There were some questions about the 330 heads. I finally had a chance to do some flow work on some Intake ports, here are the gains.

.Stock
.LIFT......................CFM..............Modifi ed.............Gain CFM

.200......................118..................118 ............................0
.300......................176..................181 ............................6
.400......................228..................245 ..........................17
.500......................240..................267 ..........................27
.550......................245..................280 ..........................35

I reworked these Intake ports looking for the most gain with the least amount of labor. After .550 the port stopped gaining airflow because of the small volume. The numbers are overall down from the larger ports but for what they are it is a subtantial gain. The flange was openend up to the larger oval port. With a cam and intake change I would guess 50 to 75 ft. lbs of torque increase. This would work great if your engines have the built in rev limiters. The heads will not want to turn many rpms, 5200 max.

Hm thanks for the info, so maybe the 3 sets of peanut port heads I have are useful after all. At 5000 rpm, how would your modified heads compare to the 781 or 049 stock oval ports? Oh, and did the head you tested have the 2.19, 1.88 valves or the smaller stock valves?

Formula31,

They have the stock 2.07 intake valve. They will be down stightly from the rectangular port but because of the volume the motor wont rpm. My guess is they will a ton more torque than the rect. ports off Idle to 4000.

Do you think its worth the money to put the bigger valves in the peanut port heads or is the porting you do sufficient for 5000 rpm? My thoughts were by the time I had them ported and got bigger valves installed. Id be better off performance and money wise going up to the old large oval ports. ??

Formula31

It will bring the numbers up but I dont think it's worth it. With what I did to the heads now is at $500.00 (that includes exhaust work too). Adding valves and a grind would push it beyond it's worth.

Thanks, Thats great info. It looks like the numbers you got are as good as, if not better than the large oval ports with large valves (unported) at reasonable lifts. I would think that for a 454 running at 5000, it would be a good upgrade.

Hey Jim, you ever flowed the later Vortec heads, just to see how well they flow over the old peanut ports? I would luv to see that kinda info....

You ever ported them? I've heard they can almost flow what merlins flow, and with the smaller valves.

Jim,

Great information ! Thanks ! It came at a good time as I'm considering 049 heads, Merlin 269 cc heads, or modifying my small 330 horsepower heads. If I keep my stock heads I would port them myself. Any chance of getting a run down of how you modified them ? Is the flange that was opened up to the larger oval port, the end of the runner that bolts up to the intake ? If so does this mean that there is a big mis match here ? I haven't had this motor apart yet so I dont know. Also due to hatch clearance problems I won't be able to install a taller intake. I've heard that if you smooth out the rough edges inside the intake and cut out the divider between the primary & secondary holes it will flow as good as the taller ones. Any input on this ?

Thanks for your help,
Bo

I was told that all the marine motors had large oval ports??? How can you tell large from small oval port heads????

Jon

I think every 7.4 or 330 merc engine since the late 80 has peanut port heads because the large oval port head were not made after like 79 or something. Thats why merc then used the rect port heads for the mags which are worse then the ovals but better than the peanuts. Is this right?