I've run large oval (intake) with a stock 330 head. I'm sure it's not the BEST combo, but it does work.

ptlmveng-

The 420hp intake will work on the 330/454- won't be the most efficient intake but it will work. Depending on what is wrong with your 420/454 you might be much better off freshening that engine. The 330/454 with an intake change is not going to run anywhere as near as strong as the 420 motor.The 420hp/454's have a lot of good parts inside of them.... just my two cents.

Rick

the 420 block was cracked and had been repaired. As well as one of the heads developed a crack this summer. don't know the extent of the crack or anything. Got water into one of the heads that messed up a few valves. Not sure if that was the block, head, or riser gasket that failed. wasn't worth taking the time to find out it wasn't worth rebuilding. Didn't want to spend alot for a motor so i just went with the 330hp. Just hoping that the old 420 with over 700 hrs and other problems that it was only puttin out somewheres in the 330hp range. this way I'll be in the same boat as I have been (no pun intended). Everybody, including myself, wants to go faster. But somewheres around 60mph and the great sound of thru hull exhaust, I'm completely satisfied. I think the 330hp is a pretty reliable motor that will give alot of trouble free boating.

The 330hp is a great motor- low maintenance and very reliable. Who knows with a cam and head change it might run even better...
Good luck with it

it just so happens I'm rebuilding two 330hp mark IV's. for cash sake I will use existing heads (replacing 1 with a crack) I have some 496 take off exhaust and will be replacing the tips with 4". I'm looking for advice on what cams to get, I believe I will be going with the eldelbrock performer RPM Air Gap intakes. (had them in mind but made the decision after reading the first posts of this thread) the question... what cams, I want from the hole to 5000RPM. there seems to be a wealth of knowlege here so I will shut up and learn!!
happy new year all
Bobbo

just buy a decent oval port intake...the mismatch ports interup the flow and kill power...just like trying to put the square peg in the round hole.....now that should make it understandable....and yes they have small(some call peanut) oval ports and large(which work very well on boats...Rob

on the other question, you are right on wityh the intake, I would contact comp, crane, or rmbuilder on here, understand he is the cam guy here...Rob

I can't find a decent intake except for stock cast that has small oval ports. Only thing i can find is large oval ports on intake. Isn't that essentially going to be a mismatch also causing the same flow issue?

not nearly as bad as the rect will be....

Guess I'll have to see how it works out. I'll probably try it and see if I have any problems. What intake is everyone runnin on this motor thats not the stock intake? Edelbrock with large oval ports?