emttrevor

I bought myself a wieand 174 supercharger and I am thinking of putting it on my 67. I have a recently rebuilt short block not sure how well cause I bought this as a running car supposably its an 87 302 block it has dome shaped pistons but thats all I know Im thinking its probably bored 30 over since it was a rebuild, edelbrock rpm heads e303 cam 2500 stall c4 built tranny and 355 gears also will be running 670 holley street avenger carb. I dont know how to work out compression some say you need to be no more than 9.5 to run supercharger so Im guessing that mine is somewhere between 8.5 and 12 LOL .... My question is should I and also what would be the max rpm to run at before body parts go flying out..any thoughts or suggestions would be appreciated

MustangFTW

you should be able to run at 6-7k if your body is rust free and stiff

emttrevor

So you are talking about my car being rust free and stiff right? LOL As for my car its in one piece and pretty stiff, Ive done a lot of work on suspension, brakes etc added sway bars but I am really concerned about what my compression ratio may be and have no real way of telling since I didnt do the bottom end myself.... Most places I go say if I have 9.5.1 or more I'll blow the engine up I just have no idea on how to calculate it or if this is even a real concern or if its one of those "cover their corporate asses" type things where hey we told you not to do it. My guess is that I'm right around that ratio but I could be way off so if you or anyone can tell me a way to work it out or put my mind at rest by saying " hey its all bs" or even a "what ever just do it and c what happens if it blows it blows" then I'll go with the majority vote and go for it so I'd like as much imput as you guys can give me and appreciate the knowledge and/or been there done that info

andrewmp6

Its only a 671 blower its not going to add a ton of power it should be fine unless you drive it hard.

emttrevor

k cool I appreciate your input. Just been freakin out a little since it arrived and concerned if I was making an expensive mistake

Iskwezm

You cant guess on your compression.You would need to know the pistons you have, if they are dished or domed and what cc.You would also need to know the chamber size of the heads,headgasket thickness etc.Say your at about 9.5-10:1,with about 5-7 psi which is what those blowers put out, your compression could be as high as 13:1.i wouldnt take that chance being that its your dime to fix it.Also i would NEVER spin a 174 past 55-6000 rpm,they arent made for that.Usually its about 15 hp per PSI of boost, but that also depends on how efficient your engine already is.

emttrevor

another question should i just go with holley carb i have or get a blow through type made for superchargers ive heard conflicting stories about that also. I dont mind spending the money just dont want to if I dont need to

Iskwezm

That is not a blow through blower.They do make blower carbs, but im not sure what is changed. When i had mine built for a blow through, it cost me about $900 bucks.

JMD

I am going to admit to not supercharging anything of my own, but I have done a bit of research on this because I have always thought it would be way cool to do so.

IMO, if a person wants to supercharge an engine, this engine needs to be BUILT for this purpose from the beginning. If I were to supercharge anything, (even with a mild setup), I would start with a steel crank (cast steel or forged depending on boost), forged pistons, H-beam rods, no more than 8 to 1 CR, (probably lean more to about 7.5 to 1 or even a touch lower) and almost certainly a roller cam with good lift but not super aggressive duration.

I would also build the engine to make power at no more than 5,000 or 6,000 RPM. In other words, I would build a STOUT but MILD engine, and make up the difference with the charger.

IMO cast or hyper pistons and/or a cast iron crank with a blower is just asking for trouble, the problem with detonation on a blower motor is not "IF", it is when. Be ready for it when it happens. A stock or near stock rotating assembly would imo be a huge risk.

If you are going to do this, I would at least want to KNOW the makeup of the engine so I could attempt to properly compensate for the parts that are not ideal for your blower.

A bit of self education will go a long way BEFORE you slap that blower on.

Oh yea, the Holley carb will need to be modified because the power valve (and some other things) won't work right. Whatever you do with a blower, the A/F mixture MUST not EVER go lean, carb (and fuel system) preparation is paramount.

ozarks06

Good advice. To get the most out of a blower, you need a motor built both to handle the boost, and built to make power with boost. I would stay with about 8:1 - 8.5:1 for a roots type blower on a SBF. It will make lots of boost at low RPM so you will end up with high static pressures, equivalent to about 12.5:1 - 13.5:1 compression. You will definitely have to watch the mixture and timing. You also normally want a mild, if not stock, cam for a blower motor. Typical N/A performance cams have too much overlap and you'll just blow boost (and fuel) out the exhaust valve while both valves are open (the smooth idle is also good for fooling the 'fools' at the stoplight).

Whatever you do, do your homework (Supercharging, Turbocharging & Nitrous Oxide Performance Handbook by Earl Davis et al is a good place to start), and make sure you have it tuned by someone who knows supercharging and does it on a dyno. Too much spark advance at the wrong RPM/load or a lean condition can destroy your engine almost instantly (like less than 2 seconds at WOT - boom!). Blowers are great but they place enormous stress on the engine components (and the drivetrain too).