Compression Ratio and head part #'s

[Stan's Customs]

1983 Kayot K200 66CCZ...equipped with a 260 Mercruiser.<br /><br />Can anyone give me GM part numbers for the heads that come on that engine? <br /><br />Also what type pistons is has...flat tops, dished etc.maybe even GM numbers for them.<br /><br />I have to build an engine for that boat...before it gets here.<br /><br />Need cam number too..<br /><br />Trying to establish ompression ratio etc. to<br />duplicate old engine hp.rating...<br /><br />Thanks...Stan M.

 

[Bondo]

Re: Compression Ratio and head part #'s

Ain't goin'ta Happen Stan,.........<br />Not by GM Part #s anyway.......<br /><br />Go to your local GM Dealer,+ get a 350 for a 1983 Truck,.......<br />Change the Core Plugs to Brass,+ Install it in the boat.........<br /><br />Then just Tell everybody it's a custom built by the #s engine.......... Nobody Ever Will Know, or Notice the Difference..........

 

[Stan's Customs]

Re: Compression Ratio and head part #'s

You are right Bondo...aint goin'ta happen<br /><br />I never have been able to find out anything about these boat engines unless I had it in front of me. Seems like anything will do and no one has a clue what they are...<br /><br />I've got several good smallblocks that will make good engines. I also have several sets of heads. 30 minutes with the engine old on the old engine on the stand and I pretty sure I can match the heads and chambers...I think the short block is a flat top motor...but not sure enough to order pistons.<br /><br />I'm going to build the engine and and have it ready put to put in....We'll do it on one weekend.... when a relative brings the boat in...He's just going to stay over and help out and carry it home with him on Sunday afternoon.<br /><br />The main reason I was asking if anyone knew anything about what these motors "really" are is because of the horsepower rating. Mercruiser rated these engines at 260 hp back then...and they performed pretty good stock. Gm's stock crate motor is 190 hp...Considerable difference there. I'm wondering what Mercruiser did to get their rating....The cam isn't anything special, nor is the motor to my knowledge....but I have no clue what the compression was. Seems like a place to start . With the heads likely to be some better than the "el henchen" motor too.<br /><br />Thanks ...Stan

 

[Bondo]

Re: Compression Ratio and head part #'s

I think you're putting Too Much Stock in a # that's used for Marketing,.........<br />

Mercruiser rated these engines at 260 hp back then

Gm's stock crate motor is 190 hp...Considerable difference there.

A 4bbl. Carb. would just about "Make up the Difference"...............<br /><br />You seems to know your way around a SBC,.......<br />Just build up a Long Block, around 9/1 compression,+ the cam of your choice..........<br /><br />Like I said,............<br /><br />Nobody will Ever Know the Difference............

 

[Stan's Customs]

Re: Compression Ratio and head part #'s

I'm sure that's right Bondo..<br /><br />Only me...<br /><br />I did find out the answer by the way. 2 bolt block, cast crank, flat top pistons with 76cc heads..<br /><br />With the standard .038" composition head gasket and the 76cc combustion chamber the flat top piston produces an approximate 9:1 compression (depending on how much piston to deck clearance the engine has)....<br /><br />You were on the money Bondo, as usual...<br /><br />For anyone that would like to know the part number for the early flat tappet cam used in stock marine engines it is...Chevrolet Part Number 340284.