Blower on 500HP
 

Hey guys. I have a 500HP in my 280 Velocity and want to put a blower on it. My buddy had a Wieand 256 with dual 4's he is getting rid of so he can put an 8/71 on his engine. My question is, Can I bolt this blower on to my engine or will I have to change pistons and cam? I am looking to boost around 5psi with it. I believe that the 500HP is 8.75:1 compression?

merc 500 is 8.75 to 1 comp. mercruiser uses a 114 lobe separation on that motor. should be perfect for a blower.

Change the head gaskets too.

Don't go over 5 lbs. unless you add an intercooler or use really good gas.

Blown85,
I have a Darren Mayer Performance Enginnering prepped Mercury/Weiand256 and Whipple intercooler for sale off my 575 that I am having rebuilt as a 540.
I have the matching blue crank pulley and 2 or 3 blower pulleys. The Whipple intercooler is much lower profile (1 5/8"s) than the others and more efficient too. I paid $3000 for the Whipple and will sell the 256 and intercooler for $3500.
I am keeping the injectors. This will work well with carbs or throttle body injection.
Here's a pic.
Steve

HP500 has a 110° LSA. The 500EFI and 525EFI motors have 114°LSA.

True, but I don't think it has much more overlap than the EFI cams.

HELL OF A DEAL!!!

I installed a b&m 250 on my HP500..it is a 509 now...but I called crane to find out a good cam to put in it & they told me the stock cam was a good choice...110* is not ideal in my opinion, but it works fine..only problem I have is my knock sensor comes in around 4000 RPM...air is too hot and fuel aint good enough..I do suggest some sort of air cooling system...definately run the knock sensor system..but no more than 5.5-6 psi boost MAX!...no real need to replace the head gaskets..just make sure your water pressure stays below 20psi..and do NOT run a t-stat if you ditch the water pump and use a crossover..set timing @ 30*-32* no more

Hey Steve, Shoot me all the info on the setup you have for sale. What all comes with it etc. [email protected]

Well Dustin @ Whipple will disagree with you there. But hey, go nutz....

Might be cheaper in the long run to replace head gaskets. You may be tempted to check cylinder walls while you are in there. Hard to beat the Cometic gasket for boost applications. You can also get Cometics in various thickness to change CR slightly.

I went with the cometics when I did my hp500efi.

Check your email!
Regards,
Steve

Stock head gaskets are aweful on 500EFI's... Had them going at 185hrs on both motors when I freshened the heads....Do a search on the board and you will see plenty of confirmation.

After seeing the merc head gaskets I would replace them just to be safe even without a blower. I am suprised they hold up at all.

500
blower, cometic head gaskets, new head bolts, good fuel, 700 plus h.p , and hold it.

What he said, and change to crane 651 spin 6k and throw down 850hp on 93 Octane @8# with no chiller (8-71 4% under).....:drink: definately "on the edge" though....:cool-smiley-011:

Well, no doubt it would be a good idea to change the head gaskets..I did too..used the cometic .051 and I also went with the JE dished pistons...but it is not a have to....if the motor is strong now you would most likely be ok, for a short time...but one way or another, you will be freshening and changing head gaskets sooner or later.

As per Dustin @ Whipple the other small concern are the pistons. Rings postion more than the material. I didn't swap pistons, only head gaskets. Oh, and went with Dart Aluminum heads. Stock heads are cast and don't disipate the heat generated by the blower as well as aluminum. They also don't flow anywhere near as good.

Touch wood, my engine is stong and I have seen a 14 mph increase in a single 28' boat.

monstaaa 500
blower, cometic head gaskets, new head bolts, good fuel, 700 plus h.p , and hold it.


DITTO!!! I cant tell you how many head gaskets I have replaced that are trashed on stock 500's, including EFI's! Do yourself a favor and do the above.

John

I also did a complete port and polish on my heads and my intake manifold to make them match up better..and flow better...but one other thing you will need to look at is your fuel delivery...you will need to work your fuel pump over to make it flow a little more fuel..or buy a higher volume pump...I just drilled mine out in all the right places and tried not to use any more 90* turns than were needed..my fuel pres. never gets below 6 now.

Below 6 what?? Not lbs...

Remember , talking about carbs. My fuel pressure stays between 7-9 PSI also.



Darrell.

Right, getting two threads mixed up.

Yes..stays mostly at 7 PSI..but will go as low as 6 in full boost...you do not want it below 5 ever

Steve's Z's deal below is a pretty good deal. In general, the 256 is too small for that motor, or it's capability, but is a nice little bump in torque and hp. Would certainly only install it with intercooler. 6psi with intercooler is no problem. If you want a bit more power too, change the cam, that cam literally sucks for HP with SC. You gotta get in the 600+ lift and 240+ duration. With Steve's setup, you should get 650hp pretty easily. If you want more, go with our SC or 871 Blower Shop. Stock pump is too small, we typically use Mallory 140m electric pump, but there are some rebuild kits that will allow you to use mechanical if you want to stay that way. Stock carb needs virtually no jetting, in fact, it will need to be leaned out. 650-700hp is max for that carb.

$3500 is a steal for a good 650hp, after that, your going to double your investment. New SC, with IC, new carb, etc. Forgot to add, with 5-6psi, set max timing at 28-30deg. Stock module has 34.

Thanks