354 bore limit

Discussion of the 331-354-392 HEMIs.

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354 bore limit

Postby mrossbach » Tue Oct 18, 2011 7:36 am

Hello fellow hemi heads, I just burned up a rebuilt 354, crank went bad after 2,000 miles...just found out about the lack of zinc ect in oils now days.
Any ways, what is the limit for a 354 bore....4.0''?
If I can only go .060 what is the best cam?
A special regrind or.....
I have a 700r4, built for 500hp, dana 61 with 4.56 spool....
It is in a 1946 studebaker pick up.....tubed , 4 link, 30 x 15s on back, discs 4 wheels...
thanks Bob.....

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Re: 354 bore limit

Postby 392heminut » Tue Oct 18, 2011 8:12 am

A lot of folks have bored 354's to 4.0 and used stock sized 392 pistons. The only sure way to know how much you can bore a particular block is to have it sonic checked though.
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Re: 354 bore limit

Postby George » Tue Oct 18, 2011 9:44 am

With those gears sounds like you'll need a lot of C/R & a cam matched to it. If you go 4", the 392 pistons will be 1 point lower C/R than advertised. 10:1 in a 392 is only 9:1 in the 354 because of shorter stroke.

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Re: 354 bore limit

Postby mart » Tue Oct 18, 2011 1:10 pm

A 4-inch bore is *probably* safe, but as others here have already said, the only safe way to tell is to have the bores sonic checked first. It's not just core shift from when the block was new that you need to be concerned with, but also, on a 50-plus year-old engine block, there is probably a fair bit of rust and corrosion on the water-jacket side of the cylinders that could make the bores abnormally and also, unevenly thin.

About your oil problem and the lack of zinc in modern oils - usually the lack of zinc only affects flat tappet cams and lifters. I've never heard of it causing crank problems - unless maybe your cam and lifters got smeared first and then metal from them ending up getting into the the main and rod bearings and scoring the crank. If your cam and lifters don't look excessively worn, I'd look for some other oiling system or clearance problems before assuming straightaway that the crank problem was (just) caused by a lack of zinc in the oil.

On your rebuild, if you can afford it, due to the oil situation - and due the fairly radical nature of the rest of your build - ie - 4.56 gears etc. - I'd be definitely looking for a roller cam. Roller cams and lifters aren't affected by the lack of zinc in modern oils. A good guy to talk to, for either a roller or for a flat tappet cam for a 354 - either a regrind on an existing core, or a new one one a brand new blank - with either a custom or off-the shelf grind, is Donny Johansen at Contreras Cams. (See my previous post on this topic for contact information - viewtopic.php?p=14792#p14792)

About oil too. If you have to go with a flat tappet cam on your rebuild, you might want to try using Shell Rotella motor oil. Shell Rotella 15W-40 is formulated for use in heavy-duty turbo-diesels, and as far as I know, it still contains a generous amount of zinc additive.

Hope some of this helps. Good luck and keep us informed of your plans and progress getting you hemi up and running again! - mart

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Re: 354 bore limit

Postby mrossbach » Tue Oct 18, 2011 1:54 pm

sorry must have been the bad coffee today , the cam went out at 2,000 miles

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Re: 354 bore limit

Postby George » Wed Oct 19, 2011 10:41 am

Match the actual grind to your C/R, roller cam eliminates the zddp problem. If your block & heads haven't been milled/decked & you don't have adj vavle train you may be OK buying a new cam w/o the adj parts. If you want to run, or have adj. parts, then regrinding the cam can save some money.

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Re: 354 bore limit

Postby Matthyj » Thu Oct 20, 2011 8:03 pm

STP still is a very cheap form of zinc to add to oil, also your valvoline racing oil is loaded with zinc, I just got my new 354 cam from Iskenderian and it says the best oil with zinc they have found is Brad Penn oil (formerly Kendell oil) Brad Penn I have found is really, really inexpensive compared to others also generally under $5 per qt.
Also make sure when the motors broke in that the RPM's are over 2200 or so, don't let it idle at first for at least 20 minutes is what Isky says due to the oil on the tappetts is generally not pressured oil s at low rpm's its not getting much and thats when the parts are surfacing together. Best of luck Matthyj

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Re: 354 bore limit

Postby budmspeeco » Mon Feb 20, 2012 8:38 pm

To George ; The difference in the stroke does not determine the final compression, the compression distance of the pin center to the top of the piston does. I think the 392 has a longer distance, therefore the compression will be higher. The added amount of material to the top of the piston acts as a dome and squeezes the charge more, increasing the compression; swept volume divided by compressed volume, or something like that !!! More of my pennies worth. Since I have not measured either one, this is just another opinion based on here say. Buddy
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Re: 354 bore limit

Postby wayfarer » Tue Feb 21, 2012 12:06 pm

Swept volume determines the compression ratio. A longer stroke has more swept volume.
Assuming that the combustion chamber cc is constant, then it goes kinda like this:
A 354 has a swept volume of approximate 44.8 cubic inch or 734 cc. This is the volume of the cylinder. Imagine that you will squeeze this volume into a 110 cc chamber. For simplicity, I am ignoring the dome volume, and yes, the stock Hemi piston has dome volume even though it looks flat... so, 734 / 110 = 6.67:1 comp.
Now, a 392 has a swept volume of about 49 ci or 804 cc. 804 / 110 = 7.31:1 comp.
Simply, you are cramming in more stuff. In this very simplistic example the only change was the stroke.
The location of the wrist pin does not factor in.
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Re: 354 bore limit

Postby DavidBraley » Thu Feb 23, 2012 11:07 pm

Beautifully explained Gary!
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law

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