diveboy

Questions for you blower experts:

I'm planning on removing the efi system from my stock hp500efi and replacing it with The Blower Shop's 250 low profile blower, full MSD ignition, a single 1050 Holley carb, and a water cross-over (without thermostat).

Do I need to make any other modifications to the engine before thinking of making these changes? Is there anything to consider regarding the fact that my motors are hp500efis and not hp500's (carb) when making this change?

I'm planning on using the stock fuel pump in addition to adding a Holley (black) pump.

Will I have any problem with retaining the stock mounting and location of my alternator and power steering pump?

Also, most importantly, what kind of power can I expect to make at 4-5 lbs of boost? I'm hearing mixed figures, some say to expect around 600hp other swear I'll see more like 675hp. I'd like to add an intercooler but: 1) can't afford it right now and 2) I'm trying to keep everything under the hatch.

Is this a safe, reliable way to get more out of these motors or am I risking serious damage to an expense engine?

Thanks for any input!!

Jon-

RumRunner

Jon:
One thing you really should do have your cylinder heads cut to use theFel-Pro O'ring head gaskets, and install inconel exhaust valves. The Blower Shop has pulleys for the blower so you can re-use al of your stock accesories. I just dynoed one of The Blower Shops 250s on a 468 yesturday, with better heads, and cam, a 1095 King Demon, but with less compression. It made over 700 HP and 650 FT/LB TQ on the third pull. We haven't even begun to fine tune it. There is at least another 20 HP in it. If you have any questions give Marv a call at the Blower Shop, or you can call me directly at (706) 864-8544

Doug.
Tech Support Barry Grant Inc.

paradigm shift

First off I am no expert. I would think the blower shop should be able to answer your HP questions. Really depends on the boost you run. The 500hp is an excellent base to build on in my opinion. Keep the boost low. Head gaskets should be changed. You may want to consider changing the valves if you go big on the boost. I do have a couple of questions though.
1. Are you selling your EFI set up to offset the cost of adding the blower?
2. Have you looked at Whipple or Procharger.
3. Why a 250 blower kinda small for a 502. Bigger blower turning slower would build less heat and is more efficient. 871 or 1071 would be a better choice I think.
4. What kind of HP are you looking to get to?

Just my .02 Good luck with your project.

Dennis Moore

Diveboy,
I am sure that you have already thought of this but the main difference between a naturally asperated engine and a blower engine is the compression ratio. You really won't be able to safely crank up the horsepower of your engine with the 8.75:1 compression ratio of the stock pistons. You will need to swap out the pistons to a quench style blower piston with 7.5 or 8.0 to 1 compression ratio.
The camshaft is not really suited for a blower either. It should have a wider lobe separation angle and be a single pattern (same intake and exhaust duration) cam.
The engine should work ok the way you are going about it but it won't be a really efficient supercharged engine and it could be sensitive to detonation.
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

diveboy

RumRunner: Thanks for the input, I'll look into running the Fel Pro gaskets (one's you're refering to are with the steel fire ring...correct?) What kind of boost are you running? Are you using an intercooler? What did your motor make before the blower was added? I'm running these in a 32 Dominator, you? Thanks for the help!

paradigmshift: Thanks for the advice! I was plannig on keeping the efi systems to put back on when I go to sell the boat. Although, if someone was interested in it, I would be willing to get rid of them (it would help absorb some of the cost of the blowers). I 've looked at both Whipple and Pro Charger: I can't afford the Whipples at $6500-7000 per kit and I just don't feel confident in setting up and dialing in a ProCharger system (nothing against them, just not for me).I did look into a pair of 8-71's for the reasons you stated, however, my girlfriend and her friends will dis-own me if I put big scoops on their sun platform. I'm really trying to keep it under the hatch hence the Blower Shops 250 which is a lower profile blower. I'd like to see 650-675hp with 4-5 lbs of boost.

Dennis: Good points, I was a little nervous with regard to the compression at 8.75 (hadn't considered the cam lobe). What is your opinion of this route: Dart Pro 1's (310 cc/ 2.3 intake 1.9 exhaust/CNC and ported, flowing in the 380's), cam change, still replace efi with 1050 carb, and MSD ignition? Can I make 650hp this way? I would feel more comfortable with regard to reliability!

Thanks Again!!!

Thankyou!

diveboy

One more question guys: With the compression ration being on the high side for a blower, would adding intercoolers make this more feasable? I know it would help, but to what degree? Can I safely run the blower with an intercooler at compression ration of 8.75? If I run an intercooler I would bump the boost from 4-5 lbs to 6-7lbs. Yes/No/bad idea?

Thanks!

Dennis Moore

I would save the money from NOT buying the heads or ignition and pull the engine and install blower pistons. The stock heads will work fine with a blower. By installing the bigger intake valves in the stock heads you will be within a few horsepower of the more expensive heads. You don't need fancy and expensive heads/intake ports for a supercharged engine. Just BIG intake ports! (remember the stock rectangle port heads have large 320 cc intake ports)

The MSD CD ignition is actually weaker than the stock induction style ignition in the 3000 to 5,500 rpm range (less spark duration with no multiple spark in this rpm range).

With the correct pistons, camshaft and exhaust you should be able to crank up the boost to get close to 600 horsepower on premium fuel.
Sincerely
Dennis Moore

Whipple Charged

I do have one used 500HP EFI setup, about 6 months old, only 20-25 hours. Blue finish. Complete kit, $5000. This is the new style top mount SC.

If your interested, email.

Thanks,
Dustin

PS I'll be at SEMA all this week so it may take me awhile to get back with you.

paradigm shift

Dive Boy I hear you on the height. My wife said the same thing DO NOT TOUCH the sun pad or engine cover!! I am running a non inner cooled 1071 for the same reason. I would like to go to a whipple inner cooler manifold some day. $$$$ I am not sure on how much HP I am running but if you are running a Bravo1 you already know that is going to be the weak link. If you stay with 8.75cr at 4lbs boost you are looking at roughly 11.1cr depending on altitude. At 7lbs you will be pushing 13.1cr and without an inner cooler you will have trouble in my opinion. Look at Keith E 675hp it is not inner cooled. I would say this is the top edge you would want to go HP wise without inner cooler but that is just me. Depends on how hard you drive and how long you hold the sticks down. I would think that exhaust ports on stock heads are the weak spot. What goes in must come out. The blower Shop can help you with a cam when you decide what CR and heads you are going to use. My cam is on 114 and has 12 degrees more duration on exhaust than intake.
If you run it hard for long periods stay away from the blower in my opinion. Good heads and correct cam I would say 625 is very much with in reach with your 502. You will never have the torgue of the blower motor.

RumRunner

Jon:
Yes, the Fel-Pro Lock Wire head gaskets are a good safety investment. 6 Pounds of boost. It was a 415HP motor before I did anything, but the only thing the same is the block, and crank from before. I went with a set of Brodix heads (since I'm fresh water only) because of the better exhaust flow, and less chance of detonation using the aluminum heads. If you're going to put on a new set of heads this is one case where bigger is actually better, just make sure the exhaust is good, if you were going to spend moneyto have someone work on the heads have them just do the exhaust ports. Running the intercooler would help with your compression ratio situation, but probably hurt you in respects of fitting under your hatch. I didn't put one on this motor.
Next word of advice is if you can swing it in any way (even if it takes a little longer) build complete blower motors. If you change the cam & pistons you're not going to want to switch that stuff back to put the efi back on to sell the boat. Having the spares sitting there is great insurance anyway. They'll never break if you have spares !!! If I had it to do over I would have done that !!!