6/71 score! Now I need blower help

I bought this Supercharger off of craigslist for $400!!!! I scored big time!! Ive always wanted one of these! The kid needed $400 to get his truck back from the tranny shop!

So now I need advise. The manifold is a race manifold without water jackets... What can I do? Drill and tap for water jackets? It came with an external thermostat housing. And what is the extra pully thing? Theres no ribs on it. Its not the idler pully because Ive already got that one.

And the drive is made out of magnezium, is that ok?

Let me know what you think and any advise for the reasembly. I am going to do a write up on the rebuild so I can finally add something constructive to the hamb!

I have new bearings and seals comming in the mail. I am thinking my only option is to sell this manifold and buy a new weiland.
Tell me what I have here if anything special. I want to get this on my Modified as soon as I can. I have to change to a short water pump and buy another 600cfm carb.

 

That's awesome! I have been itching for a Blown 303 Olds in my Roadster lately. Nice score, unfortunately I have nothing to add as far as tech goes.

 

Uuhhh...what engine? If it's for a Chevy, by all means, sell it and buy a Street manifold. That "extra pulley thing" is just that...an extra idler pulley...

 

It looks like the bold pattern would make it bolt on to my water pump? Would that run my water pump off of the blower belt? And yes its for a SBC.

 

Did the seller tell you what this ran on originally? If this was a drag setup then you will need to have it re-stripped to drop the pressure down to a street friendly level.

And yes, get a street manifold, otherwise get ready to do some creative plumbing!

 

please put it back on craigslist and let me know....my coupe need it! Good score!

 

does the rear bearing blower plate say gt on it???? and you can just plum the manifold for water...that is how isky sold there blower kits with an edelbrock manifold..that is an isky blower drive ,,dose it have a tag on top of the snout???

 

Yup, thats GT on the rear plate. I figured it was an aftermarket item because of the lettering.
No, no tag on the drive. But I do know that the belt tensioner is an Isky part.

 

what is the compression of the motor you plan on puttin this on???

 

Make sure your carbs are boost referenced. Holley makes special carbs for putting on top of blowers. A roots type blower will always have vacuum above it. This means the carb's power valve will never open, causing a dangerous lean condition under load. There is a way to modify it to work, I would have to dig around to remember how to fix it. I found a pair of boost referenced carbs for my setup.

You will also need to get your drive pulleys setup with the correct drive ratio for the motor you are using, compression ratio and fuel you will use are the most basic consideration. Also a cam specifically for blower app helps a lot.

 

I have a stock 350 block with a set of vortec 2.02 heads from RMS. A mild lunati cam. I planned on using two 600cfm edelbrock carbs, one with a choke. The blower doesnt have any strips in it so I dont think it is going to be a real high boost setup. It has a fairly large pully on top wich should under drive it a bit correct? My goal is around 5-7 lbs of boost. I want the blower look and feel but without sacrificing reliability.

 

you should change your sig, unless your looking for another one!

No need to restrip, and if it has no strips it will make less boost, and yeah the big pulley on top is underdrive.

Good buy!

 

I was hoping squirrel and some of the other blower experts could help me out here. Is this setup going to work?

 

How do I figure out what pitch my pulleys are? I was looking at a chart for calculating the underdrive.

 

Still lookin for help here from the "people of the HAMB"

 

Re- your question will it work? Can't see why not, if you set everything up how it should be. 1/2 fuel line out of the tank is good then at the regulator reduce to 3/8. If you run a harmonic damper( as opposed to a crank hub) make it an SFI spec one as cast ones are known to break. Boost referencing Holley and Demon carbs is not hard. If you can't find out how shoot me a PM and I'll send you an article on how its done. That extra pulley looks more suitable to driving the water pump than a spare idler to me. 4 holes instead of a big one for a couple of bearings. If it does that, thats cool. In the pix, your pulleys lok like 1/2 pitch to me, but hard to tell for sure in pix. These pix will show you how to tell.

 

Yeap!

nice score

 

That setup should work fine on a street car but you are going to have to drill and tap the front of your heads for water ports. The pulleys are 1/2" pitch and this will help you figure out your drive ratio and boost http://dyersblowers.com/nstallation_instructions.html

 

Also before you install anything check the popoff valves out. I'm pretty sure they are supposed to have castle nuts w/cotter pins, but in your picture they look to have lock nuts that also don't appear to be on all the way and could possibly come off causing all kinds of damage.

 

Blower Drive service has some good charts for drive ratios, and overall compression ratios. For carbs you can also run 2 600cfm Edelbrocks. If you get thier tuning book it list there recomended jetting specs for a blower setup. The water pump is usually run by the alternator belt, not the blower. The vortec heads are a problem though because you need a specific manifold for them. But since you need a street manifold anyway, it's not that big of a deal. You will be amazed what a blower will do for your power and the "WOW" factor is pretty cool too!

