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At what point to replace pistons?

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4thgenceli

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Been looking around and have decided upon a machine shop to do the block/head work for me. Thing I'm not sure on though is how far to take the build --

Just ordered a full engine gasket kit. I'll pull the intake, heads, oil pan and all that fun stuff here this weekend to get it to the shop next week. They'll be rebuilding the heads, turning the crank, getting the block cleaned up (possibly overboring to allow for new pistons/rings).

Besides the obvious cracked piston -- are there any other considerations to take into thought about just replacing all pistons & rods at once? I do not know the status of the pistons or cylinders at this time until I pull everything out. I've heard 30 over is a common 'upgrade' to do if replacing pistons. At this point I'm assuming everything is stock sized until I crack the beast open.
 
When you have the block into the machine shop they will measure everything and determine what it will take to clean up the cylinders. Its not so much that "30 over" is an upgrade, it is the size of piston needed after they clean up the cylinders. Start with teardown and inspection. It happens all the time that a block cant be cleaned up and you may need to go another direction.
 
not to burst your bubble but have you added up all the parts and basic labor to get the engine done ?

now go find a create engine for prob less money and bolt it in with a warranty .

i have just seen and read so many story's about rebuilds done local and all mix and match parts and such .

but back to topic . yes the machine shop SHOULD check the whole block and tell you what you need then tailor that to your wants .
 
I agree. GM has some great crate engines available. Same with some of the other large rebuilders out there.
 
HankScorpio said:
I agree. GM has some great crate engines available. Same with some of the other large rebuilders out there.
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Yes they do. From wheezy TBI replacement engines to full tilt boogie.

I priced an engine locally with proper upgrades, and bought a GM crate engine
 
No worries - no bubble burst here.

My background is more import than domestic (been through 5 celicas with #6 sitting in my garage awaiting it's heart). With the with the domestic stuff out there there is SOOOO much more available performace or stock aftermarket than what I'm really used to. Cost wise -- it's around $1000 from what I'm gathering.

Shop's prices --
$160 for block machine work
$100 for crank turning (optional but recommended per shop)
$299 for head work (re-manning and machine work)

Comes out to about $700 bux if they install pistons/rings. Add in the reseal and new pistons/rings its right around $1000-$1100.

I'll have to look into that. I must of not found the right article - only GM sections I'm finding are all performance build related.
 
There are a lot of other major and minor things that will push your long block price WAY higher than $1100, even if you assemble it yourself.
 
$1400 for machine work, another $600 for assembly, just on the bottom. No heads or cam

The cam and heads worth using added $2600

I bought the SP350/385
 
Bent77 said:
$1400 for machine work, another $600 for assembly, just on the bottom. No heads or cam

The cam and heads worth using added $2600

I bought the SP350/385
Click to expand...

Exactly. Hot tank, magnaflux, bearings, can of ORANGE engine paint, etc. Some of your fasteners are even torque to yield and need replaced, it all adds up quick.
 
HankScorpio said:
Exactly. Hot tank, magnaflux, bearings, can of Black engine paint, etc. Some of your fasteners are even torque to yield and need replaced, it all adds up quick.
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Fixed lol


Yeah little parts. Crate engine for the win
 
76zimmer said:
On an engine of this era? explain please.
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Aren't the head bolts supposed to be replaced? Its been about 10 years since the last one I had rebuilt but I thought we had to buy some stuff from ARP.
 
If I was doing a garage rebuild on iron heads, I’d probably use the factory bolts.

On a new engine especially with aluminum heads, I’d buy all new ARP
 
Have you priced hypereutectic pistons? For the cost, if I was putting an engine together, I wouldn't even consider re-using pistons. In terms of parts cost, non-cast and non-forged pistons (ie, hypers) are so cheap it's not worth considering reusing the stock ones. All IMO, however I just went down this road. The cost to do *proper* work, with proper parts, on an older block was far in excess of just buying a crate engine.

I ended up with the L31 crate for right around $1800. I think you can get some more appropriate for a carb (provisions for mechanical fuel pump) for about the same price. For the benefits of the L31 though (no worry about cam going flat-roller camshaft, higher HP and TQ than most stock engines from prior, one piece rear main, one piece pan gasket, etc) going to an electric fuel pump and needing a specific intake would probably make it more worthwhile over the "lesser" crate engines. But if you want to spend money, there are definitely higher HP/TQ crate engines available. When I crunched the numbers though, once you exceed L31 output, the cost per HP increases exponentially.

Edit: Don't get me wrong...I love to build stuff, and putting an engine together is cool. I did my first one, and it ran ~17 years or so, and was still working when I pulled it. But machining costs have gone up too much, and there are too many good components out there to justify anything but running the crate L31 for me. It was near exactly what I wanted (everything but a better oil pump and larger oil pan), out of the box, with a warranty, for hundreds less than parts and machining would have run, excluding my time! :(
 
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Interesting guys -- thanks again. As stated before I'm used to import work and builds. It's been a while since I've done a domestic build. Last one was completed on a barter basis so no cash was exchanged.

It won't be by any means a performance build - just want to get another 'wheezy TBI replacement 305 engine' back in there. Guess I got some more research to do and see about tracking down stock crates...
 
Sorry, but I have the best question so far.

Smog or no smog?

That is the difference between keeping a turd of an engine VS upgrading to something better.
 
You said TBI, so that pretty much limits you, unfortunately. 305 makes it worse. Any modifications from a crate 305 TBI motor requires tuning, and that isn't particularly cheap/easy for GM OBD1 such as the TBI trucks.

You have a lot of decisions to make. The first is to decide if you want to stick with the 305. Most are going to tell you not to, I'd be inclined to agree. The 350 is far more common, and gets same economy under same conditions as the 305.

I *think* this is the L05 replacement (TBI 350/5.7L) which you may find elsewhere, like ebay, for less: https://www.jegs.com/i/Chevrolet-Performance/809/12568758/10002/-1
Dealers seem all over the place on warranty requirements, but generally it seems that if you don't monkey with the crate engine, just bolt it in, there is a two year warranty. I got my L31 (Vortec/5.7L) crate engine from Radley Chevrolet, and I felt I got a good price.

The good thing with a crate replacement is that you can go with a "stock" tune. A TBI PROM for a 5.7L engine is going to be easy to get your hands on, should be dirt cheap (if not free) and an easy swap. A few other components will need changed as I recall, but not ridiculous. If you start doing things like headers, cam, intake, etc., you are back to needing a tune. These systems are old enough not many, if any, shops are equipped to tune TBI.

Sticking with a stock 305, whether crate or rebuilt, will be the absolute easiest. Whether it's cost effective, and what you want in the end, is up to you to decide. Varying at all from that baseline starts to incur additional cost and complexity.
 
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