• The Roadster Factory Recovery Fund - Friends, as you may have heard, The Roadster Factory, a respected British Car Parts business in PA, suffered a total loss in a fire on Christmas Day. Read about it, discuss or ask questions >> HERE. The Triumph Register of America is sponsoring a fund raiser to help TRF get back on their feet. If you can help, vist >> their GoFundMe page.
  • Hey there Guest!
    If you enjoy BCF and find our forum a useful resource, if you appreciate not having ads pop up all over the place and you want to ensure we can stay online - Please consider supporting with an "optional" low-cost annual subscription.
    **Upgrade Now**
    (PS: Subscribers don't see this UGLY banner)
Tips
Tips

General Tech Plasti-Gauge on Rod Bearings

KVH

Darth Vader
Silver
Country flag
Offline
My TR was rebuilt twice over the past 20 years. When I replaced the rod bearings 14 years ago, they were sized 1000 under and the crank looked great, so I just used the same. I remember the plasti-gauge being inconclusive back then, seeming too tight, but I ignored it and the car ran great.

Well, I want to replace the bearings again since I'm inside the engine doing all sorts of mischief (new cam, etc.), and I just plasti-gauged the rod bearings again with new 1000 under bearings. The result showed about .0020 (or maybe even .003, like .0017 less) clearance, and factory spec, if I'm reading it correctly, is .0028. In other words it's still too tight. Is plasti-gauge that exact, even from a package 14 years old?

I'm inclined to ignore this as I did 14 years ago and drive scenic roads with a big foolish grin on my face.

Any serious caution out there?


(thoughts for all hurricane victims and those displaced; they have some issues worthy of real consideration)
 

Rut

Obi Wan
Country flag
Offline
I don't know the clearance specs, but I always use Plastigage to confirm any work I've had done and shoot for the tighter range of the spec, never outside it.
Rut
 

TomMull

Darth Vader
Silver
Country flag
Offline
You can get a decent digital caliper for very little money today that will confirm or contradict your plasitgauge. You also get the advantage of seeing the shells and journals independently.
Tom
 

trrdster2000

Luke Skywalker
Country flag
Offline
KVH, you clearance is fine, most would love to be that good.

Wayne
 

poolboy

Yoda
Country flag
Offline
While plastigage if fine for verifying freshly completed machine work, the problem with using plastigage on old work or higher mileage is that usually the problem with journals, if damaged, is that they are 'out of round'.
Plastigage is only checking a few of the 360 degrees.
 
OP
KVH

KVH

Darth Vader
Silver
Country flag
Offline
My TR was rebuilt twice over the past 20 years. When I replaced the rod bearings 14 years ago, they were sized 1000 under and the crank looked great, so I just used the same. I remember the plasti-gauge being inconclusive back then, seeming too tight, but I ignored it and the car ran great.

Well, I want to replace the bearings again since I'm inside the engine doing all sorts of mischief (new cam, etc.), and I just plasti-gauged the rod bearings again with new 1000 under bearings. The result showed about .0020 (or maybe even .003, like .0017 less) clearance, and factory spec, if I'm reading it correctly, is .0028. In other words it's still too tight. Is plasti-gauge that exact, even from a package 14 years old?

I'm inclined to ignore this as I did 14 years ago and drive scenic roads with a big foolish grin on my face.

Any serious caution out there?


(thoughts for all hurricane victims and those displaced; they have some issues worthy of real consideration)

I'm so sorry. I miss-typed. I meant to say: "I just plasti-gauged the rod bearings again with new 1000 under bearings. The result showed about .0020 clearance (or maybe even .0003 less than that, like .0017), and factory spec, if I'm reading it correctly, is .0028. In other words it's still too tight." I could be .0008 too tight, maybe even .0010 too tight.
 

trrdster2000

Luke Skywalker
Country flag
Offline
KVH, if you are not typing these clearances wrong, you have way too much. I think you are reading the plasti-gauge wrong.

I think your new bearing shells are .010 over and you say the results is about .0020 clearance or maybe even .0003, that is a lot of difference. I think all is OK, you are just interpolating it incorrectly.

Look on the paper part of the plasti gauge and count the zero's, a .0001-0003 in very small, just room enough for a oil slick.

Wayne
 

TFB

Jedi Knight
Country flag
Offline
Good points on checking journals for roundness( a quick had polish with some 600-1000 paper quickly shows any wear pattern) with an outside mic which is fairly easy to get accurate repeatable readings.I use Starret inside snap gauges for cylinder id's but repeatability,for me anyway, is hard to get better than .0005 1/2 thou.Fine for cylinder work but the plastigage is pretty much fool proof repeatable for closer work like bearing journals if you don't have an expensive bore mic in the correct range.
Tom
 
OP
KVH

KVH

Darth Vader
Silver
Country flag
Offline
I'm so sorry. I miss-typed. I meant to say: "I just plasti-gauged the rod bearings again with new 1000 under bearings. The result showed about .0020 clearance (or maybe even .0003 less than that, like .0017), and factory spec, if I'm reading it correctly, is .0028. In other words it's still too tight." I could be .0008 too tight, maybe even .0010 too tight.

