We really need alot more info! What brand intake? How big is the cam? What cylinder heads? What are you using for a carburator? You question is very very vague! Im sure you can get some answers, but we need to know more about your motor!!!!

i got schooled on this when i first got on hear too. caps means your yelling FOOOOO, SO UNLESS YOU HAVE TO YELL AT SOME1, keep the caps off. 

WHY AM I SCREAMING?better??

just messin with ya. =)

yeah i understand that for sure.i was under the impression that i would have to mill"or hog out" any intake out, to match fit,so i figured :screwy:that i would just put a little more work on this one if need be...but is it going to make that much of a difference on the 502??

Pro Comp bought the rights to use the Professional Products molds for their intake manifolds.  Interestingly enough, those manifolds have been proven to make more horsepower than other USA name brand intakes in at least some instances.  I have put them on several dirt track racing engines that I have built.  I have also put them on a number of boat engines, and never really experienced a problem with fit, sealing or leaking. 

One important question that has been left out is what type and size boat is this in, and what rpm range are you running?

The thing is to me, is the cam doesn't seem close to large enough to FULLY support and take advantage of it, and you did NOT mention compression ratio,  but the tunnel will probably perform just fine set up properly with what you have. Not a BBC fan, Barry is more schooled in them than I..............

You hit a fantastic note on the "port matching" part........Tunnel rams depend (and work on) velocity, volume and immediate delivery. Port matching is critical. Gasket matching is one thing, port matching quite another.

You fail to mention your compression ratio, which is a VERY big part on how and why tunnel rams work.  I'm going to guess it's on the very modest side, in which case, with that cam, an 8.5:1 compression ratio, a couple 660 CFM's or bigger on it, doubt seriously you'll see much, if any, of a MPH increase. You WILL see a fuel consumption increase, harder to start, and the plugs should read all over the place.

Just my .02, but yeah, it WILL look cool! 

Ray

PS, I'd personally stick with what ya got, and build the engine for your Tunnel later when it's tired, you can afford to, or want to do it right, whichever comes first. I first built Moo with a highly modified RPM intake, 950 CFM carb and mostly blower spec cam (comp cams  OLD Xtreme marine 305) and it ran like a smart child from Neverland......Tunnel upgrade with 750's actually slowed it down, lots of problems, water in the oil...........anyway, turns out, had the manifold milled to fit the engine, PORT matched it, LOT of machine and file work, right 750  marine carbs, added 800 RPM on the boat. And quick? WOW!

Ray