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JaysinSpaceman 09-28-2012 10:52 AM

Tight bearing clearances are much more common these day then they were in the days of the Gen 1 SBC that you are used to. In looking to free up HP and MPG the factories have gone to thinner and thinner oils to reduce the parasitic losses from pumping the oil. I know it kinda scares me when I read about how tight they are making crank and rod bearings these days but then they are also running 0w5 or 5w10 weight oils instead of 20w50 or thicker. As long as it is in the middle of the spec I wouldn't worry too much but I would also give it a pretty long break-in.


TheBandit 10-11-2012 05:01 PM

Thanks for the reply Jaysin. I think you are absolutely right. After a bit of reading, I decided the tight clearances were not appropriate for my build, so I ordered a set of MS-2199HX (add 0.001 clearance) main bearings. The machine shop installed the new bearings and measured the new clearances. Here are the before/after clearances (P vs. HX)

#: P/HX
1: .0015/.0026
2: .0010/.0024
3: .0010/.0025
4: .0012/.0025
5: .0011/.0026

From what I've been reading, the new clearances are spot on, so I will run them. The shop checked a number of other clearances as well. Here they are:

Rod clearance: .0021 (only checked one)
Piston to Bore: .0035 (4.0305bore/4.0270piston)
Wrist pin: .927
Wrist pin to rod ID: .0009
Wrist pin to piston ID: .0009
Deck height: 9.2240
Top ring gap: .019
2nd ring gap: .021
Oil ring: 0.010

The block is now in my possession, ready for assembly.

JaysinSpaceman 10-11-2012 06:59 PM


Originally Posted by TheBandit (Post 123398)
The block is now in my possession, ready for assembly.

Yeah, 'bout time.


TheBandit 10-13-2012 07:05 PM

Okay so here it is, finally back after 3 months sitting at QMP. It looks good as far as I can tell by eye.





Below is the no 2 cylinder which was sleeved. You can see where the sleeve mates with the block both at the deck surface and near the bottom of the cylinder. It was machined after install and I can not feel the transition with my fingers.




Do these mains look straight to you? The old eyecrometer just isn't accurate enough to tell, but I know cybermeasurements are trustworthy. They were line honed.


Chocflip201 10-13-2012 07:12 PM

Can't wait to see this smoke the tires!

TheBandit 10-13-2012 07:18 PM

Here is the crank which got a just a light polish and balance.



So the first thing I did was attemped to measure the main clearances. I started by measuring the crank main journals with outside micrometers. They were all between 2.5870 and 2.5875 according to my mic. Next I put the dial bore gage between the mic with the mic set at 2.5870. I tried desperately to zero it, but God help me that thing is impossible to hold steady and zero at the same time. The act of pressing the zero button is enough to move the whole thing and throw it off. Eventually I abandoned getting a perfect zero and just worked from the minimum displayed value. I measured the first main bearing and calculated a clearance of 0.0028. Then I went to do the next bearing and found the damn thing had changed it's zero somehow. I couldn't get a consistent reading, so I finally just gave up.

On to plan B, plastigage. I started by pulling all the main caps.


Then I laid strips of plastigage on top of each of the main journals.


And torqued the main caps on.


Then I removed the caps and here's what I saw



The plastigage is showing something between 0.0015 and 0.002, closer to 0.0015, and is consistent across all 5 mains. The machine shop said they measured between 0.0024-0.0026 using their bore gage. Now I have to decide which I trust. I think I will try my bore gage again and report back. Any thoughts?

JaysinSpaceman 10-13-2012 10:45 PM


I wouldn't worry much here. the consistency across all the mains is good and I would guess that the machine shop did you well on this motor (even if it was all a pain), after all 1000 great motors and you're known as a good machine shop, one bad one and you're out of business.

Plastigage is just for checking anyway and I would guess that it's got a +/-.0005 tolerance dues to lots of variables.

Don't over think this and scare yourself.

For god sakes man get that thing together already! HAHA


TheBandit 10-14-2012 01:09 AM

Okay after much frustration I figured out what was wrong with my bore gauge. Pretty much everything on it was loose. It had a plastic guard over the indicator which hid from my view the clamp meant to hold the indicator. The clamp had no screw at all! After I found a screw and tightened everything I was able to get consistent measurements.

