Technical Hemi crossover for blower application (From idea to production)

Guys, no matter what gets made shrinkage on a pattern is always an issue. When any material is heated up, it expands a certain amount, and when something is cooled it shrinks. Think of your exhaust system and the noise it makes after it gets shut down. Who has ever stuck a sleeve in a pizza oven to aid in a press fit? You get the picture.

Liquid metal is no different, each has a different set of characteristics and expansion rates. For aluminum, a very good working number for shrink (shrink rate) is 5/32 of an inch per foot. As a decimal that is .15625. To get this down to something more usable, we divide by 12 to get .01302083. The last digit 3 is repeating. Now we're dealing in shrink per 1 inch. Add 1 to this in your scientific calculator, and store this number in memory. (1.013020833333...)

Now if you're working with a blueprint, you can enter every number into your calculator to multiply by this shrink factor and get the dimension adjusted for shrink. If you don't have a print, just use your raw numbers you measured off an actual part. Use rounding practices to 4 places.

If you needed to have a cast aluminum block that was 3" x 4" x 2" and you added shrink onto each of these dimensions, you would end up needing a pattern that measured 3.0391" x 4.0521" x 2.026". A pattern has draft, which allows it to be removed from the sand mold. Unless otherwise noted on a blueprint, draft always adds stock. Then, depending on what the part is, there may be machining stock added additionally to ensure that a rough casting can clean up to the desired specifications.

As you can see, smaller parts are more forgiving, but shrink doesn't go away.

 

That is a thought, so you would be able to use a 354 intake on a 331?

 

35 Dodge Hot Rod, thanks for the actual numbers. That will be helpful. The thing that I was getting at is with a connector hose the length wise shrink was not as critical to make the part land perfect on the head's. It also will fix any problem with the difference in expansion rates of aluminum and cast iron during the heat cycles of running the engine.

 

You've got a good plan going now, I think it makes sense.

 

Yes.
That's the Short answer to your question,
However that's not the point I was making.


Below are 2 different 331 engines and 2 different was to get around the lack of water outlets.
First is the blue one with truck heads. He's running a 2x1 factory manifold with adapters for 2bbl carbs. That manifold sucks and choked down 2bbls isn't going to run really great, however he needs that thermostat housing. This guy could run any other hemi intake manifold with and your water crossover & adapters.


This guys has a 331 with a way better designed after market intake manifold , but he needed to go with a remote mount thermostat housing and a hokey bracket.



The blue guy is going for simplicity, but still looking for performance, why else bigger carbs.
The copper guy is going for performance and got a thermostat with a compromise.
There's no other way to do this. It's either a junk factory manifold, a rare and stupid expensive intake or some sort of BS remote thermostat housing. Check my earlier post to see three more examples how Bass did it and the Chrysler engineers did it with the 331.



You can buy these all day long, they fit the 331 but there's no provision for water

 

Thanks, I try to think of everything. I am thinking that I could still cast them as one piece for ease of holding the parts for machining. Then where the hose goes on the cast in hose nipples just cut it in half after machining. At this point what are your opinions on where to put the bypass hole or holes. If it is kept in the stock location then it works with stock water pumps and can be made to fit with the Chevy conversion pump. I can also add bosses that can be drilled and tapped for other nipples. Thoughts on this? If this is done right it will work with almost all applications and that's a good thing in my book.

 

So that is a separate issue that can be addressed with machining the heads and installation of adapters. As long as it can be done so that it matches stock water crossover location or if I make the two piece unit then it doesn't matter about the exact location. Correct?

 

This is the factory manifold for 1951,52,53 - 331 some 1954 331 if it had a 2bbl. that's it.
Who is going to run this thing ? it weights 50 lbs too. It has the T STAT THOUGH.

This is a 1954 (one year only) 331 intake. It's the only one ever with a 4bbl and t stat.

Then Here's the 1955 331 the 1956 354 and the 57-58 392 intake.
It remained basically the same. No T stat because in 1955 Chrysler put the water ports in the heads.


Ever wonder why the 392 is 4-5 times the money than a 331?
Well there are 61 cubic inches but that's not quite an equitable transference, right?
How about there's no way to run a decent manifold for performance with out some ass ache getting water out? Just grab the 392 and you get more cubes, EASY manifold upgrade and EASY water. Easy sells more than sex and the demand for 392 easy drives the price up.

