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-   -   Camshaft for Gen7 BBC... (https://www.offshoreonly.com/forums/general-q/380835-camshaft-gen7-bbc.html)

Dragracer_Art 10-13-2023 02:06 PM

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


getrdunn 10-13-2023 02:23 PM

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?

Griff 10-13-2023 03:29 PM

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

Ryan00TJ 10-13-2023 08:36 PM


Originally Posted by Dragracer_Art (Post 4882528)
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-mari...ck-gen-vi.html

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.

getrdunn 10-14-2023 05:05 AM

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!

Ryan00TJ 10-14-2023 08:32 AM




Originally Posted by getrdunn (Post 4882557)
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


getrdunn 10-14-2023 09:29 AM


Originally Posted by Ryan00TJ (Post 4882571)


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?

Dragracer_Art 10-19-2023 10:15 AM


Originally Posted by getrdunn (Post 4882557)
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!


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.

Dragracer_Art 10-19-2023 10:20 AM


Originally Posted by getrdunn (Post 4882580)
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?

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.

Ryan00TJ 10-20-2023 08:50 AM


Originally Posted by Dragracer_Art (Post 4882959)
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.


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