I have a 2002 31 sonic twin 496 ho's running 73-74 mph with labbed props want to hit the 80mph mark. what reliable engine builder makes some bolt on mods to get me there ?

Raylar!

Do not waste money on headers! The stock exhaust flows fine for this engine, especially if you have the aluminum manifolds. I personally wouldn't (and didn't) invest in a raylar kit. You can repower to more desirable 502 engines for near the same cost. Your cheapest way to hit 80 is pro-charging. I ditched my 496 and never looked back!

Its a decision you will have to make. The price to do full rebuilds on the 496's and turn them into 600's is slightly less than buying two used 525's but then you can sell your 496's (but you are buying used engines). This is the kind of thing that I lost sleep over. The 525's are bulletproof but they will require some light valve train work if they have 100-150 hours. The Raylar rebuild needs to be done by a reliable builder and they seem to be few and far between. Its not an easy decision, there are reasons for and against the whole way. There are several guys pushing over 600 HP with repowered 496's and several new 525 (540) rebuilds doing the same. They are very similar in cost usually only $1500 one way or the other...

The 496's can be good if built right. The 525's are obviously good if they didnt come out of a boat that was thrashed for 100 hours.

However, the one thing I recommed against is NOT upgrading the 496 unless you put new pistons in. You really cant reliably upgrade a 496 unless you replace the cast pistons with forged pistons. Been there, done that, have the bent connecting rods and a block with holes in it to prove it.

Now that I have crapped all over your project, just leave them in there. Its almost spring, wait till next year.

whipple sells a supercharger kit that should get you to the speed you are looking for BUT i agree with the others that said to leave it alone.the 496 is a great engine and will run for many trouble free hours if left stock.it is not a good engine to modify unless you are willing to spend a ton of money imo.good luck no matter what you decide to do.

Leave it alone. If you want a faster boat go buy it with the speed and power already in it. This advise has nothing to do w 496s just my advise in general

+1 Yeah, Pete is right and I agree with him.

https://www.youtube.com/watch?v=7fdh6Nnoa3s

This is a 496, I did with a Whipple 3.3,, 8# boost 900 torque @ 4000, 889 hp @ 5900 these are observed numbers. Corrected was less with the correction factor of .998. This is not a inexpensive project. Dart Heads with Inconel exhaust, severe duty stainless intake valves, springs with titanium retainers, Scorpion Extreme Rockers, Manley adjustable guide plates, Scorpion Shrouded Lifters, 3/8 .125 wall pushrods. This does all fit under the stock valve covers, no modified parts. Modify 1-4 bearing saddles in block to accept the standard BBC main bearing uppers, before line honing. Crane dual roller timing set for 8.1. Insure cam sensor is between .040-.060 air gap, due to changes in sensors or timing cover this can be an extra .080, which you will loose cam and crank sync at some point. This will be corrected by machining cam sensor mounting surface for proper air gap.
It would be nice to switch over to a better balancer, with some machining or spacers alignment of accessories and blower drive can be achieved. I believe; the stock block and main caps are at the limit at this point, pushing more power would cause a failure.
You can not use a lifter with a .750 wheel, even though they are the same, the oil galley is not in the same location. It will dump oil @ full lift if not using a fully shrouded lifter with a .700 wheel. Crane and Scorpion offer these lifters.

Bore 4.255r
Stroke 4.375 Custom 4340 Crank
CP Custom Dished Pistons 8:1 Alloy 2618
6.700 Rods
Dart 8.1 Heads
Hydraulic Roller Custom : Marine Kinetics

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MER Per - NICE NUMBERS! You definitely did it right.

Why did you select cast over aluminum heads? Any porting?

I have wondered if the DART blocks have modified bearing saddles - I know they state stock but they also modified oil passage ways. A nice upgrade would be their DART Vortec 8.1 block with 4.5 bore. (yes, they will do it...)

I tried to buy heads from Raylar, it was about the time Ray & Larry, split-up. Larry, didn't respond to my emails, he was under the impression I was friends with Ray. I knew all the details on who developed the heads, the place they were cast and who did all the machine work. Only due to the fact; I have been a customer of Ray Franks, Profiler since early 2000. They are no longer done by Profiler, nor are they machined in North Carolina.

I did work on combustion chambers and slight clean up in bowls.
The Dart block accepts the stock main bearings upper and lower as reading the spec. sheet.