hp 500 info

[pleasantcat]

ok what needs to be done to the merc hp 500 carbed motors to run 10/71 blowers? not looking to run 18lbs of boost but would like to see around 700hp out of it without it dying in a short time.

[Havasu Hangin']

I would think about 8lbs of (intercooled) boost should get you around 720HP...
:D

[pleasantcat]

ok but do you have to change valves,cam,etc.etc? or can these engines handle 5-10lbs of boost?

[Havasu Hangin']

ok but do you have to change valves,cam,etc.etc? or can these engines handle 5-10lbs of boost?
Mine used to be carbed HP 500's. Cam, valves, heads are the same. Timing is backed down to 30 total. I've heard (no personal experience) that the only weak spot is the stock head gaskets, and the valve springs can get tired.
I keep good gas in it if I change pulleys (over 6lbs)...but that's just me.

[pleasantcat]

what blowers did you go with?

[Havasu Hangin']

what blowers did you go with?
Just B&M 250's. GT dyno'ed them at 720HP aside.
http://www2.***boat.com/image_center/data/504/74engines_4-9-05.jpg
How many hours does it have on it?

[HP350SC]

I agree with all the answers except 36 deg. total is too much for the stock carb'd cam. 32 is max., it won't make any more power above that. Head gaskets are a MUST, exhaust valves are inconel so OK. Fuel system upgrade including high flow separator, replace valve springs with comp. 929-16.
Is the motor going in your 25 Daytona?

[pleasantcat]

I agree with all the answers except 36 deg. total is too much for the stock carb'd cam. 32 is max., it won't make any more power above that. Head gaskets are a MUST, exhaust valves are inconel so OK. Fuel system upgrade including high flow separator, replace valve springs with comp. 929-16.
Is the motor going in your 25 Daytona?
no not going in the daytona. i hope to see it drive away soon. the boat im looking at has hp 500's in it and after running my boat at speed i need a little more.

[Beer-30]

If you take a step back and look at the big picture, the bottom end should be just fine as long as the boost is intercooled and kept to a logical level.
After that, it is the focus on fuel, fuel supply system, ignition and cooling that will keep the motor alive with boost. That rotating assembly will stay real happy as long as none of the other elements fail.
Earlier HPs were known for valve spring failures, as mentioned.

[cjordan]

Here are the specs on a HP 500 I know of that was converted to roots blower.
Fel Pro Head gaskets
Isky 8205 Plus valve springs
Crane 13532 lifters
Stock chevy heads, stock 8.75:1 CR
Crane 651 cam
Comp Pro magnum rockers, replaced crane golds
Littlefied 8-71 blowers UNDERDRIVEN 4%, no chiller, no thermostat.
Demon 825 blower carbs
31 degrees timing
NGK plugs -8 heat range gapped to .035"
Aeromotive A1000 fuel pump, bypass regulator.
@8# of boost motor made 847HP@6100 and 762 ft/# @4900.
Another friend of mine made 730HP @6100with a B&M 420, 700 hollys, no chiller, crane 651 cam, flat top pistons and 5# of boost, stock GM heads. 30 degrees.
These (above) motors have stock 7qt GM marine pans, stock oil pumps, and stock oil coolers with no problems.
Another 502 mag I know of with brodie heads and a chiller makes 10# of boost at 1:1 8-71, littlefield as well. 32 degrees
All of the above motors run 93 octane PUMP GAS.
Don't get me wrong a 10's are cool blowers, but they are just to big for a 502. Also, If you build the motor right you don't necessarily need a chiller, especially to only make 700HP.

[pleasantcat]

thank you for the info cjordan and everyone! all i need is for mine to go away and it's time to play with the 502's