[496z/28]

Hey all........

I'm kinda new to power adders and have several questions about building a "street" supercharged 383.

1. What compression ratio would be best?
2. Can I use a cast crank?
3. What kinda carb setup should I use?
4. What type of cam would work best?
5. I have a set of Dart Pro 1 heads(215cc-64cc-2.05in-160ex- as cast)
6. What kinda driveability can I expect?
7. How much more power can I expect?


This motor is going in a '73 z/28 with a M22 4spd and a Dana 60. The chassis is set up with ladder bars and moroso springs, also has adjustable shocks front and rear
Sorry for so many questions gotta learn somehow...lol.......

[sc68z28]

I'll assume, a roots blower?

1. Depends on fuel & boost levels, pump gas & about 8#'s,= roots 8 to1, centrifugal 9 to1 with an intercooler.
2. I would not use a cast crank.
3. I run fuel injection, if it must be a carb check out these guys http://www.customcarbs.com/
4. I'm using a comp solid roller #12-704-8, its 255/ 262 @ .050 & .575 lift or .613 with 1.6 rockers. makes power to about 6300rpm with pro-1 230cc.
5. That head should work well.
6. With a good cooling sys, should not be a prob.
7. That all depends on how much boost. My 383 makes about 450hp with out boost, add 15#'s of boost (one additional atmosphere) you will double the power. 450 + 450 = 900, less what the blower uses 100 to 150. If you added 7.5#'s boost, (1/2 an atmosphere) expect 1/2 of 450hp less 50 to 75 used by the blower. 450 + 225 = 675- roots blower 75 = 600hp.

A good book on this subject is Forced Induction Performance Tuning, by A. Graham Bell , amazon.com has it. He even covers engine building requirements.

For a stout short block check out this http://www.speedomotive.com/725_h.htm I'm using there long block with 6" rods and 9 to 1 pistons.

[camaroman7d]

It really depends on your goals. If you just want the look, then you can build a mild blown engine with a cast crank (not the way I would do it). As far as boost on pump gas it depends on your combo and attention to detail. I am running 12lbs of boost on 91 octane, with 8.47:1 compression and a roots blower.

Your heads are fine, shoot for 8:1 (8.5:1 max depending on your goals), you can always make up the power with boost (it is actually the better way to do it). You will want Forged pistons, a forged crank, good rods, and good rod bolts. You will need to open up the ring gaps a little. You want a cam with an LSA of 112-114 (some will say 110 these days but, I think that is a band aid to help with pump gas). You will want a split duration cam, more exhaust duration to help get the burned gas out.

I prefer Holley carbs.

Power will depend on boost and flow. The power willbe plenty and the torque will be even more. It's the torque that a roots blower creates that's amazing. Don't worry to much about HP numbers. Drivability is a non issue, it will make tons of power and torque down low. It might be a challenge to hook with a 4 speed and that tranny will live a short life if you put the power to the ground.

I am assuming we are talking a roots blower. If you are talking centrif, then most things apply except you will want a littl more compression.

Another good book is "Street Supercharging" by SA Designs. It doesn't have all the answers and secrets but, it will give you a good foundation to build on.

If you click on my "pictures" link in my signature you can see a fairly detailed blower engine build. I tried to give plenty of detail. Just click on the new engine folder.

[496z/28]

Thanks for the info..... you guys are great......It will be a roots type blower(6-71) with a dual carb setup......... Couple more questions....

What determines the carb CFM?

How much can I safely boost?

The M22 tranny has been rebuilt w/a supercase and a billet mid plate. The gears and shafts have been custom made using "stressproof" materials such as carburized 8620 for the gears and M48(HSS) for the shafts. It was behind a blown 540 that went 9's in the 1/4.(sold it me because he wanted to go clutchless.)

[camaroman7d]

Good to hear the tranny is up to the task.

The amount of boost you can run is anyones guess. If you pay attention to details 10lbs should be do-able. There are a few things that effect that, heat is your enemy. The hotter the intake charge the higher your chances of detonation become. Your compression ratio will have a huge influence on how much boost you can run. Available fuel octane makes a big difference (we only have 91 here). Timing and boost retard ignition has a huge effect on how much boost a given engine will tolerate. Your cam will have an effect on boost. If you have to tight of lobe seperation like 108, you will blow boost right out the exhaust. You don't want much if any overlap (both valves open).

You will want to run two 750cfm carbs on a 6-71 and an engine of that size. It seems like a lot but, blowers move a lot of air. You want a nice cool intake charge so you don't want to choke the blower. Of course this aaaumes you are trying to make all the power possible. If it is a cruiser then smaller carbs can work.

