plastigauge

[ianv3]

what is it, hows it work, whats it do.

thanks.

 

[DSMJim]

Its a strip of soft plasticy type stuff that out put under something to measure the clearance. People use it to gauge the clearance in thou for crank and rod bearings. You put it in the bearing put in the crank and torque it down. The plastigauge stuff squishes depending on the torque applied and clearance of the bearing. You take the cap off and measure the size against the "pastigauge" to see what the clearance acctually is.

It's a way to make sure that at 65ft/lbs you have 3 thou clearance (or whatever) on your bearings. Just a way to measure really.

 

[Suparata]

Plasigauge can make a measurement of 3 things at one time : bore size, shaft size and bearings size ("thickness").While bore and shaft sizes should be measured before assembly it is very difficult to measure the bearings size so plastigauge should be used before assembly to make sure every thing is correct and eliminate surprises.
Mitch

 

[jukematt]

Old thread but I was curious about this stuff too. I believe I have spun a bearing and getting rod knock so am buying new bearings. I was curious what the actual use is. People have recommended it when getting new bearings but I still don't understand exactly why it is so highly emphasized?

(First time changing bearings and new when it comes to engine internals.)

 

[crash89]

This stuff is used to check the clearances between crank journals the bearings, mains and/or rods. If your clearances are off you could/will most likely trash a fresh motor due to insufficient lubrication.

What ya do is, before you place your main/rod caps on, place a piece of plastigauge on the journal. Then torque down your cap. Then remove, with your package you'll have a little sheet with widths equaling x gap. Compare your plastigauge width with the sheet to find out the clearance.

I know its a v8 but still same concept.. Plastigauge is at 1:30
http://www.youtube.com/watch?v=3qPRRE_tSBo

 

[jukematt]

OK so once you find out the clearance, how is that useful? Like what should be the clearance? Like for instance, I was planning on buying these rod bearings:

EXTREME PSI : Your #1 Source for In Stock Performance Parts

but there are three different size choices. Which ones would be best to get?

 

[bryanwheat]

You wouldn't know until you pulled your old bearing and see what size they are. If you have a spun bearing though a new set of bearings isn't going to help you. The crank will need to be turned and the rod will have to be rebuilt.

 

[jukematt]

As far as I know my engine is stock. So are there different sizes for stock then?

And we're hoping since the sound is only just beginning and cannot even be heard at idle that it's not bad enough yet. My friend's friend had a Talon TSI AWD and he was able to catch it early and just replaced the bearings and was fine. He used AutoZone bearings but I don't want to do that.

We are going to pull it apart this weekend but if I can get by with just replacing the bearings, I wanted to have them on hand.

 

[livedsm4g63]

There are different sizes but that is only if the crank has been cut.

 

[98zx23369]

whatever you do. DO NOT spin the crank when plasticgauge is in there!!!! or when its in the rods. and make sure you clean it off after, completly cleaned off

 

[jukematt]

Alright thanks for the advice and information.

 

[turboglenn]

all engines and engine builders will have a certain number they're shooting for when building an engine. I have my machinist measure everything when he does my engine builds, and then he labels which rod/piston combo go in which bore, and althouigh i know he's already checked them with high quality micrometers/bore gauges, i'll always double check when assembling with plasti-gauge. For instance some people will build a 4g63 with main bearing clearances "loose" at .003", but my machinist is too picky because he backs his builds and i went through 3 cranks and lord knows how many sets of ACL tri-metal main bearings untill we had a combo tbat measures .0025 for every journal. And that's what i would look for with plasti-gauge when assembling the engine.

Not sure what his piston to wall clearance was but it was something that didn't need double checked, but i did have to individually file each of my rings accroding to the bore size multiplied by a certain number that varied for what rung it was (top, second or oil control) and by the use of the engine (n/a, turbo, turbo with nitrouse, etc..etc...) as the more expansion needed to accomodate the added heat from the harder abuse dictated how much ring gap was needed. (and the number you multiply by is usually provided by the piston/ring manufacturer)

i know tht goes a littler beyong plasti-gauge use but i figure if you're going into an engine these are other thingsd you should know that need to be certain specs

 

[jukematt]

Wow thank you very much, turboglenn! That was very helpful!

 

[herms99gst]

and you won't know what size rod are main bearings to get untill you have your crank checked by a machinist. If it turns out that you have to have your crank turned, he/she will let you know how much material was removed so you can take that number and add it to the standard bearing size to make up the difference in material lost. Keep in mind that our OEM cranks are nitrade hardend to 30 thousadths deep on the main and rod journals....I believe this is rght correct me if im wrong. But by losing this hardness you take away some of the strength of the crank. Im not saying you cant have it turned because you can and have a good running motor. You just cant push the motor to crazy numbers with one. And for a standard build i would just use the oem clearances for your rod and mains and call it a day.

 

[arrowhead]

Plasigauge can make a measurement of 3 things at one time : bore size, shaft size and bearings size ("thickness").While bore and shaft sizes should be measured before assembly it is very difficult to measure the bearings size so plastigauge should be used before assembly to make sure every thing is correct and eliminate surprises.
Mitch

Could you explain or are you talking about another product.

 

[crimsondragon]

Plastigauge should only be used on final assembly as a verification check, not as something to go by as a measurement. It's inconsistent at best. Plus, if you're crank is out of round, it will vary depending on where the out of round is in comparison to the stuff. Disassemble the engine, have the crank checked or do it yourself. Correct if necessary, then do final assembly with plastigauge for verification.