IT_SS

iTrader: (5)

Hey folks, here's the situation. I'm working on my 370 LQ4 bottom end, I just got my block back from the machine shop (cam bearings, hot tank, .030 over bore, ARP main stud install/line bore and crank polish) but they didn't give me bearing clearances. Now I have a micrometer set, and a buddy who deals King Bearings gave me a set to test with.

So here's my question, in order to verify proper clearance, is the procedure;

1. Mic the 5 main journals
2. Install the X main bearings and torque cap down to ARP spec
3. Set bore gauge (which I don't own yet) to X journal measurement and check the bearings to tightness or looseness?

Thanks in advance! I don't do this for a living, I just want the learning experience!

ckpitt55

iTrader: (4)

Usually most shops will close and hone your main caps so you can run stock bearings, maybe call them to verify what they did.

But your procedure is right, just a couple notes:

1. Make sure you calibrate your mic before you use it - room temperature variances day to day have an impact on what it reads, and so does heat from excessive handling. I've seen it change by as much as 0.0002" day to day before recalibrating. If you're using a cheap chinese set I'd recommend picking up some quality calibration standards to help improve your accuracy. I bought 1" and 2" Starrett standards from mcmaster carr for about 20 bucks.

2. Zeroing out your bore gauge at your journal measurement saves you some math, but isn't absolutely necessary. I didn't have a vice to set my mic in which made referencing that kind of difficult. Instead I measured the initial tool length of the bore gauge (without moving the needle) and subtracted my readings from that at the end. In the case you zero your gauge to the journal, you should end up with a reading shy of your tool reference when measuring the block - that is your clearance.

3. You're going to want a 0.0001" resolution gauge, the cheaper bore gauges with the 0.0005" increments aren't really all that great when you're dealing with tolerances that tight and want to measure with accuracy. I bought a cheap one but later upgraded the indicator.

Just take your time and think about what you're doing, you'll be fine. Good luck from one diy'er to another

IT_SS

iTrader: (5)

Thanks! much appreciated!

Gunslinger09

Yep unless you had the crank turned down stock bearings are what you use. I don't know about checking with a micrometer though, I have always used Plastiguage.

IT_SS

iTrader: (5)

Crank wasn't turned, just polished, but with the line bore I'm sure there would be a bit of looseness with the stock spec's bearings, better safe than sorry. I've heard mixed reviews on plastiguage readings how ever.

ckpitt55

iTrader: (4)

if your clearances were on the tight side to begin with you might be ok, depends on how much material the polish took off the journals. if it was only a couple tenths then you're probably fine. i know the ls1 clearance specs are 0.0007-0.00212", not sure about the LQ4 but I'm sure it's comparable - probably tighter if it's an iron block.

if you want to guess, use plastigauge. if you want to know for sure, use a micrometer / dial bore gauge. plastigauge isn't that accurate. good for sanity checks or for instances where you aren't completely disassembling the short block, that's about it.