6/71 score! Now I need blower help

When you said, I need to drill and tap my heads, where do I do this? Should the rear of the motor have water passages also?
I need to know how to run the coolant if I were to stick with this intake. This would save me $400. Would it keep it cool enough?

 

You just need to drill and tap for pipe thread on the front of each head so you can connect to the remote thermostat housing you already have. One hose to each head. If you look at a standard intake you'll see that it's basically the same set up, the thermostat is plumbed to the front of each cylinder head and the only real reason the heads have ports on each end is so they can be used on either side. Also if you ever use the heads without the supercharger, just turn them around so the plugs are in the back.

 

Looks like you got a hell of a deal. I love the sound of a SC, can't be beat. Good luck with it. Teach us some more about them when ever possible. Thanks.

 

Someone just contacted me about a brand new intake that I can buy for a real good price. No need to disasemble my motor to drill the heads!

 

I am looking for heads for my motor, what would a good chamber size be for running a blower?

 

you need to figure out what will give your motor 8.5 to 1 or less. do a google search and find a compression calcultor to figure out your compression ratio. Do you know your deck height, stroke, piston configutation (flat top, dish, eyebrows?)

You can get away with 9:1 if you don't configure the pulleys to create more than 5 psi of boost. Check www.blowerdriveservice.com and read the technical information. They have charts for 671 showing amount of safe boost using pump gas vs compression ratios.

76CC heads are good. GM has a 76cc casting with a casting number that ends in 883 that will lower most small blocks into the right area. Read up on that thing. Its not difficult, but there are some guidlines to follow.

 

Dude, I hate you! Just kidding, nice score. I've always wanted to do a blower motor. I'm kicking it around for my 235 inline. Post some pics as you go please...

 

Like Tudor said, you'll need to figure the static compression ratio and adjust the boost accordingly to run on pump gas. You may already know how to do this yourself, but I'll run through it for others who may not know. Online calculators are OK, but I figure everybody needs to know how to do it themselves.

To figure static compression ratio, you will need 5 values.
1. Swept cylinder volume. Use the constant .7854 times bore times bore times stroke times 16.387 to find cc's in the cylinder. A +0.030" 350 Chevy will be .7854 times 4.030 times 4.030 times 3.480 times 16.387 and will compute to 727.41 cc's.
2. Combustion chamber volume. Find this by surfing mortec.com with the head casting number if you don't already know the volume of your heads. Or, you could pour the chambers with a graduated burrette and colored alcohol. If you don't know how to do this, kite me a PM and I'll explain.
3. Piston crown volume. Most flat-tops with 2 valve reliefs will have 6 to 7 cc's in the eyebrows. If you have dished or domed pistons, look up the specs by piston part number or use a graduated burrette with colored alcohol to find the volume. Dome volume can be found by sliding the piston into the bore and positioning the dome to just barely below the block deck. Use a dial caliper to determine the depth from the block deck to the flat part of the piston right next to the bore. Let's say the dome sticks up 0.350" above the flat crown of the piston and you have positioned the piston in the bore so that the top of the dome is just below the deck to enable you to put a clear piece of Lexan or other material on the deck to "pour" the piston. You determine with your dial caliper that the flat crown of the piston is down below the deck at 0.360". Using the same formula that you used to find cylinder volume, compute the volume in the bore assuming that the piston was a flat top (visualize cutting off the dome down to a flat-top). If the bore is 4.030 and the piston crown is down in the bore 0.360", then .7854 times 4.030 times 4.030 times .360 times 16.387 will result in a volume of 75.25 cc's. Now pour the top of the piston. Let's say it takes 51.3 cc's to fill the space. Deduct 51.3 from 75.25 and find a dome volume of 23.95 cc's. Use Vaseline to seal the piston to the bore for the pouring operation.
4. Piston deck height volume. Most small block Chevys will have a piston deck height of +/- 0.025". Measure yours. Let's say it is 0.030". Using the formula, multiply .7854 times 4.03 times 4.03 times .030 times 16.387 and find 6.27 cc's.
5. Head gasket volume. Most of the time, the volume will be listed. If not, measure the bore of the gasket and use the compressed thickness published by the manufacturer. Let's say the gasket bore is 4.100" and the compressed thickness is 0.039". Using the formula, multiply .7854 times 4.1 times 4.1 times .039 times 16.387 and find 8.43 cc's in the gasket.

