454 Pistons WAY Too Heavy!

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bigmike
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Re: 454 Pistons WAY Too Heavy!

Post by bigmike »

Many years ago my roommate worked at a automotive machine shop. Guy comes in with a 454 long block no harmonic balancer or flexplate, wanted it rebuilt for his truck were talking about 1971 or 1972 truck. He never said anything about going from a 402 to a 454. So they did a complete rebuild including boring and new pistons, cranked turned. Heads done ect. everything worked on. Guy comes and picked it up. About two months go by and 1000 - 1500 miles later. He is back with the long block talking about bad bearing knock and wanted a warranty claim. OK so they take it a part and the bearings are just hammered none of them actually spun but they are ugly. Not knowing what happened they rebuilt it again free of charge. Well about two months go by and 1000 - 1500 miles later. He's back with bad bearing knock and the long block again. Same drill they take it apart again the bearings are just hammered again. My roommate wanted to see the truck and transmission ect. So they go out to this guys place out of town in the shop by the truck is a 402 with no harmonic balancer or flexplate? Turned out he was using the 402 internal balanced harmonic balancer and flexplate on the 454 that need an external balanced harmonic balancer and flexplate. Truck guy had know idea about the balance issue. The 402 was stock in the truck. So there is a limit somewhere there on how far you can be out for even a stockesh 4800 RPM 454.
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Re: 454 Pistons WAY Too Heavy!

Post by Keith Morganstein »

I seem to spend plenty of time looking through the catalogs for piston/pin weights, and weighing the old stuff before buying the new. Sometimes there isn’t so much choice tho. Can you return or resell the pistons that you have?
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Re: 454 Pistons WAY Too Heavy!

Post by My427stang »

Not re balancing with new parts, you never really know, but I am not sure you know that it was balanced correctly with the last combo either, you just know the weight difference in parts

It could have been overbalanced and now you are as close as you were before. What if you calculated the bobweight you needed and just had the crank spun? It wouldn't cost that much and it would give you peace of mind

The other end of the spectrum is to match weights yourself with the parts you have and just run it. My WAG is it would do fine, but again, who knows where you are starting from
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Re: 454 Pistons WAY Too Heavy!

Post by Dave Koehler »

burbfixer wrote: Thu Aug 16, 2018 11:13 pm Thanks for the help!
I am shooting for 10:1 or a touch better on this one.
These are hypereutectic, not forged.
I experimented last night with a spare identical connecting rod as the ones in the engine, and they do have a big balance pad on the small end. Shaving it down as much as I'd care to lightened the rod by 30 grams.
What you said here bothers me.
1: How on earth did you get 8 rods in a set with thick balance pads? Not the norm.
2: Did you hang the rod so you measure only the small end or just weighing the rod as a single unit?
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Post by dwilliams »

burbfixer wrote: Wed Aug 15, 2018 8:44 pm5000-5200 rpm max ... 69 grams heavier ... re-balancing the crank is not an option.
Not an ideal situation, but Racer18 is right: bolt it together and drive it. You're dealing with, what, 2400 grams of bobweight? Not enough to make a noticeable difference.

One of the surprises when I bought a balancing machine was how far out the bobweight could be and still make no apparent difference when the engine was running.

I'd never let something like that go out in a customer's motor, but for my shop truck I wouldn't sweat it.
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Re: 454 Pistons WAY Too Heavy!

Post by pdq67 »

The only problem I had with my old junk301 that was made out of, well, junk parts and wasn't balanced was that it would throw a damper off every so often..

And it went to 7500 rpm MANY times!!

Warn out SJ early 327 block just ridge reamed and ball honed;
W/JCW, cast steel strutted 1/8"over-bore 283" pistons with the 1/2 round 1/8" tall dome on them like the 290hp and 315hp/stock 283 piston=s have, (all of $39.95/set of eight). I think I moved a piston over on one rod and stuck a .015" feeler gauge down it to check for piston/cylinder clearance too??);
'55, 265" truck stock forged engine crank;
'55 heads, (that I ground hell out of), with no sparkplug water troughs;
Stock .020" thick steel shim head gaskets;
Unknown thicker 283 rods vs the skinny stock '55, 265" rods;
A coffee canned liftered great old -097 Little Duntov cam;
My 350's stock Q-Jet carb and intake; AND
My 350's stock cast-iron exhaust manifolds.

