THese things are great low end and in the middle. You need great flow to get them to make HP. It's the wet exhasut that hinders them. They need duration. The torque is awesome though.

I too am running 496 combo with dart pro 1s good trq like you say. What can I do to help top end mine seem to 5k realy good and then stop . Seems like they pull way to strong to just stop at 5k . O yea stock exhaust manifolds, for now.

That is a big head. Shouldn't be the heads runnng out. Maybe change exhaust and then go to a more agressive cam, without knowing what you have in there. I have allways had luck running a 950 carb.

I dont know what all you have for cams and head size, props, etc, on your 496cid, but the stock exhaust manifolds are probably the reason why you're running into a brick wall at 5000rpm and killing your top end RPM. The more power you put in to an engine, then the more it needs to breath out the exhaust---especially as you increase cubic inches.

I would like to see what would happen with your 496's just by swapping out your stock Merc exhaust manifolds with some aftermarket Stainless Marine exhaust manifolds!

i'm sure i'll be corrected if i'm wrong , but isnt it fairly inexpensive to buy 4 bolt main caps and while the block is being clearenced for the stroker crank to have the machine shop add the 8 studs , making it a 4 bolt main ?
i'v also read alot about making 600hp and less with 2 bolt mains w/o any problems
but again , i'm still a novice at this

my .02 , with the money your talking , i would either buy something built , or buy a new 502 (around 6k) keep your exhaust and get a nice intake carb combo for it.

As far as the conversion, it just depends on what he is paying his machine shop. Good 4 bolt cores can be found all the time for between $5&600. I have an engine that makes around 550 at 6000 that is a 2 bolt that I had studded. A studded 2 bolt block is very comparable to a 4 main that is bolted. Maybe even stronger becaue the studs go all the way into the block and bottom out.

My non expert advise is that its the cast cap that fails not the bolts. And spayed cap blocks are stronger than a stock 4 bolt. Any opinion?

Ill have to get cam specs but its a hyd. roller the heads are the alm. 310 cc runners, elderbrock intake,9.5 comp. and 750 marine demons

Get rid of the demons and go with a race series 950 Holley, or have someone build you some. I get them built. Costs the same and they more consistent.

310 CC head shouldn't be running out on that engine. Maybe it is the cam. If you are still running stock merc exhaust, then cam probably isn't that agressive and that is hindering you.

Exhaust is definately to small if it is stock Merc.

Here's those specs Let me know what u think . I thought 56k was good for my applications, Im using Eagle,SRP stuff also

Part Number: CRN-139011
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 1,600-5,600
Intake Duration at 050 inch Lift: 226
Exhaust Duration at 050 inch Lift: 234
Duration at 050 inch Lift: 226 int./234 exh.
Advertised Intake Duration: 288
Advertised Exhaust Duration: 296
Advertised Duration: 288 int./296 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.587 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.610 in.
Valve Lift with Factory Rocker Arm Ratio: 0.587 int./0.610 exh. lift
Lobe Separation (degrees): 112
Intake Valve