Add 1 through 5 together. Add 2 through 5 together. Divide 1-5 by 2-5 and you'll have the static compression ratio of that combination.

When doing these calculations with dome pistons, visualize cutting the dome off at the piston crown and glueing the dome into the combustion chamber. Using the dome volume we computed above and using 76 cc heads, just think of it as deducting 23.95 cc's from the 76 cc chamber (76 less 23.95 equals 52.05 cc's). So, you would compute the static c.r. using a 52.05 cc chamber head and a flat top piston which would have a value of zero.

Here is a list of general recommendations from Blower Drive Service.....
http://www.blowerdriveservice.com/recommend.php

And here is the chart for determining final c.r. from static compression ratio and boost. Find your static c.r. down the left hand side and the boost you will run along the top of the chart. Pump gas friendly ratios will be shown in gray.....
http://www.blowerdriveservice.com/techcharts.php

 

Wow!!! That is a mouthfull!!!

I understand, but I wouldnt want to have to figure this out on my own! I will do that once I find all my components. My motor now is running about 10:1(a guess) ratio so I dont think I am going to run it. I am going to build a new motor for it and save this one for something else. I am looking at a 383 stroker setup with dished pistons. And aluminum high flow heads. Any suggestions? I am selling the 59 pickup this week and I am going to put the money into this motor. Keep it cheap!

 

It's easy. Seriously - find an online compression calculator. here is one
http://www.csgnetwork.com/compcalc.html

you can play with different head CC sizes to see what compression it gets you. Typically 72, 64, 76 CC heads are availabe. Double humps are 64 or 62 CC. Or less if they have been milled.

Heads are less important with a blower engine unless you are going for max effort. Obviously the more flow the more power. The supercharger more than makes up for high flow heads.

Use mortec http://www.mortec.com/borstrok.htm to reference all the bores and strokes for the different configurations. The stroker motors are harder to build with lower compression. Play with the calculator and you'll see. use .021 or .035 for compressed head gasket. Use .023-025 for deck height. Or less if you deck the block.

383 = 4.030" x 3.75" (5.565" or 5.7" or 6.0" rod)
350 block and a 400 crank - the crank has to be cut to 350 main bearing size. Most 400 cranks are cast - so for a blower stroker blower motor - you'd buy an aftermarket 400 crank with 350 journals. Nothing would have to be cut.

 

Keep it cheap means cast crank and hyper pistons and that means very low boost to keep from blowing the bottom end out and runnin' over the crank. I would probably feel comfortable runnin' up to 8 lbs at 8.0:1 static compresssion ratio with non-forged components, as long as you keep the motor cool and most importantly, KEEP IT OUT OF DETONATION. David Vizard has used a Scat cast steel 3.750" crank at 550+ hp for the past several years with zero failures. Cast STEEL, not cast iron. I might choose the Scat capscrew rods to use with the crank under low boost conditions. The capscrew design prevents having to clearance the rod for the cam lobes. The block may require minimal grinding at the pan rail for rod big end clearance, but that's no big deal.

A blower will cover up a multitude of mistakes in the selection of components. For instance, you can make good power with stock cast iron production heads because they are no longer seeing natural aspiration. They won't be optimal of course, but they'll be o.k.

If I wanted to go aluminum....and cheap.....I might take a look at the Patriot heads. I never have used them, but testimony from others indicate that they are, for the most part, o.k. Do a thorough inspection on them for casting flaws and measure all dimensions.

Here's a KB hyper 28cc D-cup that will make 8.04:1 with a 75cc head. I wouldn't necessarily use this particular piston though, because of the thin rings. I would want to start with 5/64ths top and second rings.
http://kb-silvolite.com/performance.php?action=details&P_id=91
But the point is that you will need some pretty good dish and pretty large chambers to make this a pump gas motor. I also would use 5.7 rods. I don't like gettin' the wrist pin up into the oil ring with a longer rod.

 

I am looking at kits for forged dished pistons, and cast everything else. I wonder if I could save money by going with a stock 350 setup? Im looking at 76cc heads also.

