Have been looking for Cams to my 509cid upgrade. looks like custom cam is the only option, or using the cam from my old combo. Ordered a set of flotek 290cc bare heads that gets ferrea 6000 series valves, looking the flow numbers, it seems i need very little duration split if any. Intake manifold is replaced with edel RPM oval, or modified 502 mpi intake. dont know about compression yet because of so many open questions, but anything from 9.2 to 10.6 is possible by milling my new srp 17cc solid dome pistons.

Current combination, 520hp @ 5300/5400rpm, +600lbft @3600rpm
- Gen6 short block, mahle powerpack( 9.5 to1), 6.385" h-beams,4" eagle forged crank.
- Gm iron small ovals, ported, crane gold 1.7 rockers.
- Weiand street warrior dual plane, Rochester g-jet 850cfm
- Custom 3 lobe hyd roller, intake 228/230 @ 050", 0.620" lift. Exhaust 236 @ 050", 0.620" lift. 112lsa.
- Gm zz502 lifters.
- Stainles marine exhaust, 4" taller and dry to transom risers.

Several proven shelf cams with your combo that’s been around a long time will suit you fine but ya a custom grind is a great option also but will need your flow numbers and CR.

If you’re staying the same cubes and rpm the oldie but goodie crane 741 etc has been proven over and over again but there’s a bunch of similar cams with less split that would work well also. Heads being ported?

Ck out the comp HUC lobe family.

I'm also keen on the 290 Floteks.

Have you seen the Eric Weingartner youtube vids on the 290 and 317 Promaxx? Essentially the same 290 as Flotek.
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The link is for the dyno results on the 290 heads on a 496.

He has vids on the comparison of the 290 and 317. It was neck and neck.

There are also vids on the Flotek 290s stock flows.

Is Flotek putting your 6000 series valves in for you? Are you able to fit 2.25" Int on the seat?

Sounds like a great combo.

If memory serves...the 290 Floteks can benefit from a simple seat blend in the bowl.

JaniH,
your exhaust , including water, is an extension if your exhaust port, right ? Asking for a friend.

If i remember right, few have used the gm dogbone lifters with this cam. Most builds i find with the 741 are 540cid engines. What rpm this 741 peaks in 509cid?

4" taller vs stock and dry to transom riser.

I bought bare heads from flotek, and 2.3" intake must be used, wich is Lil overkill at this level. I would have bought the promax 290 (same casting as flotek) wich are set for the 2.25" intake, put those were out of stock at promax.

The smaller runner and 2.3 int valve will create better velocity and air speed. Engine will be happy with right combo. Your CI warrants either single plane or dual but I’d lean towards SP for port consistency etc.

What kind of boat?