Need advice on a 7.4 rebuild

[rrrr]

I sold a buddy my old boat, has a 7.4/BI. It's a 24' bow rider. Natchurly, he broke it. Mechanic found a hole in a piston, which I thought was weird because the Thunderbolt V ignition has a knock sensor with retard.
BUT, speaking of retards.....he ran regular in it. Oh well. Anyway I told him I would come up with a parts list for a good rebuild, nothing crazy. Told him to remove the Y-tube and run different exhausts. I think the Gen VI block and crank are fine for this boat. He needs forged pistons, a different cam? Since it needs new pistons, might as well make 'em bigger. :D It has an Edelbrock air gap manifold with the stock Weber square bore carb (AFB type).
Yer wife won't listen to your advice, but I might. :D :D

[Beer-30]

Here is a 502MAG (EFI) rebuild that was done on a "budget". He wanted to stay at $5K for the rebuild and wanted 100 more HP. He only went over by adding exhaust and a few other things, but for the most part he hit his goal.
Just substitue 454 and carbed, but I am sure you could get a kit/directions from Crockett Marine.
http://www.***boat.com/forums/showthread.php?t=98928&highlight=kevnmcd

[rrrr]

What? No one? If I said it had a jet with an inducer and a snoop droot (whatever the fawk those are) there would be a hundred replies here already.......:idea: :D :D

[Beer-30]

Here is the "454Mag" replacement long block. Minimal down time, just swap all other parts right onto it. 385hp upgrade, too. All forged and a roller cam:
http://www.cpperformance.com/detail.aspx?ID=3360
Or, the original "7.4" 310hp replacement:
http://www.cpperformance.com/detail.aspx?ID=3460
I think they have the prices switched, though.

[paradigm shift]

Here is some info I picked up that some have used and been happy. Really depends on the budget. This is a nice rebuild on a budget in my opinion.
Here's the Federal Mogul parts list for 454+.030, which dyno'd at Tom Earhart's shop at 505 chp@5500;
L2465F+.030 forged pistons, 9.6:1 c/r
E233K+.030 rings
4400M main brgs
3190CP rod brgs
1404 cam brgs
381-8009 brass core plug set
KT3-171S timing chain set
CS1140R cam, 234intake/244exhaust@.050, .553/.578 lift
HT817 lifters
VS1581 valve springs
VSR7015 retainers
VK338R keepers
V-8007R intake valves, 2.19 dia.
V-8006R exhaust valves, 1.90 dia.
Merlin oval-port heads, Performer intakes, Holley carburation
This combo has also been built using H693CP+.030 hypereutectic pistons, 9.5:1.
Depending on bore thse have worked well also. H426CP+ .060 hypereutectics, 8.6:1 and a slightly smaller cam, CS1139R, 224/232@.050, .527/.553 lift, GM rectangular-port heads, GM aluminum intake, Holley carb,
Some will poo poo the hypereutectic pistons but if you hole a cast piston from preignition you will hole a forged also. Like I said just some info to think about and there are lots of choices. Tyler Crokett is as good a resource for help and info as you can find. I have done the 502MPI upgrade and it works well. Good luck with the rebuild. :)

[SmokinLowriderSS]

Here is some info I picked up that some have used and been happy. Really depends on the budget. This is a nice rebuild on a budget in my opinion.
Here's the Federal Mogul parts list for 454+.030, which dyno'd at Tom Earhart's shop at 505 chp@5500;
L2465F+.030 forged pistons, 9.6:1 c/r
E233K+.030 rings
4400M main brgs
3190CP rod brgs
1404 cam brgs
381-8009 brass core plug set
KT3-171S timing chain set
CS1140R cam, 234intake/244exhaust@.050, .553/.578 lift
HT817 lifters
VS1581 valve springs
VSR7015 retainers
VK338R keepers
V-8007R intake valves, 2.19 dia.
V-8006R exhaust valves, 1.90 dia.
Merlin oval-port heads, Performer intakes, Holley carburation
This combo has also been built using H693CP+.030 hypereutectic pistons, 9.5:1.
Depending on bore thse have worked well also. H426CP+ .060 hypereutectics, 8.6:1 and a slightly smaller cam, CS1139R, 224/232@.050, .527/.553 lift, GM rectangular-port heads, GM aluminum intake, Holley carb,
I agree. I was going to come up with something very similar, with a few differences reflecting py parts preferences such as Clevite 77 bearings and (not looking up the part here) a set of good bleed-down lifters like Rhodes or my Isky Superlifters, not so much for float-protection but to use the bleed-off cam "shrinkage" at idle effect to help the pull off of idle.
My very similar Isky cam custom ground for faster valve opening/closing that I bought from from HTP pulls very hard off the bottom, yet will idle with a smooth lope at 850 to 900 RPM (with the old stock ignition, we'll see what the new hotter MSD Ready-to-run dist/coil/S.C. wires setup will do).
I think the key to 500 HP in a boat-usable RPM range is in heads/head work and exhaust. The rest of the good parts choices run into the stock heads which need work and or restrictive exhausts.
Do ya hnow what head castings he ius runnning?
Some will poo poo the hypereutectic pistons but if you hole a cast piston from preignition you will hole a forged also.
I am one of them who is nervous about Hypers, but do not say much since I only have other peeps experiences to draw on, not my own. The troubles others have had seem to me to either be out-of-proportion, or just have gotten noteriety, I don't know.
if you hole a cast piston from preignition you will hole a forged also is definitely true. Detonation isn't the piston's fault.
Like I said just some info to think about and there are lots of choices. Tyler Crokett is as good a resource for help and info as you can find. I have done the 502MPI upgrade and it works well. Good luck with the rebuild. :)
Good luck to you and your buddy in this.

[paradigm shift]

I am not exactly sure which GM rect port head was run on the second choice and it was not put on the dyno as far as I know. Pretty sure they had a little work done on them on the exhaust side anyway. :D Owner was happy and ran well. The first list ran merlins and parts are a budget rebuild. Not all the choices I would run. I am not necessarily recommending Hyper pistons I just know some run them with good luck.
I totally agree with this: I think the key to 500 HP in a boat-usable RPM range is in heads/head work and exhaust. The rest of the good parts choices run into the stock heads which need work and or restrictive exhausts.

[Jetaholic]

What HP figures can I expect to see with this BBC combo?
L2465F .030 over pistons
9:5.1 Compression
Stock rods + crank
Double roller timing chain
Isky 280 Mega Single Pattern Jet Boat Cam -
280 Seat-Seat duration
232 .050 duration
.323 cam lift
.565 valve lift w/1.75 rocker ratio
110 lobe centers
60* overlap
4* advance ground into the cam
Edelbrock RPM Air Gap manifold
Holley R-80537 750 double pump carb
MSD Ready To Run distributor
MSD 6M-2 Ignition Box w/Soft Touch Rev Limiter
MSD Blaster High Vibration Coil
2.19" intake valves, 1.88" exhaust valves
353049 Heads
Bassett long collector water injected headers

[SmokinLowriderSS]

Jetaholic, I'mm gonna ballpark ya in at pretty close to 600 pounds torque (between 550 and 600) arround 4500 RPM, and pretty close to 600 HP peaking right arround 6,000 RPM.
Those are my spots on the "motor pool", where do I send my 1$. :D