Gordo

Since I don't run the One Vision Active Thunder in Factory 1 anymore, I've been thinking of adding a blower to my carbed (1998) HP500.
So, to all of you supercharger experts out there, what would be the best "Bolt On" blower? 6-71? 8-71? 250? 420? (What's the difference in all these anyway?) Is an intercooler worth the money? Single carb or twin? Can I keep my stock ignition?
Thanks,
Gordo

tomcat

The HP500 is an excellent candidate for supercharging, but you should freshen the heads and use better head gaskets. An upgraded fuel system and modified carb are mandatory. "Bolt on" is never just bolting something on, especially when it comes to supercharging.

All your options were Roots blowers so if you aren't considering centrifugal blowers, ignore the following.

An Rtech supercharger system with a single Nickerson carb has been proven at 800 HP on this type of engine with stock heads and cam. The large centrifugal blower and the efficient intercooler makes it possible. You can keep the stock ignition system with different plugs and timing.

In the 600-700 HP range the smaller Roots blower will do the job, but you will have to lower the compression ratio. Above 700 you will need an intercooler to be safe on pump gas, and the larger Roots blower with twin carbs is required.

Good luck,

Tom

AIR TIME

how much $$ for the carb ed rtech ,I have the merlin 310 heads cleaned up isky cam 509 600hp at5050rpm 647 at 5900, what hp would I get low to high tq is like 627 at 4800,comp,is 9.5 to 1 thanks for any thoughts ART ps dart intake, s/m dry ex, 850 bg carb

tomcat

Talk to Dean Nickerson @ (215) 781-1370; he's our dealer your way and has an engine like yours in his personal boat making 950 HP. You won't be able to run that much unless you drop the compression though. Retail on a complete system is ~$6700.00.

Sorry Gordo, didn't mean to hijack the thread. You will get lots of info from members experienced with Roots blowers too. At least we're keeping the thread near the top for you.

CIG3

Sure "Now You Want to Go Faster"!!!!!!!! How Things???????? Look around for a used whipple set-up.

A.B.

tomcat

"Dealer may sell for less." I'm just supporting my dealer network

Gordo

Tomcat,
I should have qualified my version of "bolt-on". I have already installed larger fittings and fuel lines, have a fuel pump with slightly higher pressure and MUCH higher volume than the stock one. I would like to stay with the stock ignition if I can.
For efi applications I think the centrifugal supercharger would be a no brainer. The reason I have been looking at roots blowers is I am not a fan of centrifugal blowers with carb motors. My only experience with these applications is with Prochargers, and I don't like the idea of a pressurized box around a carb. I'm sure there's better ideas out there, I just haven't looked.
Andy,
How Ya Doin !! You know me, I always like to go faster, just couldn't afford it. I'd love to find a Whipplecharger, but haven't seen one used anywhere.
Tell everyone up there I said Hiya!

KCHOTBOAT

Mike call Ed with the other HTM. He had a 250 for sale which is setup for a single carb or dual carbs.

tomcat

Not trying to change your mind Gordo, any supercharger is better than no supercharger and I wish you good luck in your project.

For others reading this post, negative impressions of blowthrough centrifugal systems are usually based on experience with an engine that never had the proper fuel curve. OSO members who have fought their way through this problem on Procharged engines will support this statement.

But a properly setup centrifugal system can make more power and have better dock manners than a Roots system. Ask Nickerson, he has done it both ways. For further proof, we just converted an 8-71 intercooled 555CID engine with aluminum heads to the Rtech system above. Two things impressed the owner; the extra 7 mph and the "stock" behaviour around the dock. And this was on an engine that really had the wrong (Roots required) compression ratio and cam.

Enclosing the carb is a smart thing to do in a boat and is probably required by the Coast Guard. The big Rtech supercooler box has another advantage; the elimination of pressure robbing elbows and pipes.

Getting the fuel curve right isn't any easier on an EFI system; it takes just as much if not more time, and when you figure in larger injectors and the reprogrammed ECM, about the same money as buying a properly modified carb.

As I said above, get supercharged any way you can, I just like to keep the record clear on the performance of centrifugal systems.

Von Bongo

Gordo,

Mine have Blower Shop 250's. Chief dynoed them at 719. We are backing down a bit with the rebuild to around 650.