up grading the 500 EFI....to run 8 lbs boost
11-29-2007, 07:42 PM
#1
up grading the 500 EFI....to run 8 lbs boost
Well after A season of fun with the procharger M3 SC with the big intercooler...I am going to do some upgrades this winter....want to run 8 lbs of boost.....
the plan is as follows:
pull the motor and add new heads Dart pro 1 's Aluminum
replace the fuel injectors and go to a 2 bar map sensor
install new cam to take advantage of the heads
install cometic head gaskets
Dyno tune the motor and then reinstall.....can the bottom end handle it?
Am I missing some thing here?
What do you think?
Boat has run a best of 85 GPS ......looking to break the 90 MPH barrier...is it possible?
Bryan
the plan is as follows:
pull the motor and add new heads Dart pro 1 's Aluminum
replace the fuel injectors and go to a 2 bar map sensor
install new cam to take advantage of the heads
install cometic head gaskets
Dyno tune the motor and then reinstall.....can the bottom end handle it?
Am I missing some thing here?
What do you think?
Boat has run a best of 85 GPS ......looking to break the 90 MPH barrier...is it possible?
Bryan
11-29-2007, 08:22 PM
#2
Registered User
In my opinion, the aluminum heads are a waste of time and money. At 8 psi with the chiller, you're at entry-level supercharging anyway. You do need a set of JE blower pistons to bring your CR down to about 7.5 or 8 to 1. ARP rod bolts and beam grind the rods, grind the crank throws, ARP main studs and a good balance job and you're good to go. Maybe a little more cam- 610 lift, 235 duration on 110 centers- hydraulic roller. That bottom end will take more power than what your setup will put into it.
11-30-2007, 06:39 AM
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I also would sugest new pistons. I am currently port matching my Dart Pro one heads, they didn't match the same a stock. You might want to look at that if you replace the heads.
11-30-2007, 04:03 PM
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Depending on how much time is on your bottom end I would consider leaving it alone. Stock 500 short blocks already have JE pistons and are pretty stout, you DO NOT need to lower CR. Most "modern" blower motors are ~8.5:1 static anyway...yours is 8.75:1. If you change heads you obviously can pick up power there and are even less prone to detonation...If you do have quite a bit of time on the bottom then I would go eagle rotater, 8.5:1 and bore to 4.50 to unshroud the valves. Cam will also help you a bunch. 
11-30-2007, 05:21 PM
#5
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Nobody knows more than Mercruiser about making reliable engines- why not follow their blueprint for success?
Anyone can build a high-horsepower engine. Making it last is the key. Merc does what they do because they need to provide a hassle-free product that people don't come to sites like this and biitch about. There's no trick to building an identical motor than what Merc offers yet puts out 10 to 20% more horsepower- push it harder.
That's why Merc uses 7.5 CR and iron heads ay 6 psi (non-intercooled). can you do it? Sure. Can you get away with is? Maybe. Will you see a big return for the chance? Nope.
Anyone can build a high-horsepower engine. Making it last is the key. Merc does what they do because they need to provide a hassle-free product that people don't come to sites like this and biitch about. There's no trick to building an identical motor than what Merc offers yet puts out 10 to 20% more horsepower- push it harder.
That's why Merc uses 7.5 CR and iron heads ay 6 psi (non-intercooled). can you do it? Sure. Can you get away with is? Maybe. Will you see a big return for the chance? Nope.
11-30-2007, 07:23 PM
#6
Depending on how much time is on your bottom end I would consider leaving it alone. Stock 500 short blocks already have JE pistons and are pretty stout, you DO NOT need to lower CR. Most "modern" blower motors are ~8.5:1 static anyway...yours is 8.75:1. If you change heads you obviously can pick up power there and are even less prone to detonation...If you do have quite a bit of time on the bottom then I would go eagle rotater, 8.5:1 and bore to 4.50 to unshroud the valves. Cam will also help you a bunch.
Plan on next season stroking to a 540 and then it will be balls to the walls....done right with really good parts, just want to increase the fun factor for next season.
Bryan
11-30-2007, 08:09 PM
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Nobody knows more than Mercruiser about making reliable engines- why not follow their blueprint for success?
Anyone can build a high-horsepower engine. Making it last is the key. Merc does what they do because they need to provide a hassle-free product that people don't come to sites like this and biitch about. There's no trick to building an identical motor than what Merc offers yet puts out 10 to 20% more horsepower- push it harder.
That's why Merc uses 7.5 CR and iron heads ay 6 psi (non-intercooled). can you do it? Sure. Can you get away with is? Maybe. Will you see a big return for the chance? Nope.
Anyone can build a high-horsepower engine. Making it last is the key. Merc does what they do because they need to provide a hassle-free product that people don't come to sites like this and biitch about. There's no trick to building an identical motor than what Merc offers yet puts out 10 to 20% more horsepower- push it harder.
That's why Merc uses 7.5 CR and iron heads ay 6 psi (non-intercooled). can you do it? Sure. Can you get away with is? Maybe. Will you see a big return for the chance? Nope.
Ask the hundreds of people who have utilized whipple, pro charger (granted, scarier) roots, etc on stock 8.75:1 bottoms with iron heads, stock (un-ideal) cams, with 100's of trouble free hours their thoughts...maybe they should went through their bottoms and lowered to 7.5:1...
Bryan, 540's will be sick with dart heads (especially CNC) and custom cam, smitty made something like 1100hp with his through a custom mpi manifold on kill.
