will 87 5.0 gm block switch with 98 5.0 block both marine

[brogden31]

both marine motors and the difference i see is the older head have a bigger center water port but the intake on 98 block is solid

 

[brogden31]

the heads are both center bolt

 

[Scott Danforth]

98 is a vortec, 87 is not. Different intakes needed You are replacing whole motor, correct

 

[brogden31]

can I just switch blocks my 98 block cracked

 

[Scott Danforth]

NO NO NO NO NO NO NO NO NO

you can rebuild a motor with the new block. this includes line-honing the block, decking it, boring it and honing it, new pistons, rings, bearings, and having your crank and rods machined. you CAN NOT simply swap blocks. once the motor has been run, the pistons, rings, etc wear into the cylinder bores.

your 98 is a roller motor, the 87 is not.

if your on a budget, go to car-part.com, find a 1996 or newer truck with a 350 in it that is running with low mileage and buy the long-block from them. then get new marine head gaskets, new brass core plugs and bolt on all your marine accessories (including the circulating pump) and you have a marine motor. for about $500

you will need NEW manifolds and elbows as if your block is cracked, most likely your manifolds and elbows are too

 

[Scott Danforth]

can I just switch blocks my 98 block cracked

in case you didnt get the last post, no

 

[brogden31]

Yeah just thought I got lucky on those older blocks but that's why I get on here to find out for sure , thanks

 

[Scott Danforth]

when in doubt, ask your machinist.

FYI, you can build a brand new 377 stroker long-block with new stuff for about $3k (using a few things from your current motor) same cost as building a new 350. that is new block, new heads, new rotating assembly, new oil pump and new timing set. Cam set may or may not push the price up depending on what you buy for a cam.

New 1-piece block GM part number 10105123 $935 (price went up in last 3 months)
New vortec heads GM part number 12558060 $740 (price went up in last 3 months)
New SCAT 9000 series rotating assemblies $710 (either 3.48" stroke or 3.75" stroke)
new Felpro Gaskets $150
New Clevite bearings $100
New Meling oil pump, shaft and fuel push rod $60
New timing set $50 (or less)
New lifters $60
New roller tip rockers $72
New pushrods $40
getting the rotating assembly balanced $180

getting a used block machined is about the same price (core block $300, Clean Block, $60, Line hone - $140, Deck, bore, hone $180, Clearance for stroke crank - $60)

a new to you 350 crate motor can be had for about $2300