momofx

Getting ready to do some pre-assembly so I was wondering if I could get some idea of what numbers would be good for the main and rod bearing clearances using a plastigage as I can't seem to find any for an LSX Iron Block. Crank, Rods, Pistons all forged. FI as well (TVS2300). Thx!

Onbusy

iTrader: (4)

I always use .001:1 clearance to journal size as a general rule of thumb.

So about .0025" on the mains and .0021" on the rods for the LS engines.

Factory LS1 specs are:
Crankshaft Bearing Clearance (P): 0.018-0.054mm / 0.0007-0.00212"
Rod Bearing Clearance (P): 0.015-0.063mm / 0.0006-0.00248"

I would stick to the looser end of these tolerances. I stay between .002 - .0028

Crank and Rod manufacturer can give you specifics of what they prefer for their specific parts.

KCS

iTrader: (20)

What power level are you shooting for? What kind of use (street/strip, drag race, endurance)?

momofx

We are hoping to get to about 800whp at least. Car is mostly a weekend street car. No real track or strip use but just maybe once or twice a year to strip.

Also, this is a wild shot but does anyone know if all the fastener tightening sequences and specs are the same as any other Gen IV LS (LS3 maybe?) or does the LSX Iron block have its own? Can't seem to find anything about all the fastener specs for this...

01CamaroSSTx

iTrader: (3)

Look for 0.025 to 0.030 on the mains and rods and you'll want more if your building a racing engine. A micrometer and dial bore gauge will give you more accurate results than plasti-gague and perhaps it was just me but it showed that I had less clearance when using it compared to my tools. Torque sequence for the mains are the same as for all LS engines and your paperwork for the ARP hardware should provide you the torque settings and sequence.

jasons69chevelle

What oil do you plan on using? Shoot for that spec recommended by that oil.
if you don’t have a oil in mind here’s a nice chart.
first column is less the 160f oil temp
second column is 160-220
third is over 220
invest in a good digital bore gauge. Don’t count on platigauge. I ending up with about 3 different sets of bearings to get the clearance I wanted.


Iron block mains

Steel rod

Aluminum block main

Che70velle

iTrader: (6)

I set up bearings based on power level. I like to use a 30w oil for street performance builds, so I’ll rate the pump on the viscosity and whether or not the build includes an aftermarket oil cooler that requires more volume.
On a race build, I’ll tighten it up some due to 20w oil or less being justified. Windage robs big power, not only in the crankcase, but under the valve covers as well, so a thinner oil is free power, but you have to design the entire build on the oil weight. Of course block material will change numbers. Al blocks grow far more than iron blocks.
For the intended 800hp build in this thread, with an iron block, I’d go .0025 mains and .0025 rods. .0025 on the rods allows for more boost later. Boost Is tough on rod bearings. With low boost settings, you could do .0022-.0023 on the rods no problem.

Mavn

iTrader: (3)

I always find it funny how machine shops love to open up bearing clearances . But sbe 5.3s will hold 1000+ wheel and never have a bearing issue . And every 5.3 I've measured was TIGHT like .0015 rods and .0018 mains . Every loose engine ive had build by machine shops spins bearings lol

Mickyinks

With my lsx block my clearances are .0025 mains and .0027 rods and .0004 thrust

01CamaroSSTx

iTrader: (3)

I'm running Clevite H-Series and found those same clearances and all I ever run in the LSX is Red Line 5w30.

momofx

Initial break in on Lucas 30w break-in oil and then eventually 5w30.

Lot of great answers - thanks guys!

Mickyinks

i use driven gp1 10w40 semi synthetic... lsx blocks run hot, semi synthetic is easier on lifters

ddnspider

iTrader: (26)

I rather err on the side of a little more cushion and thicker weight oil than too thin/small. Similar to spark plug heat range. A little cold has minimal down side.....but run too hot of a plug and things go wrong quickly.

momofx

Before the rebuild, I ran Penzoil 5w30 synthetic and it always stayed around 260 - 270 oil temp on a hot day. This was with an oil cooler installed too...

ddnspider

iTrader: (26)

Dang that seems toasty!

momofx

Well guys I finally got around to checking the clearances and I'm getting no more than .0015 clearance on the mains and rod bearings as well This is with ARP hardware on everything and going by their recommended procedure and Molnar's procedure as well. Cannot get past that .0015...

I'm guessing I'm gonna have to get the new forged crank turned down .001 or so right?

BTW I plan on running 5w30 eventually and this iron block ran well over 220F previously...

Mickyinks

You change the bearings to ones that will give you the clearance you want.

jasons69chevelle

Plastigauge isn’t giving your actual clearance. If you want your engine to last spend the extra $185 for a digital bore gauge. Or $50 for a analogue. Digital calipers come in handy for bearing journals. I’m sure some have had good luck with plasti gauge but others have not.

momofx

Managed to borrow a nice Mitutoyo digital micrometer and an analogue bore gauge. After working out the readings on the mains and rod bearings, the plastigage was only around .002 / .003 off (wow not bad for something so cheap). We did it twice and more or less then same thing :/

So does this crank need to be machined?? It is the Summit LS Pro forged crank for LS3 that I was told would work in the LSX block just like most of the other stuff.

Here is link to the crank I am using : https://www.summitracing.com/parts/sum-180ls362258x

The main bearings are King MB5013XPC : https://www.summitracing.com/parts/kgb-mb5013xpc
These are the rod bearings King CR807XPNC : https://www.summitracing.com/parts/kgb-cr807xpnc

Let me know if I'm doing something wrong here. Thanks.

* Update : After some digging, I somehow have a feeling these are the wrong bearings!

01CamaroSSTx

iTrader: (3)

When you mic'd the crank and measured the mains and rods with the bearings in what did you come up with? I presume you measured and double checked your math and that the crank journals and rods are to specifications and your just needing to find the correct bearings to achieve the clearance you want.