L31 Quality Rebuild kit

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Orpedcrow

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I’m looking for a quality rebuild kit for my L31. I’ve only put together a handful of engines and they were odd ball stuff with just random parts availability so I’m not sure what the good stuff is. I’ve used a bunch of fel-pro gasket sets over the years, is there something better?

Re-ring kit from summit or piecemeal together my own kit?
Clevite 77 bearings? King bearings? Mahle rings or sealed power ok?
Is the cheap Amazon kits just as good?

I just don’t know and would like your input. I’m looking for reliable stock internals. daily driver, it MIGHT get a small cam like an lt4 hot cam or something similar, depends on the condition of the heads when I pull them off. Stock intake, MAYBE headers eventually.

I saw re-ring kits that come with cranks, is that a common issue? Engine dosnt smoke but makes some noises I don’t like so I want to rebuild it before I HAVE to.

Why do so many re-ring/re-build kits come with pistons?

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GoToGuy

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Your deciding on rebuild time is yours of course.
But what is the actual state of health of your engine? How many miles in service? What is total compression? What does a differential leak down compression indicate? Diagnostic scan of overall running condition.
What " noises " are concerning you, are you sure those noise are not accessories generated, as in worn belt, tensioner, idler bearing, alternator/ bearing whine.
Just curious, as I ask a customer the same thing, as the Vortec series are capable of long ( miles ) service life.
Good luck.
 

Orpedcrow

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Your deciding on rebuild time is yours of course.
But what is the actual state of health of your engine? How many miles in service? What is total compression? What does a differential leak down compression indicate? Diagnostic scan of overall running condition.
What " noises " are concerning you, are you sure those noise are not accessories generated, as in worn belt, tensioner, idler bearing, alternator/ bearing whine.
Just curious, as I ask a customer the same thing, as the Vortec series are capable of long ( miles ) service life.
Good luck.
Unknown mileage, it’s at least the second engine in the truck ( the one I pulled out was a 5.7, this one is a 5.7, vin, ECU, and RPOs show the truck should have a 5.0) I re-sealed/gasketed the engine before I put it in… oil was very dark, a little bit of sludge but nothing real bad.

The noise is a kuchunk-kuchunk-kuchunk noticed at idle. Noticed more pronounced with fresh oil. All accessories have been ruled out. Flexplate isn’t cracked but kind of the same sound. Once oil is at operating temperature, the pressure will be close to zero at idle.

I don’t remember the exact results of the compression check before installing but the highest to lowest delta was within 10 percent. Overall runs great, no misfires or hiccups, no smoke, doesn’t bog when passing someone on the highway. Loves running 80 mph.
 

Erik the Awful

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I wouldn't buy pistons until the engine is apart. If you don't need to bore it, don't. I'm a fan of only boring as much as needed. Head gasket thickness matters as it can determine your quench distance and your propensity to knock.

Re-ring kit from summit or piecemeal together my own kit?
Clevite 77 bearings? King bearings? Mahle rings or sealed power ok?
Is the cheap Amazon kits just as good?
The Summit ring kit's fine, Clevite, King, Mahle, and Sealed Power are all okay, and no I don't trust Amazon to get it right. I typically buy the bread and butter parts from RockAuto.

it MIGHT get a small cam like an lt4 hot cam or something similar, depends on the condition of the heads when I pull them off.
Don't set your mind on a cam. Personally, I think the GM hotcam is way overpriced at $650. Your favorite cam company can hook you up with a better cam for $300. Call them, tell them your setup and expectations, and they can hook you up. The factory cam is weaksauce and the Vortec injection setup can handle significantly more power with a tune. There's no reason to not go bigger. Even if you want better fuel economy, there's a better cam hiding in someone's catalog.

Check your heads carefully for cracks. Send your block and heads to a machine shop for magnafluxing. After you get them back, port your heads. Just a mild clean-up port job is fine. There's a chance at least one head will be cracked. If you can get a good replacement for under $100 from Pull-A-Part, it's worth it. Otherwise make the jump to performance heads.
 

95burban

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Take the long block to the machine shop and pick it a week later. They will check the heads, line bore the block, check everything over and assemble. Even if you want to do it yourself it worth having them do it.
 

Orpedcrow

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Bi-metal or tri-metal bearings? Clevite has confused me.

I know a double roller won’t fit so what’s the recommended timing set? I’ll be using the cast aluminum Holley timing cover.
 

Schurkey

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Bi-metal or tri-metal bearings? Clevite has confused me.
Clevite "77" used to be a specific model of bearing, with multiple part numbers to fit various engines. Now it's an entire line of bearing models.

When it was me, I bought King SI-series Bi-metal rod bearings, and Summit house-brand Bi-metal main bearings. The machine shop provided the cam bearings.

I know a double roller won’t fit so what’s the recommended timing set? I’ll be using the cast aluminum Holley timing cover.
GM used a single-roller timing set. No doubt there are aftermarket alternatives, but be sure they fit the step-nose roller-cam. The flat-tappet timing sets won't work. I re-used the same timing set the core short-block came with. Not a thing wrong with it. Cam degreed within one degree of advertised spec.
 

rebelyell

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I realize this is an older thread but its subject (choosing an engine kit) is always relevant.

FWIW, I don't usually like a kit because, at best, it's usually a combination of compromises; I don't like to begin a project with a compromise. Suggest learn about the pros & cons of all the different types of parts; then choose what's best individual part choice to meet Your requirements.

Lotsa folks choose a kit because they believe a kit will alleviate some of the need to think through the project's planning phase. Another reason to choose a kit is to get a better price. Then that often leads to bottom-of-the-barrel parts n pieces. Lotsa kits have the cheapest piston that'll fit the hole. Your L31 motor has a good piston with modern design thin metric ringpak. GM speced that type ring for good reason. Most cheaper kits have a piston with thick wide antique design farm tractor rings.

Cheap cranks typically have relatively small/narrow fillet radii; wider fillet radii typically stronger.

Also, majority of cheaper replacement pistons have a Very short Compression Distance aka Height. Your typical OE sbc piston has a CD about 1.560" while short 1.540" CD are prevalent in cheaper pistons And in budget kits. Without decking block, that positions piston Way too far down in hole And that'll wreck any attempt to optimize Quench height.

Rod/main/cam bearing insert material types: Clevite 77 are Tri-Metal...
But, Most sbc came OE with Bi-metal bearings; a steel backing with an Aluminum-Silicon alloy facing. All evidence points to fact they provide Very good service.

Suggest study-up on tech aspects of parts n pieces, use the sense God gave ya and make your own choices ... OR pay a pro to spec out your motor and to build it for you. Good luck on your project.
 
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