hogie roll

If you spin them to 6.5-7k then going with a lower pitch prop will make up for the torque difference.

Rookie

iTrader: (4)

My original engines were Merc 420’s, stock flat tappet cams, pocket ported GM rectangular heads. Boat would run 71mph every day. (might have been more than 420HP)

After I dropped a seat and took out an engine. I replaced the TRW 2399 pistons with SRP 212137 small dome pistons. Replaced the GM heads with Jim Valako’s Wedged Merlin steel heads. Compression was bumped to ~9.8:1. (heads were cut) I replaced the cam with an UltraDyne soild roller 252°/264°, 108° Lift 0.632”/0.632”, Isky Red Zone lifters and 1.8IN and 1.7Ex roller rockers. On the dyno the engine pulled 564TQ @ 5200RPM and 590HP @ 6500RPM. (Still pulling a little bit of power, but I stopped the dyno there) Boat would now run 76-77mph every day. (93 gas)

Next, Valako had Dart cast 7 sets of their PRO1 heads replicating his hand porting with the elevated floors, his port geometry and his combustion chambers. He asked me if I would like to buy couple of sets for R&D purposes. (these heads were also put on a pair of 575sc’s 750HP, Jims N/A 565 787HP, and some 572’s with Vortech superchargers 1050HP) These heads netted me 9.7:1 and had 2.30”IN and 1.87” EX valves. With another pushrod change I bolted them on the existing short block. Boat would now run 78-78.7mph. (89/93 gas whatever was available)

Next phase: I did not want to spin these engine 6500RPM’s and 4800RPM’s to cruise with small props. So I decided to put smaller cams in, have Valako do another chamber port (I believe 128cc’s) to get my compression down to 9.0:1. I got in touch with Bob M. and we decided on a cam. I wanted to make enough power N/A and when my balls were big enough I would slap on my B&M 250 blowers and run some mild boost. With just a cam change, chamber port, new timing set (old set did not work with Bobs cams, GEN V blocks) and another pushrod change, I currently still run78-79mph a @ 5500RPM’s. I have run with some friends that said we were running over 80mph, but I could never confirm it. (I am still running the solid Isky Red Zone lifters on hydraulic roller cams and 1.8/1.75 rockers) (87 gas)

So, to summarize.If I was to do this all over again I would have bought 1 set Great heads to start off. None of my components would work from head to head. Valves springs needed to change with cams, valve stem lengths and diameters changed. Springs, pushrods and top of the line valves are not are not cheap to just keep replacing. Keep the TQ and HP splits closer, build as much power at a conservative RPM range. I went from spinning 24” props to 27” props at the same top end just different RPM’s.

Sorry for some errors and run on sentences. I wrote this off my phone. Hard to proofread.

Rookie

iTrader: (4)

Wedged Merlins and the PRO1's.

MILD THUNDER

iTrader: (3)

Good post Rookie. Lots of info there

dereknkathy

You know rook that nice long post is exactly why OP started this thread. He wants to know what works well for a long time without going back to the well. Somebody already mentioned stock 365 mag all forged bottom end. Iron heads. Merlin or dart. Cam is his own choice. But stay conservative. GM goes 550 lift max for a reason. But ditch the oe valvetrain components for the best he can afford.

Budman II

iTrader: (1)

Not a 454, but not that far off - I'm running a 489 with flat top pistons, AFR 265's, Dart single plane oval intake, Holley 800, and a Marine Kinetics hyd roller with very mild specs - 226/230 on a 114, .596/.610 if I recall correctly. On the dyno it made 585 HP at 5400 RPM and 604 ft/lb of torque around 4000 RPM's. Very broad torque curve, with close to 600 ft lb available all the way down to 3000 RPM. Similar combo in a 454 would probably run quite well. I'm not sure how much HP and torque you would back off with a 4.00 inch stroke - wouldn't guess it would be more than 30 / 40 HP. Or you could go a little more aggressive on the cam and spin it a little higher and probably be close to or above 600 HP. With that cam I am probably just starting to tickle the potential of those heads. Bob M. told me that those heads will easily support 625+ HP.

picklenjim

Hey Rookie, just curious what keeps those wedges in place?

Budman II

iTrader: (1)

Rookie would have the definite answer, but I think I recall seeing pictures of a set that was using some type of mechanical (i.e. screw or bolt) retainer.

Rookie

iTrader: (4)

The wedges are first expoxied in, then drilled and tapped from the bottom then affixed with a bolt that is red loctited or expoxied in. This is the process for steel GM and steel Merlins. He has wedges for both.

picklenjim

Thanks!