I have always taken "the chance" when it came to building a engine and not used plastiguage at all so I have no idea how to use it now that I have!

It says there are the colors on the strip I have:

CLEARANCE RANGE .002 to .006 INCH

USE SPG-1 (GREEN) for .001 to .003 INCH
USE SPG-1 (BLUE) for .004 to .009 INCH

I have (red) which includes the measurements for .002 to .006 inch.

Now, I know about how to use the stuff, but not how to read it. All the engine building manuals say to read the package, lol but I'm lost! This is a pic of what it looks like:

http://www.xbox-connection.com/hoste.../clearance.jpg

My engine is line bored .10 over on the crank journals, so do I have the wrong plastigauge? or do I use one of the shown numbers?

Thanks!

 

I use the green one (.001-.003). It's easy to use. Lay the bottom set of main bearings in the block saddles (I'm presuming engine block is on a stand, upside down). Put them in dry without the rear main seal. Lay a strip of plastigage across the journal you want to check. Then install the cap with the main bearing seated all the way in it. Torque to spec. Remove cap gently. Tear off a 1" section of the plastigage package and use it to compare the thickness of the squished plasigage with the band on the plasigage package it most nearly matched in width.

e.g., if the squished platigage is as wide as the .002 band, that is the clearance.

Do this for all main journals, then the rod journals. You have to measure rod journals with both rods for that rod journal installed, cause just one would allow rod end to skew over and ruin the reading. Needless to say, don't put the rings on the pistons till this procedure is done.

Then take it all apart, clean and prep one last time, and put it back together for real.

 

But, how do I know how much clearance I NEED? Does'nt each over size need a diff clearance? or is it fine as long as it has clearance, like I said i knew "how" to use the plastiitself just not how much clearnce i needed, so i still need this answered, lol. although thanks for the excellent explanation on the other part.

 

Sorry, didn't understand your question. No, each size does not have a different clearance. Standard, .010 , .020, all the same. The clearance specified for your engine bearings is all you need to know.

 

well i started w/ a bare block w/ no id code (decked off) but I think it's a pre-85 block at least, so I hope the Clevite77 bearings I bought (should be in today ) have that clearance number, or heck I'll be lost for the third time. If it isn't, whats do I do? lol.


*digs* Where's that jougi board?


-David

 

[UPDATE]

Checked all main journals, they all are exactly .002 In. That good?


PLASTIGAUGE READINGS!


-David

 

There are many ways to find out what the clearences should be.
The easiest is to call the shop that did the machine work and ask them.
The next is to read the Chevy Engine Overhaul Manual. It will tell you what the min and max clearence should be.
Or you could get a book, like How To Hot Rod a SBC. It also has bearing clearence info.
Finally there is no single number, it depends on what you built the engine for. In some application you want more clearence, in some less.

 

Well, it was line bored and it is meant for mild street use, so I assume the more HP intensive, the more clearance it needs?

Also, the book I have shows the caps to be torqued at 78 lbs. It states that all Gen1 Small blocks are at 78, regardless of the bolt number of the cap. (2or4)

Are these 2 items correct? thanks again....

-David

 

.002" is ok, but that 78 is wrong. It should be 70. Maybe a misprint.

http://www.racersguide.com/chevy_sma...ck_torque.html

 

Well after some more "research" I discovered why that website says 70, when my book says 80.

(difference between 2 bolt main and 4 bolt main)
2 bolt=80 lbs. 4 bolt = 70 lbs. inner/65 lbs. outer


Why is it better/good to oil the threads? I have never done this, I've only added lubricant to a bolt when they were ARP or Stalger fasteners. I tested the clearance without oil, and im afraid if I add oil it will throw off the clearance. Also none of my rebuild books have this little "trick". But looks like it's widely accpeted now.

Anywho, I just got through torque'n all the mains and rear cap to the above number without oil. Maybe the oil just prevents galling. Either way I've never done it and i've been okay many times before. And the crank is now snug and installed. One less worry off my shoulders. Now to take the rods and pistons back to my dumb455 machinist, he left the caps on when he bored them and I can't get them off. Not even my air tools can do it. I miss my old machinist ( ) he always had them layed out, caps off, and even put the rubber hose ont hem for me. Now that's service, but he was from a different time.

Thanks alot for the help...
-David

 

I hope you had the rod ends in a rod vise or in a regular vise between 2 pieces of wood when you were cranking on the nuts. Otherwise there is a risk of tweaking the big end of the rod. If you clamp the big end this way, it is easy to take the nuts off with a torque wrench.

If a bolt isn't going to be installed with antiseize, sealant, or threadlocker, it should be oiled or moly lubed. This is to lube the threads so that the torque reading is accurate. Otherwise a large part of the torque is taken by friction, meaning the bolt has less torque on it to properly load it so that it provides the correct clamping force. Lightly oil the threads and the area under the bolt head that clamps the main caps.

Cliff notes: no oil means bolt might be under torqued, even if torque wrench says 70.

 

Whoah, did'nt know that! Guess I'll just have to remove the bolts and oil em' up good. Although, I have been thinking about threadlocker on them, hmmmm....... Would either work?

And yes, like I said before, this is NOT the first motor I've built. So try not to be so con-de-send-ing next time k? lol. But I do appreciate the help though. But I'm not a newbie, just always done things "by the old book" doesnt make them the wrong ways, just makes them out of date. And obviously all my motors have done great and been very reliable, so I am obviously doing something right huh?

Now with that said, yes I had it on my big vise between two 2X4's and my impact couldnt budge it. Neither could my 3/4 longbar!!! I figured he left them at whatever ungodly torque factor he used when he machined them, so HE SHOULD be able to safely loosen them for me, the jerk.

-David