My biggest issue is what do I do about the balancer? I cant run a balancer with this setup. I need to run the special hub for my pullys. Is the balancer a big part of the "fully ballanced part"?


http://cgi.ebay.com/ebaymotors/SBC-CHEVY-383-FORGED-ROTATING-ASSEMBLY-DISH-TOP-12CC_W0QQitemZ270378442303QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item270378442303&_trksid=p4506.c0.m245&_trkparms=65%3A3%7C39%3A1%7C240%3A1318

 

your bottom pullys should bolt to the bal. just like stock ones, just have to check how they line up with the other pulleys. you can if under driven can run up to 9.5 to 1 compression ( i did on a stock ford 390) on the street with pump gas back in the 80's

 

The "balancer" isn't a balancer at all, with the exception of a 400 with the eccentric weight on the hub that, along with an eccentric weight on the flexplate, helps to externally balance the reciprocating assembly. It's a harmonic damper. When the plug fires, the piston, through the rod, exerts a force on the crankpin. This causes the crankpin to spring a little (bend) in the direction of rotation. It will only bend so far, then it springs back the other way to its limit, then the other way, then back the other way. Hold a 12 inch ruler on the edge of a table with maybe 10 inches of it hanging out in midair. Twang the ruler and see it spring back and forth. This is the same thing that is happening with the crankpin (rod journal) when the plug fires. If left unchecked, these vibrations or oscillations or "harmonics" will result in the cracking and destruction of the crank. So, we hang a driven hub on the snout of the crank, put some elastomeric material between the hub and an outer inertia ring and the inertia ring helps to cancel the vibrations, thus we have a "harmonic damper".

A harmonic damper is not necessary on a blown motor. The large rubber blower drive belt serves the same function of quelling crankshaft vibrations that the harmonic damper would accomplish. You can run a harmonic damper if you want to, or you can just run a solid hub to attach drive pulleys to run the alternator and fan.

Of course, if you run without a damper, you won't have the eccentric weight to help balance the motor externally using a 400 crank, so you'll want to purchase internally balanced parts and use a neutral balance flexplate.

As far as the size of the motor, with a Roots blower bolted on top, the ring & pinion won't know the difference between a 350 and a 383 in my opinion.

 

AH, thank you for the brake down. This is why I love the HAMB! And the fact that this information has to be accountable! If you said something wrong, there would be a shit storm!

Anyways, thanks for the help guys.

I will have lots more questions on this topic and my goal is to combine al the information into a tech for everyone else in my position!

 

I edited post 44 since you read it. You might go back and give it a once-over.

 

I went to jefferson this weekend and I got some awesome deals!!
I got a 400 crank that has had the journals turned down for 383 use. I got a screamin deal on another edelbrock carb and I bought some other SBC stuff for cheap. It was raining so everyone was getting the heck outa there.

Im looking for some forged dished pistons. If anyone here sells them, that would be great.

 

With a 6-71 - you really want to run a FORGED crank. The blower drive puts a lot of stress on the crank nose and first journal. I have seen a lot of cast crank motors with blowers and broken cranks.

A forged crank will crack, a cast crank will break.

 

I'd dig through a wrecking yard and find a forged crank, myself, it's not like they are that rare, just check truck motors. It's good assurance

 

um - I am not sure they made any forged 400 cranks at GM. Callies has them If you buy nice forged crank, go ahead and get it double keyed.

http://www.mortec.com/cranks.htm

man, if you are not going to make a lot of boost and mostly drive on the street, the cast cranks will work. Forged pistons are nice to have, cast will work. Just don't get crazy with the boost. They take crappy crate motors and throw blowers on them, with 5 lbs of boost and make an extra 100 150 HP all the time. Use a timing retard ignition box, run good gas, stay away from detonation and you'll be fine.

Use a billet SFI balancer not a cast balancer to drive the blower.

 

Drill intake back by the distr to get into the rear water crossover in the head, that is where the sending unit is on the left side, just drill and tap the right side and run -12 hose back to the remote 't'stat housing, i'm sure it'll be tapped for fittings and that'll run back to the radiator.
No need to restrip, it isn't stripped to begin with.
To get intake to work with vortek heads i think you'll have to drill for stock style manifild bolts, no big deal.
What material is the blower case made from, looks like magnesium and that would be an oddity because that would make it a race piece but the rotors aren't (unless i'm seeing wrong) stripped, ie: street application. If it is magnesium don't cut it loose, that'll be a keeper or work a deal with somebody that needs one for a fed, comp coupe type project that has some pretty authentic stuff anyway.
What else you are missing is off-the-shelf from weiand or bds, just have to deal with the 'newness' issue and give it some patina. Very good score.
Stay away from vacuum secondary carbs, block off double pumper powervalves and drill out the idle restrictors and bolt a pair of 5-600cfm carbs and have fun.

