horsepower estimate
08-08-2006, 09:01 AM
#1
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horsepower estimate
Hi Guys,
You may remember a recent thread where we were discussing heads, etc. Thanks for your input on that one.
After that discussion, and more with some knowledgeable friends locally, I've decided to raise my compression the correct way to 8.5 to1 with new pistons, in addition to a Comp hydraulic roller and Dart Pro 1 (possibly ported) heads. I'll probably have AZSM recurve the ECU again. If not, EB Marine here is now working with a friend with modified 575s (same cam) to fine tune his motors (we think they are a little fat).
I'm having my blower refreshed at TBS now.
So estimating my horsepower currently at 725ish, I'm looking for another 100 to 150, hopefully for a 6 to 9 MPH increase.
Current specs are Merc 575:
with whipple intercooler, 3" blower pulley currently making 7 PSI boost intercooled, MSD 6M, AZSM ECU, currently spinning a 28" P5-X or 30" B1 5400 to 5600 depending on weather and load, from 82 to 86 GPS.
Bob, Dave, Linster, what do you guys think about this plan?
Is my horsepower estimate with these mods realistic (100 to 150+, 825 to 875 total)?
Plan B is to build it to a 540" with similar specs, but I'm not sure the W256 and Merc injection will feed it. What do you guys think?
Thanks,
Steve
You may remember a recent thread where we were discussing heads, etc. Thanks for your input on that one.
After that discussion, and more with some knowledgeable friends locally, I've decided to raise my compression the correct way to 8.5 to1 with new pistons, in addition to a Comp hydraulic roller and Dart Pro 1 (possibly ported) heads. I'll probably have AZSM recurve the ECU again. If not, EB Marine here is now working with a friend with modified 575s (same cam) to fine tune his motors (we think they are a little fat).
I'm having my blower refreshed at TBS now.
So estimating my horsepower currently at 725ish, I'm looking for another 100 to 150, hopefully for a 6 to 9 MPH increase.
Current specs are Merc 575:
with whipple intercooler, 3" blower pulley currently making 7 PSI boost intercooled, MSD 6M, AZSM ECU, currently spinning a 28" P5-X or 30" B1 5400 to 5600 depending on weather and load, from 82 to 86 GPS.
Bob, Dave, Linster, what do you guys think about this plan?
Is my horsepower estimate with these mods realistic (100 to 150+, 825 to 875 total)?
Plan B is to build it to a 540" with similar specs, but I'm not sure the W256 and Merc injection will feed it. What do you guys think?
Thanks,
Steve
Last edited by Steve Zuckerman; 08-08-2006 at 09:14 AM.
08-08-2006, 01:05 PM
#3
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Thread Starter
Re: horsepower estimate
Customryder,
I agree with the gears issue. I am running a new XR upper and new XR lower gears in an Imco case.
The last set went about 85 hours stock, and another 175 with the current setup (725hp). I'm aware that it's on the edge already, so I try not to beat the crap out of it (others may disagree
).
There are several guys running Max Machine upgraded XRs with good success. One them has a similar Heat running 900+hp and close to 100mph.
Looks like an outdrive upgrade, as well as new props (or gear ratio change) will be in the cards if this comes together.
How's the NorTech coming?
Regards,
Steve
I agree with the gears issue. I am running a new XR upper and new XR lower gears in an Imco case.
The last set went about 85 hours stock, and another 175 with the current setup (725hp). I'm aware that it's on the edge already, so I try not to beat the crap out of it (others may disagree
).There are several guys running Max Machine upgraded XRs with good success. One them has a similar Heat running 900+hp and close to 100mph.
Looks like an outdrive upgrade, as well as new props (or gear ratio change) will be in the cards if this comes together.
How's the NorTech coming?
Regards,
Steve
08-09-2006, 04:07 PM
#5
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Re: horsepower estimate
Steve,
Here's what I think is happening.
I am quoting a fellow who has been in the Marine Dyno business and done many blower 502 Motors. He is in Annapolis MD.
He tells me a HP500, 8.75CR, with a B&M 250 Blower, twin 750 Carbs, 5 psi boost, makes 675HP with the Merc correction factors. He also told me every additional pound of boost he added after 5 made 30 more HP.
I do not know how much boost you started with but I would guess it would have been 4 to 5 lbs, going to 7 added either 60 or 90 HP if 1 pound of boost did the same at 7.5CR as 8.5CR. So I would say you have 635HP or 665 HP now depending on the boost from the start.