First l set my mic up lightly clamped in my vice and adjusted it to the crank journal diameter, locking it in place. My mic only reads to .001 and I was reading .0005 by eyeballing the half way mark, so id guess my measurements are at best accurate to +/-.00025 and that may be pushing it. Next I recorded a reference reading on the bore gauge when placed in the micrometer. Finally after torquing the main caps into place, I measured the bearing ID and calculated my clearance. All of the bearings were round within .0002. Here is what I got for main clearances:

1: .00245
2: .00260
3: .00255
4: .00240
5: .00230

I think that agrees pretty well with the shops measurements, just not with the plastigage. I feel more confident with the measured values over the plastigage.

TheBandit 10-14-2012 01:30 AM

Looks like these guys had a similar experience with plastigage being significantly off from their Mic measurements.

I think I will trust the mic!

TheBandit 10-15-2012 01:00 PM

I got a few more hours into this yesterday and measured the rod journals and bearings. I am getting more confident in my bore gauge measurements because I was able to get very repeatable measurements: journals all measured 2.0990 time after time (shop measured 2.0989), setting the mic to that reference, I got repeatable measurements of the mic with the bore gauge and when measuring the rod bearings I got repeatable measurements too, all within .0002 when remeasuring. However I am measuring looser rod bearing clearances than the machine shop. I got four rods torqued down with bearings in them and measured 0.0034, 0.0035, 0.0036 and 0.0036 clearance. The machine shop measured only one rod and got 0.0021. I can't explain the discrepancy. For the rod they measured, I didn't even re-torque the cap, so I'm pretty sure I'm measuring the same physical bore as them. I'm not sure if it's my tool, my technique, or if I really have loose clearances.

Here is my method. It follows this method:
- Prepare rods by installing bearings and torquing bolts to spec w/ dab of assy lube on threads and under heads
- Use outside mic to measure crank journal and lock into place
- Place mic in vise with very light clamping pressure, just to hold it for the next step
- Place bore gauge into mic and rock/tilt slowly until the smallest dimension is measured: record the indicator value as the reference/zero
- Place the bore gauge into the rod bearings and rock/tilt slowly until the smallest dimension is measured: record the indicated value
- Subtract bore gauge reading in the rod from the reference value to get the bearing clearance

I am using this bore gauge, which reads to 0.00005 (although practically I've found it is only 0.0001): http://www.amazon.com/dp/B000XYND0M/ref=cm_sw_su_dp

And a 2-3" outside mic from this Harbor Freight set, which has 0.0005 graduations and a lever lock:

Sadly both Chinese tools.

ScooteK 10-15-2012 09:56 PM

I cant help but notice the backround. You up to something?

Chocflip201 10-15-2012 10:09 PM


Originally Posted by ScooteK (Post 123490)
I cant help but notice the backround. You up to something?

Just an old TubeBandit banner ain't it?

TheBandit 10-16-2012 01:16 AM


Originally Posted by ScooteK (Post 123490)
I cant help but notice the backround. You up to something?

I hung that for inspiration! It's nothing new, but I needed a reminder of what I'm capable of.

Tonight I refined my technique and I think I've figured out why my measurements weren't in line with the shop's. After watching some videos on micrometer techniques, someone mentioned you should be able to move the object through the mic and feel just a slight drag. What I had been doing up to this point was carefully tighten the ratchet thumb adjuster while rocking the mic a little to make sure I was perpendicular. I was getting very repeatable results, so I thought I was good, but what I discovered tonight was that after adjusting the mic in this manner, I could not get the journal to slide completely through it. This tells me I probably have not been measuring across the absolute widest part of the journal, but instead some offset dimension. It probably has something to do with being a newbie to this and also the lack of visibility due to counterweights etc on the crank.

I revised my method to instead adjust the mic so it could just slide fully across the journal and found my measurements to be larger by about .001. After referencing my new journal dimension with the bore gauge I start getting values in line with the shop's measurements: .0023, .0022, .0026, .0024. Now that's more like it!

