Why is the Gen 7 496 such a bad platform to build
09-21-2015, 10:45 AM
#31
Registered
I realize the torque of the 496 and if you notice I said in a 24 to 25 ft boats for the average boater. Never mentioned anything about 30 or higher ft boats. Like I said its a heavy engine compared to whats out on the market place currently and the largest gas side production engine thrown into a boat. I own a 496 in a 2007 - 28 ft boat myself. I like the low end and mid range of the stock 496 but top end is a dog. IMO if I had a choice I would rather have a 502 because there is so much more in the market place and engineering done for the end user to buy and play with. Just saying.
Also many boat builders installed the 496 during its timeframe in the market place but in a very poor manner. Especially mid level bot builders and down.
Also in my day ( @ one timeframe) my shop worked on close to 200 - 496's per year. Merc & Volvo combined, so how can I not like them.
This year I have worked on only 25 - 496's. That's it.
For a NON CAT engine they are one of the hardest engine's to work on in a boat. Access is the main problem. Wiring harnesses is the other problem. Then related fuel issues especially Gen III cool fuel along with its poor design plus does not drain water very well for winterization and then a poor designed IAC operation and then a poor quality Gen VII water pump housing. . I am talking about stock OEM apps here
Also many boat builders installed the 496 during its timeframe in the market place but in a very poor manner. Especially mid level bot builders and down.
Also in my day ( @ one timeframe) my shop worked on close to 200 - 496's per year. Merc & Volvo combined, so how can I not like them.
This year I have worked on only 25 - 496's. That's it.
For a NON CAT engine they are one of the hardest engine's to work on in a boat. Access is the main problem. Wiring harnesses is the other problem. Then related fuel issues especially Gen III cool fuel along with its poor design plus does not drain water very well for winterization and then a poor designed IAC operation and then a poor quality Gen VII water pump housing. . I am talking about stock OEM apps here
09-21-2015, 11:08 AM
#32
Banned
Bandit I understand where you are coming from and agree with what is said.
But less add - you do not even have a stock black production 496 - 375 hp nor 425 hp in your boat. Hell your engine is far above that - its the GM Vortec HP3 8100 version well over 500 hp and that relates to over 1 hp per cubic inch like it should be.
Matter of fact here how much I know about the 496 and the GM HP3..
GM Vortec HP3 8100 had MEFI 4 controller, Dyno numbers were more like close to 600 ft lbs of torque and something like 550 hp. GM really did not list the exact rating but listed 525 + hp and 560 + ft lbs of torque.
CNC ported cylinder heads and port matched intake manifold, sintered power metal exhaust seat inserts, premium race style Valve springs 1.7:1 ratio roller rockers, rocker arm studs - HP3 push rods, CMI headers, connecting rods forge steel, 75 mm throttle body. Compression ratio 9.1:1 - Valve train Hydraulic roller, crank mounted water pump housing / impeller and that's all I can think of at the moment.
And If I remember correctly this engine was under 750 lbs in weight.
But less add - you do not even have a stock black production 496 - 375 hp nor 425 hp in your boat. Hell your engine is far above that - its the GM Vortec HP3 8100 version well over 500 hp and that relates to over 1 hp per cubic inch like it should be.
Matter of fact here how much I know about the 496 and the GM HP3..
GM Vortec HP3 8100 had MEFI 4 controller, Dyno numbers were more like close to 600 ft lbs of torque and something like 550 hp. GM really did not list the exact rating but listed 525 + hp and 560 + ft lbs of torque.
CNC ported cylinder heads and port matched intake manifold, sintered power metal exhaust seat inserts, premium race style Valve springs 1.7:1 ratio roller rockers, rocker arm studs - HP3 push rods, CMI headers, connecting rods forge steel, 75 mm throttle body. Compression ratio 9.1:1 - Valve train Hydraulic roller, crank mounted water pump housing / impeller and that's all I can think of at the moment.
And If I remember correctly this engine was under 750 lbs in weight.
09-21-2015, 11:56 AM
#34
Registered
Thread Starter
Don't be! All of this talk opens up a dialog on an engine that isn't really discussed from a performance perspective. The common thought is the 496 is good stock, junk if you want to mod it. I want to find out if that is true, or if it is more that people try to cheap out on modding it properly and then suffer the consequences. Frankly, if my boat had 502's or even 454's in it, I wouldn't give a thought to repowering with 496's. But that is what I already have to work with, so now I want to know if I set realistic goals and build them properly, can they do what I want reliably, if there is such a thing in a boat.
09-21-2015, 06:18 PM
#35
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Thread Starter
I also asked about exhaust requirements. If running the 600HO cam, the exhaust needs to be upgraded. They have a cam between the 525 and 600 cam called the BP205, it essentially runs the duration of the 525HO cam with the higher lift of the 600HO cam. According to Larry with the added displacement from the stroker kit it will end up at 580-590 stock exhaust friendly horsepower. Running that cam also eliminates the need to have the ECM reflashed.
Other upgrades he recommended were upgrading to the Melling 10778 pump and running a larger oil cooler, but for the water I boat in the stock heat exchanger should be sufficient.
09-21-2015, 06:59 PM
#36
Registered
Man, I used to have the HP3 cam specs in my folders. Can't find it. So for now, I'll just have to say I remember it as very similar to the 525EFI cam, but of course the firing order swap.
09-21-2015, 07:06 PM
#37
Registered
Thread Starter
09-21-2015, 07:11 PM
#38
Registered
I like this thread, and like to see something different for a change, other than the typical "540" or 496 "stroker" build.
I really like the sound of MER's 900HP 8.1L whipple build. You should do that Matt. Those would wake up the Cafe for sure.
I really like the sound of MER's 900HP 8.1L whipple build. You should do that Matt. Those would wake up the Cafe for sure.
09-21-2015, 07:23 PM
#39
Registered
The Gen 1 HP3 had a cam like the 500EFI's (Crane 230,236 HR on a 114LSA) but, again, with the firing order swap.
According to all this 8.1L HP3 research:
http://www.pacificp.com/forum/viewtopic.php?t=10543
There was a Gen II HP3 which added some more compression, much more cam and etc.
Pretty good read. I think.
09-21-2015, 07:46 PM
#40
Gold Member
Gold Member
In the general performance world, always proceed slowly hearing statements like that last sentence above in quotes.
Man, I used to have the HP3 cam specs in my folders. Can't find it. So for now, I'll just have to say I remember it as very similar to the 525EFI cam, but of course the firing order swap.
Man, I used to have the HP3 cam specs in my folders. Can't find it. So for now, I'll just have to say I remember it as very similar to the 525EFI cam, but of course the firing order swap.
Before blowing them up... I had the HP3 heads (which was a CNC program on stock heads with bigger valves). I ordered and installed the HP3 cam (from a builder on OSO) and it was a gnarley cam. We are talking 7+ years ago but I remember a PV clearance of about .020 or maybe .030 with stock flat top pistons. Needless to say I took it back out and used the Raylar HO 525 cam. This was the typical OSO builder story of yes of course they will work... But after a little homework it just wasnt a good idea. A few years later I suffered reversion from my exhaust and ate a valve anyway, but it was fun while it lasted. The HP3 II is nastier than a 731 and I think the Raylar 600 cam is actually a little hotter than the 731. My guess is the Raylar 600 is very similar to the HP3 cam. Similar... Not a copy. Be careful, I have been know to actually decrease other peoples IQ from a few feet away. Just my .02 cents.