Increasing the static compression as you are doing is the right thing to do to make more power. A flat top piston is best for detonation control and should get you right in the 8.5CR range. Make sure when you hone out the cylinders you add at least .0015 extra clearance to the bore so you will keep black death away. .002 will not hurt. If you are staying with the 502, 4.470 bore, hone it to 4.4715 to 4.472. The extra clearance will be needed with that static compression and boost level. You also will need to add Valve stem clearance to the heads to keep the valve stems from seizing to the heads. Also have at least a .080 Intake valve seat and at least a .100 exhaust valve seat to cool the valves.
By going from 7.5CR to 8.5CR with 5 lbs of boost should be 675HP plus 60 more HP for 2 more pounds of boost to get you in the 735HP range.
The pulley you have is designed to give you the extra 2 or 3 lbs of boost at 7.5CR. When you go up in compression, it probally will give you 3 or 4 lbs of boost at the higher CR. You may end up with 8 to 8.5 lbs of boost with the same pulley and 8.5CR. If you get 8 lbs you should make 765HP.
Do not do a 540 with your blower.
My 2 cents
GOOD LUCK, keep us posted on the results.
Here's what I think is happening.
I am quoting a fellow who has been in the Marine Dyno business and done many blower 502 Motors. He is in Annapolis MD.
He tells me a HP500, 8.75CR, with a B&M 250 Blower, twin 750 Carbs, 5 psi boost, makes 675HP with the Merc correction factors. He also told me every additional pound of boost he added after 5 made 30 more HP.
I do not know how much boost you started with but I would guess it would have been 4 to 5 lbs, going to 7 added either 60 or 90 HP if 1 pound of boost did the same at 7.5CR as 8.5CR. So I would say you have 635HP or 665 HP now depending on the boost from the start.
Increasing the static compression as you are doing is the right thing to do to make more power. A flat top piston is best for detonation control and should get you right in the 8.5CR range. Make sure when you hone out the cylinders you add at least .0015 extra clearance to the bore so you will keep black death away. .002 will not hurt. If you are staying with the 502, 4.470 bore, hone it to 4.4715 to 4.472. The extra clearance will be needed with that static compression and boost level. You also will need to add Valve stem clearance to the heads to keep the valve stems from seizing to the heads. Also have at least a .080 Intake valve seat and at least a .100 exhaust valve seat to cool the valves.
By going from 7.5CR to 8.5CR with 5 lbs of boost should be 675HP plus 60 more HP for 2 more pounds of boost to get you in the 735HP range.
The pulley you have is designed to give you the extra 2 or 3 lbs of boost at 7.5CR. When you go up in compression, it probally will give you 3 or 4 lbs of boost at the higher CR. You may end up with 8 to 8.5 lbs of boost with the same pulley and 8.5CR. If you get 8 lbs you should make 765HP.
Do not do a 540 with your blower.
My 2 cents
GOOD LUCK, keep us posted on the results.
Last edited by Linster; 08-09-2006 at 04:10 PM.
08-09-2006, 04:24 PM
#6
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Thread Starter
Re: horsepower estimate
Linster:
I agree with your #s on the supercharged HP500.
From your description, I don't think it was intercooled?
I am, and running 2 PSI more boost.
My motor only had 4 PSI boost when it was stock (4" pulley)
The AZSM boost kit came with a 3.5" pulley, raising my boost to 6PSI, non-intercooled. After I added the Whipple intercooler, my boost fell back 4.5PSI, but the motor felt stronger. I went to 3.25" pulley to get the boost back, but only got 5.5PSI. I settled on the 3" and got to 6.5/7PSI, depending on weather, and it really woke the motor up.
Another guy here with 575s did a similar build up on his, except he used the Teauge/Superchiller version and his motors dynoed 730 HP. We think the Whipple is a better unit than the Superchiller.
Thanks for advice on the extra bore clearance.
I'll keep you posted on the project. Hopefully, we'll get to dyno the motor to fine tune the ECU and get some hard #s.
Steve
I agree with your #s on the supercharged HP500.
From your description, I don't think it was intercooled?
I am, and running 2 PSI more boost.
My motor only had 4 PSI boost when it was stock (4" pulley)
The AZSM boost kit came with a 3.5" pulley, raising my boost to 6PSI, non-intercooled. After I added the Whipple intercooler, my boost fell back 4.5PSI, but the motor felt stronger. I went to 3.25" pulley to get the boost back, but only got 5.5PSI. I settled on the 3" and got to 6.5/7PSI, depending on weather, and it really woke the motor up.
Another guy here with 575s did a similar build up on his, except he used the Teauge/Superchiller version and his motors dynoed 730 HP. We think the Whipple is a better unit than the Superchiller.
Thanks for advice on the extra bore clearance.
I'll keep you posted on the project. Hopefully, we'll get to dyno the motor to fine tune the ECU and get some hard #s.
Steve
Last edited by Steve Zuckerman; 08-09-2006 at 10:29 PM.
