BY U BOY

from a mark IV 454 4 bolt main.

I will use my heads which are the aluminum ZZ502
marine power exhaust
BG demon 830 carb

all else will need to be replaced after a crank failure.
Will keep it NA
any recommendations?

stroke it?
compression?
cam?
intake?

GTOFFSHORE

10.1 compression with alu heads that will work
stroke to 496
go as big as you can on cam are you running dry or wet tails?
Turn til 5800 may have to use a single plane for the rpm but I think an air gap will work and you will keep good strong low speed trq.
A true 600 is not impossible but 1 to 1 power ratio is very easy and a starting point in what will have to be done. So gaining 100 hrsp will take work.
I did a 496 set up and it made 560 and was reliable as hell only turned it 55 5600 so not too push it too hard.
bigger ci+ comp+rpm= more hp

Young Performance

The heads are going to be the biggest hurdle. They are not the best flowing heads in the world. They have relatively small ports.
With some port work, 10:1 comp., and enough cam for 6000 rpm, you will be close. Should make 575+ hp.
I wouldn't waste the money to put a 4.25 crank in it. If you start with a 502 block, you can bore it to 4.600, making 565 ci. That is 70 ci more than you can make with the 454 block. That equates to over 100 hp with of the larger, more efficient bore unshrouding the valves. Start with more inches if you want to spend money on a crank and rods. Just my opinion.
Eddie

BY U BOY

wet exhaust.

I figure if i stroke it with the right cam and compression I should not be far off.

560HP would be good. Do you mind sharing you specs?

BY U BOY

I value your opinion and have given the 502 a lot of thought.
At this point I am just gathering info and will start to get my parts in order for a winter build. Hard to do anything with a 1yr old running around. Boat has not been in the water for 2 years whats one more summer

GTOFFSHORE

That motor is long gone. The cam was decent. The motor was built by ATECO in 02. Young is totally correct. Those heads are a stumbling block with that power out put. I am redoing my 572 and if you use the 1 to 1 ratio it shows you what is possible, and you are doing it with cubes alone. I am changing cranks and going to a 598 with my combo it will push 750 with a solid lifter cam. On your set up look around and you WILL a great deal on a strong longblock since you are in no rush.

brian41

iTrader: (1)

This 572 made 754 HP at 5900 rpm with hydraulic cam.

GTOFFSHORE

That's awesome. I was at 721 with mine but was using the zz572 heads. On the new set up I am using a set of cncd brodexs. Can't wait to tune it on the dyno. Once you get into these big motors it's amazing to see the capabilities. We used to drool over 500hp 502's now they are considered tame(;

Rookie

iTrader: (4)

My 454's made 590HP @ 6250RPM.
I have Dry to the tip exhaust, Solid roller cam duration @ .050 252 / 264, lift In 0.667" Ex 0.632" on a 108*, Worked over Holley Barry Grant carbs, fully ported heads, bore notched block and 9.7:1CR. If you don't mind lashing valves and have dry exhaust it is doable.

That being said I will be going with bigger cubic inches eventually with a hydraulic roller cam.

rob vanharten

That's some nice power out of those 454's Jason. Hey have you seen Jim or talked to him latley? Just wondering how the reversion problem was coming on my motor. Wondered if he had anything figured out yet? We will need to run our boats together this summer, see who is chasing who