HEMI Tech- PISTONS! rods and related

Ill join in on this one with A question or 2, i have a 331 that im building, its gonna be blown, and i need to buy some pistons, im thinking around 8-1 and not a ton of boost, itll be a motor i can beat on a little but im not gonna all out race it, what is the stock compression ratio that an aftermarket piston will have?

and, also, what does putting the pontiac rod into the hemi require? just the big end being honed out .004? how about the small end, i know the stroke is the same.

JEFF

 

Stock replacement pistons are 8.5 An old catalog from Bob walker says to resize big end of rod to 400 Pontiac size & use 400 bearings.

 

Not sure that you want to use stock replacement cast pistons...so when you order your forgings, you will specify what compressionn ratio you want and you can also specify the Poncho wrist pin size.
You must also verify that the Ponch rod is the proper width at the journal so you can control oil flow/pressure.


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of course im gonna run forged pistons, its a blower motor, i still may run my stock rods after i recondition them too, but not sure.

JEFF

 

I see this thread's a few months old, but I have acquired a '55 331 Hemi (C300) block main caps, heads and rockers, all appear to have been reconditioned and the block has been cross-hatched marked. I will be having a shop check for cracks and such and to check the cylinder and line bores. I have the original 2 x 4 manifold as well, and will probably run progressive linkage (I will have to find the carbs, probably go with new Edelbrocks and have the manifold drilled or adapters used).

It's going in my '50 Hudson Coupe, a street machine and daily driver. I am disabled and don't drive lots of miles anyway. I was thinking of upping the compression a bit and a little hotter cam.

I would like some recommendations on some good set-ups for me. Oh, a blower and all that would be cool and great to look at, but there is none of that kind of cash sitting in my pockets or liable to fall into them anytime soon. I am also trying to finish my son's '56 Dodge project (no, it's got the Poly! LOL).

Thanks,

Jay

 

Jay, there is a whole "root thread" that has an Index to all the Hemi Tech stuff. The link is in my signature line. Just click on the link. There is a section for each.

I would really like to see you start a new thread on your engine, if you haven't already. The C300's are just awesome!

 

OK boys and girls, I finally have the new forged pistons
(276 DeSoto) in hand and they are nice! http://www.racetecpistons.com/rt_athome.htm
Here are a couple of pics:


sorry about the glare on top...




although it is difficult (impossible?) to see (above),
each piston has ID info etched into the area under the pin boss.


and there is no mistake who the manufacturer is...

One last pic; Wrist pins in the box, each pin wrapped in a plastic sleeve.
The level of shipping protection is the best I have seen.



If anyone has a forged piston need (any make/model) I will be happy to call the manufacturer, check on your application, and offer a quote.

As with custom pistons, making changes is pretty easy. These 276 pieces
are set up for a slightly longer rod (6.125 vs 6.067) and a smallish 0.927 x 2.5" pin. These pistons are 10:1.

Sorry in advance for not having a web site so you can 'look around'...


Gary
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Here you go for the Auto Tec Web Site... http://www.racetecpistons.com/rt_athome.htm

 

Thanks Tony, somehow that little bit of info got left out...edit, edit edit...

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what's a set of 30 over 276 pistons worth?

 

What about 291 prices also.

Tommy

 

Todays 'good guy' price for pistons shown (276-291) is $675, with the 0.927 x 2.5 pin. Pin prices vary depending on size. By using a very common pin like the .927 some money can saved, however, the stock rods will then need to be bushed.
PM with exact needs so I can offer firm quotes.

Thanks

Gary

 

You cannot find a better piston at any price than those made at Wayne Brook's Racetec/Autotech mfg.,they are on the leading edge of piston technology

 

They look beautiful!!!
Must be good quality as well.
What about the pins,,what pin is a .927?

Tommy

 

Any info on a Jahn's 1108C piston for the 354?

 

Have a recollection of hearing that Olds 455 rod bolts, with a little clearancing, would fit & were cheaper than hemi specific bolts. Any thoughts on it?

 

Could be...we have always just used the A-LA or B-RB rod bolts depending on application.

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Pontiac 400 rods are the ones to use for 354.

 

What is the difference between "forged" pistons and "drop forged" pistons? I was looking at 331 specs and they said the stock pistons were drop forged. Is this another way of saying "cast"? I am seriously thinking of going the street blower system for my '55 C300 331 and read that you should use forged pistons for a blower set-up less than 12psi boost. I was wondering if I was going to use 7-10psi boost (and I don't know yet what is best for mine) would stock drop forged pistons be okay, or should I just go with forged pistons purchased aftermarket?

This is a confusing topic with so many opinions on what to use, it will take me some time to figure out all the right pieces of the puzzle for me. But I'm working on it.

 

There are a number of ways to forge something however, casting is not one of them. Stock 331 pistons are cast, NOT drop forged...

 

...have never heard of pistons being 'drop-forged'...oem early Hemi stuff is/was cast...

