Cam, PCM calibration, and throttle body (adjustment only). Also, all 375hp motors have cast cranks, early HO 425hp engines have forged, and later, all had cast. This is not a worry though, cast crank is plenty good.

You can get cam from Mercury Marine, very easy swap. You can buy a brand new PCM, or send it to us your stock unit for recalibration. Then put it back together, slightly open the butterfly or drill out the current hole and your done.

It's an easy 40-50hp. I've had quite a few customers do it.

Dustin

Dustin,
I converted my mags to ho's cam and ecu change , What is the throttle body butterfly modification for ? I did'nt know about this. What size drill bit ? or how much more do you open the butterfly ?

Dustin,
Can you please explain the throttle adjustment? I'm trying to figure out what motor I'm facing. My customer bought it as a HO but the serial no plate is missing as well as the sticker on the top cover. The block has the Std 375 hp code stamped into it, it has the HO ECM (or at least the sticker saying so), next I'm going to check cam lift to find out if it has HO cam or not.

Thanks, Alex

Dustin,
No need to reply. Obviously I didn't read your message in full detail. The adjustment procedure is already there. Thanks anyway for the info

Is it true that the early GM 496 have stock a forged crank?
I got a 2001´shortblock and think about a build up with some high performance parts but if it got the weak crank I let it.


Hannes

At least the Mercruiser 496 HO had a forged crank during the first couple of years. Later they skipped it for the same cast crank that's used in the 375 hp std engines, reason is said to be the relatively high strength even though cast.

They also tried floating piston pins for a couple of years but as the previous example they went back to pressed pins. Reason unknown.

Thanks so far, does anybody know if the the pin hole in 496 is at the same location and with the same diameter as by a usual 454 (at least they have the same bore)?
I would like to know if I can use usual 454 pistons for a 496.

Is there any difference between a Mercruiser 496 HO plenum and a stock GM 496? A friend got one to sell but if it brings no performance advance I leave it.

By the way, I would buy any used 496 afjermarket parts like alu heads, cams, plenums, forged parts...

Just come in touch by [email protected]


Thanks Hannes

Another question, are that the data´s of the 496 connecting rods?

Tall deck 6.535" length

2.200" big end bore (stock)

990" small end (stock)


Answer would be highly appreciated

Hannes

Thought I would chime in here also and answer a few questions in this thread and offer some biased advice!
First, the only difference between 496MAG and 496MAG HO's are the camshaft and the program in the ECU. Some of the 496MAG's have a smaller bleed hole in the throttle plate in the throttle body so when and if they are converted or equipped with one of our kits or an HO cam and ECM conversion the throttle body plate needs to be drilled out ot 1/4" to 5/16" depending on which cam is used. This extra bypass air keeps the idle air motor at a lower count (operations per second) and thus keeps from having the idle air motor in constant motion.
This is not needed on a stock 496MAG or 496 Mag -HO unless each is modified.
Some early 2001-2002 496 HO's had the forged crankshaft until GM Powertrain - GM quit using them in lieu of GM's own new pressure rolled fillet nodular iron special 496 crank (bean counter decsion). Its nothing like an earlyier GM cast iron crankshaft, much better part and nitirided too.
The forged units are a bit stronger and lighter than the cast crankshafts but both are very capable of handling 600-700HP without failures.
We purchased all the remaining un-used forged crankshafts and we have them in stock still and we use them in our 496 - HO525's and HO600 motors when requested. We also have 4340 forged crankshafts for the 496's and a stroker size crankshafts for the 496-8.1L engines.

As for the 496 connecting rods, they are forged rods, early ones with pressed pins the later ones with full floating pins.
These rods are metric length in stroke (6.683") and will not interchange with 454-502 sizes because they also have a metric daimeter pin (actually measures about 1.043") which is larger than the standard BBC .990" size pin.
The reason we do not use these rods with our custom Mahle 496 pistons is because they are not in our opinion strong enough for over 600HP and the metric 10mm dia. rod bolts are not as strong as good ARP 7/16" rod bolts we use in our Raylar H-beam billet rods that come in our piston & rod sets for the 496-8.1L
You could rework the stock rods for some forged pistons or have custom piston sizes made, but the cost of rework and custom pistons is higher than we sell our Raylar/Mahle piston / H-beam billet rod sets for and they are capable of handling 800-1000 hp quite easily!
We also have quite a few 496HO cams in stock that are take-outs for those who are convinced they need to convert their Mag to an HO, but they will still have to have Whipple or us reprogram there ECM to a HO spec.
My suggestion is to put on a good exhaust like Dana or CMI and get 40HP plus and then when they can see or afford to upgrade their 496mag with our Raylar BCK103 kit and ECM reprogram they will have 560HP - 496 without wasting to much money and time when they will most likely want to upgrade from an HO cam in the future.
One could use this package for the life of the short block, then upgrade the shortblock with one of our exchange shortblocks or build their own with our parts and depending on bore and stroke size chosen they could still have a 496 based engine that delivers between 625 and 675HP, normally aspirated on 89 pump gas.
We can also supply forged supercharger blocks or block upgrade kits with supercharger pistons , special cams and inconnel exhaust valves, then with the addition of the great Whipple supercharger system you can boost up to 750-800 HP levels
Wholla- no built-in obsolesence or wasted use and money!

Just something to ponderwhen considering what to do with your 496.

Best Regards.

Ray @ Raylar

Hello Ray @ Raylar,

sorry for my bad english, I hope you can understand it.

can you please give me your email adress, I would like to contact you for talking about the Raylar HO600 for replacing my 496HOs. I have a Sunseeker 37 Tomahawk.

A friend of mine is interested in changing his 496HO to a HO600 or a LS 550 too(Baja 252).

Please give me your e mail adress.

regards,

Norman