Camshaft for Gen7 BBC...
 

Im still dicking around with this 8.8 build and now looking at camshafts a little bigger than the 496HO cam I currently have.

This build is a 4.350 bore x 4.500 stroke. 10:1 forged flat tops.
Heads are yet to be settled on, but will likely be the PSI heads with much flatter valve angles.
This is the cam im looking at now...
Thoughts on reversion with wet exhaust ? and possible ideas to mitigate it without running dry to the tips ?

https://www.compcams.com/xtreme-marine-242-248-hydraulic-roller-cam-for-chevrolet-big-block-gen-vi.html

Stick with a 112 LSA and least amount of overlap. I would get your heads in order before cam selection. What’s peak RPM goal?

The cam you have listed is a Gen VI cam???

Your best info will probably come from Raylar Vortec 8100 8.1L Chevy GM Performance Parts - GEN 7 Big Block - 496MAG HO Marine Performance Parts - Raylar Engineering

As stated that is a Gen 6 cam. No way your going to run stock exhaust dump location with that cam. I would say you need minimum dry to transom.

I have no experience with the 8.8 heads and PTV clearance. On the 8.1 you can't run much bigger than the HO cam on the stock small valve relief flat tops.

I’d imagine his flat tops have some pretty decent valve pockets cut into them. BUT…. not certain

BTW - psi heads? Just curious what those are!

Check this thread..........

https://www.offshoreonly.com/forums/...ter-550ci.html

Now I recall. I hadn’t kept up on the entire thread however post 56 stands out. Pretty impressive and seems like a custom grind would be best option. Probably not an old school one either. Be interesting to see what comp would come up with. How large are the int runners on those heads?

With the 15 degree valve angle in the PSI heads... PTV clearance is not an issue.
With the 496HO cam and 1.8 rockers @ .540lift there is a ton of clearance. I've clayed them already and had so much room (.250+) I didnt bother measuring.

The ports, valve angles and chamber shape make them far superior to the cathedral port heads.

A custom grind would probably be best... but comp cams is terrible to deal with.

I've contacted them twice via email. Got one reply asking questions, I answered and never got a response back.

I dont have a ton of cash into these engines... so a typical off the shelf cam will be fine.

I already have the XM296HR on my workbench.
If the reversion issue cant be resolved using some creative exhaust mods, I will just stay with the HO cam and see how it runs in the boat. I can still use the bigger cam anyway since I have a 2nd one Im building for my kids pickup truck.

Extend your inner exhaust pipe on your risers to transom. Plenty of threads on this forum. Definitely run the xm296hr in your build. The HO cam would be much better suited for a truck application. Good idle quality and big low end powerband.

Side exit exhaust. Might be a bit tricky to do.

Your Fuked.....HO cam it is......

lol... thats what I keep coming back to. The V-plane transom and current switchable side exit Corsa system really limit my options here.

Yeah and some fuzzy math is telling me this xm296hr grind has 75 degrees of overlap. I will use this cam in my kids pickup truck. Should impress his buddies at school. lol

The 496HO seems to make the most sense. At least with the 1.8 rockers it will breathe a little better.

Can h pipe it to help fend off a little of the reversion tendencys.

And side exit exhaust usually has greater rate of fall then typical thru transom i believe

There is already a large crossover hose that connects right near the riser tips on each side. I wonder if thats why its there from the factory.
My subscription expired so I cant upload pics anymore. lol

You don't have to have a subscription to upload pics.

https://cimg6.ibsrv.net/gimg/www.off...b5cbc4864b.jpg
https://cimg9.ibsrv.net/gimg/www.off...0b726e591e.jpg
ok i figured it out.

My Nordic has a similar side exit exhaust to yours. I'm running a Whipple with the Raylar 800HP package. That's a big cam and I haven't had any evidence of reversion even with the factory exhaust. Oil samples have come back clean of moisture too.

https://cimg4.ibsrv.net/gimg/www.off...bcd9fc2aab.jpg

I may need to just try it and see what happens. Worst case... I will need to lift the motor out and do a cam swap.


I think I will get it running on a test stand first and try to simulate conditions with clear exhaust tubing to observe what happens.