I am in need of new intake manifolds for my 454 mags. The engines currently have 6055 edelbrock aluminum heads with the stock merc al rect port intakes. I have learned from this board that rect port heads/intakes may not the best selection on our low rpm marine engines, due to slow mixture velocity in the intake runners at our 5000rpm or so. I have also heard that putting good quality oval port intakes with good quality rectangle port heads is awesome on marine engines. Combines good mixture velocity with max flow at the point of operation (heads). That makes sense to me, but before I go to the expense and work of changing them, I'd like to hear from you guys... good, bad or indifferent. I am considering Edelbrock Performer 2-0 #2161 intake, which I think has ovals.

BT

Yup, the 2161 has the spreadbore carb flange while the 7161 is set up for a square carb flange. Both are oval-port. Holley also makes a very good oval port intake. Be sure to check on E-Bay for intakes as I've been seeing some good deals on there.

Thanks Crazyhorse... I'll look on ebay. Any feel for how the rect head/oval intake combo would perform in a marine application?

BT

I could be wrong, I've never mixed port types- but I think some oval port manifolds may not cover square ports correctly and you may have major vacuum leaks. The top of the square port is near the top of the tapped bolt hole between the ports. With some oval port manifolds the manifold casting follows the port contour and does not cover that area- there is only a small ear with a bolt hole.

If I remember correctly, square port manifolds fit OK on oval port heads, but not neccesarily the other way around. It depends on the individual manifold casting.

Good luck!
Bulldog aka Ronnie

Good thoughts Bulldog. I was thinking that myself. Also, if they did by chance fit ok, which gasket would one use?

Thanks for the input.

BT

Like Bulldog, I haven't mixed ports either. The only intake manifold that I KNOW can cover both types of ports is the the Dart.
Just a thought.

DAVE

DaveF is right about the Dart manifold and I believe Crazyhorse is correct also . I know this because when I bought my boat it oringinally had 468" engines in it with Merlin Oval port heads and Dart oval port intakes. However, I wanted 540" engines and went with the Dart PRO-1 aluminum 310cc rectangle port heads. I wanted to retain the Dart oval port intakes that originally came with the boat. I probably could have left them the way they were, but opted to have JimV port them out to fit the new rectangle heads. We were barely able to get the ports to match perfectly, but as far as how they bolted up to the heads was not an issue. Being that my engines are 540's and make a lot of torque by cubic inches alone; modifiying the ports didn't hurt my application (704ft lbs of torque @4800rpm). However, If my engines were 454's with rectangle port heads on it then I would consider an oval port intake or even a rectangle port DUAL PLANE intake manifold. This is my personal opinion, but I believe rectangle port heads are too large for a 454 and are even controversial on a 502.