650 to 720 swap, cooling problem

[stap007]

Replacing the 650 in my 93 XP with a 720. Bought it on e-bay, was suppose to be a 650 but got a SBT rebuilt 720 shortblock of unknown year. Hooking up the cooling hoses to the 720 with 1 cooling hose hookup on the head in front and two in back is the problem. The 650 had 1 big hose in back where the water left the head, a small er one where the flush hooked up to and a bleed hose on top. The fill hose on the 650 hooked upto the exhaust pipe and I guess from there thru the engine and out the back of the head. The 720 looks like you would hook the fill hose to the back, left of head. It would come out the front of head and into the exhaust pipe then out the right rear of head. The 720 head does,nt have a bleed hose fittind on top. Does this sound like It would work? Anyone else do a 650 to 720 swap?

 

[Dr Honda]

Yup... the 650 and the 720 are different, but you basically have it right in your description. The 650 fills from the pipe, and enters the engine via that exhaust manifold.

The 720 fills from the nipple closest to the pipe, on the side of the head shell that has 2 nipples.

 

[stap007]

Do I need some kind of water flow regulator or restriction in the outlet hose to control flow out?

 

[Bills86e]

NO, but what are you doing about the exhaust? The tru-hull on the '93 is small, the
720's are bigger and the exit is in rear? The cyl drain outlet nipple ID is smaller.

 

[stap007]

I'm using the stock 93 exhaust manifold, pipe and muffler. I'd tried a pipe from a 720 for the water line hookup but it was one piece. It fit in hull but was to long couldn,t move muffler far enouhg back.

 

[stap007]

The exhaust exit the hull in rear to the side of the jet pump.

 

[Bills86e]

two muffler length sizes

I'm using the stock 93 exhaust manifold, pipe and muffler. I'd tried a pipe from a 720 for the water line hookup but it was one piece. It fit in hull but was to long couldn,t move muffler far enouhg back.

The 720 stinger uses the shorter muffler/waterbox. Bill