350 engine replacement options

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carcraze

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Good day

My buddy got his boat ready to go for the season and was greeted with a cracked block.

Something went wrong with his winterization. It is a 89 305 with center valve cover bolts so my assumption at this point is a single rear main seal motor. Not sure if these had roller cams in them or not.

We decided to start looking for a motor (350) we could throw in and have came across more Gen 2 motors than single rear seal motors.

Depending on where the motor comes from I assume we may need a cam change?

Is there issues changing to 1990 on motors as I believe they are reverse cooling?

Thanks
Mat
 
Don S

Don S

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Re: 350 engine replacement options

Is there issues changing to 1990 on motors as I believe they are reverse cooling?
Click to expand...

Never heard of that one before.
 
Bondo

Bondo

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Re: 350 engine replacement options

Don S said:
Is there issues changing to 1990 on motors as I believe they are reverse cooling?
Click to expand...
Never heard of that one before.
Click to expand...

Ayuh,.... I believe he's thinkin' the LT-1 motors,.... found in Corvette's, 'n Police cars...

Those are Not boat motors,...

The SBC, up to 2000 will fit, 'n is what yer lookin' for... preferably outa a pickup truck....
If outa a truck, a cam change isn't required...
 
C

carcraze

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Re: 350 engine replacement options

Thanks for the link I will pass it on.

Around 92 some applications went to the LT Gen 2 small blocks which I see a few around which were reverse cooled in the auto applications anyhow not sure they were ever used as marine.

The truck engines remained as Vortec if I am understanding the changes.

In 1992, GM created a new-generation small-block engine called the "LT1 350", not to be confused with the high-output Generation I LT-1 of the 1970s. It displaced 5.7 L (350 cu in), and was a 2-valve pushrod design. The LT1 used a reverse-flow cooling system which cooled the cylinder heads first, maintaining lower cylinder temperatures and allowing the engine to run at a higher compression than its immediate predecessors

Gen 3 Ls motors were introduced around 97 ish I believe.
 
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carcraze

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Re: 350 engine replacement options

Okay so we found a motor it is out of a Z71 1998 Votec motor truck was Tboned.

So a couple of questions the 5 L in the boat is 89 probably 1 pce rear main as it has center bolt covers.

Will the 5L intake, carb, starter, and such swap over?

ALso I assume since the 1 pce requires the flex plate for balancing that we have to use the flex on the Vortec motor as the 5L plate is different?

Mat
 
SWD

SWD

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Re: 350 engine replacement options

Carb and starter for sure not.........not marine compliant.
 
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Dawg'sLife93

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Re: 350 engine replacement options

No, you will need to buy a Vortec style intake to run the 98 engine. You can get the summit performer knock off for about 150.00 bucks. Everything else will swap over. A far as the LT1 Gen II, the blocks are the same. The reverse cooling is in the heads and cam driven water pump, plus a LT1 runs an Opti spark Dist and Water+Opti= real bad day. LOL. You can also run the L05 350 out of a 87-95 chevy truck. They have roller provisions for the factory roller lifter and spider hold downs, but most do not come roller. You can add roller for a little extra smoothness, if you choose.

http://www.summitracing.com/parts/sum-226018





Edit: I just saw your flex plate question. The L03/305(88-95), L05/350(88-95), and the Vortec 305's/350's all run the same flex plate. I would just run the flexplate off the 305, cause it works with the starter,since there is 2 flex plate options (153 and 168 tooth)
 
Bondo

Bondo

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Re: 350 engine replacement options

carcraze said:
Okay so we found a motor it is out of a Z71 1998 Votec motor truck was Tboned.

So a couple of questions the 5 L in the boat is 89 probably 1 pce rear main as it has center bolt covers.

Will the 5L intake, carb, starter, and such swap over?

ALso I assume since the 1 pce requires the flex plate for balancing that we have to use the flex on the Vortec motor as the 5L plate is different?

Mat
Click to expand...

Ayuh,... That motor will work, the Intake has a different bolt pattern, so it won't swap,...

Ya need the Right Flywheel, not a Flex-plate,...
The 1 off the 5.0l, Might/ should fit ok,... that'll depend on the starter's bolt pattern,...
 
Idlespeedonly

Idlespeedonly

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Re: 350 engine replacement options

You cant use a lt1 block. They are different than a regular 350 block. So dont try that.
 
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Dawg'sLife93

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Re: 350 engine replacement options

I almost forgot. I don't know what kind of fuel pump the 305 is running, either a block mounted mech or a electric, but the Vortec blocks have the provision for a block mounted pump,but are not machined for the fuel pump rod to operate the block mounted mechanical pump. If the 305 is running the block mounted pump, you'll need a good electric pump with a regulator to keep the fuel pressure to 5-6psi for a carb application.
 
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carcraze

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Re: 350 engine replacement options

Thanks for the replies.

I assume the starter mounting is the same as I would rather not have to go searching for a replacement marine starter?

I would assume the starter tooth has to do with the change from 2 pce rear to 1 pce rear years?

The flywheel has me a little concerned. So the concensus is the 5L 1989 Merc flywheel will fit the 350 1998 Vortec?

There is no difference in the 5L to the 5.7L ballance weight as the weight was added to accomidate the 1 pce rear main seal changes can anyone confirm?

Can the fuel pump area be knocked out?
 
Bondo

Bondo

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Re: 350 engine replacement options

carcraze said:
Thanks for the replies.

I assume the starter mounting is the same as I would rather not have to go searching for a replacement marine starter?

I would assume the starter tooth has to do with the change from 2 pce rear to 1 pce rear years?

The flywheel has me a little concerned. So the concensus is the 5L 1989 Merc flywheel will fit the 350 1998 Vortec?

There is no difference in the 5L to the 5.7L ballance weight as the weight was added to accomidate the 1 pce rear main seal changes can anyone confirm?

Can the fuel pump area be knocked out?
Click to expand...

Ayuh,... Chevy starters come in 2 flavors, staggered bolts, 'n straight across,...
The diameter of the Flywheel, 'n the mountin' holes in the block determine which is used,...
Nothin' to do with tooth count,..

Both the 305, 'n the 350 are neutral balanced, so the flywheel should swap,...

'n,... No, the fuel pump drillin's can't be done, unless by a Machine Shop, 'n swappin' in an electric pump is easier, 'n Much cheaper...
 
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Dawg'sLife93

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Re: 350 engine replacement options

As long as the 305 is a one piece rear main engine, the parts should swap.

No, you can not knock out for the fuel pump rod, it'll need to be machined open.

The flywheel on your 305 will work with the 98 Vortec. I dug out an interchange manual, cross referenced a few 168 tooth flywheels between the 2 engines and they match.
 
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carcraze

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Re: 350 engine replacement options

Got it thanks for all the help!

I guess my terms of externally balanced was a little misleading.

The 1 pce seal cranks had the outer flange removed from the crank due to the block changes I believe. This flange weight was added to the flex plate or flywheel for balance purposes. I guess that flange size was the same for 5 AND 5.7l making the weight the same.

Thanks again
 
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