350 chevy engine rebuild question

[treeeman00]

I am new to this site and I have a couple of questions as this is my first marine rebuild. I have a 1987 2450 Bayliner Trophy. The boat has an OMC outdrive. Its not the king cobra. The boat had an OMC 305 chevy in it. The previous owner did not drain the block abd the block froze and cracked. I pulled the motor and was going to install a 350 chevy. I bought a cheap 350 longblock but am going to rebuild it so I know what I have. Is there anything I have to watch out for when changing from the 305 to 350. The motor I bought is an 81-84 with the 2 piece rear main. I know I will have to use different oil pans and valve covers. The 305 was a one piece rear main and was wondering if I can use the flywheel from the 305? Also I am wondering what cam to put in the 350. The 350 is all stock. I am keeping everything stock as well when I rebuild. I am having a vlave job done on the 350 heads, and reusing the 350 crank and rods. The block looked real good. One other question the 350 I bought was a reverse rotation motor because it was gear driven and the cam was way different. Is the crank on a reverse rotation motor the same as a standard rotation. I know there is alot of questions but I would appreciate all the help I can get. Thanks guys.

 

[Bondo]

Re: 350 chevy engine rebuild question

One other question the 350 I bought was a reverse rotation motor because it was gear driven and the cam was way different. Is the crank on a reverse rotation motor the same as a standard rotation.

Ayuh,... Welcome aboard,... Lets start here,.... You've got the Wrong motor....

Sell it...
Buy yerself a long block 350 on a pallet for a pickup, 'n bolt all the accessories from the old motor onto it...
Get an '87 or Newer....

The flywheel 'n coupler don't fit the 2 pc. motors...

 

[RogersJetboat454]

Re: 350 chevy engine rebuild question

The 305 was a one piece rear main and was wondering if I can use the flywheel from the 305?

Nope. Different bolt pattern, and I hate to be the t**d in the punch bowl, but if your drive coupler bolts directly to the crank (which I believe it does) the drive coupler from the 1 piece RMS engine will not bolt on either. There is a company out there making couplers to adapt 2 piece RMS engines to OMC/Volvo SX Cobra drives. Don't know if this would work with an older Cobra drive, as the shaft size and spline count may be different. In other words, you may be bumming using this engine if you can't find a compatible coupler. That is why it pays to get a donor engine as close to the year of manufacturer as possible.

Also I am wondering what cam to put in the 350. The 350 is all stock. I am keeping everything stock as well when I rebuild.

A marine specific cam as close to stock as possible.

One other question the 350 I bought was a reverse rotation motor because it was gear driven and the cam was way different. Is the crank on a reverse rotation motor the same as a standard rotation. I know there is allot of questions but I would appreciate all the help I can get. Thanks guys.

Man, you really are a glutton for punishment. :facepalm:

As far as I know the crank is the same. The cam is different. You will need a timing chain instead of the gears. The crank seals need to be for a standard rotation engine. The distributor gear will need to be swapped for a standard rotation engine. The starter will need to be standard rotation, and compatible with the tooth count on your new flywheel.

Before I spent a penny more on this project, I would be finding out if a 2 piece RMS compatible coupler is available for an original Cobra drive.

 

[treeeman00]

Re: 350 chevy engine rebuild question

why wont the coupler work? What options do I have. I have already sent the heads to have a valve job. Guess I shoulda researched a little more..lol

 

[RogersJetboat454]

Re: 350 chevy engine rebuild question

Ayuh,... Welcome aboard,... Lets start here,.... You've got the Wrong motor....

Sell it...
Buy yerself a long block 350 on a pallet for a pickup, 'n bolt all the accessories from the old motor onto it...
Get an '87 or Newer....

The flywheel 'n coupler don't fit the 2 pc. motors...

Bond-o beat me to it...

That's what I get for taking so long to type out a response. I even use all my fingers too!!!

 

[Bondo]

Re: 350 chevy engine rebuild question

why wont the coupler work? What options do I have. I have already sent the heads to have a valve job. Guess I shoulda researched a little more..lol

Ayuh,... The bolt holes don't line up, by 'bout a 1/4".....

Get an '87, or Later motor....

