crossflow v4 part # 502,503,504 ??

Trying to figure out the right head part number for a 98 crossflow to raise the compression. Read a old post by Dhadley here at iboats and he listed the numbers 503 and 504. But over at scream & fly B.Leonard listed 502 and 503. My motor has 504 and 505 on it. I'm confused on what part numbers to look for.

Re: crossflow v4 part # 502,503,504 ??

You need heads from a 1973 135....tightest heads made....you'll be looking at 93 min octane, and most likely a little more...<br />317848, & 317849....problem is, these heads don't have coil towers, but you can make mounts to work...The next best heads with coil towers would be 1978-79 140's...

Re: crossflow v4 part # 502,503,504 ??

Does anyone know about the 326502,503,504 part number question? Kenny, do you walleye fish in the winter, thats when we do here on the mississippi.

Re: crossflow v4 part # 502,503,504 ??

The 502 & 503 are a matching set as are the 504 & 505. You have the latest heads for your crossflow. There is very little difference in the two sets. <br /><br />Higher compression is not the number 1 thing we look for in a two stroke. We look for the heads that have the best "swirl pattern" for a more complete combustion of available fuel depending on what port timing and configuration youre using and where your target rpm is. The heads you have are darn good heads up to the mid 6K range. About the same range that the stock reeds start to flutter. Once you get into the upper 6's and lower 7's with stock V4 stock port configuration, there is a better set but again it depends on what you want to do with the motor.<br /><br />If you simply want the "tightest" stock V4 crossflow heads available there are some tighter than the early 135. Think about it, it'll come to you. And they dont work near as good as the heads you have.<br /><br />Good luck!

Re: crossflow v4 part # 502,503,504 ??

Too far away from any good river systems for winter Wallys'.....<br />Dhadley, I was told by an old OMC Racer in Denver, CO.(worked for OMC, not a dealer), that the highest comp heads for a 99 cube was the 135, '73 model...I was told as well that you could make a set of 85hp heads work with a little grinding, granted not something a guy wants to do without spare parts and play time.<br />I'm confussed on this issue, and I trust your wisdom, so I gotta know what heads are best.<br />Mr. Laker from S&F told me about the 78-79 with the towers, and I guess I opened my mouth too soon...

Re: crossflow v4 part # 502,503,504 ??

See? I knew somebody would think of that! But it takes more than some grinding (need a bridgeport, dye and the stuff to cc the heads). We ran those 70's heads too and they worked good on real high rpm. I was hoping Mr dpg5 would give us some more info in regards to the intended use (top end only, drag, skiing, 6K rpm, 6.5K, etc).

Re: crossflow v4 part # 502,503,504 ??

Just for general use, 6000 to 6200 rpm. Trying to make the best I can with a small motor. Thanks Mr. Dhadley for the info! and also thanks to Mr. Walleyehed !

Re: crossflow v4 part # 502,503,504 ??

Dhadley is the true leader, but I make a great follower.....

Re: crossflow v4 part # 502,503,504 ??

Kenny, youre too funny!<br /><br />dpg5, those heads should serve you well. I would expect a very good idle quality, decent acceleration and no problem reaching 6200 as far as the heads go. <br /><br />Where are you now with your set up (rpm / performance-wise)? What kind of boat?

Re: crossflow v4 part # 502,503,504 ??

Just to add my experiences: <br /><br />I once had a 1984 35Hp twin crossflow, I rebuild and assembled from 3 different motors. I discovered it had 1988 20HP head on ( low compression ) but with another swirl pattern, round corners in head. Compression was 122. I put the original heads on and compression jumped to 135 on both. I gained almost no speed. <br />Its not always compression that does it.