The OMC Cross Flow Thread

The 9 pages is too much for an every day engine, the bigger ports with smaller radius mean less ring support and more chance of bridge movement. A 5/8 or 3/4 cutter would be better. Any time you add power from porting, compression etc something has to suffer and that is generally longevity. The 9 pages was meant for race engines, I cant take full credit but had a LOT to do with them. They were also done early on before even fire cranks etc at the end we ran a lot more rpm than mentioned in those pages and not for short drag type burst.

I also dont agree these engine are port grabbers, if they do its because of any one of a number of reasons.

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Originally Posted by racer

The 9 pages is too much for an every day engine, the bigger ports with smaller radius mean less ring support and more chance of bridge movement. A 5/8 or 3/4 cutter would be better. Any time you add power from porting, compression etc something has to suffer and that is generally longevity. The 9 pages was meant for race engines, I cant take full credit but had a LOT to do with them. They were also done early on before even fire cranks etc at the end we ran a lot more rpm than mentioned in those pages and not for short drag type burst.


I also dont agree these engine are port grabbers, if they do its because of any one of a number of reasons.

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About what RPM did these motors modified to the specs in the 9 pages make the most horsepower at ?

Mid to High 6k range later on in the low 7k range but they had more done to them

Last saturday at the NEODA end of season cookout.

http://i54.tinypic.com/2a4vi45.jpg

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Originally Posted by racer

The 9 pages is too much for an every day engine, the bigger ports with smaller radius mean less ring support and more chance of bridge movement. A 5/8 or 3/4 cutter would be better. Any time you add power from porting, compression etc something has to suffer and that is generally longevity. The 9 pages was meant for race engines, I cant take full credit but had a LOT to do with them. They were also done early on before even fire cranks etc at the end we ran a lot more rpm than mentioned in those pages and not for short drag type burst.

I also dont agree these engine are port grabbers, if they do its because of any one of a number of reasons.

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So are you saying that with an everyday performance engine you should leave the ports a little more round than mentioned?

so where is the porting on a CCC compared to these?

I know I have seen pictures of the ccc ports here somewhere. They were a lot wilder. I think Chris Carson posted them if I remember correctly.

Yes for lake use they should have larger radius in the corners. Ports are similar but different than a ccc as it is a larger bore than a ccc and meant to push more weight so the ports are a little lower and less compression. Ports are as wide as the block/bore will allow.

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Scribed also.... missed this one! Gary

Well you stated anything crossflow so v-4 mod on a 15ft pacecraft race boat 7200@ 85mph gps 26 cleaver pretty good for 4cyls and was very dependable,raced it for 3 yrs untouched built 6 off them never had one blow up just my 2 cents

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Originally Posted by racervboat

Well you stated anything crossflow so v-4 mod on a 15ft pacecraft race boat 7200@ 85mph gps 26 cleaver pretty good for 4cyls and was very dependable,raced it for 3 yrs untouched built 6 off them never had one blow up just my 2 cents

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Thats very impressive!!! Which motor were you starting with (140 etc.) Thanks Gary

Ok so sorry for just budding in and don't mean to step on anyone's toes but I have a question.

Is there a certain point, when a crossflow v6 is jetted right, that you should not stay at full throttle for long distances for the chance or burning it up?

I have a 1980 hydrostream vandal with a mod 200 crossflow that 90 mph in 1000 ft at 7000 rpm with a 28 et. I have not tried a bigger prop yet but am considering it. It's not like I can stay in if for super long as it is, being such a small boat but I would like to put a crossflow on a fast family boat some day.

Thank you for any info
Scott

I know this thread is a bit old but I’m hoping some of you guys are still around. I’m an OMC V6 (and V4 fan), and am wondering where you should run a factory bone stock XP? And while I’m asking, what about a 1985 175 (also stock, crossflow, my baby, does 50 on a really nice 4Winns Horizon 190 at 5800 RPM with the original stainless 21 inch. Thanks….

These guys are still around and I’m sure will chime in. However, I think you need to be more specific about what you mean by “where you should run”? Do you mean RPM? Timing? Also, be specific about the Year model and horsepower of this “bone stock” XP and you’ll get all the answers you need from these guys. Forkin has helped me a lot in the past and he knows what he’s talking about so maybe he will opine. Good luck.