 

if I make the two piece unit then it doesn't matter about the exact location. Correct?

Bingo !!!

Your product will be applicable to every single early hemi reguardless of squat and easy. If the machinist of off a schooch it won't matter.

 

It is looking like if we can deal with the water then it opens up numerous possibilities.

 

Now for the bypass location/locations.

 

I stopped by the machine shop that will be doing them to go over how to clamp them. The offset from head to head is 5/8". Out of all the combinations that can be done it seems that the least likely would be 392 heads on the smaller engine. I could be wrong but it would require that the intake manifold would be narrowed along with the crossover being moved in and down.

 

Let those people buy a u-fab intake, and the ugly crossover from Hot Heads.

 

As it stands I will make the crossover two piece with a connector hose in it. It will have provision for the bypass and the temp sender on the passenger side half. The other side will have the thermostat. I am thinking that the connector hose will be 1-1/2" and will be located in the driver's side of center. Any thoughts or opinions? My thinking is to cast it in one piece have it machined then cut it in two for the hose.

 

As long as it will mold okay, that sounds good.

 

I get closer to 7/8" offset.

 

All of my stuff is in different places from where I am right now, but hear me out. The cylinder head offset should be the width of one connecting rod. If I am not mistaken, the rods are .994 (354) and .995 (392).

I have my crossover waiting for me at work. I was out today when it arrived doin' hospitaly stuff.

I will clamp it down to a true surface, and measure it tomorrow.

 

Ok I will wait to hear what the offset is to make sure I don't make something that won't work.

 

Your are the winner, sir. I have a stock crossover bolted to the deck of the mill at work. I have measured it in three placed, bolted down in three placed on the deck, to rule out any sampling error.

Two different calipers, too.

The measurement of the offset, in each case is 0.875", fractional 7/8"

 

So we clamped it to the mill as well but had 1.5" block under it. The other side was .625". I was tired and not thinking last night. 1.5-.625=.875

 

No worries. More than one set of eyes is always helpful, especially when beginning a long series of tasks that would only amplify the error.

I have a decent-size pile of ooopsies. It can get expensive.

 

That's a brain fart !

I hang the oopsies on the wall, quite a few times they work about perfect someplace else

 

If different combos of heads on blocks have different offsets, it would be very easy to build the extra thickness needed into the backside of the pattern (one side). Then just machine off the unneeded for the thin version and leave it on the thick. Same thing with the bosses for the senders and bypasses. Unneeded ones can just sit there, or be machined smooth after casting.

 

How far over from center for the thermostat ?

 

Whatever is going to work the best. I have the cad drawing done for the water jet to have the flanges cut out. I can weld one up for test fitting, then just ship it whoever willing to test it with a blower.

 

From the grid, it would would appear that the far right edge of the machined surface for the water neck is dead center between the blot holes, give-or-take a little, on the PAW blower one. That seems like a good place.

 

Hi there, they originally had a temp sender unit in the rear threaded hole. When they run a Chev big block water pump, you have two run adaptor spacers (two) , one per side, so make allowances for this if connecting small water bypass, hose. The small water by pass hose is to circulate a small amount of water when motor cold and Thermostat closed, also if Thermostat seizes shut, so water will still flow through to pump, instead of blowing hose, or more likely a lens type frost plug, I made plates with two bolts to bolt over lens frost plug, as when engine is revved hard, these lens frost plugs are known to blow out. Also when changing water pumps, make sure pulley sizes are correct so water pump is not driven to fast, as water will circulate through engine too fast and not cool engine properly, and also pressure in block will get to high and blow those lens frost plugs out, my 392 blow a lens frost plug out , the frost plug under engine mount, hard to replace on side of road!!!! Hope this helps you out? Bretto

 

Or use these:


These lock in. These plugs are technically core plugs, for getting the casting sand out.

I have seen plenty of cracked blocks, with every single core plug still in-place, and intact.

If you are worried about freezing, there is a solution for that, and it has been around for a long time.

 

Hi

 

I had a PM from someone on here who really wants me to stay with the one piece unit as exact as I can make it to the PAW unit. So with that thinking in mind I can make a convertible pattern that has nipples and can be cut in half but also has cover pieces that makes the outside straight all the way through. A different core box would be needed as well. That would cover everything. Thoughts?