Hot Rods Blown Caddy? Pics? Help? SUPERCHARGER 101

BOBBLEED - You do NOT need to cut up the 4X2 intake to put a blower on it. Read Post #51 on this page...

 

As mentioned, we have these 6 x 2 for the 4-71:

 

A blown engine is probably the most fun you can have with a fire suit on. Being young and eager I put a 2" Winfield carb on my 6-71, you talk about a restriction, driving around town ice would form on the blower case. Later I installed 2 AFB's. The 4-71 had a home made 3" 2bbl with Hilborn nozzles, it was almost streatable, blower drive ratio was 120% over with 8:1 comp on a Z28 302. Listen to others but still do it your way, looks like you have the interest to get it done. Pat

 

Those are some neat pictures! I have been considering adapting some sort of plate to an intake to mount the blower, but I don't want it to sit too high.... I actually want to have a full hood....

I also think I could pull it off where it looks like it's a real cragar intake.... or very similar to the Homemade one Brock showed........

I have been putting alot of thought into making the pullys as well.... I'm looking for pullys that could be adapted...... but seeing the Flat Power ones is super inspiring!

 

Off on a tangent... For you Y-block guys, here's something Steve Sellers is working on... It's in the prototype stages, it sounds like. Something to keep an eye out for in the future.

 

The 3 rib sbc chevy pullies are very close to the caddy ones

 

Update...... I scored a cragar mainfold, so it is all coming together.... Basically, I have good friends.....

So now its on to pullys, I am going to make them... Unless cragar ones happen to fall in my lap!

One of the guys at the shop has some pretty decent machine skills and his dad is amazing.... so with their guidance I think I can pull it off... I'm pretty much just going to help them.....and learn some stuff along the way...

I guess my question it what should I make? the engine is pretty stock so I want to build it under driven..... someone said to just run it one to one and I would be fine..... I'm thinking I need the crank pully to be smaller, but How much?

10%? 20%? How do I figure How much boost I am getting? and what is safe? I do plan to build another engine as a blower engine, but what should I do for this one..... basically I want to run as much boost as possible without breaking everything...

thanks for all the help.... you guys rule. This is all coming together way faster than I thought it would.....

 

Bob Im running my 471 @6% under it makes about 7 PSI on my 331 SBC its really going to depend on the specifics of you motor as to how much boost will work well

 

Way way way over my head. Please make sure to include all your findings. I am super interested in this stuff and would love to know more.

 

great thread, ive learned lots. thanks.
good luck with the blower build.

 

So maybe I start with 10% underdriven and see how it all works?

 

You could I guess but... anything less than 5 psi of boost is really just a waste. Do you know what the static compression ratio is on your Caddy? I would try to stay between 8/1 and 9/1 that way when not under boost it wont be a slug and you can use a MSD BTM box to control timing and still run on pump gas.

 

No I don't know anything..... How do I figure that out?..... the engine is rebuilt, bored over but has flat pistons....

 

If your comression is 8:1 to 9:1 go 1:1 on your pulleys with a 4-71. If you are making pulleys it will be a lot of effort to just try a ratio. You could start with gilmer pulleys until you decide on your ratio, then make the ratio you like the best.

Study the charts for pulley ratios & compression ratios for pump gas with a 4-71 on www.blowerdriveservice.com

It's a little conservative to you'll be fine with 1:1. The guy at Dyer's told me 1:1 (which was a little more than the BDS charts indicated) with my 4-71 drive with no uncertainty when I told him about my engine. He was right too. Call them.

To figure out the compession ratio, you'll need to measure the stroke and the volume of the cylinders and the combustion chambers. You're lucky the pistons are flat so you won't need to worry with the volume of the depressions. hopefully it isn't a 10:1 engine. You will then need to change pistons or get bigger volume combustion chambers in your heads to lower the compression. You have to be below 9:1.

Glad your friends pulled through on the parts.

The distributor advance curve is the next big thing. Get the compression and the advance curve right and you'll have a good running little engine.

 

Hey Bob, are you just going to run the cam that's already in it for now?

If so, do a compression test and talk to one of the blower companies for a pulley ratio recommendation. They can work with you if they know your cranking cylinder pressure.

I feel pretty safe telling you that 1:1 will work fine. It's just a little 4-71, take that thing 30% over you sissy.

 

Bob, not that long ago Dyers blower service in Summit IL. told me they can and have made v belt blower pulleys, probally worth a call.
please keep us up to date on this project. early caddy motors are the coolest!

 

yep Gary was very helpfull when I was putting my 471 together. They made my 2" gilmer drive for mine but it wasnt cheap, then again good stuff seldom is

 

I have heard this also as I need a set of three grove but I have not confirmed myself yet.

Also, I do not think you need to double key the balancer on a triple V as belt slippage would always happen before you sheared a key, Maybe five V or any cogged belt.

 

Manifold came this morning...... fuck yeah!

1 to 1 seems like it might be the way to go...... I'll call dyers and see what they say....

Check it out..... I'm pretty excited!

 

That is badass!!

 

WOW! Looks killer Bob!

 

Rad!

 

Oh my. I want one.

 

Thats a whole lotta of Awesome!!

 

yea I AM DIGGIN that! btw I did some checking the stock compression ratio on those was 7.5 on the early and 8.25 on later so if its stock compression you will be good to go @ 1to1 just to be safe I would get a cranking comp. reading and verify what heads are on it i think 365 and 390 heads bolt on those too

 

Very Cool looking Forklift parts!

Are you running a stock cam?

 

yep, what he said.

 

That looks wicked!

 

Get anywhere with this motor bob? Looks really good so far.

 

The sound those half pitch belts make is way cooler than V belt pulleys