Offshoreonly.com - New 496 aluminum heads

Offshoreonly.com (https://www.offshoreonly.com/forums/)

- General Q & A (https://www.offshoreonly.com/forums/general-q-20/)

- - New 496 aluminum heads (https://www.offshoreonly.com/forums/general-q/72206-new-496-aluminum-heads.html)

I trust that Ray will not hesitate to tell me what he is comfortable sharing and what he is not. I will ask what I need to make my personal buying decisions.

Ray,

Should I assume that the 111.5mm stroke for your special stroker crank is a typo and should read 115mm or.....?

Will the standard 496 bearings and rods fit your special stroker crank?

Are your special stroker cranks in stock ready to ship?

Best Regards,

Bill

Yes that was a typo the stroke on the stroker crankshaft is 115 mm and we are in build on 4 units as we speak and they should be on our shelf ready for shipping 9-18-07. This is also the crankshaft we use in our HO750 600 cubic inch engine. I currently have orders for three units so if you need one from this production run I would suggest ordering now.

Best Regards,
Ray @ Raylar

Quote:

Originally Posted by Raylar (Post 2252408)

Jimv:

Understand you may have reworked a set of iron heads for more flow, but our heads and a much smaller cam make with our 106 kit just over 620HP at 5200rpms and a lot more midrange torque from 3500rpm to 4200rpms on a 496.
This is where the big blocks will see much better hours of reliable usage under 5400rpms and the big cams that move peakpower on these motors up to 5700rpms are a lot more prone to reversion with the larger durations and the idles tend to get a little rough and require more than 650 rpms to stay lit which is hard on Bravo drives when shifting.
Just my opinion, but I say make big power at lower rpms with more torque and you have a better recreational performance marine engine, racing, thats another animal.

Ray,
No offence I was responding to tornado's question.
The stock heads are somewhat limited due to the castings. The intakes won't support a 2.300 valve without getting to thin so I used a 2.250 intake. The same with the exhaust, I stayed with a 1.820 exhaust. The flow numbers, even with the small valves were decent

Lift..........CFM...........EX CFM
.2............157................141
.3............230................190
.4............292................221
.5............330................238
.6............348................249
.65..........353................251

Jim:

Those are very good flow numbers from the stock heads and I am sure they would support pretty decent horsepower numbers. Some of the limiting problems we discovered with the stock heads were the shouding and overhang they create over the top edges of the bore because the chamber diameter is so much bigger than the bore. this also leads to some detonation when the timing is increased in some areas and its aggrivated by the heat of the iron head. The stock heads will not quite flow on a cylinder what they will flow on a flow bench due to this shrouding issue. The thin spots in the exhaust port casting and the oversize combustion chamber was what made us decide to develop the aluminum head, not to mention the 100 lb. savings in weight, more timing allowance and better burn of our redesigned chamber. Just some information only.

Regards,
Ray @ |Raylar

Quote:

Originally Posted by Raylar (Post 2277139)

Thanks, The detonation issue was resolved by bore notching the block. Tom advanced the timing enough to see a drop in power with no detonation problems. I'm sure the slight volume loss helped as well.