Kaama- I would call Crower and ask where the adv. duration figure is taken from...if it is taken from .006, then you have very slow "ramps" and are really not making good use of a hyd rollers' inherent advantages. Hopefully the figures are a gross duration number. It would really be nice if some of these cam grinders would give us some lobe profiles better suited to a boats duty cycle....150# on the seat and more than 400# over the nose is just plain hard on everything @ 5300rpms continuous.
Next, I'm with Cobra Marty, I really don't understand your cam selection. You have a great set of heads, great exhaust by boat standards[tube tops?] You have thought backwards in a very nice manner [exhaust first, that is] CW tells us we do these things so we can shorten exhaust duration, reducing overlap and thus, increasing cylinder pressure while efficiently liberating the spent combustion charge. If your exhaust flows even close to 80% of the intake, then it's just a waste to have more exhaust duration than intake duration.
As for your over scavenging/rich looking exhaust...the reasons above, but also consider retarding [still advanced] the intake lobe C/L to 112deg[if you are at 114lsa]. The car guys will always have you advanced 4-6 deg....your boat engine will like 1-3 deg advanced.
Enough of these facts and truisms...LOL....Now for my opinion. I'd love to have your motor and if it were mine[your earlier stated goals are similar to mine] I'd use the Crane HR1 lobes 230/230....114 LSA...Intake C/L@ 112 deg. You will have a nice idle,little or none over-scavenging issues, little or none reversion issues[intake or exhaust]...pull very hard from tip-in to 5300rpms. A very user friendly motor making somewhere over 600hp.....on the dyno of course. Take care...sounds like fun.

Thanks for the repsonses again---very interesting! From .200" to .700" between intake and exhaust the average percentage of flow on my heads is 75.8%. I can be more detailed here about the flow of my heads if need be.

Kaama- Were your E/I %'s done with or without an exhaust flow pipe? If done w/o the pipe, that is a very respectable %....and I would without a doubt go with the single pattern cam. I would throw out the .700 figure and weight the .600 a little less [assuming your peak lift is .600].....then see what the #'s look like. I like the way you have avg. flow numbers, makes sense to me...a lot of hot rodders arebig into the ratio @ .400...the valve spends alot of time at other places ya know! Regardless, pipe or no pipe, you have a proper flowing set of heads and would need little, if any additional exhaust duration. A cam is a great place to split hairs because it dosent cost you anything extra to do a custom grind...just the way you want[within reason]. take care

Liquid Lounge,

Those flow numbers are WITHOUT a pipe! I also called Crower today and they said those cams I have with an advertised duration of 300*/307* are figured at .006". So they probably don't have as much overlap as the Ultradynes when comparing the same @.050 duration numbers. Plus it will definately be even less compared to the Ultradyne 244*/244* on 112*lobes. A little smaller cam doesn't bother me because the heads will help carry it. Perhaps the Crower cam (236*/244* on 114* lobes) with its slower ramp speeds might be a little more torquier over the Ultradyne cam with the same 236*/244* numbers as the Crower. Enjoyed all the input from you guys---jump in any time!

I say get those babies running so we can see you flyin at Hardy in a couple of weeks.

Kaama- The overlap event @ less than .050 is still very valid...for our purposes, overlap is all we have below that figure. So, its just the oppisite of what you are thinking: The Ultradyne with less gross duration,but with same .050 duration [and lift, assuming] will be "torquier" as you say, than the Crower with the greater gross duration. For discussions sake, we could say the Crower would have a VERY small HP advantage over the faster ultradyne because of the greater gross duration, but at the GREATER expense of less cylinder pressure and rougher idle. Hope this helps.

I think I am confused.

KAMMA, read page 123 , Opening and Closing Flank Speed, in Dennis Moores book BBC Marine...
He explains it quite well.

Dave

KAAMA, you have obviously forgotten the Team Chaos credo- it just don't matter because it ain't my blank. Fill in the blank with whatever toy you happen to be working on. Now, as you are one of the few (but proud) members of the elite Team Chaos, you need to have the proper mindset to be truly effective in your mechanical endeavors.

Just so happens I have Dennis Moore's book and I did read the article. I thought I was eliminating some of the overlap in that cam, but I guess not! I'm just sitting here shaking my head. When I first ordered the cams from Crower I originally ordered a 234/240 and they ended up sending me the 236/244 and I took them because I was tired of messing around with it---oh well. Guess I will either go with a solid mechanical flat tappet cam over the winter or send the Crowers back for a re-grind.