More info could be helpful. Which engine, which exhaust manifolds, what setup? Many things are possible...
yes. recently did 2 streetable pump gas and vacuum friendly BBB's dyno showed 631 hp with headers. Use ported iron manifolds subtract maybe 30hp. met the goal. cam specs would be slightly different to account for poorer exhaust scavenging. one motor went in a full boat 70 electra 225, he ran 11.40 first time out.
470 or 482 using a 76 block edelbrock heads flowing 316/222. 11.75:1 compression. B4B intake. Cam to be determined
Well with that much compression cam choice will have to ve carefully selected to keep things pump gas friendly for sure. But your goal will be easier with the much added expense of a roller cam. And I'm still thinking you will need more airflow and someone to open up those manifolds for sure
A roller isn’t out of the question. Heads were done by JW and he said it isn’t worth the expense to go any farther. I’ll just have to lower my expectations
Dunno if you've ever taken off and looked at your stock cast-iron manifold. There are imperfections and giant bumps everywhere, and the ports are never as large as they should be. It's an easy modification to take a drill and clean all that up. If you have ported heads with a manifold that doesn't match what a waste of time and money
There is the process of abrasive flow porting that does a great job of fully smoothing out and polishing all the areas inside of things like this thst are very hard to reach
If you want it to run on pump gas with close to 12:1 compression, you'll need a pretty big cam, something like the TA 510, http://taperformance.com/proddetail.asp?prod=TA_510-455 That means more RPM for peak HP. The SP1 or SPX intake will be much better for your goals. More info on ported exhaust manifolds in this thread, http://www.v8buick.com/index.php?threads/aluminum-heads-with-cast-iron-exhaust-manifolds.319045/ I think Jim Rodgers might be able to help you with porting exhaust manifolds.
https://extrudehone.com/ I had them do a nailhead intake and heads. Nice job, they run great. I opted out of the solid lifter max lift cam though, i just drive on the street.
When I was looking to upgrade from my fully-ported SP2 intake,I knew I would need to have any other raw or unmolested intake ported. Prices ranged from $1k-$1500.00 for the porting,depending on the extent of it. I was able to find an intake with all the headache and hard work done for $1500.00,and gladly paid it. It could not duplicate it for that.
Would be great if you could test this on the dyno Gary.. I know for sure headers are about 10 HP on a 400 HP motor, about 25-30 on a 500 HP motor... never tried a set on a 600 HP motor, but to my mind, I am thinking 50-60 HP loss with manifolds at that airflow rate. The more air you try to flow thru them the more they cost you. The biggest thing with the ported manifolds is enlarging the outlet.. I think Jim Rodgers actually welds on adapters to be able to go to a full 2.5" diameter outlet, yet still have some sealing surface left. You would need that type of manifold for sure.
I agree jim, that's why I believe different cam specs would be in order. I'd like to dyno a street setup with iron manifolds too. Haven't had that opportunity though.Jim R. actually did some 3" outlet manifold he sent to me for testing a while back, they were awesome but not put on a dyno . The manifolds we've opened up were 2 3/8" plus to use with a 2.5" exhaust.