496 stroker

[Anonymous]

Alumitech recomends a 496 stroker built in Orlando. The 496 has 425hp---but has mucho torque---and was designed for 87/89 octane. Anyone running one ? I've heard bad things on the 502's. I'm going from aircraft to auto & just don't wan't to make a costly mistake. They also suggested a gear drive and 2.38 or 2.58 with 2 or 3 blade Powershift. Any and all comments appreicated. oh yeah--- I was looking at a 15 x 8 boat. Thanks

 

[Anonymous]

you mentioned 496 stroker, is this some aftermarket setup? Or are you talking about the crate engine directly from chevy? I have a friend with the "leviathan" 8.1 liter, 496 cubic inches, fuel injected, with a belt drive and a 3 blade powershift. The boat is nearly 20' and still moves along pretty good. He hasn't had any problems that I know of. I have a 425 hp 454 and the only difference I see between us is he uses less fuel.

 

[Anonymous]

they said it was built by a shop in orlando. the cost was $8900---1k more than the crate 502. I was told the 502 required extensive head torque maintenance ( removing the headers each time).---also the 502 would self destruct on anything less than 93 octane. The 496 was designed for 87/89 and came with a 1 yeay warranty. ?????? I'm curious---but maybe I should just consider a 454 crate. Thanks

 

[Anonymous]

The 2.38:1 reduction with the 3 blade Sirius Power Shift didn't perform as well as the 2:1 with the 3 blade power plus Power Shift.
The 2.38 needs a 4 blade power plus.
These tests were performed on 2 identical 15x8 hulls with 502's.

 

[marshmaster pat]

I don't know what exactly the 496 stroker is, but look at the torque curve or output for it versus a 454 and 502. The greater torque output the faster the propeller RPMs will increase. This will increase the ability to get unstuck or get the boat moving. I do know those 454s can take lots of abuse.

If it runs on regular unleaded, that is something to really consider. Those 454 and ZZ4 350s all sputter and diesel when you shut them down on low octane. And half the time they back spin which can destroy things inside.

I have been around a few 350s that were modified to increase torque output and the increased performance was unbelievable when compared to ZZ4 engines.

 

[Anonymous]

Most 496 Big Block Chevy’s are a 454 bored .060� over which gives them a 4.31� bore. Then they put a ¼ inch stroker crank in the motor. A stock 454 has a 4.00� stroke so they put in a 4.250� stroke crank. You can also build a 496 motor by using a stock 454 bore (4.250�) and running a 4.375� crank which is 3/8� more stroke. I personally know several engine builders in Orlando do you know the name of the shop. If they are using the older Mark 4 block the 496 is far superior in reliability to the generation Mark VI 502. The new Gen VI (502)block design is much weaker the main web area has less material and the block deck surface (where the heads bolt to) is much thinner. They also changed the main oiling passages. Most people want the new crate GM motor but if it’s a competent engine builder and the 496 is based on a mark 4 block the 496 will be far superior. The easiest way to find out is ask him if it’s a one or two piece rear main seal block. The stronger (OLDER) blocks are a two piece rear main seal.

 

[harvey]

I just talked to Alumitech again. Dave wasn't in but the other guy said this 496 was a marine crate fuel injected engine;and, just to confuse me more he said another option would be to take new 454 to a machine shop at a cost of about 800 and do "something " to it to make it much better. Duh? I may be too ignorant for this decision. I like having a warranty as with the 496 and the fuel injection sounds good, the 87/89 fuel really sounds great--- I had to haul av gas around before and that got old and expensive. Thanks for your reply's.

 

[Anonymous]

The Marine 496 has a 454 bore which is 4.250 with a 4.375 stroke crank. It has the same bore and stroke configuration that comes in the Big block Chevy one ton trucks. It’s a good motor I just prefer the older block design. As long as you don’t increase the horse power levels too much. You will be fine. The very best modification you can do to that motor to help reliability and help prevent detonation (so you can run cheap gas) and beat the hell out of it. Is to put aluminum heads on it. If G.M. has this option I would strongly recommend it. Aluminum heads pull heat out of the combustion chamber by transferring heat more efficiently than iron heads. Plus you will remove a lot of weight off the rear of the boat. It’s a rule of thumb that you can run a whole point higher of compression with aluminum heads and still be less prone to detonation. Here are the differences between a 502 and a 496. The 496 uses the same block as a 454 they booth have a 4.250� bore. A 502 uses a larger 4.500� bore block. The 454 and 502 both have the same stroke 4.00�. However the 496 has the most stroke it has 3/8 more stroke than the 502 and 454. Like I mentioned earlier it has a 4.375 stroke. Just about everyone will tell you this is better in an airboat. I could talk about big Block Chevy’s all day but I better get back to work. If you can afford it and Chevy sells it get the 496 with aluminum heads. If that’s not available go with the 496 because it will be less prone to detonation.

 

[Anonymous]

I have had 2 boats that were marine fuel injection motors and both were problems, even with code readers my mechanic could not keep them in tune. I still like the old saying, (keep it simple simon)