IMO your bottom is good for another 150hrs the way it is....
11-30-2007, 11:32 PM
#8
Registered User
No...you are referring to Merc's "cupcake" IE.... long warranty, low rpm motors. They are set up stupid safe. See what just about any well known after market blower motor builder uses for static...I bet anything most are closer to 8.5:1 then 7.5:1...
Ask the hundreds of people who have utilized whipple, pro charger (granted, scarier) roots, etc on stock 8.75:1 bottoms with iron heads, stock (un-ideal) cams, with 100's of trouble free hours their thoughts...maybe they should went through their bottoms and lowered to 7.5:1...
Bryan, 540's will be sick with dart heads (especially CNC) and custom cam, smitty made something like 1100hp with his through a custom mpi manifold on kill. IMO your bottom is good for another 150hrs the way it is....
Ask the hundreds of people who have utilized whipple, pro charger (granted, scarier) roots, etc on stock 8.75:1 bottoms with iron heads, stock (un-ideal) cams, with 100's of trouble free hours their thoughts...maybe they should went through their bottoms and lowered to 7.5:1...
Bryan, 540's will be sick with dart heads (especially CNC) and custom cam, smitty made something like 1100hp with his through a custom mpi manifold on kill.
IMO your bottom is good for another 150hrs the way it is....
12-01-2007, 07:43 AM
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Chris:
Why do you not think Aluminum heads will give any benefit over stock 088's? This is where many people get it wrong IMO. GM heads flow AWEFULLY on the exhaust side, and not great on the intake side. At ~800+HP with forced induction the heads are literally done flowing no matter how much boost you throw at them and will not carry power above 6k rpm even with a (big) Crane 651 with a 12 degree split to help the exhaust get out. Throw a set of BB2's or Dart CNC heads in the mix; power and especially TQ picks up dramatically everywhere and the heads will carry power to 6500+.I've seen it on the dyno. You will also have to drive the blower harder to make the same amount of boost you were making with the iron heads because there is less "restriction" with the CNC'd heads...
Most people will agree you can run another .5 to 1.0 of compression by going to Aluminum over Iron heads without changing anything else. Think of it this way, on a NA 500HP do you not think there are very noticable gains by going to a set of say 315 AFR's and a different cam? You can run 10:1 easy on pump gas and the heads flow way better...I've never done one of those, but I'm sure there are plenty on here that have.
All I'm saying is that most "modern" builders try to make as much power as they can on "motor" (NA) and let the supercharger take care of the top end. They run less boost to get to the same power point than a lower CR motor would need... I know a lot of people running around at 10# with a chiller on 8.5:1 with no problems.
Why do you not think Aluminum heads will give any benefit over stock 088's? This is where many people get it wrong IMO. GM heads flow AWEFULLY on the exhaust side, and not great on the intake side. At ~800+HP with forced induction the heads are literally done flowing no matter how much boost you throw at them and will not carry power above 6k rpm even with a (big) Crane 651 with a 12 degree split to help the exhaust get out. Throw a set of BB2's or Dart CNC heads in the mix; power and especially TQ picks up dramatically everywhere and the heads will carry power to 6500+.I've seen it on the dyno. You will also have to drive the blower harder to make the same amount of boost you were making with the iron heads because there is less "restriction" with the CNC'd heads...
Most people will agree you can run another .5 to 1.0 of compression by going to Aluminum over Iron heads without changing anything else. Think of it this way, on a NA 500HP do you not think there are very noticable gains by going to a set of say 315 AFR's and a different cam? You can run 10:1 easy on pump gas and the heads flow way better...I've never done one of those, but I'm sure there are plenty on here that have.
All I'm saying is that most "modern" builders try to make as much power as they can on "motor" (NA) and let the supercharger take care of the top end. They run less boost to get to the same power point than a lower CR motor would need... I know a lot of people running around at 10# with a chiller on 8.5:1 with no problems.
Last edited by jdnca1; 12-01-2007 at 07:54 AM.
12-01-2007, 08:33 AM
#10
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Again, I'm not disputing what you're saying about aluminum heads vs the stock heads on the 500. My point is this- He's not going to be near the 800 hp mark with 8psi on pump gas and probably will be turning this motor about 6000 rpm. Now, if he were saying he wanted to run 12 lbs boost at 6800, then I'm right there with you- he'd need the heads. To your point of being able to run another half point or so of compression- you're absolutely right. Yet, that half-point won't give him any useable horsepower and the heads are going to cost substantially more than the blower pistons, yet won't give him the increased life or enhanced durability that the pistons would.
Lastly on the stock HP500. Yes, the heads and cam will do alot for the motor. The cam will do 80% of it though and that's on the NA motor. The intercooled 8psi supplants the need for the enhanced flow the aluminum heads would provide on a NA motor. I just don't thing the negligible gain that a $3000 set of heads would provide is worth the cost. If cost were no object, then it's a no-brainer. But in my mind, there's alot I could do to upgrade things with that extra $$.
Lastly on the stock HP500. Yes, the heads and cam will do alot for the motor. The cam will do 80% of it though and that's on the NA motor. The intercooled 8psi supplants the need for the enhanced flow the aluminum heads would provide on a NA motor. I just don't thing the negligible gain that a $3000 set of heads would provide is worth the cost. If cost were no object, then it's a no-brainer. But in my mind, there's alot I could do to upgrade things with that extra $$.
