Ok, here's the deal: I am putting an 89 5.7 TPI motor into my 84 Camaro. I'm doing the whole swap for my carbeurated engine. My dad and I will be rebuilding this motor before we install it.
My immediate mods during the rebuild are: complete exhaust system (w/headers), new cam, adjustible fuel pressure regulator, JET Stage 2 ECM, and a low-temp thermostat.
Possible future mods:
porting of intake and/or heads, new ignition system

My question is: Do I need to replace the pistons or rods that are in the motor right now? It has 88,000 miles on it. Also, how much power can the stock ones handle? With my immediate mods, do you guys have any idea as to what my horsepower/torque might be? Any help would be much appreciated. Thanks.

 

X84,

Stock cast rods are more susceptable to RPM failure than from higher power levels at lower RPM.

As long as you are freshening the engine, you should at least remove the pistons to inspect them, the rods, and pins. That could answer your question for you. If the skirts show only normal hazing instead of heavy scuffing, if the pin bosses are not elongated, if the ring lands are not worn open, use your original pistons. If the cylinder bores are straight and truly cylindrical, you shouldn't have to overbore to clean them up. If you have to bore, new pistons are no longer a question.

If you are concerned about power levels, properly reworked stock cast rods are rumored to tolerate 425 HP without failing. Stock Powdered metal rods are supposed to hold their own at 450 HP, and anything beyond that should definitely indicate better con rods.

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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

Hey Vader SBC rods are forged. I just wanted to correct you on that. The rest of what you said is true. But for as cheap as you can get as set of stock pistons I would go ahead and get them. And it's not that expensive to rebuild a set of rods.

 

Snow, Vader is right. Typical sbc production rods are nearly all cast. Most HP rods were always forged, ie the obsolete "pink" forged sbc rods. It's only been the last couple of years that GM has started introducing the powdered metallurgy rods for crate motors (ZZ4 and to replace the "pink" rods) & such. My 92 L98 definately had cast rods because you could see the casting flash marks. I bought a pair of the GM pm rods for my 383, but decided they were marginal for the power, so I went with some forged rods.


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KevinP92Z
92 Z28 383 SLP cam,SLP headers,SLP 2ontheLeft,Trick Flow TW heads & pistons,Edelbrock base,Accel SuperRam,52mmTB,Scat Crank & forged ConnRods,MSD 6AL,SLP convertor,Baer 13/12" Track,Moser axles,Hotchkis,Genuine GM 3.42s,SLP HD Torsen,17x9" chrome SS rims
96T/A w/SLP Ram Air,SLP 2ontheLeft, Bilsteins, Baer, Hotchkis, Genuine GM, Torsen
76 4X4 Blazer 400TPI project

[This message has been edited by KevinP92Z (edited November 22, 2000).]

 

Guys, I believe Snow may be right. All SBC rods are forged. Some are better than others in their quality but they are all forged.

Now that may have changed in the 80s without me knowing about it (or ever noticing). But all my usual go-to information sources say they are all forged. And of the few times that I compared older 60s rods to 80s and 90s rods they sure looked the same to me- forging parting line and all.

When did CHevy start putting cast rods in their small blocks?

 

One small caveat if you haven't already run into it: your 84 flex plate or flywheel will be incompatible with the later motor. You'll need the late-style one of those.

I would approximately echo Vader's advice about the stock components. The main cause of stress on the rods is RPM, and on the pistons, it's combustion pressure and heat. In a N/A motor with a TPI you're not going to bump into any limits from either of those sources.

It would make a whole lot more sense to do any head porting while the motor is out; it's about 1000 times easier to swap heads on a motor on the stand than in the chassis. Don't put it off.

I would suggest a Comp 262HR cam for it. A set of 1418 rockers would be good to, although they may require that you have the spring pockets in the heads machined out. Comp may have some conical valve springs available to solve that problem.

My guess would be 270 HP and 350 ft-lbs at the crank, with mild head porting and other mods as described.

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"So many Mustangs, so little time..."

 

If you do decide to pull the pistons to inspect for wear, I would lightly hone the cylinder walls and install new rings.