 

I'd think the best route would be to swap to a set of big chamber late model heads and drop the compression while allowing the use of the Edelbrock manifold which is specific to the Isky spider (idler bracket).

 

I would agree with that. Most 350 heads from the 70's or 80's have 76cc chambers and 1.94/1.50 valves. That will get your compression ratio in a more boost friendly range. They don't flow quite as good as the vortecs but the blower will more than make up for that.

 

Also, the Isky drives were originally intended for competition use and had an offset to them to help align the top and bottom 2" wide pulleys. Later they sold street setups that drove the water pump off of the blower pulley and had a V groove machined in the crank hub to drive a generator/alternator. If your hub has a tight press fit and you use a good aftermarket bolt that's snugged down well you should be good for under 10 lbs. boost. Or you can swap to a non offset lower pulley and use a standard accessory pulley,hub/balancer etc. and drive your alt and water pump the normal way.

 

So the piece that the bottom pully mounts onto replaces my balancer? It has a heyway like my balancer and also has a V groove to drive my altenator/water pump. I figured I would have to ger a short water pump to be able to use that groove.

I think It would be cool to run the water pump off or the 2" belt. You dont see that very much. And I could make up a mount to relocate my altenator down low. If that is what you mean... I just recieved the rebuild bearings and gaskets so I am looking for a new manifold ASAP!! I also need the front cover breather valve and I need to drill some holes so I can tripple pin the rotors to the shafts, oh and buy another 600cfm edelbrock(because im poor and I already have one of these). I will write up a step by step deal for those who dont know(like me). I think it will really help new guys to the blower stuff!

Now, the heads. I paid good money for these heads. I cannot remember what the chamber is(I am in the procces of finding out from the manufacturer). What would be a unacceptable number?

 

Yes, that is an Isky crank hub and the groove is probably too far back to line up with a water pump pulley by about 1". If you use the water pump drive pulley it should only have slight tension on it and about 1/4" of play on the long side when hot, 3/4-1" when cold. Too much tension can damage the crank bearings and drive parts. Also you may or may not be able to use a mechanical fan? on the water pump because of the added load. A 6-71 manifold for vortec heads will be hard to find, if anyone even makes one and it might be easier and cheaper to have a machine shop re drill your heads for a standard bolt pattern if you are dead set on using them. I still think you should consider a set of budget big chamber heads if you use the blower. Once you are force feeding the motor any cylinder head work (or lack of it) doesn't mean a whole lot and you can sell your current heads to help pay for things. The lower compression will allow for higher boost and make it more streetable as well. Also take care pinning your rotors and get a junk set to practice on if possible so you don't mess them up. If there is more than one pin on the driven end of each rotor, they have already been done and leave them be. Then just make sure your rotor to rotor clearance is good when you reassemble it. Most shops will tell you to split the difference on a street blower and make sure that you don't forget to fill the front cover half way up w/gear oil before you use it.

 

Nice score!!!

 

So, I can mount the alternator off of the side of the block and run that off of the crank pully, and run the water pump off of the 2" belt. I can be happy with that(I like the wierd looks at car shows, they love my headlights!). Any hints on were to run the alternator?

I thought the trick to running an old style manifold on vortec heads was to oval out the two/four center mount bolts? I have access to a HUGE machine shop and I have the knowledge to use it ALL. Just tell me what I need to do. Is there a trick to pining the rotors? Just drill a 1/4 in hole in the bridgeport and use a punch to peen over the top 30-40 thousandths to hold in the dowel correct? Should I ream it to have a press fit?

Without measuring, do I need a short or long water pump? (I already have an electric fan... sshhh dont tell the H.A.M.B.ers)

 

If you hack on that nice looking Edelbrock B10 intake, don't tell me about it! Yes there are some tricks to pinning rotors as far as where to drill and how deep. The June 1973 Hot Rod magazine has a detailed article on setting up a GMC blower with information on how to do it with tapered pins but goes for dowell pins as well. The pins need to be a press fit and the 1/4" holes should be drilled through the rotor and just through the rotor shaft while being careful not to go through the other side of the rotor. Then shake what aluminum you can out of the hole. The hole should be located 7/16" from the front edge of the rotor to the centerline of the hole. The pins should be driven just below the surface of the rotor and staked so there is no chance it could ever work it's way out. The factory installs one pin on each end and only one extra is needed on the driven end of each rotor for a street blower. You should run a short water pump. FYI when disassembling a GMC blower don't remove the non driven ends of the rotors by tapping the center of the rotor shafts. They have pressed in plugs that are driven in from the back before the shaft stubs are pressed in the rotors and are nearly impossible to get back into place.

 

Also when installing the rotors in the case, the rotor marked upper goes to the right side and the one marked lower goes to the left when looking from the front and make sure the missing serrations on each rotor shaft is pointing to the right when looking at the front of the blower as well. As far as sealing goes I've used Loctite 515 flange sealant between the bearing end plates and case.