Now I will have to go back and remeasure the main clearances to see how far they were off.

JaysinSpaceman 10-16-2012 10:43 AM

Precision measuring is most definitely a learned skill. I have an old friend that just got hired at an aerospace company due to his measuring skills. At his word he can shut the whole line down so he has to be spot on with measurements. And it sounds like many measurements are to the .00001". He happens to be a 55ish year old machinist, one of the finest manual machinists that I've ever met. Manual inspection is a dying art.

Glad you got it figured out.

I understand the cost savings of Chinese tools but measuring is one place I will always try my best to find European or American or Japanese even if I have to buy them used. When you can afford to replace yours I would start with a good set of mics with standards. Until then measure every tool and part in your shop that your mics will fit around and write the measurements down so that you can measure again tomorrow and check your new measurements against the recorded. I like to feel the tension required to zero a mic on a standard (assuming that the mic is zeroed correctly) to get the feel for measuring other objects.

Enough rambling.

TheBandit 10-16-2012 12:04 PM

Lots of good points. I am happy to be learning and gaining confidence in my measurements. I have had my feelers out for months to get a decent used quality mic, but the local classifieds are bone dry. Machine auctions come up all the time, but they are selling things in lots and I can't afford to buy a metrology lab worth of equipment. eBay prices are inflated. I will keep looking though - something is bound to turn up, just not in time for this job.

TheBandit 10-18-2012 11:36 AM

Okay I give up on measuring my own clearances. Last night I went back and remeasured all the mains. I was consistently getting between .0017 and 0.0018. Then I went to remeasure the rods I measured a few days ago. I noticed right away I was getting .001 smaller measurements on the journals with my mic but I was using the same method and checked several journals. I referenced my bore gauge against the mic and not surprisingly ended up with about 0.001in additional clearance on the rods compared to my previous measurements. I have completely lost confidence in my measurements, especially with the outside mic. The only thing I can say really is that for one measurement setup, I get very consistent measurements across all bores & journals, so at least if they are good or bad, they appear to be consistent. I will have to put my trust in the guys at QMP. I'm sure they not only have better measurement tools but also have a lot more experience in measuring these things. I hate that I can't independently confirm their results, but I trust their results.

I cracked open the Comp Cams 104 engine assembly lube I bought for putting this together and was surprised to find it is a white lithium grease, not the typical "red stuff". I did some digging around and didn't find anything against using it on main & rod bearings, though it seems less common.

As of last night, all oil passages have been cleaned by brush and solvent. Bores were wiped clean with ATF and coated lightly with 10W30 engine oil. The main bearings & journals are coated with assembly lubed. The crank is in. The main caps are installed. The crank rotates freely. I went to bed with dreams of rotating assemblies spinning in my head.

TheBandit 10-18-2012 01:28 PM


Originally Posted by TheBandit (Post 123596)
I cracked open the Comp Cams 104 engine assembly lube I bought for putting this together and was surprised to find it is a white lithium grease, not the typical "red stuff". I did some digging around and didn't find anything against using it on main & rod bearings, though it seems less common.

I continued reading this morning and found a few arguments against the lithium lube. Apparently it does not dissolve well in oil at all. Some people reported finding bits and clumps of the stuff in their engines still after many miles and oil changes. Since it's easy enough to do I think I will pull the crank back out, clean the stuff off and use something else.

The local speed shop carries Permatex Ultra-Slick. Any issue with that stuff?

juicedz4 10-18-2012 07:28 PM

Good to see you finally got the motor back and things are moving forward. :beer:

Keep up the good work.

I probably overlooked it, but any plans for a cam in this?


TheBandit 10-18-2012 09:46 PM

Thanks man! Yes, I am putting a cam in and keeping variable cam phasing. The new cam is 227/235 .614/.621 113LSA.

JaysinSpaceman 10-18-2012 10:46 PM

I think the last motor I assembled I used Lucas brand assembly lube. It looked exactly like the old Comp Cams red assembly lube. All other motors I assembled I used plane motor oil except for the cam lobes themselves. As long as the motor isn't going to sit indefinitely before it's started the first time I don't bother with the assembly lube.


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