BBC 0.700" wheel, hyd roller lobes.
 

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.
https://cimg3.ibsrv.net/gimg/www.off...69fa965f45.jpg
https://cimg4.ibsrv.net/gimg/www.off...c71c357fc1.jpg

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?

Old 26ft cc stinger. Intake manifold is a big question for me right now? I have ms2 efi collecting dust at ny carag, that i could use. Option 1=ms2 efi with single plane intake. Option 2= ms2 efi with modified 502 mpi intake. Option 3= edelbrock rpm dp 7164 with 850cfm rochester q-jet.

https://cimg3.ibsrv.net/gimg/www.off...74ed54f16f.jpg

Okay, so how do you know it needs less duration split ?

Actually i dont, thats just what i have read from several topics. Have been thinking how the current cam would do, i quess the better heads could shift the peak hp/tq upper in the rpm range by severeal hunred rpms, dont know.

That’s my point.
So why seek one out ?

Wait.
2.3” intake on 4.25” or 4.310” bore. That gonna work okay ?

030 over 502= 4.5" bore, bores are already notched.

oh, few. For a hot minute thought you had a 496. (Stroked 454)

No not drunk just can’t sleep! Your rod length one more time???

Im kinda surprised your current cam with said duration is peaking 5300/5400. With that said and you plan to stay around the same I’m not so sure I’d change your cam. Heads will be a big improvement… they’ll make your power.

(Comparison) The 236/244 dur cam in 509 was pretty much done at 5500. I definitely would be careful with to much duration on single engine heavy V bottom. (Looks nice btw)

In regards to the split I’d (think) 4 to 6 deg would be about right with those heads. GM heads with chitty exh ports maybe 12 - Just sayin! My worked over promaxx’s like 4 deg split. The ratio btwn int and exh is pretty efficient.

Rods are 6.385". The peanut head was the bottle neck in the old combo, 220cc ported/ 2.35sq" intake csa, I/E ratio around 72%. Flotek I/E ratio is atlest 80%, and intake csa is 2.95sq". Anyhow the samll ovals made suprisingly good power, flowing only 280cfm at peak lift, low lift flow was good. Floteks outflows the current heads starting from 0.500" lift.

Suddenly this popped out at facebook marketplace, i had to buy it with gaterman gp1002 roller lifters. comp cams custom marine grind. Have to get the floteks flow tested after seat/valve job and see wich cam suits the best. The new comp has less lift, but with 1.7 crane golds it is right at 0.600".

https://cimg4.ibsrv.net/gimg/www.off...4b5841a044.jpg

oops, double post.

The limiting factor would be how much the 2.3" In valve shrouds the bore.

​​​​For an undervalved engine like the BBC, bigger valve is mostly better for sure.

I think the Flotek seats were cut so you could use a 2.25", as the seat area was quite a ways into the valve face. So your're getting the 2.3" valve shrouding without the best port opening width. But that may have just been those heads...or they've changed their process etc.

Bore notch the block.
0.340" lobe is still only 0.578" lift with 1.7 rockers. Throw 1.75 or 1.8's if you want more lift. What do the heads flow at 0.600"+
That single pattern cam looks like a cam my engine builder has. Where was it located?

These flow numbers are from Eric weingartner, bore 4.310", lift 0.600", bad port 320cfm, good port 340cfm, exhaust 248cfm without pipe. Bores are notched allready and the crane golds have more ratio than stamped, 1.7 is closer to 1.8 than 1.7, the 1.8 golds are almost 1.9 in real world. The cam came from Chicago area, i also have dyno sheet of 540cid, 8.5 to 1 comp , 3 psi boost, with this cam.

Here is the dyno sheet with this comp 236/236 112lsa cam, 540cid, 8.5 comp, 3psi boost. Wonder how much the blower extends the power band?
https://cimg6.ibsrv.net/gimg/www.off...12a2ab600.jpeg