 

I think its aluminum. I will only be running on the street. No Drag(cars way to light)

I plan on running this cast crank 383, Forged pistons -21cc D shape dished pistons from summit(prob forged rods to) and im looking at a set of stock 76cc heads that have 2.02 valves in them for $300. The pully I have will push about 8lbs so I think it will come close to right. I can run a thicker head gasket to get the compression down right? I think this setup is sitting right at around 8-8.5. And the blower doesnt have strips in it so it should run lower than a normal blower correct?

 

Is that paint on the casing? Don't think so, if it was aluminum it'd look just like the intake.
Not crazy about the cast crank - even for an unblown - get a 'cast steel' as was reccommended; stay away from thicker head gaskets, problem matching things up and sealing; stay away from patriot heads, had a pair in here last week and they were warped, brand new & the guy was just puting them on his engine, took an odd intake gasket extra thick with double bolt holes anyway he bolted them up and got zero compression - warped.
I wouldn't worry too much about making boost. Its' not a given thing and this setup has probably got a bit of 'clearance' built in. Just plan on building a good solid hotrod motor and you'll be fine.

 

Me again. Do you know that 383's are generally externally balanced which requires the flex plate and balancer/crank hub to be counterweighted and the Isky hub you have is not. The setup could probably be internally balanced with heavy metal but from what I hear it can be fairly expensive.

 

That's why I was suggesting he run a sfi billet balancer.

 

So, can I put the pully right on the bottom balancer? Or would this push it to far out??? I dont want to have to change the drive(there expensive). You dont hink that the pullies will be outa line?

The blower is aluminum, it is powdercoated black. Not very well but thick.

Now, I can cut a slot in the crank for a second keyway but how do you cut the balancer? I searched for a dual keyway but I couldnt find one. I imagine that it is 180 from the first one right?

Other than that, do you think this will work? I plan on running about 8 lbs with this setup. And my blower doesnt have strips so it will be even lower than what the chart says(says 8 but I think lower). And it wont ever be on the strip. Its got skinny tires and wieghs 1400lbs

 

actually most blowers are not stripped unless they are race blowers. It'll still make boost - how much will depend on the set up, cam, carbs, etc. Your intake will be in vacuum most of the time. Boost gets made when you have the carbs 75 to 100% open.

That is a good question about the balancer, I never did find a balancer with a second key way. A call to the blower shop may solve that question. The blower shop actually recomends the balancer vs. the hub for damping the harmonics. the second keyway is 180 opposite the stock one.

The hub Ihave is the same thickness as a balancer - it should not change the location of the bottom pulley. You will want a v belt pully for the alternator then the blower pulley. You can shim the upper pulley if they don't line up.

 

Ok, awesome! How much is a sfi balancer? Is it just rated sfi or is it a brand name?

Are 600cfm carbs going to limit my boost? Maybe a possible way to lower the boost?

So, I need a balancer and a flywheel from a 400 right?



So, I was thinking. My Rod is getting Blown and Stroked...... Who comes up with this stuff!!!!

 

B.D.S. has Romac balancers w/double keyway's for $337.00, carb size will not effect your boost and yes use a balancer and flexplate/flywheel for a 400. Also you might as well drive the water pump off the crank with the accessory pulley while you're at it. Just keep putting the Isky stuff in a pile w/the Edelbrock intake as you replace it piece by piece and sell it together when you're done.

 

"I can run a thicker head gasket to get the compression down right?"

No. Head gaskets are for making a seal between the block and heads, not adjusting the static compression ratio. You do that with the piston crown and combustion chamber, then set the piston deck height to add to the gasket thickness to make the proper squish (piston deck height plus gasket thickness). Shoot for 0.035" to 0.045".

There are two ways that I know of to keep the mixture homogenized and prevent detonation on pump gas. One is with a swirl head, the other is with squish. If you use production heads that have little or no swirl, then you had better be settin' the squish.

Don't ever use thicker head gaskets to lower static compression ratio. The motor will detonate worse with the lower static compression ratio and thick gasket than it did with the higher static compression ratio and thinner gasket.