The last time it throwed the balancer, I went to my Buddy's scrap yard and used a RR track jack bar and knocked one off an old engine and put it on and went on down the road!!

Oh, and btw, it had three harmonics that it went through up to 7.500 rpm so by just listening to it rpm up or down, I could tell my rpms!!

Sure it knocked and rattled and used oil, but dam the little bugger would rpm!!

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Re: 454 Pistons WAY Too Heavy!

Post by cgarb »

A die grinder will run 25,000rpm....but wouldn't power a car very fast.
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Re: 454 Pistons WAY Too Heavy!

Post by Dave Koehler »

It's ok. Everything I had 40 yrs ago runs better today, don't ya know.
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Post by GerryP »

dwilliams wrote: Thu Aug 23, 2018 12:32 pm ...You're dealing with, what, 2400 grams of bobweight? Not enough to make a noticeable difference.

One of the surprises when I bought a balancing machine was how far out the bobweight could be and still make no apparent difference when the engine was running.

I'd never let something like that go out in a customer's motor, but for my shop truck I wouldn't sweat it.
I'm not an expert in any of this and I'm not disputing your experience. My curiosity here is how can you have five pounds of mass being slung around and unaccounted for in the crankshaft balance? I understand the difference between reciprocating and rotating mass, but that just seems like a lot of mass. And, when I think about it, I'd be concerned if my machine shop said they could balance the crank plus or minus five pounds.
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Re: 454 Pistons WAY Too Heavy!

Post by pdq67 »

cgarb wrote: Thu Aug 23, 2018 5:18 pm A die grinder will run 25,000rpm....but wouldn't power a car very fast.
My old die grinder does 30,000 rpm and every time I turn it on, it scares the shit out of me!

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Re: 454 Pistons WAY Too Heavy!

Post by burbfixer »

Sorry guys, I didn't realize this had gone to page 2!
I could calculate the bobweight & just take the crank in to the machinist, yes, but it would almost for sure mean heavy metal to balance it which gets pricey.
I would rather just weight match the parts and try to get as close to the factory weights and balance as I can.
I appreciate the suggestion about taking weight from the big end too, hadn't thought that through enough. It's a target bobweight I'm after, but I'd been thinking I had to find 69 grams of reciprocating weight to remove. Not possible, really.
I weighed one complete spare rod before lightening the small end, then weighed it again after. It's a junk rod, so I didn't care about it. I cut off the knob with my cutoff wheel, then shaped it on my bench grinder - rough work, but it was actually a touch over 30g lighter after.
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Re: 454 Pistons WAY Too Heavy!

Post by burbfixer »

Thanks again everyone for your input.
There seems to be a wide range of opinions. But that's why it's fun!
I'd rather not give up on these pistons just yet.
There would be a standard bobweight used by the factory when they did the nominal balance job on the crank.
Whatever that bobweight is, I would be ok with matching this combo to it. In my job, I probably drove 30 or 40 Vortec 454 trucks in 96-99 and I don't ever remember thinking they vibrated or felt imbalanced. GM also trusted it enough to warranty them.

Now I just need to know what bobweight might have been used by Tonawanda when they made these engines. Anyone?
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Re: 454 Pistons WAY Too Heavy!

Post by Racer18 »

Years ago we checked the balance on several stock engines, as they came from the factory. Some were way off, but had been in service for years without any known ill effects. Believe it or not, of all the externally balance engines, 454 and 400 chevys were the worst! We also had a 440 chrysler that had 50 grams variation in rod weights that had over 150,000 miles on it, and looked like new inside. Don’t sweat it!
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Re: 454 Pistons WAY Too Heavy!

Post by pdq67 »

I had Lunati, "Detroit Balance", my 496 only because I made it to be a a great big, "Tow-Truck", motor is all..

CC 282S solid cam so I set it at 5500 rpm max power.

Stock, "thumb rods"...

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Re: 454 Pistons WAY Too Heavy!

Post by pdq67 »

Who still sell's, "Badger", pistons??

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