Olds ticket to 9s... LS swap adventure.

[Northernregal]

Did you go 6.098 or 6.125 length rods? 9.6 or 10.7 compression?

Rod and piston kit was SUM-PR36L0052
4.005" flat top +2cc pistons
6.125" forged rods, 0.927 pin

Tool Steel Wrist pins 0.927"x 2.250" SUM-S719

The wrist pins that came with the kit at about 103g and the tool steel was about 135g. So that makes a difference.

 

[Turbolq4]

Gen4 stuff is heavier.

 

[fleming442]

3 grams is an 1/8 oz. Am I the only one not comfortable with that difference? It's a nice bag, 8 times, maybe.

 

[Northernregal]

Pulled the motor finally today. Started stripping and investigating for signs of rod flex.

The culprit showed itself quite quickly.

Pulled 7 and 8 out of the motor for detailed inspection. Seems 7 is very slightly bent.

It was just enough for the crank to gently tickle the piston and do some very subtle self clearancing.

I finished weighing out the gen 3 stuff.
Average 1268.24g
ES 8.06g
SD 2.98g

The summit goodness
Avg 1275.43g
ES 1.57g
SD 0.44g

The 2 gen 4 pistons I have out are:
7 628.65g
8 626.53g

Rods
7 645.21g
8 648.52g

Combined
7 1271.75g
8 1277.15g

Keeping in mind that i never weighed and matched up the rods and pistons when I put the motor together they might have been more weight sorted.


Some good lessons learned here.

 

[64nailhead]

Is the bore still decent?

 

[Turbolq4]

I'm curious. Let's say you just ignored the tapping noise until the parts played nice again. I wonder if you could have noticed a difference in power output🤔

 

[Northernregal]

Is the bore still decent?

Going to finish disassembly tomorrow and start measuring everything out. I was confiscated for family socializing tonight.

I'm curious. Let's say you just ignored the tapping noise until the parts played nice again. I wonder if you could have noticed a difference in power output🤔

I'm guessing if I would have leaned on it, it would have folded. Never know how fatigued metal will react.

Real eye opener for the pressure that would cause it to bend at old 10psi. I never expected it.

 

[64nailhead]

Real eye opener for the pressure that would cause it to bend at old 10psi. I never expected it.

NA a bad tune will live for quite a bit, but still will break good parts. I'm not too proud to say, but I've broken good parts NA and with boost.

You either had something well wrong with your tune or a lean cylinder. Something such injector issue, coil auto-firing or something.

 

[Northernregal]

Got a later start than I wanted today. Went to watch the local sports car club time attack. Sadly no G bodies in the event...

After I got home I finished the tear down on the motor, got the gen 4 internals all measured up.

Gen 4 rods were in the 643g average, pistons about 628.5g average.
Weights of piston/rod combo:
Avg 1278.6g
ES 8.71g
SD 2.92g.

So as a recap the gen 3 was
Avg 1268.24g
ES 8.06g
SD 2.98g

The summit Pro LS rods/pistons SUM-PR36L0052 was.
Avg 1275.43g
ES 1.57g
SD 0.44g

So, take that info for what it is, just data. Make your own decisions.

I then pulled the crank out and checked the mains, and this is where things took a turn.

This is what I learned.

2 and 4 were pretty beat up. There was very minor marking on the crank but nothing deep enough to catch a fingernail, it looks like a bit of the bearing scuffed into the finish. This was one of the worst. Everything measured out even, to the best of the resolution of my caliper. I think #2 cylinder might have had some flex in the rod but without a surface plate I can't really tell for sure, if anything its slight.

I gave the journals a quick polish with some 1500 grit and they all look good. So I think that's going to be OK, just need some new bearings.

I then turned my attention to the cylinder bores and started to measure them.

I got really lucky, everything is good and square. Maybe 0.001 more wear on the thrust surface but still good. So I started the honing job for the new pistons. I spent a year in a machine shop for work experience in high school so I was not concerned about being able to do it... I was incorrect.

I spent about an hour on cylinder 8....

And 0.005 of the 0.007 to go.

I'm calling the machine shop tomorrow. F%$@ this. I need new mains anyway.

 

[Northernregal]

NA a bad tune will live for quite a bit, but still will break good parts. I'm not too proud to say, but I've broken good parts NA and with boost.

You either had something well wrong with your tune or a lean cylinder. Something such injector issue, coil auto-firing or something.

It was bad tune. 1000% sure.