I agree that all of the assembled merlin heads have 2.30intakes, bare castings are 2.19". I also agree that the guy I'm talking to about porting is one of the best. On the same hand so is the cam guy! So I need to call and make sure he knows this is for a 439. Bob's thought in this was that there would be to much shrouding in the bore with the bigger valve. He said he has never seen any improvement on a dyno with that big a valve on a 4.31 bore. Maybe with bore notching that would resolve some of the issues here. I'm not bashing anyones opinion on any of this, I just am a firm believer in getting other opinions before I make a decision. I really hate spending money on stuff I don't need. Also PM me your e-mail so I can send you the info we talked about.

If I remember correctly those 468's I once had DID have the cylinder bores notched....and I am a firm believer in that! I have always liked getting other opinions too....but sometimes it can become a bit confusing. And spending good money after bad is something I never liked either. I wish you the best with you project...and have FUN! Mark

I see the dilema your in. Good thing your doing the assm. or you'd with out a doubt have a 3rd opinion. LOL.....

lol- Tell me about it! Sometimes it's a can of worms that you shouldn't open.

If you already own a good set of 2.19" valves, stay with them and don't just hog out those intake ports. do most of the work in porting at the bowls and throat of the valve.
If you've got to buy new SS valves you could also use 2.25" because they are the most popular size and can be usually purchased at less cost per valve. You won't need 2.30" on those heads and it will be difficult to blend bowls and have good transitions into the chamber and pretty good shrouding of the valve on that bore size.
Have the head rework person keep the bowl throats at 87% of valve diameter and use a good 4-5 angle valve seat and throat job. This is where your velocity and power will come from with those Merlin Oval Ports. Also have a 20degree back cut made on the intake valve to improve the low lift flow numbers. Big flow numbers on a flow bench are not the last word in marine engine performance, the really productive work is in the little details! Bob knows his cams and he knows that bigger is not usually better in these type of engines, he won't steer you wrong!

Best Regards,
Ray @ Raylar

I kinda look at this a different way. Are you building a cam to match you heads? or are you porting heads to match a cam? The heads dictate how the air is distributed to the cylinders. If the heads only flow so much air at certain lifts then the cam has to be designed to achieve the the best efficiencies at these lifts. If you have a cam designed for this (X) duration and (Y) lift but your heads don't work their your F'ked.

I assume you are matching a cam to the heads. Give your cam guy your head flow #'s and have him go from there. You are going to be spinning the RPM's to be making the power. Rule of thumb from what I have been told. As big of an intake valve that will fit and as small of an exhaust valve that does not hinder flow.

And don't forget to the Bore Notch, that is 15-20HP on a built 468 when you unshroud the valve.

Heads first- then cam!

Where is our boy?

With the kinda domes you're showing in those pictures, the valve unshrouding would be critical as you show, but I am thinking Endeavors engine will have flat tops and the bore notch is good but not as critical and won't net that much power with a flat top piston on pump gas especially if he is using a 2.19" or 2.25" intake valve size. The intake probaly starts opening about 4-10 degrees BTDC and At about 10 degrees ATDC that intake valve is really chasing the top of that piston down the bore for awhile. The notch tends to really help the hopefully swirling air/fuel mixture spiral down the bore with the piston and not create a vortice at the top of the block deck to combustion chamber joint.

When we have done BBC intake air flow shots around the intake valve seat where the charge enters the chamber its amazing to find out that about 75-80% of the air charge actually exits over only about 25% of the total valve seat diameter!!
This why air charge direction in the port ,swirl and tumble are so important to packing an air fuel mixture into a cylinder with a piston on the way down. The more you can pack into a cylinder, the more you blow up! and that makes more power!

As for cam or heads I would say its important to get a good head/cam package match taking into consideration the rest of the air tract like induction system and exhaust system. Once all these parameters are covered and known, I still think Bob Madera will get it right for this guy. Again this the best system approach that will net the best overall results based on Endeavors needs and wishes.

Best Regards,
Ray @ Raylar

In reality I think what he is looking for is the most power he can get out of a 439 CI and stay within his budget.

Back in the mid to late 80's I ran a single BBC 24 Challenger. One of the early on boats. This was shortly after Valako started raising the floors on the intake ports among other things. I remember straping on a set of his reworked Darts, while my out of the box ones were on his bench, with no other changes and was completely amazed. The mid range and top end was exhilarating. As years went by I would always try and duplicate his work however the only thing I would get is a good laugh and a chance to catch up while he would attempt to clean up my work.