Not so much these days, but in years past we had customers on budgets that 'required' them to use cast slugs in street blower packages. Not recommended then, not recommended now, but, if the boost is kept below 6lbs and you are not hammering on the thing it will live a long time.
The obvious question is simple...is the $300-$400 'savings' (cast vs forged) on a $6000-$10,000 engine, really a good deal?

As for con rods, if you feel a need for a better rod than the oem then look through the various aftermarket catalogues. The prices aren't terrible on some brands and with a custom piston you can move the pin around to accomodate a longer rod and even offset grind the journal to help out.

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Gary, I agree that its not worth a small dollar savings if they are not the right part.

Dyer's website recommends press fit pins up to 12lbs boost and full floating on 12lbs and higher. Aren't the original 331 pins full floating anyway? Since I will probably be going aftermarket pistons anyway, should I be looking at full floating or press fit pins? Or are aftermarket pistons usually already made one way?

On the rods then, if someone was going to go 6-10lbs boost, then original rods are not good then? Dyer's website recommends that "Factory High Performance Steel Rods" are recommended for most blower applications. What are "factory high performance steel rods?" Are the rods in the C300 331 (or the other 331's for that matter) of this type? If so, then a stock set of 331 rods should work for up to 7-10lbs boost? If stock is not good enough, are aftermarket rods better than those Pontiac (I think) rods I read about somewhere around here?

Also, I read some posts where guys are talking about buying "scat" or "cat" items. What do these references mean? Geez, I'm such a newbie!

I guess what I am asking is what is a good rod for up to 10lbs boost? I am not made out of cash, but I also don't want to buy crap that scatters the first time I put some weight on the pedal. I assume I am looking at forged steel rods anyway. I am going to drive this car alot and would like to take it down the strip (purely for fun, no competitions) once in awhile (I'm hoping this ol' dog can still learn how to).

I am still trying to figure out the right boost number (but suggestions will be taken and appreciated), its seems a lot of info needs to be figured out at the same time, it makes my head hurt. This will be my first time building a blower motor. I have lots of time to plan ahead, so that is a good thing.

Jay

 

Doc Fromader had a year long street blower 392 build series in StreetRodder back in the 90s. Don't know if it's available on line.

 

I checked out his website, but couldn't find it listed in the archives.

 

Jay, here are my thoughts, and of course they are 'slightly' biased.

The biggest issue for the piston and rod is the need to stop and reverse direction in a very short period of time. When using a heavy piston, stock or aftermarket, the crank and rod will want to accelerate faster than the piston, since being fat and lazy it just wants to stay where it is. Although this action happens in every engine on every revolution, the damage seems to be more prevalent on pressurized engines. The result is that the rod will be pulled in half. This is also why, at least back in the old days, aluminum rods in race engines usually found a second career as clock stands...the big end does not stay round.
If you use a high quality forged piston (and they will all have floating pins) it will naturally be pretty light and not tend to induce the same stresses as does the stock casting. However, a stock casting even as heavy as they are, with rpms in the 3-4k range, may not produce as much stress in the rod as a hot rod assembly at the drags. If you are going to make over 10lbs boost then I would call it a serious package and plan accordingly.
The stock 331-354 rod is adequate for 95% of the hot street packages, (and I sincerely doubt the Poncho rod will offer any real improvements compared to the costs) but with a blower I would be looking for a bit stronger rod. The Scat and Cat brands, along with the old timers like Crower, Oliver, Cunningham, et al, offer plenty of insurance, but as you shop you will find plenty of variation in price, and no real way to define 'why'. Additionally, as you look through the catalogues, you will not find alot of rods with the 2.25' journal or with the 1.094" pin so you will need to consider the rod and piston together when looking for either.
You can trim the journal dia, you can change to a smaller pin (highly recommended, even with a stock rod), you can move the pin up/down to work with a particular rod, the thing to watch out for is the width of the rod big end since this controls oil flow.
The stock rod is not bad, but it may be on the edge if you plan some ¼ mile work.

.

 

Thanks much for the tips Gary, I know we'll be talking more about this as time goes on. Thanks for the "Scat" and "Cat" references. I saw these mentioned many times and didn't know what they were, now I know they are "brand names."

I don't foresee going over 10lbs boost, building a lower boost motor will cost enough. I'm still trying to find my way around that question. Seems like trying to answer 10 questions at the same time, but all the answers depend on the other answers, like a circular equation! lol

I think I know where I'm going with the pistons, we'll talk about that later. Looks like its aftermarket forged steel rods, I'm just going to have to shop around and try and find some deals. I will most likely have more questions about rods when I find some and how to match the correct pistons with them, hope you don't mind me tapping your brain some more.

Wish I could sell my S10 quicker, I could use the cash! Market for used vehicles is pretty bad out here now.

Jay

 

You wonder how some names are chose, scat is a polite name for animal shit.

 

Bwawahahaha


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lmao!!!!

 

I have a 341 Desoto that is missing the pistons and rods, with custom pistons, what OE rod can I use?