305 question - NJFBOA - Home of New Jersey's Camaros and Firebirds

LTb1ow · 05-13-2009, 05:35 PM

Worth it?

In all seriousness, my family's boat has a wimpy 305 in it. My Dad wants to just drop a 350 shortblock in it but eh, theres gotta be stuff you can do to a 305 right?

I was thinking a nice heads/cam package, but I dunno how in the world you would pick that out, being as its a boat so it needs to idle and then get to WOT fast.

Ideas?

And it can't be more than like 380 hp or something, outdrive won't handle more than that.... which killed my nitrous idea...

Featherburner · 05-13-2009, 09:11 PM

Here's what you do with a 305. Pull the crank out and throw away the rest. Put said crank in a 350 block with everything else from a 350 and go like hell.

FlyingDutchman · 05-13-2009, 09:17 PM

i vote 350 or bigger

LTb1ow · 05-13-2009, 10:40 PM

What would a 305 crank in a 350 do me?

HeadlessNorseman · 05-13-2009, 10:51 PM

Quote:

Originally Posted by Shownomercy

What would a 305 crank in a 350 do me?

I think the journal size is different anyways. For a boat im sure you have to match peak power with the max prop speed. But yeah if the bottom end is good there really is no reason for a 350. 305 with heads and cam will make 300hp easily. But do you want to modfify a boat motor? They need to be reliable lol

The Fixer · 05-13-2009, 10:52 PM

On the 1-piece rear-main blocks ('86-up) the 305 and 350 cranks are the same, just weighted differently. My guess is he's telling you to save the crank for the new motor.

LTb1ow · 05-13-2009, 10:53 PM

Ahh ok. Yea, idk, my Dad likes the warrenty of getting a new shortblock, but eh, I would rather not spend a lot of money on something I could do...

ib4200 · 05-13-2009, 10:55 PM

put a snail on it

HeadlessNorseman · 05-13-2009, 11:01 PM

a turbo wont help if the outdrive is the limiting factor. Thats the trans, rear, tires, and gear ratio all rolled into one. Just get a basic rebuild kit and rebuild the 305. Who cares about a warranty! Does the boat use a carb and HEI ignition? or some sort of fuel injection? It would prob benefit a lot from some fine tuning of the carb for constant throttle use. You dont really need throttle repsone or low end out of a boat motor. I would say go for used vortec heads, decent cam, and a single plane intake manifold. high 200hp at operating rpms, prob 320 at peak. Find a way to port the water jacket exhaust manifold things, or replace them. What kind of boat is it? I want to put a 50hp outboard on our boat. Its a 12ft aluminum 4 seater. Flies now with a 25hp....just imagine

LTb1ow · 05-13-2009, 11:01 PM

Prob cost more than the shortblock, and then when the stock pistons blow up... yea... not a good idea. Marine gas = not so nice.

LTb1ow · 05-13-2009, 11:02 PM

Its a 23ish foot formula.

Featherburner · 05-14-2009, 08:43 AM

305 and 350 crank are the same size.

LTb1ow · 05-14-2009, 08:47 AM

Oh ok, cool.

WildBillyT · 05-14-2009, 09:22 AM

Quote:

Originally Posted by Featherburner

Here's what you do with a 305. Pull the crank out and throw away the rest. Put said crank in a 350 block with everything else from a 350 and go like hell.

QFT.

Don't build a 305.

LTb1ow · 05-14-2009, 09:24 AM

Ok, well I guess I tried... lol..

Pampered-Z · 05-14-2009, 12:30 PM

You can't really do much with a 305, even getting to 350 HP is a bit tuff. The 305 is such a small bore that there is no room for big valves so it just can't move air and breath.

The 305 HO/TPI heads (or something simular) have slightly larger values and thus flow a bit more, adding a mild cam will put you in the 210-235HP range. Also remember that 305s aren't designed to be spun high, keep it under 6K or you run the risk of cracking the mains.

So as others have said, unless you are running some type of class where you would be restricted to a 305 a 350, even a mild 350 would be cost effective and able to be spun higher. And don't waste the money on strocking a 305, we played with them (334 CI ) back in the 80's and a mild 250 will still pull better numbers at 1/2 the cost.

Not really a boat person, but can't you change props?

LTb1ow · 05-14-2009, 12:42 PM

Yup, same as a car pretty much, new gears in the outdrive, and at the moment we run a four blade prop for get out of the hole oomph, versus a three blade for top end speed.

mc73nova · 05-14-2009, 01:07 PM

http://cgi.ebay.com/ebaymotors/86-95...1%7C240%3A1318

LTb1ow · 05-14-2009, 01:09 PM

Expensive.
But yea, my Dad has a ton of engines he likes picked out... and lucky me, I get to play swap this winter/late summer. Woot.

baddest434 · 05-14-2009, 02:32 PM

Quote:

Originally Posted by Pampered-Z

You can't really do much with a 305,

not true. i had a 305 and in all seriousness it was faster then some of these LT1's LS1's. 13.1 on motor 11.47 on a 150 shot.

LTb1ow · 05-14-2009, 02:34 PM

See heres the thing Bill.... as much as I would love to spray the snot out of my Dad's boat, I think I would fail a few safety things and or, cost a lot every re fill.... lol