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bulding a blower engine

2K views 12 replies 6 participants last post by  deuce_454 
#1 ·
hello, me and my dad want to build up a blower motor. he plans on putting a Wieland 6-71 blower on our T-bucket, we have torn down and built up many engines before this, but this would be our first forced induction project. as of now the block has a 4 bolt main, and relatively low compression (8-8.5:1). im assuming we need the boost referenced carbs, a cam, pistons(maybe), the blower it self, new ignition (currently a GM pref. parts), and time. is there anything im overlooking? also, what are some good cams for the 6-71?
 
#2 ·
In order to anser your ?'s, there some info we need. The main one is how hard is this thing going to be driven, and how much HP are you guys shooting for. Most blown engines call good steel cranks and rods, plus forged dished pistons. This isn't nessissary if you aren't trying for big HP #'s, but can always be used for a peice of mind. The cam choice is also based on this info as well. Let us know...
 
#3 ·
Typically you can get away with stock rods and crank with a good set of rod bolts and a good balance job. You will need a set of forged dish pistons, but make sure and get a quality set that do not have the dog bowl dish that is completely round. You want the D shape dish so that quench can be maintained for detonation resistance. If RPM is kept in the 5500 RPM range, which is very reasonable for a blower engine, you should not need forged internals unless you are planning on running alot of boost. Comp cams makes several blower grinds. You should just pick the one that suits your RPM range goals.

Let us know more and we can talk specifics.

Chris
 
#4 ·
the car is not going to be constant WOT, but, we do like to get on the gas once and a while. most of the time we cruise. i was thinking between 400-500 HP, it currently makes 300-330 hp. the power is not that big of a deal, the car is plenty fast, the blower would be more for show, don't get me wrong we still want some HP+ gain, but we don't want to make more then 550-600 hp in a car like that. we would never get traction seeing that car only weighs 1750 pounds
 
#6 ·
Somebody mentioned I should have a double keyed crank and steel dampener for the larger (6 & 8-71) blowers, so I contacted Holley (Weiand) up close and personal. They gave me a definite 'yes', recommending ATI's steel blower unit. I hadn't even considered that much beef for a street application, but....with the drag imposed it makes sense. Liability was also mentioned, how embarrassing (and catastrophic) to have your parts flying around the intersection.

Just something else to consider.

Good luck, Larry
 
#7 ·
If you want a top quality blower I HIGHLY recommend www.hamptonblowers.com There IS a difference in blowers. I did a lot of research (years worth) before buying my blower.

You have gotten some very good advice so far but, I would like to add a few things.

If you are going to do it you might as well make some power, it's not going to cost much more. Your goal will be VERY easy to reach. Keep the compression in the 8-8.5:1 range and go with good rods and forged pistons. I would also recommend contacting Engle Racing cams www.englecams.com and having a talk with them about your goals and they will grind you a cam that fits your needs. You will need a cam with a LSA of 112-114 that is really about the only hard and fast rule. You don't want a lot of overlap.

As far as the crank hub or balancer it is a matter of opinion (which you will see a lot of when it comes to blown applications) I chose to go with Hampton and followed his advice (he has been doing it longer than anyone and really knows his stuff). I went with a crank hub. The problem with a balancer on a SBC is that the crank snout is so small (in diameter) that you don't want to hang a lot of weight on it (ie...a balancer) when using a blower. I would also recommend going with an 8mm drive and not a 1/2" pitch, the 8mm will make slightly more power but, the main thing is it will put less stress on the crank snout. As you can see there is a lot to thing about feel free to ask more questions as you venture deeper into this project.

I HIGHLY recommend going with Holley blower carbs as well. You can get away with a standard carb but, if you are going to do it you might as well do it "right" (matter of opinion as well). The guys at www.allcarbs.com (All State Carbs) are great to work with and I used them and recommend others to them as well (If you go that route tell them Royce sent you).

For headgaskets I would recommend Cometic MLS gaskets (you do not need to O ring the heads with their gaskets and they seal better than copper. Some machine shops are not up on these gaskets yet and might try to tell you that O ringing is needed (IT"S NOT) especially on a street engine making less than 18lbs of boost. If you keep the boost under 10-12lbs I know of some people getting by with standard composite head gaskets (I personally wouldn't try it).

If your GM ignition is an HEI style it might be a tight fit with the blower, you don't have to have an exotic ignition for a mild blown engine, but you do want plenty of fire. If you plan on pushing the limits I would recommend a Crane ignition/boost retard or MSD ignition/boost retard.

I have a pretty detailed blower engine build on my site with lots of pictures if you are interested http://community.webshots.com/user/camaroman7d

click on the album that says "new engine"

Do your research and form your own opinion.

As you can see there is WAY too much info to post it all here, hopefully this gave you some things to think about and decide if you want to go deeper.

Royce
 
#9 ·
Oh in that case. Once you know what you have let us know and that will dictate which way you should go.

Assuming a few things I would probably suggest keping the boost down in the 5-6lb range. The reason I say this is, it's a T-bucket and they are usually "mild". Without knowing for sure I would guess he didn't do anything wild to the bottom end, rods, rod bolts, crank, mains. If this is the case and you have a cast crank, cast pistons and stock rod bolts, you are going to have to keep the boost down in the 4lb range. With that being said you can dis-regard a lot of the advice I mentioned about. You won't need a "blower" cam a mild cam with a wide LSA 112-114 will do. Typically called an RV cam, the one in the engine now may do just fine. As far as carbs go just about anything should do. Keep your timing very conservative, if the pistons are cast they will not tolerate ANY detonation.

There are other issues as well like piston ring end gaps that should be wider for a forced induction application (due to the increased heat in the combustion chamber).

Hopefully this guy has all the engine specs and kows exactly what's in it.

A blower is a pretty big investment, so you might want to bite the bullet and build the engine to take advantage of it.

One other thing I forgot to mention you will also want to runa short water pump, this will help keep the load on the end of the crank to a minimun.

Royce
 
#10 ·
we may skip the blower all togeather, we stumbled upon a tbucket that needs a little TLC for $3500. it would be a nice project for me. the only problem is that some things dont add up, he says the motor is a 289, but the heads are BIG and the distributor is in the front, i thought 289's had a distributor in the rear, it was hard to tell, the place it was stoed was dark.

edit: oops, distributor is in the front on 289's i wonder why the heads are so big.
 
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