I'm freshening up a pair of HP500 carb motors and was wondering if anyone has found an improved (horsepower)intake manifold over the Dart intakes. Mine show alot of corrosion inside the water runners and I want to replace them anyway. The Dart intakes on Mercury engines are very similar to(single plane) drag racing intake manifolds you see at the strip. If the HP 500 motor is intended to turn only up to 5200 rpm why use a manifold desighned for 6000-8000 rpm?Would a dual plane manifold make better power up to 5200 rpm?.....just a thought...........gofast

Can't realy help you on the manifold choise but was wondering how long yours lasted.I just put on and new aftermarket manifold (Holly 300-42)which is good to 5200 and was thinking that I should have made up some of my West system epoxey and tapeing off the manifold, pour in the mix and try to coat the runner with it to try and extend the life a little bit.

I put an Edelbrock "air gap" dual plane on when I built this motor and saw the torque curve move down to the mid range over other single plane plane setups. I also put a 1" spacer under the carb. Peak tq was 635 at 3400 which is perfect for my setup and boat. (4500lbs)Mid range is good. Still had over 500lbs at 5400. I proped for 5300 and it seems to run good.
The downside is its alum. and will prob have to be trashed next year...but what a couple of bucks in the overall scheme of things?
Dan

Most good dual planes peak at 5,600, also your alum manifolds can be "hard anodized" and will last much longer

I just got a new pair of Team G s for my 540's and had them powder coated outside and the inside of the water passages...time will tell

Floridianson, How well did the Holley manifold run compared to the Dart(assuming you had one)manifold.I'm debating weather to go with the Edelbrock Air Gap or the Holley you mentioned.

I would like to get a little more input from others that switched from the Dart manifold......gofast