The faster you spin the blower the more heat it will make. If you are trying to make a lot of boost on pump gas then you may want to think about an 8-71. You still haven't mentioned what the car will be used for or your goals (E.T., HP, etc..). I went with an 8-71 so I could keep the heat out and make the same/more boost, by spinning it slower. A 6-71 is big enough for a 383 and you should be able to make 10lbs of boost if you get the rest of your details nailed down (cam, compression, ignition, cooling).

[prostreet69camaro]

For a blower motor the biggest killer on the street is heat. Do not skimp on any on your cooling system. I have a 502 w 8/71 blower w/ 8 pounds of boost and on a hot summer day in Texas it will run hot if I sit in traffic. I am limited to radiator size. With a 73 you should be able to run a bigger radiator and fans. Also run a boost retard box from MSD. I tried racing 850 carbs that flowed 930 each and it ran real rich. I ended up buying 750 blower carbs and finally stopped fouling spark plugs. I drive this on the street all the time.

[496z/28]

Thanks for the info......

This car will be mostly street driven w/occasional trips to the track. As far as E.T.'s go, I'll be satisfied w/low 11's--high 10's with 7-8lbs of boost.. The car weighs 3300lbs w/me in it. I 'd like to make in the ball park of 650-700hp at the flywheel.
I will also run an electric water pump(CSI), Griffen radiator and 2 -14" electric fans.
Hope to beat up on the local "ricer's gone wild" in my area, a couple 12 sec cars think they can't be beat, a blown small block and $100 says I'll spank there little bottom blue...lol

[DZ Fool]

Talk to Robby Adler From A-team speed shop in Tinley Park Il. When you are ready to go fast . Nobody better in the midwest on blower motors ............

[camaroman7d]

Prostreet, What are you running for timing? Could be part of your heating problem.

Crane also makes an ignition system and boost retard, that is what I use.

496Z,
A 6-71 will put you where you want to be. Low 11's or high 10's will not be an issue. Even with a mild tune-up the car should be able to go mid 10's. Traction will be your challenge.

I personally think going with a mechanical pump would be the way togo. Either an Edelbrock Victor Series or Stewart water pump will do the job. Go with a short water pump set-up, this will help keep the crank snout from breaking off. You don't want to hang things out on the end of the crank like you do with a long water pump.

Keep asking questions before you spend your money. I would recommend buying a "custom" blower kit and not an off the shelf Weiand. Look at Hampton Blowers, The Blower Shop, Mooneyham, BDS, Mike Kuhl, Littlefield, etc... (I think they all have web sites, www.hamptonblowers.com www.theblowershop.com www.blowerdriveservice.com ) most people don't know there is a difference, the "custom" blower kits cost you a couple hundred more but, they are better. Stiffer cases, hard anodized cases and rotors, custom tolerances for your application, better bearings, etc...

Don't forget to add the cost of linkage, air cleaners, scoop, fuel lines, and carbs to the price of the blower kit. You can basically add about $3800-5000 on top of the cost of your long block, depending on the items you like.

[496z/28]

Thanks for all the help guys..I really appreciate it!!

[prostreet69camaro]

Camaroman7d, I am running 36 degrees total on 93 octane gas. I have the MSD 6 box with boost control. Also Dart pro 1 heads, Eldebrock victor aluminum water pump, Big block be cool radiator, w/ there twin radiator fans. I also do not run a thermostat and run the moroso washer for the restriction in the radiator. I have tried the middle one and now am trying the smallest one. It will run about 210 / 220 if I sit in traffic for a long time. Other than that it runs about 200 if I cruise on the highway for a long distance. I usually will drive about a 1 to 1-1/2 hours to a show. I will be at the NHRA Nostaglia races / show in Bowling Green Kentucky this june with my car.

[camaroman7d]

Prostreet,
What is your intitial timing set at? Is it locked out? Blowers like a lot of initial timing. Mine is set at ~20* initial and a total of 34*. I started out with 12* initial and 34* total and the car didn't like traffic at all. My tempature dropped about 20* just by changing the timing. Just something to think about.

[prostreet69camaro]

Camaromad7d,
My dist. is locked. I will double check my initial timing and see where it is set at. Another problem that I have is it will some times backfire thru the Carbs. It only does it under load, like if I slow down in 3rd to about 30 mph and give it gas. If I down shift to second it will not do it. I have another dist. that is not locked that was in my 406. The one I am using now came with my motor. Thanks for the reply.