Stroking the 392?

Discussion of the 331-354-392 HEMIs.

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Re: Stroking the 392?

Postby wayfarer » Tue Apr 21, 2009 2:31 pm

[b]Cheap Hemi[/b] is the ultimate oxymoron :lol: :lol:
Our charges for sonic testing vary with the number of 'reads' in each hole and whether or not a printout is needed; its all labour. The $85 quote you have sounds very fair. Be sure to ask around, any shop doing high performance or diesel work should have the test equipment.

Sleeves = dollars, we get $100 per hole. It is not often practical to install 8 unless your block is very special. A bare 392 block can easily bring $800 these days so it is a trade off. If properly installed, neither you nor the block will ever see any operational issues or signs of them, whether wet or dry.
Personally, I would not use any block filler in a street driven block; I want the most cooling help I can get. I know that others have partially filled their blocks and swear they have no ill effects, but I'll choose the conservative route.
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Re: Stroking the 392?

Postby polyspheric » Wed Apr 22, 2009 10:37 am

.
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Re: Stroking the 392?

Postby wayfarer » Wed Apr 22, 2009 4:22 pm

We will continue to disagree. Pick a new fight with someone else.
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Re: Stroking the 392?

Postby polyspheric » Thu Apr 23, 2009 6:02 pm

.
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Re: Stroking the 392?

Postby wayfarer » Thu Apr 23, 2009 8:50 pm

.....[i]to the same consideration as mine[/i].....

You appear to be an arrogant pompus butt. You are, it seems, unable or unwilling to post your theorem for everyone to read and discuss, so I'm done and the soap box is yours. Use it wisely.
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Re: Stroking the 392?

Postby polyspheric » Thu Apr 23, 2009 9:51 pm

My interest in teaching 10th grade math class has expired.
Google: "plane geometry" for a remedial.
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Re: Stroking the 392?

Postby NE57 » Sat Apr 25, 2009 12:10 pm

OK about rods again. I picked up a 440 6pak rod. I'll post the comparitive pics for general info.

>" I do not recommend using the stock 392 rod. They have a fairly small cross section under the pin and they will pull apart at that point."<

Yup, the difference is quite clear. I measured that area under the pin boss and its an amazing 15/32" wider in the 440 rod, and about .070" thicker in the other dimension. The overall wider beam 'may' mean a little more clearance grinding at the cylinder bottoms, depending on how the geometry really is. I'll do a mockup with the 440 rod and stock crank/piston in the block, just to see how much room I have now, which will suggest how to proceed.

I know some of you guys can do this with your eyes closed practically. I just need to satisfy my self before I start grinding up a valuable block and popping for expensive machine work and custom parts.

One other thing...bearings. I know the 440 rod would need to be narrowed at the big end, which bearings would you use, 392 or cut down the 440 bearing width?

OK one MORE thing. The 440 rod is noticeably heavier. Given a longer stroke how does this affect crank balance?
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Re: Stroking the 392?

Postby wayfarer » Thu May 07, 2009 9:17 am

Sorry for the 'down time'...I am not accustomed to personal attacks in a public forum and needed a break. I am surprised that no one has stepped up to help you in the last 2-weeks...I'll attempt to finish what is in front of us.
The 6-pak rod is very heavy, I do not recommend its use unless a blower is part of the equation. The standard 440 rod is quite capable of 500 hp and aftermarket pieces considerably more. You should not need to do any block work in order to use the std 440 rod or any of the 2.2 rods on a stock stroke.
Our preference for bearings is to use the the uncut rod and off-the-shelf 440 bearings. The 440 is about 0.020" fatter than the 392 and we will just bump the (crank grinding) stone a bit when we rework the journal. As with building a stroker, this allows us to precisely set the side clearance. If you have expectations of 500hp or more then you need to weld up the rolled fillets and grind in a proper radius. If the crank is worn then this is an opportunity to return to std diameter. The difference in the bearing prices and the additional cost of grinding the rods will nearly pay for the journal work.
As stated, the 6-pak rod is very heavy and the std 440 rod is no lite-weight, so balancing the crank is required, but you would be doing this anyway, right?
Look for a PM.
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Re: Stroking the 392?

