gm 305 to new350 swap

sarantis · Sep 6, 2008

hello again.i 'm thinking about replacing my gm305 1979(mcm 228) and keep for some years the pre-alpha 228 outdrive. I 've found in good price a new block 350 but i'm afraid if i can use all the stuff i've got for the 305 or not.Distributor,cooling system with the long manifolds and the elbows at the back end(thermost.housing with the 8 hoses) and starter.I read a relative thread .Do i need a new intake manifold? Will my coupler ,flywheel,flywheel cover fit to the new 350?
Thanks in advance

Don S · Sep 6, 2008

Re: gm 305 to new350 swap

If you are talking about a NEW, 2008 350 engine, no, a lot (MOST) of accessories won't fit.
Intake, flywheel, flywheel cover, coupler, starter, alternator brackest, pullies, belts, none of it will fit, and putting a points distributor on a new 350 is just plain wrong.

xltier · Sep 6, 2008

Re: gm 305 to new350 swap

sarantis said:
hello again.i 'm thinking about replacing my gm305 1979(mcm 228) and keep for some years the pre-alpha 228 outdrive. I 've found in good price a new block 350 but i'm afraid if i can use all the stuff i've got for the 305 or not.Distributor,cooling system with the long manifolds and the elbows at the back end(thermost.housing with the 8 hoses) and starter.I read a relative thread .Do i need a new intake manifold? Will my coupler ,flywheel,flywheel cover fit to the new 350?
Thanks in advance

just finished up that same job.went from 1980 to 1988.never again.had to send out carb.distrib. was the same.coupler was different because of different crank.new coupler doesnt fit in old bell housing.newer bell housing takes a different motor mount plate.[transom plate.]new motor mount plate doesnt fit around old y-pipe.new y-pipe doesnt fit old gimbal housing.around and around.hth

sarantis · Sep 6, 2008

Re: gm 305 to new350 swap

i don't know if we talk about the same blocks.My dealer here says these motors are designed to replace motors 1980 and later.Can you understand something from the pics?

Don S · Sep 6, 2008

Re: gm 305 to new350 swap

Can you understand something from the pics?

The one on the right WILL NOT WORK. Newer style with composite timing cover, 14" flywheel and different intake mounting bolt system

The one on the left is of the same vintage and should work.

mtnrat · Sep 6, 2008

Re: gm 305 to new350 swap

As Don S said. You will need a 1985 or older 350 longblock to swap in for that 305. Everything will work. Been there done that and it is very easy.

xltier · Sep 6, 2008

Re: gm 305 to new350 swap

mtnrat said:
As Don S said. You will need a 1985 or older 350 longblock to swap in for that 305. Everything will work. Been there done that and it is very easy.

it was when they went to that smaller diameter cranshaft that things got crazy.

sarantis · Sep 7, 2008

Re: gm 305 to new350 swap

i found a little more information trying to be ready for the swap about the new non-vortec 350.
The advertisements' notes say that this block has one piece rear cranksaft seal and 4 bolts cranksaft base . I think that my 305 79-82 has 2 piece rear seal. Does this mean a different coupler? Will my coupler fit directly to the 350?

Uraijit · Sep 7, 2008

Re: gm 305 to new350 swap

You need an engine with the 2-piece rear main seal. Your coupler won't work with the 1-piece.

Are you looking to buy a new engine, build one, or use a working pull?

Either way, just get a 2-piece main seal engine, and drop it in. Everything from your 305 will bolt right up.

sarantis · Sep 7, 2008

Re: gm 305 to new350 swap

the discussion here is bacause i don't want a rebuilt block and the one i've found at the picture above as the dealer says it may replace all 350 from 1980-1995.So the 350 from 1980 -1995 were one piece rear seal?
If i ask him to give me the 350's coupler ,will it fit my flywheel

sarantis · Sep 7, 2008

Re: gm 305 to new350 swap

Thanks a lot ! I think my only choice is a rebuilt engine or to rebuild my engine.
I've found a car 305 block with good bores.I'm thinking about rebuilding it with the stuff of mine.Do the metals of the car block have the same resistance to salt water as a marine block?Is the same metal?

Bondo · Sep 7, 2008

Re: gm 305 to new350 swap

Do the metals of the car block have the same resistance to salt water as a marine block?Is the same metal?

Yes...

So the 350 from 1980 -1995 were one piece rear seal?

No...

