Modifying my 330 hp 454 cu in to ??
 

I have a 28 ft Checkmate with twin 330 hp 454 cu in engines that runs 67 mph on GPS. I plan on installing ported World cast iron heads part # 3004 with 269 cc intake port volume, a hydraulic roller camshaft with 224 degrees intake duration, 234 exhaust duration, .527" intake lift, & 544 exhaust lift. I plan on using the stock 8.0 : 1 pistons and due to hatch clearance I plan on using the stock intake but it will be cleaned out as best possible. Also I plan on running a richened up stock quadrajet carb. No exhaust system mods are planned for this year. What horsepower gains can I expect ? What MPH gains can I expect ? Anybody ever do anything like this ? Am I making the right moves ? Any recommendations, help, or input is greatly appreciated ! THANKS !!

in order to really get that thing breathing healthy I would look to change the intake and go with a Holey carb. The stock intake is designed for what they call peanut port heads. Its a very small oval port. I would make sure it will work with your heads. You would be better off with 454 or 502 mag intake or even a open plenum. adding a set of roller rockers isn't a bad idea either. also changing the cast iron risers on the exhaust to stainless would be helpful with out having to spending thousands of $$$ on new manifolds. finding these parts on this board should be easy.

Modifying 454/330
 

Your subject is one that has been on OSO hundreds of times. Seems like everyone who ever owned a stock 7.4 wants more power. Myself included.

The parts you are buying are really good pieces I believe. If you were building from the ground up I believe they would be good choices. By themselves and without the supporting pieces, Im not real sure that's where I'd spend my $$. The 7.4 uses small pushrods, cheap rockers, cast pistons and the stock intake/carb setup will hurt you lots. The heads and cam are "air flow" pieces and without improved intake and exhaust, you will greatly diminish their value. The cast crank, small rods, two bolt mains you can live with.

Lots of money, not lots of go power.


There are lots of people who swear by the successful 7.4 buildups they've done. I certainly won't argue that point. It certainly can be done. Most don't spend the big bucks for heads you are spending though. With the improvements we've seen in blowers the past five years, it would be hard to beat the power and flexibility they can provide. And, there are blower packages specifically designed for your motors. The guess work is eliminated for you.

Good luck with your project.

From my own experience having done things very similar to what you are doing, I was dissapointed in the engine mods I did until I spent the money and put the Gil manifolds on. Then it woke right up. You didnt say what year your engines are? Thats seems very mild for a roller cam, Its close to what I use for flat tappets. Unless you already have a roller cam engine, I would stick with flat tappets (hydraulic) for the lift you specified and spend the money elsewhere. Edelbrock Torker 2 intake manifold is a good replacement for the stock and is no higher so clearance is not a problem. Some people have made there quads work but I had more luck and speed with holleys. Also, If you havent bought the heads yet, consider the edelbrock oval ports. They have 110 cc chambers and will up your compression ratio. Hm, sounds like I work for edelbrock, I dont. I use their intake and cam but havent used their heads yet but if you dont plan on changing pistons, they might be worth looking at.

Good Luck

The weak link in that motor is the rotating assembly. you only have a cast crank , cast pistons, and light duty rods. Its not good to push that engine to high RPM's for long. I think they are only rated for 4700 rpm unlike the mag. engines that we push to 5000 rpm and sometimes more.

The exhaust will limit you to about 430 hp but that is ok for now. The edelbrock torker intake is very very close to the dart on a 454 under 5000rpm and is about the same height as the high gm rectangle intake. Otherwise you are basically copying the Hp450 merc top end but with better heads. Oh you may also need an engine oil cooler if you don't allready have one.

I built a set of 330's on steroids last winter stock bottom end but 9 to 1 merlin heads, roller rockers, 850 holley, rpm intake and emi exhaust gained 10mph.....run it 5100 never had a problem SuperV runs the same set up but forged pistons and turns it 5700 neve misses a beat! ran four seasons before a rebuild....my.02

And Dyno and SuperV have the cast crank/small connecting rod combination referred to in another post. The roller cam you are considering would be a good choice for these engines. You really should upgrade the exhaust though.

You most likely have 4 bolt main blocks. Do change your rod bolts to a good quality like ARP. The cast crank is good to about 500 HP. You should upgrade the 5/16 push rods to 3/8 inch, and go to a good set of roller rockers. I used Comp Cams Steel Magnums. The peanut port intake in not going to work well, if at all, on the big oval heads, you may want to consider a change. The Q-jet can be set up to work fine on an engine of that HP. Infact I think they work great. I did change my cast pistons to hypernutectics. You can get into a set of exhaust manifolds pretty cheap like Eddie Marine, IMCO, or Gil. I think they will help you get the benefit of your other mods. For what you are doing I'm not sure I would go with the roller cam. That is alot of money that you need to spend elsewhere. A wisely choosen flat tappet will do a good job.
Good Luck

Very well said, Whitenuckle. I prefer flat-tappet cams but hydraulic rollers are becoming very popular, and they make good power as well as reducing the internal friction.