RR46

So I took a gamble on an early LS7 that had a failure from running lean on cyl 7 when it was in stock form. It was put back together by a Georga-based engine builder a few years back and has run allegedly well in a mid engine project car for 6+ years including a couple of track days. Katech blue pump and Aviaid scavenge kit.

The Georgia based builder invoices show that they bored the cylinders 0.030 over and installed .035 rings, .030 forged pistons , new std main and std rod journals,and cam bearings. Also the heads were worked on; titanium exhaust valves were replaced with a kit of steel valves, retainers and dual spring kit, together with a custom spec'd torque oriented cam with .650 lift, .

I started to prepare it for installation in my project car but first had to change out the pan and have a look at the components, then install a RPM B3 + Mamo ported MSD intake. Power target 550-580 rwhp for road racing, not crazy. Have Kooks headers into 3" collectors with racecats.

Findings:
- Piston skirts have scarred the cylinder walls. All of them, both sides of each piston. Touch test doesn't feel much, nail test is hard to reach, not extreme.
- 1st Main bearing has deep grooves and also has some spots on it.
- 2nd main journal looks tolerable to my untrained eye. Haven't looked at the rest.
- Crank casting is blue in the middle of the motor (could be from early failure)
- Rod journals look tolerable
- Heads aren't off but a pre-shipping leakdown revealed hissing at a couple of valves which should be a simple fix . Results varied from 90-86, 90-78, and a couple of hissing 90-60. Cold. Will do another one tmrw hopefully.
- Head ports look like someone did some work on them at some point.

The challenge is what to do next. Machine shops around here are backed up for months and are expensive. I've been planning to do this swap in Nov Dec.
Working on this without the right tools, means it's going to be $$ for every minute someone helps get it good and reliable, which might require a full on rebuild from the ground up.

Thoughts:
1. It might be better for someone who can do journals and honing themselves and for me to go with a fresh short block or long block?
2. Or salvage some value out of it and slap it together until it makes noise or drinks too much oil and swap motor then? --> kind of ruling this out since I'd be concerned about throwing oil under my rear wheels at the wrong time, or instantaneous engine lock up followed by oil and rod out the block

Thoughts from those with knowledge and with understanding of senseful use of $$ towards a good outcome?








Head port inlet


Head port exhaust side





Does anyone recognize 71161 pistons?

Double06

iTrader: (1)

The LS7 motors have very thin walls and you are only suppose to bore them out only .005 - that's right 5 thousandth. The only thing that can do an over bore like that is a sleeved block (Darton Sleeves). So if its 30 over with no Darton sleeves you have a problem. Some machinist LS7 guys can chime in here if they think different. MID out of California does sleeving. If you do have the Darton sleeves you need to check with a machinist but you might be able to go .010 over what you have. The bore damage you have maybe due to the fact it is overbored with stock sleeves. Also check the titanium rods in situations like this the begin to wear against each other and they need to be recoated. You can find details on this and the over bore on the Corvette Forum Z06/ZR1 section. And of course don't forget to check the valve guides.

Darth_V8r

iTrader: (4)

I'll tell you what it looks like --

Engine was salvaged from a race team. Slap some rings and bearings in to get it running, sell it off to recover the money. Been there, unfortunately. First thing, trust nothing. I sold the heads off mine when I went through this, and they guy I sold them to called me up to say he could put a toothpick between the stems and guides. I felt terrible and refunded him a bunch of the price to try to make it ok. So, assume nothing is good and negotiate up from there.

Here's the kinds of options you have.

1. Call up a reputable shop and obtain a new shortblock. Go through the heads on your own. Thing is, it's getting into winter and the wait lists are already growing. Call HPR for example and you're 90th in line. No joke. However, a 468 would be a great option to just swap under your heads. Some of the other builders out there like Shafiroff or Schwenke might have stuff on the shelf. TSP might have some short blocks on the shelf ready to go. As you noted, machine time and parts are hard to come by right now.

2. Send the block to Steve at RED for Darton dry sleeves. If you go this route, you're likely 2-months in line. Have him rough bore to just under your piston size. If you go this route, you're going to pay the same for whatever displacement you want, in which case, I'd suggest doing a 440 - 4.185 x 4.000. You can order your custom pistons while you wait for your block, which will take a bout 5 weeks or so, depending on who you order from. You might find companies have some on the shelf. When you call around, don't just call the usual names. Call all of them to see what's available. if time is your biggest concern, and you can't find 4.185 but you can find 4.155, go that route, make sense? Have Steve rough bore to 4.150 in that case. Final bore and hone needs to be done with pistons in hand. In the meantime, you can also order crank and rods, which stand a reasonable chance of beating your block back to the house. You might find you can get rods and crank off the shelf faster than getting what you have turned down. You'd be all in around $7K-$8K if you go this route, but you'd have a far better bottom end in the long run.