Postby NE57 » Thu May 07, 2009 11:31 am

Thanks Wayfarer. I was concerned about the sixpack rod's weight in that I thought perhaps mallory metal might be needed to balance the crank, yes it'll be balanced in any case, but I heard mallory is expensive. And lighter reciprocating weight is a good thing, no? In the meantime though, I contacted Don Garlits on the question of rods, I was surprised to get a response, just because I figured he would be a very busy guy, but he was nice and had this to say...he used stock rods in Swamp Rat I for years. 750 Hp @ 6500 rpm 50 degrees lead, 100% nitro. He thought my "gas street motor would not be so badly abused". Isn't that such a Southern way to phrase it?

So, I have to make the decision of rebuilt stock rods or 440 rods as you suggest, or steel h beams. Decisions decisions! The more I consider the whole package I'm beginning to wonder if I should step down my power goal, because I DO want it to be streetable, and frankly, affordable. Its cool to think, "I'll build it to the max" but when you start adding up the budget, it makes you think twice. Common sense tells me to put the money in the bottom end, but how much is enough is the question I'm wrestling with right now.

Earlier you said something about stock rods breaking under the wrist pin. Under what conditions did this happen?

Thanks again.
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Re: Stroking the 392?

Postby wayfarer » Thu May 07, 2009 11:45 am

The rod pulled apart somewhere around 7000 rpm. It was a 3/8 stroker running 11:1 comp. Of course it could have been a defect in the rod, not just because it was 'skinny'. The advantage Mr Garlits had is that parts got changed fairly regular as where you will probably want to avoid scheduled teardowns. Back to that 'conservative' position.
And Mallory metal is a bit expensive, but we lack viable alternatives.
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Re: Stroking the 392?

Postby NE57 » Fri May 08, 2009 11:08 am

Well, nice to know a 3/8s stroker will still turn some rpms. I had read some things that suggested otherwise. Conservative is wise. If I hold it to 5500 that should allow some parts safety and lower cost overall.

Its not just 'speed cost money, how fast do you wanna go'. Its also how often do you wanna do it? I don't think I want to sacrifice durability for the occasional wild butt thrill. Just a plain thrill is sufficient at my age.
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Re: Stroking the 392?

Postby dan miller » Wed May 13, 2009 7:54 pm

As I previously have mentioned, Eagle rods appear to be an inexpensive alternative. Danny
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Re: Stroking the 392?

Postby budmspeeco » Mon Jun 01, 2009 9:08 am

After you consider the cost of the 440 rods, the trouble and expense of preparing them for use, trusting the work is done correctly, the Mallory Metal thing adding all this weight, the welding/grinding crank work, why not contact Crower or Manley, to name two, and just order the set you need? They will be brand new, have the exact length, width, pin size/location, rod/stroke ratio, etc. for your parameters. (As an aside, you could just offset grind your crank for a big block rod and get enough stroke the clearance issues will be minor if at all. Without doing the exact math I think you could easily get a 1/4 to 5/16th, maybe 3/8th arm for minimal expense). They will probably even be lighter . Rod bolt to cam issues disappear. Bearing options would give you a less expensive yet bigger selection from which to choose. New bolts are included and not another "expense". Strength will certainly not be a problem. I will stick the old neck out and say you will come out cheaper than using all the discussed alternatives so far. Surprised no one said it after the piston issue came up and "Just order what you need" popped out. And they will be overkill for any HP combination you can muster in a streetable engine. AND it keeps a cap on the hypertension level as well as saving a jillion brain cells from being burned up just thinking all of the things that could/ would/ probably will go wrong and ruin the whole thing during its maiden voyage on your first cruise night !!! Buddy An outside of the question comment. I REALLY like the way the QEC guy thinks. I have tried to locate him before. Will he PM me for contact info or just post it here for all to see?
'48 anglia
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Re: Stroking the 392?

Postby NE57 » Wed Dec 30, 2009 12:43 pm

dan miller wrote:A nifty way to accomplish this is to offset grind the crank to BBC (2.200") and utilize Eagle 7.100" rods with a set of aftermarket pistons. We utilize Ross, and a call to Pat O'Neil will get you all squared away. Ross makes a beautiful and very light piston for this application. You'll end up having around $1500 in a killer rotating assembly that you can lean on as hard as you want, without any fear whatsoever.

