What should I add in during a rebuild?

[351FUN]

1992 blazer, having the 350tbi rebuilt due to blowby and age (270k miles.) I'm having the axles redone to 4.56 while it's there, and probably a hotter cam that's still factory computer friendly since I know there's not much tuning out there anymore. The exhaust will get done at the same time, but is there anything else I should have done while it's happening?

 

[351FUN]

Something else I was considering was raising compression with flat top pistons. Would it be a noticeable difference, and would the computer be okay with it?

 

[Schurkey]

The service-replacement " '92 Caprice " TBI crate engine I put into my '88 K1500 had flat-tops. Computer had zero problem adapting to the 1/4-point increase in compression ratio. Compression ratio should have been higher-still, but excess piston-to-head clearance offset that. Pistons are typically .025--.030 in the hole, plus the thickness of the head gasket which might be .028 but is more-commonly nearly .040. Pistons are dirt-cheap as OEM replacements, but the compression height has been dicked-with.
www.summitracing.com/parts/slp-h597dcp30

Sealed Power H597DCP 30 Speed-Pro Hypereutectic Pistons | Summit Racing

Free Shipping - Speed-Pro Hypereutectic Pistons with qualifying orders of $109. Shop Pistons at Summit Racing.

www.summitracing.com

"I" would have the block square-decked if not zero-decked, to get the pistons high enough to create proper "squish" or "quench" with the cylinder head and gasket selected.

The engine going into Mom's Concours (Nova) got the crank offset-ground rather than shaving excess material from the block. The extra stroke will bring the pistons up (and down) an additional .020. Either way--shaved block, additional stroke, or custom pistons with proper compression height, will get you correct squish/quench distance. Remember that most off-the-shelf pistons are "destroked"; an industry term for deliberately sabotaging the compression height and destroying squish.

Consider better cylinder heads. This is going to be difficult if Summit has discontinued their aluminum TBI heads. Vortec heads suck on the TBI platform due to EGR problems, the hyperexpensive TBI-to-Vortec-head intake manifold, etc.

www.summitracing.com/parts/sum-162108

Summit Racing SUM-162108 Summit Racing™ 62cc Aluminum Cylinder Heads for Small Chevy | Summit Racing

Free Shipping - Summit Racing™ 62cc Aluminum Cylinder Heads for Small Chevy with qualifying orders of $109. Shop Cylinder Heads at Summit Racing.

www.summitracing.com

Assure that the radiator is in decent condition to support the renewed engine with--hopefully--additional power. Verify that the A/C condenser isn't restricting airflow with bent/corroded fins, sparrows, 'hoppers, etc. Verify water pump, fan clutch, and fan. High-flow thermostat?

New rubber: Radiator and heater hoses, fan belt (and tensioner?). New engine mounts if you can find decent ones--far as I know, there's no such product available for 4WDs.

When it's my engine, I install brass draincocks in the block-drain holes that aren't occupied with knock sensors. I also install a block heater even though I rarely use 'em.

With the engine out, it may be worthwhile to consider replacing A/C evaproator and/or heater core. The job may/may not be easier with the engine out of the way. Probably need a fresh Dorman replacement heater-hose quick coupler on the intake manifold.

All the usual "tune-up" parts--plugs, plug wires (Route them exactly as original, get fresh plug wire looms as needed.) Distributor cap 'n' rotor. Assure that the distributor mainshaft magnet is in good condition (replace mainshaft as needed). Fuel and air filters, complete scan-tool evaluation of all sensors. Probably replace O2 sensor. Verify fuel pressure.

New transmission torque converter seal? New TV cable?

Adjust DRAC to provide proper speedo readings with 4.56 gears and whatever tires you're using.

All the usual warnings about having the brakes/steering/suspension in adequate shape for safety.

 

[PlayingWithTBI]

Also, if you want to, now's a good time to run bigger wires to the starter and/or the power distribution block with the engine out - makes it real easy.

 

[arrg]

probably a hotter cam that's still factory computer friendly since I know there's not much tuning out there anymore.

The EBL is very easy to install and get up and running. If you want more, you don't have to limit yourself because of the factory computer.

 

[351FUN]

@Schurkey very good points, I know very little about the internal details on engines. The entire a/c system is actually being replaced, I bought all the parts last year but a cross country move stopped me from doing the job. I've already done the brakes on it, and cylinder heads are something I'm kicking around but I wish I'd bought those summit heads last year when I was considering it.

@PlayingWithTBI I'll have to look at it to be sure but I believe that's all been done already, it's usually one of the first things I do to a vehicle along with upgraded grounds.

@arrg I spent most of yesterday reading about the EBL. I might end up getting that, it just feels like a steal at that cheap.

 

[GoToGuy]

How about punch it out to 383? It's already apart.

 

[351FUN]

That'll depend on if the crank is good or not. I don't know enough about rebuilds to know if that's usually replaced or not though.

 

[Schurkey]

How about punch it out to 383? It's already apart.

"Punching" refers to bore *********** enlarge_ment embiggening. The "383" uses the semi-standard .030 cleanup on a 4" bore.

The big deal with 383s is the stroke.

REALLY? "ENLARGE_MENT" IS CENSORED? WHAT MORON DECIDED THAT?

That'll depend on if the crank is good or not. I don't know enough about rebuilds to know if that's usually replaced or not though.

Not "usually" replaced. Sometimes reinstalled with mere cleaning, sometimes polished, sometimes re-ground depending on the amount of wear. Replaced only if there's significant wear, outright damage...or someone wants to have more fun than the original crank provides.

IF (big IF) you're intending on a custom computer tune anyway, there's little reason to NOT add some stroke. More displacement makes more torque, and additional horsepower. Adding stroke tends to make that power lower in the RPM range, which is fairly wonderful in a pickup or other truck. Of course, the powerband is also affected by port/valve size, and cam grind.

 

[351FUN]

And that's why a 383 or even bigger stroker would be great, I'm happy with the 4500rpm redline and want this to be about low end torque more than anything. My holdup is cost, I'm not sure how much I really want to put in to a 30 year old Chevy. It's also most likely keeping the awful tbi heads too which will limit it regardless.