THRILLSEEKER

What does it take to turn a 260 into a 300? Cam,carb, intake, and heads??

I reccently blew appart my stbd. 300 tempest and the port side engine is pretty tired so the boat needs repowered and im on an extremely tight budget.

Low and behold I may have found a smokin deal on a pair of low hour 260s. Can I use the above mentioned parts off if my current engines to make up the hp with no problems??

Dangerous Dave

Theres always some sort of problem but you should be able to make the swap pretty easily. You should be more than able to make up the hp with the cam, intake and carb. What carbs do you have now? What happened to the stbd motor? Do the 300 Tempests have forged cranks because I'm pretty sure the 260 are cast but I know few of them that have been run hard and stayed together for a long time. I'm assuming the 260's are non vortec heads.

THRILLSEEKER

Eddlebrock 650s (I think) havent really been able to find much out about the carbs, nor have I been able to find out any specs on the Tempests.

Theese are mystery motors, I bought the boat from a repo sale back in 01 no one in the area has any knowlege of it or its owner and the engines seem to have mix and match parts in them, judging from the break in the crank Im guessing it had a cast crank. Im thinking it hydrolocked somehow @ 5k when it happened. Yes non Vortec heads on the 260's I have bowtie heads on my current motors.

k24u

I do know this because I have had both apart: the 260 and 270mag are the same except the intake on the mag is taller everything else is the same the starters are the same that comes in the chevy 4x4 trucks Had that apart also. The cir. pump part number came from a 68 small block vette. The cranks and pistons were cast. The heads were 1.94/1.50 64cc. they have harden pushrods and a double roller steel timing chain and a 2-bolt main they both were 89 motors 1 piece real seal.

Full Force

iTrader: (5)

I still love that pic tony,I would have to think the cam and intake plays the biggest role in the 260 vs 300 hp,what year are the 260's?

cuda

The 300 Tempest had the exact same parts as Merc 320 Efi's, other than the fuel injection. The engine had all the best parts in it, four bolt main blocks, forged crank, forged pistons yada yada yada. What blew on the Tempest? I'd rebuild that if possible. Here's what my 320 Efi looked like when I brought it home.

Full Force

iTrader: (5)

The block/crank was toast,he may need some super glue to rebuild that one

cuda

I'm sure with a little hotter cam, a high rise intake, and a 600 to 650 cfm carb, and decent exhaust, you'd be well over 300 horses.

You can buy 1.94 heads pretty cheap if you need them. Look for con rods on ebay, I bought a set of powder rods pretty cheap, and had them checked. Check the pushrods and rockers. The mistake I made when I put the 320 back together was I bought a set of "rebuilt" 2.02 heads with screw in studs etc, and just bolted them on without checking them. The valve guides were out of whack, and the push rods weren't hitting the lifters every stroke, so I took it to a shop to find out what was wrong. After they found that, they put it back together with different heads, the next thing I knew they were telling me I had a knock in the engine, and water in the oil. There was no water in the oil when I took it to them, so I suspect they didn't install the intake properly. Next was a new (rebuilt) shortblock, so I didn't have all my good stuff in it. Here's what it looked like while I was assembling it. You run in mostly fresh water I imagine, so any aluminum intake will work. I have a Performer on the SBC that currently resides in that boat.

I'm pretty sure this is the cam I used on the original build.
http://www.cranecams.com/?show=brows...tType=camshaft

cuda

Btw, I do have a drop in 350 ready to go. Only problem is I don't want to have to ship it.