1BIGJIM

My current setup is 454 stroked to 496 CI
781 Large Ovals with original size small valves.
118 CC chambers. With SRP pistons 9:1 compression ratio
Comp Cam Extreme Marine 226/236 @ .050
BG Sea Demon 750 DP
Edelbrock Performer Intake
I do not want to spin this over 5,500 RPMs
Last year after spinning a bearing(long story, stupid mistake) I stroked it to a 496 and only gained 100 RPMs same compressing rato, cam heads etc.
I obviously have a bottle neck somewhere, and I am thinking the heads?

Edelbrock Oval Marine Heads 110CC
290 Intake Runner. What would this raise the compression ratio to?
I am guessing around 9:6.

Dart Iron Eagle. 119CC chambers, 305 Intake runners same size of valves as the Edelbrocks. Probably flows better out of the box. These can be had for about $1,500.

Any other IDEA’s

Thanks in advance for your input, and based on it will determine what I will purchase in the next few days.

PatriYacht

I'm leaning towards changing the cam. Can you give more info on it, hyd.flat tappet or hyd roller? Since you have small ports and probably good torque, I'd put in a Crane 741 or the Merc 525 efi cam. Also get a Dart or Merlin single plane intake.

Wobble

Bear in mind that 91 octane will be the max pump fuel available from 2007 on, if the new EPA regs go through. I read this in another thread about the 800hp NA 572.

In any case it's worth considering, 9.6-1 should be OK with aluminium heads.

Pat McPherson

How about the new Dart Marine Aluminum heads?
I think they are right at 2K.

TC

1BIGJIM, I used Canfield with 119cc chambers and 310cc runners on my 496 stroker. Not sure how they would compare to others since these are the only heads I have run on this engine. I am running 10.2 SRP's and a bit more cam than you and they seem to work great. They are marine version (coated/anodized) and were $2k.

1BIGJIM

The cam is a COMP 270 Extreme Marine
hyd.flat tappet
544 547 Gross Lift
112 center line
Adv Max RPM 5,800

PatriYacht

That's what I suspected. You don't have enough cam for your cubes. That cam is similar to the Merc 420 cam that was rated for 5200 max on a 454.http://www.cranecams.com/?show=brows...tType=camshaft If you have the money do cam and heads. On a 500 cid engine, my favorites are Canfield 310 rectangular.

1BIGJIM

That cam looks very similar or milder than the one that I have. The duration and lift are almost identical and its on a 114 center line. What am I missing?

PatriYacht

I'm saying that Merc used that in a 454 with good idle and warrenty and now you're using it in a 500. It's too mild for what you want to do. You need to do a cam change as well as a head change. An engine is a system. All parts have to work together and produce power at the same desired rpm. Look at my first post.

1BIGJIM

TTT