NewbVetteGuy

If I can get out of work early enough, I'm going to head to the machine shop tomorrow; what questions should I be asking?


What I already know:

• There was very little wear
• The bores were honed (no torque plate)
• My stock L82 forged 2618 alloy pistons had "good" piston to wall clearances (4.5 thousandths) and I can reuse them
• The crank was polished
• Block was hot tanked and repainted, new cam bearings installed, that's it

Questions:

• OD of the crank after polishing? (to help estimate whether I need oversized main bearings)
• ????

Thanks,
Adam

stingr69

Adam,
If they polished the crank you do not need oversized bearings. Torque plate is not an issue if they are only breaking the glaze. 4.5 thousandths average piston to bore is fine and could go 100K miles with proper maintenance. Aftermarket forged pistons are specified to run .005" clearance depending on alloy but the stockers run pretty quiet that way

If you have not already done this - run a thread tap through all the bolt holes to clean them now. I know the shop tanked the block but I would still drop the block in a rubbermaid tub full of soapy water and run brushes all over/thru it anyway. You will be AMAZED at what is left in the bottom of the tub after a final brushing at home. Power washer would be perfect if you have access to one. Spray it down with a mix of ATF and White gas (kerosene) from a weed sprayer when it comes out of the bath or it will rust before your eyes. Get a big old garbage bag to cover the assembly in between build sessions.

Have fun!

-Mark.

lars

That's awfully sloppy on the piston clearance. Forged pistons, when in-spec, run at .0025 to .0030 (two-and-a-half to 3 thousands). Pistons with .0045 slop are usually considered worn out and out of tolerance in a street car. Is the shop really recommending that as a "good" spec...?

Lars

NewbVetteGuy

ezobens

cv67

Sounds like a basic refresh, hard to expect a tight clearance with a hone/ring job using the original pistons. (yours only had 15k on it to start with?)
Long as the rings seal youre good....seen some run much looser than that especially on older forged pistons.

Easy Mike

When can I pick it up? How much? Do you accept VISA?

Rescue Rogers

how much to balance the lower end? While the stuff is there you could have it balanced,
how much to put Viton seals on the valves? I'm guessing your heads are in there as well. If not you should have them gone through too.
Do they offer a shop discount on parts? Ive talked to 2 different shops that offer Summit parts at a discount as they are wholesalers

stingr69

Respectfully - I have seen specs all over the place. Haynes manual says room temperature L82 standard piston to bore clearance is .0046" to .0056" with service limit at .0061". That forged piston alloy expands a lot at operating temp.

With the miles as low as we have here, how can it be already trash? If it was going to be sloppy and noisy at start up, he would have already noticed it before turning a wrench.

NewbVetteGuy

I took the block apart and sent the machine shop a completely disassembled block except for 2 freeze plugs, and a 1/4" square plug that requires tons of heat to remove. I also dropped off the pistons (attached to rods), rod caps w nuts attached, and the crank. -I then randomly dropped off the old 882 heads and L82 intake that I will NOT be using (after tearing the heads down) so that I could get them hot tanked to remove all the carbon deposits for the next owner.

-They removed the old cam bearings, installed my new CHP-8T coated cam bearings, painted the block, polished the crank, gave the the cylinders a quick power hone, and supposedly wrote down the piston OD, bore ID (after honing), crank OD, checked the mains for alignment issues (my rear main bearing had more wear than any other main bearing for some reason).


Agree I need al these measurements; Total Seal really wants either the grit, hone machine model #, hone RPM & # of passes or the finish roughness for specing out the rings; I'm going to mail TS one piston so they can have the rest of the specs they need.



Adam

NewbVetteGuy

I'm just going to run it as it came balanced from GM; some people estimate my HP peak as low as 5,000 RPM, but the folks who are familar with this intake and have actually modeled my combo in EA Pro estimate 5,850 RPM; Mike Jones who specced my custom cam estimated a peak of 5,800 but the HP not dropping off significantly till after 6,200. -I don't think it needs a super balance for such low RPM and I'm not sure how well such a rotating assembly can even be balanced with different pistons being slighly different sizes from GM. (There's a thread on here about what the letters stamped into each bore and written on the underside of each piston mean, and GM basically measured each bore and assigned a letter representing a narrow range of cylinder ID, and Piston OD and the engine assemblers just made sure to put a "K" piston into a "K" bore and so on. ---I'm not convinced anything near a race balance can be achieved with varying piston sizes, but I could be wrong.)


Adam

NewbVetteGuy

Yes. The car and engine have 14.6k miles on them.
-I am going with a thinner ring pack and spacers, which I'm hoping will help deal with any minor bore roundness/conformity issues (shop said torque plate honing without an overbore was pointless) AND because it just fits with my build theme of having a 1979 L82 Vette modernized with 2018 tech. (Yea for a gapless metric ring pack and spacers, I now have a $400 ring pack instead of a $100 ring pack for very little HP gain, but its what I want. Steel gapless top, napier 2nd, standard tension 3/16" oil.) TS is trying to tell me 15-20 HP vs a stock ring pack, but I've never seen a dyno result even close to that; maybe at 8,000 RPM... -Still, I like the modern lower friction ring pack and any torque, longevity, and MPG benefits it comes with- cost effectiveness I don't care about. This is my play toy and the first automotive play toy I've allowed myself, so I'm going to do ith my way.



Adam

JoeMinnesota

itsforfun

Just a word of advice. Check the oil pan behind baffles and/or the windage screen- a lot of crud can hide there. Also thoroughly clean the oil pickup screen and tube. Good Luck

JoeMinnesota

Very true. I typically replace the pump and the pickup both, or get the welded assembly. The pick-up is like an $8 part. Go at the crevices in the pan with brake-clean and an air nozzle outside.

stingr69

Hes not reusing the pan, windage tray or oil pump/pickup.

427Hotrod

You're going to invest in a $400 set of rings/spacers to install on old pistons and a bore that I can all but guarantee has high/low spots? You'd be much better off spending the $$$ on quality machine work to get a perfectly straight bore that is round and use a $50 set of rings....just my opinion. You're not far off the cost of a set of 4032 pistons and rings that could be installed in a bore with .002" (or less clearance) and have a very tight sealed engine.

A torque plate without a bore is a very common deal...but if clearances are already that loose it will only get looser. So there's a chance it might take too much and render pistons too small.

JIM

jb78L-82

Adam,

FWIW, I did not torque plate my block either in 2014 when I did my rebuild/upgrade on my L-82 with 66,000 OEM miles but I did need to bore the block .030. I did have to replace the TRW L-82 OEM L-82 pistons/rings with JE Forged Pistons/Rings. I also reused the OEM forged L-82 crank, polished and Straightened, New bearings, reconditioned the L-82 rods, everything balanced with a new clutch kit etc.

Assuming that pistons seal reasonably well (9:1?), what cylinder heads are you using and specs?, and cam type and specs, roller?

Assuming a compression of >10:1 with top quality heads and a roller cam with moderate specs for peak mid range torque, you will be shocked at the power potential in the L-82 350, as it is.

cv67

Id use a thread chaser rather than a tap, but thats nitpicky stuff.

lars

That's what I'm saying, too... You're spending good money on a half-done job with sloppy tolerances, and if those bores are at 4.5 thou clearance at the top, they also have taper and low spots as Jim states.

Lars