

[hard-3]

Re: 305 chevy to 406 chevy swap, V/P 280

take the flywheel from the 305 to a good automotive machine shop that can balance and have it machined for an externaly balanced 400