Danny


Do the eagle rods need any mods? Are they the same journal width as 392? I see the pins are slightly different diameters. Should the pistons be fitted for BBC pins or is it better to rebush the rods for 392 pins?

I see on Eagle's website they have 3 different part numbers for the BBC 7.100 rods. Any advice there?

Am I right in figuring that the stroke will increase by the difference in journal sizes? The crank has never been ground before although there is some light scoring that might limit the effective offset, but minimally I'd guess. So that 2.375-.220=.175 3.90+.175=4.075(new stroke) If that's right, with a 4.060 bore new displacement would be about 422 CI. Did I do the math right?

It seems to me that there are 3 benefits from doing this. Stronger rod, longer rod, more displacement. If the rods don't need extensive reworking, I should consider this before I order custom pistons(the long awaited money is starting to burn a hole in my pocket!). Hell, the crank needs grinding anyway, need new pistons anyway...
I've ruled out a welded stroker but offset stroking is looking better and better to me.

Many thanks for advice.
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Re: Stroking the 392?

Postby wayfarer » Wed Dec 30, 2009 2:21 pm

Danny and 'bud' make good points about aftermarket rods. High strength, light weight, and the prices have certainly moderated over the last few years.
As you noted, in addition to wrist pin and journal diameters it is imperative to know the rod width. If the rod is skinny then you will need to weld up the journals and refinish the width. As for rod length, you need to have some idea of who's piston you want to use. As the rod length increases the pin moves up closer to the ring groove, add in a bit of additional stroke and some mfgrs will be better able to accomodate this than others due to the blank they start with.
Also keep in mind that the crank mods, rod selection and piston design should be planned together. Some juggling will be needed to fit everything into the space provided.
With regards to wrist pins, we have started using the ever-so-common .927" x 2.5" simply because our new piston supplier makes them available at a very low cost. Although some rods require special pin bushings we have not found any operational issues. The benefit is a considerable weight savings.

For your offset stroke: back in the old days we used alot of 440 rods, and to make up for the shorter length (6.96 vs 6.75), 0.21", we welded up the crank and used off-the-shelf pistons in the stock location. (a FM pin bushing #4-67314Y was required) and we found the displacement to be 411 at 4.0 bore, which would be about 420 at 060 so you are in the ball park.
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Re: Stroking the 392?

Postby NE57 » Sat Jan 02, 2010 11:15 am

I found out that the Chevy rod is the same width(.994") as the 392(assuming the online info is correct, I'd certainly double check in the flesh). So that leaves the pin and yes, can the piston maker squeeze it all in. Between the .175 stroke increase(.0875 being the actual radial increase) and the .149 longer rod that should put the pin .2365 further up the hole,. That's less than a stock rod with a 1/2 arm(not sure if that combo is done). Maybe OK as far as ring location and the minor diff in pin size. At least in theory and IF I figured it right.

Additional question... I would assume in offset grinding I'll lose the rolled fillet. Should this be a major concern? Its not a racing application per se, but I'd maybe go to the track now and then.

Thanks
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Re: Stroking the 392?

Postby oldngood » Tue Jan 05, 2010 8:08 am

I would not put EAGLE RODS in an early Hemi- Eagle forgings and castings are made in CHINA. I seriously doubt a pump gas early Hemi build would need anything more than the stock Chrysler rod, it will easily handle 500HP and is a quality made in USA forging with high nickel content.

Another option is the high quality GM Pontiac SUPER DUTY 455 rods- they are 6.625" and forged, even stronger than the Chrysler stock rod. They were built to live in the long 4.21" stroke Pontiac motors, so they will definitely live in a shorter stroke early Hemi.
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Re: Stroking the 392?

Postby wayfarer » Tue Jan 05, 2010 2:08 pm

As noted, some rods are 'off-shore' products. The buyer must decide where to invest his money. There are many USA made rods available, but perhaps not at the same price point.
Regarding the rolled fillet; we often weld up and regrind the journal with a generous radius as this makes an overall stronger package, so losing it with an offset grind is not critical.
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Re: Stroking the 392?

Postby TrWaters » Tue Jan 05, 2010 7:07 pm

With an offset grind to 2.2 journal, you will have a radius on the lower half of the journal and rolled left on the top. Unless you decide not to take the full offset. For your application, its not going to hurt anything to have half and half.
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