I am helping a member decide between various modifications on a stock 502 efi. He is considering a small roots blower at this point. I doubt that this will be any better than 550hp at low boost (4lbs, non intercooled). I mentioned to him that it would be worth while to look at upgrading the cam and induction system for a N/A combo to compare with. He already has a set of CMI's ready to bolt on. he is looking at removing the FI either way. I am fooling around with desktop dyno to see what a more aggressive cam, intake and carb with headers will do to this engine. Preliminarily, it looks like it might make a roughly 90 hp difference. Looking at a roller cam roughly in the range of 230-240 duration at .050 with around .600 lift on, say a 112 ls. Planning on keeping the stock rec port heads, internals, ect and installing a single plane intake with around an 850 carb. Problem is, I do not know how to accurately model the rec port heads that are on this motor, or this exact cam. can any of you help?

Found a bigblockcheveyskiboat cam file that looks to be close to what I described. With massaged stock heads, it appears to predict around 550hp at 6000rpm. If I put on a B&M 250 at 4psi on this exact combo and increase the carb size, it only gains 50hp...I would think 4psi would be sane for non intercooled roots with 8.75 comp ratio...

Question is, how do I accurately model the stock rec port heads?

I know what you mean. It seems like the heads and exhaust are hard to duplicate on the desk top dyno. I use small tube headers with mufflers as the exhaust for my CMI E-Tops. HP manifolds are probably less powerful and any of the headers without mufflers are probably going to be a little optimistic compared to the E-tops. As for heads it is the same thing. Probably some close heads would be canted oval port pocket ported with large valves. This program doesn't take runner volume into account so it will probably be pretty accurate. One thing you could do is build a HP 500 and use heads and exhaust that closest match HP and TQ in a 502 with an HP 500 cam and use that as a basis for your comparison. As far as a cam recommendation I have no experience with hydraulic rollers. A good solid cam for a 9.0/1 comp 502 would be something like a 252/258 @ .050" on a 112 + 4 with around .680" lift. This will be a reliable solid roller and will probably work good in the 5500 to 6000 RPM range. Hope this helps.
Later!

That's the head I am using too. I have an e-mail in to motion software. I picked the same exhaust.

Thanks.

THIS WOULD BE SAFE AT 6 PSI IF THE WATER TEMP IS COOL EVEN MORE WE'VE DONE IT A TON JUST USE A GOOD CAM AND HIS EXHAUST AND HOLD ON ,IT WILL FLY ,P.M. IF YOU NEED MORE

I did very similar work to the 502 in my previous boat (although I did port the heads) and ran the solid roller Craig mentioned. I don't know much about hydralic rollers either, but that "mild" solid set-up was trouble free. The motor was never dyno'd but made a solid 600hp. I think you're pretty close to real world on your models. I thought about going with a small blower on this motor as well, but went this route after weighing the costs/benefits of both.