86,+ Older are 2 piece, and 87,+ Up are 1 piece....

Uraijit · Sep 7, 2008

Re: gm 305 to new350 swap

What makes you think you need a reman.?

How much money you looking to spend? For only a couple hundred dollars more than the cost of a Rapido reman. You can buy a brand new GM Goodwrench 290 HP crate motor like mine.

Just replace the head-gaskets with composite ones (I used the blue Felpro ones from Autozone), and put some brass freeze plugs in it. Wammo, marine engine!

If you feel like spending a few extra bucks, you can get some Vortec heads to slap on there as well.

It all comes down to what you're looking for.

There is NO difference between a "marine" engine, and a truck engine, except the head gaskets and freeze plugs. Some of the "marine" cams, are the exact same cams they put in truck engines, but if it gives you peace of mind, you can spend another $150 and get a "marine" cam for it as well...

If you just want a simple swap, with a warranty, just buy the Rapido Reman. You'll void the warranty of a GM Goodwrench crate engine by marinizing it...

There are plenty of options out there. It just depends on what you want, how much you're willing to spend, and how much time you want to spend on it.

Oh, and the GM Goodwrench Crate motors were made in Mexico. The "Mexican Blocks" used an iron with a higher nickle content, which makes them a little bit stronger than Canadian and U.S. made blocks. Nothing to write home about though. Any block will do...

Don S · Sep 7, 2008

Re: gm 305 to new350 swap

Some of the "marine" cams, are the exact same cams they put in truck engines,

Wrong, truck and rv cames are close, but not exactly the same by any stretch.

If you just want a simple swap, with a warranty, just buy the Rapido Reman. You'll void the warranty of a GM Goodwrench crate engine by marinizing it...

He lives in Greece guys, no Rapido. and no GM crate engines.

Uraijit · Sep 7, 2008

Re: gm 305 to new350 swap

Perhaps I've been misinformed. I was told that the cam that's in my 290 horse had been used in several marine apps.

Way to catch his location though. No Rapido.

So that leaves him with the option of finding a rebuilt 350, and marinizing it.

BTW Sarantis, if you need help getting your hands on those head-gaskets, I'd be happy to purchase them for you, and forward them on to ya. Or you can just buy 'em from Summit, if they ship to Greece...

wca_tim · Sep 7, 2008

Re: gm 305 to new350 swap

My understanding from a few books, some articles, comparing part numbers and talking to engine builders, is that Bond-O's on the mark. The gm marine cams have a different part number and I understand a little different lobe profile than the "similar" truck / rv cams.

sarantis · Sep 8, 2008

Re: gm 305 to new350 swap

Thanks for your willingness Uraijit but my problem is a little more complicated.Can you or somebody else tell me if i can do this combination since the bellows flanges of my transom and bell-housing are worn :
Keep my 228 outdrive (i think it's the MR ) replace the transom-bell housing with A1 gen1 used ones ,used flywheel and coupler and new gm305 with one piece rear seal.But does my exhaust pipe(the one with the flaps at the bottom) will fit the a1 transom?

xltier · Sep 8, 2008

Re: gm 305 to new350 swap

sarantis said:
Thanks for your willingness Uraijit but my problem is a little more complicated.Can you or somebody else tell me if i can do this combination since the bellows flanges of my transom and bell-housing are worn :
Keep my 228 outdrive (i think it's the MR ) replace the transom-bell housing with A1 gen1 used ones ,used flywheel and coupler and new gm305 with one piece rear seal.But does my exhaust pipe(the one with the flaps at the bottom) will fit the a1 transom?

no it wont.the width of the motor mount holes is different.so a different mount plate is used.the horns come up at a different angle.the way we did it was to put everything back to stock and have the bell housing machined to accept the new style coupler.customers decision.not recommended.

sarantis · Sep 8, 2008

Re: gm 305 to new350 swap

Bond-o
i noticed now at an older thread about swaping 305 350 ,a reply of yours
saying there is a Sierra coupler specially designed from going from 2piece to 1piece rear seal engine.Can i use this?And everything else stay the same?

Bondo · Sep 8, 2008

Re: gm 305 to new350 swap

saying there is a Sierra coupler specially designed from going from 2piece to 1piece rear seal engine.Can i use this?And everything else stay the same?

Ayuh,...

But I can't find the catalog with the part #.....

I'll keep looking...

gm 305 to new350 swap

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