Sell that 1....


edit;,... Ayuh,... Lot's of Us here, Right now,...
Btw,.. The gal from the company office thought my single digit, Smokes alota her associates...

 

[RogersJetboat454]

Re: 350 chevy engine rebuild question

why wont the coupler work? What options do I have. I have already sent the heads to have a valve job. Guess I shoulda researched a little more..lol

Because the coupler has the same bolt pattern as the 1 piece flywheel. The Cobra drive came out about the same time GM made the switch from 2 piece RMS to 1 piece RMS, so there is a good chance OMC never made a compatible coupler to fit a 2 piece crank.

 

[treeeman00]

Re: 350 chevy engine rebuild question

the flywheel is the same as a manual tranny flywheel right? So if I were to get a one piece donar engine could I use my heads that I had a valve job done on that motor or is that going to mess up the intake fit?

 

[RogersJetboat454]

Re: 350 chevy engine rebuild question

the flywheel is the same as a manual tranny flywheel right? So if I were to get a one piece donar engine could I use my heads that I had a valve job done on that motor or is that going to mess up the intake fit?

As long as you have the older style intake that matches the heads, they are a direct bolt on to a newer style block.

 

[RogersJetboat454]

Re: 350 chevy engine rebuild question

Treeeman,

Do some research on this...
There is a Sierra coupler, Part number; 18-21751

It's on page 712 here;
http://www.sierramarine.com/sierra/2012sierra/2012searchmain.html

It may or may not be what your looking for. If you have a friendly person at a NAPA, or marina who is willing to order it for you and return it if it doesn't look right I would order it up and see if it will fit both your crank and the shaft to your drive.

 

[RogersJetboat454]

Re: 350 chevy engine rebuild question

Treeman,

Did some more research for you.

OMC part # 0983902 is a drive coupler for a 2 piece block with a Cobra drive.

It is available for $243.30

 

[treeeman00]

Re: 350 chevy engine rebuild question

everyone, thanks for the help! Ive learned alot already! Mostly to do more research and to ask more questions on here! I just got done talking with the guy I sent my heads to and both heads were cracked. They were the scalloped heads which are prone to cracking anyway. So with that I think im gonna look for a 1 piece RMS donor engine and go from there. Thanks tremendously for the help. You guys sved me some money already!

 

[Tommywalton]

Re: 350 chevy engine rebuild question

Dont listen to these clowns a two piece will go right in. Buy a 12" 350 flywheel, order the two piece coupler and bolt it up. Ive done it twice. No a 305 flywheel wont work. I have an omc outdrive originally i piece setup, with junkyard 1980 350 running volvo penta center risers, omc thermostat housing. All works great. If you are limited on money and industrious enough you will figure it out. Keep asking questions. If you want to know what i did to make all mine work message me. I will tell you what i did. It may work for you. You absolutely do not always have to have exact factory stuff for things to work. Keep posting and good luck!

 

[Lyle29464]

Re: 350 chevy engine rebuild question

The CW crank has grooves going the wrong way. If it would run you will pump your oil in the bilge.

 

[Bondo]

Re: 350 chevy engine rebuild question

Dont listen to these clowns a two piece will go right in. Buy a 12" 350 flywheel, order the two piece coupler and bolt it up. Ive done it twice. No a 305 flywheel wont work. I have an omc outdrive originally i piece setup, with junkyard 1980 350 running volvo penta center risers, omc thermostat housing. All works great. If you are limited on money and industrious enough you will figure it out. Keep asking questions. If you want to know what i did to make all mine work message me. I will tell you what i did. It may work for you. You absolutely do not always have to have exact factory stuff for things to work. Keep posting and good luck!

Ayuh,..... Guess ya missed the part 'bout this bein' a Righthanded motor.....

 

[treeeman00]

Re: 350 chevy engine rebuild question

thanks everyone for their input. I think im just gonna geat a used low mile 87 and newer engine that is ready to drop in. Thanks again

 

[Tommywalton]

Re: 350 chevy engine rebuild question

NO bOndo i didnt miss that part. I just like to ruffle your feathers and coupler flange patterns dont care which way the crank rotates.