Darth_V8r

iTrader: (4)

For heads, I would call around and see what people have on the shelf. For example, going through your heads might cost you $500 but take two months. Mast, Mamo, etc, have their own machine shops devoted to their products. You might be able to get a set of badass heads faster than getting yours gone through.

RR46

Apologies for my typo, pistons are 0.030 and rings 0.035. Have edited original post. Seems quite a bit over 0.005 still.
Guide check definitely coming up.

The rods all look good from just looking at them.

Double06

iTrader: (1)

You can check with MID or other places but OEM block is only .005 max basically a clean up. I think the sleeve itself is .070 OEM. The reason they crack is the thin sleeve (the original running lean problem #7). Take a look at all the 4.130 pistons they offer there is a reason why.

RR46

Very interesting. I wonder why they would bore a stock sleeve that much if they could have just gotten off the shelf 4.130 pistons and bored it a smidge.
All the notes say
Bore & (Hone) 0.030
Piston: 0.030
Rings 0.035

So it's not like a misstatement meaning 4.130
Guess one way would be to measure the cylinders.

Is there a way to tell factory vs aftermarket sleeves apart? (just in case that was actually done when cyl 7 went early on)

Labsforever

take a good pic of where the sleeve and block come together at the bottom of the cylinder and we should be able to tell. As Darth stated earlier assume nothing so measure everything you can

Gripenfelter

iTrader: (1)

Talk to Jared at BTR. He can get you a deal on a DART 427 short block. You can get TFS heads from BTR as well.

RR46

This is super helpful advise and definitely puts some perspective on timing.

RR46

Snapped this were some of the scarring can be seen as well.

And yeah, who knows if the paperwork even belongs to the motor.

Labsforever

It’s hard to tell for sure from that angle but it doesn’t look like that cylinder has been resleeved. I have a RED done block on the stand here I can take a pic of tomorrow if it would help you out

Double06

iTrader: (1)

Can you measure how thick the sleeve wall is down at the bottom?

Che70velle

iTrader: (6)

There are no notches cut for rod bolt clearance, so this isn’t RED sleeved. I believe that is a OEM LS7 sleeve personally.

RR46

Hard to see from that photo but I don't recall seeing notches, all round iirc. I need better pics when I go to the shop next time and need to take proper measurements.
Just looking at them they seem thicker than 0.040 (1mm) though. Closer to 1.5 - 2mm. But the eyes can lie so easily, proper tools will tell and I guess the sleeve bottom doesn't reflect the actual bore up in the cylinder.

Leakdown are 90/86 and thereabouts, then 90/78 and two 90/60 but it blows the duct tape off the ports not below.

Time to lift heads next I guess, whether to just service and check/replace guides, or remove to sell or ship as cores...

Looked around a bit and need to make some calls to see who's got reasonable street/road race oriented heads, or full long block, in stock , that is not some junk in the back.
Maybe LS3 based stroker is the way to go but I have some really nice LS7 parts so not super keen to take that route.

Labsforever

Block is assembled so I can’t measure it but you can see the sleeve edge very clearly and on a factory one you can’t. Yours looks more factory to me

RR46

71161 pistons - search comes up empty - anyone have an idea what brand / origin they may be?

RR46

I’ll be able to Mon. Two more photos from last time checking it out, Looking fwd to measure bore with heads off bc it doesn’t appear to be so thin at the bottom, but who knows up top.

Che70velle

iTrader: (6)

Heres a pic of my 434 block that Steve at RED sleeved using Darton Sleeves. Notice the notch for rod clearance and the sleeve design doesn’t have the narrow ears for skirt support like the GM OEM sleeve does. Instead the sleeve is designed to support pistons with wide skirt designs, and of course a narrow skirt pIston will work great also. Steve notches every GM block he sleeves for rod clearance.

RR46

Thx! Definitely not what’s in my coffe table base. Sleeve thickness ”looks” pretty similar though. With luck the bore notes were wrong, a main bearing polish coulld be worthwhile in that case. But not holding my breath til the bores are measured.