I'm causing confusion. It's my fault for trying to give too much information. What I actually said in my corrected post was that my reading showed about .0020 clearance, or maybe ".0003 less than that," meaning as tight as .0017. At .0020 I'm .0008 too tight, and at .0017 I'm near .0010 too tight. Again, sorry. I'm just being too picky about the details perhaps. My local shop says that if my plasti-gauge is years old, and if I know I've been running on .010 undersize rod bearings, just put it back together, drive and have fun. I think that's my plan.
 

CJD

Yoda
Country flag
Offline
There is a technique to plastigage. You must ensure that you use no oil and pull the rod hard into the crankshaft before tightening the cap. If you get twist on the rod as you torque it, it will overly compress the gage and show an erroneous tight clearance. I agree. If you were running .010" bearings before, the crank has not grown. Unless the bearings are mis-boxed, you are golden.

As a final check, make sure the crank will turn after every rod is torqued. After all the bearings are torqued you should still be able to turn the crank without too much effort. If it acts locked...then take it apart and see what's too tight. Even then, it is normally caused by a warped bearing rather than a tight clearance.
 

sp53

Yoda
Country flag
Offline
I am not a machinist, but I knew this guy that was and he would help me all the time. Anyways, he would always have me pull the rods out and bring them to him and then he would true them up or round them out --the cost was not much. This is probably what Poolboy was getting at.
steve
 
Similar threads
Thread starter Title Forum Replies Date
KVH Plasti-Gauge Again Triumph 2
JPSmit Plasti Dip Question Restoration & Tools 5
vping Plasti-Kote MG 9
R TR2/3/3A Overheat issue, gauge adjustment Triumph 9
G MGB ugh.....the fuel gauge went to *** again! MG 8
RJS TR4/4A Smiths Oil Temp Gauge Triumph 11
J MGB Oil Pressure Gauge Gives Constant Reading -- Doesn't Seem Right MG 15
roscoe Fuel Gauge Austin Healey 0
G Smith's temp gauge repair Restoration & Tools 4
CARSINC eBay Gauge Packages Spridgets 6
Gliderman8 TR6 Excessive reading on volt gauge Triumph 17
K TR2/3/3A Wiring a voltmeter gauge to replace the ammeter. Triumph 1
Gatheringtree TR2/3/3A Gauge Set Triumph 17
jfarris For Sale TR4 Fuel Gauge with 2 Transmitters Triumph Classifieds 0
D Fuel Gauge Austin Healey 7
BoyRacer Thread Pitch Gauge from "British Tool and Fasteners" Austin Healey 0
LD-Ordie TR2/3/3A TR3 gauge service Triumph 11
RJS General TR Oil Pressure Gauge - Test Triumph 11
RJS TR4/4A R&R Oil Pressure Gauge Triumph 7
RJS TR4/4A TR4A Temp Gauge Scale Triumph 6
B For Sale BaulyCars - Gauge Bezels Triumph Classifieds 0
AngliaGT MGB-GT Gauge Repair Recommendations? MG 4
BierRunner TR6 Temperature Gauge Triumph 8
T Wanted Working Fuel Gauge for TR3A Triumph Classifieds 5
HighAltitudeTR3 T-Series MGTD Sheet Metal Gauge?? MG 0
Lairhead52 Wanted Oil Press Gauge Triumph Classifieds 0
T TR2/3/3A TR3A Fuel Gauge problem Triumph 10
B TR4/4A Jaeger Gauge Question Triumph 16
K TR2/3/3A TR3 with alternator conversion... red light stays on and low voltage on the voltmeter gauge? Triumph 1
Retired2020 TR5/TR250 TR250 smith gauge Triumph 7
L Oil Pressure Gauge Austin Healey 5
Martinld123 Problems with my BN2 Temp Gauge reading Austin Healey 13
B Fluctuating Fuel Gauge 1960 Bugeye Spridgets 4
R TR2/3/3A Amp Gauge-erratic reading after alternator conversion Triumph 39
Fanch00 Inoperative Fuel Gauge Austin Healey 10
R Coolant temperature gauge Spridgets 8
EWD TR6 Temp Gauge - 74 TR6 Triumph 11
Boink Early Mini Fuel Gauge - adjusting it British Motor Corp 0
Editor_Reid Water Temp Gauge Austin Healey 5
J TR6 73 TR6 Temp Gauge Wiring Question Triumph 6
Gliderman8 TR6 Vacuum Gauge Hookup Triumph 11
E Gauge Lights Austin Healey 4
S WANTED: Healey BN1 "Smiths" Fuel Gauge (Dead or Alive) Austin Healey Classifieds 3
K TR2/3/3A Using a dial gauge to adjust valves when rocker arm surfaces are worn? Triumph 9
R TR2/3/3A Fuel Gauge Triumph 19
nichola TR6 Smiths volt gauge needle barely moves Triumph 25
T Wanted Smiths fuel gauge for Mk 1 Bugeye Sprite [FG2530/31] Spridgets Classified 1
S Fuel gauge calibration procedure Austin Healey 18
D TR6 Disconnecting pipe from engine block to oil pressure gauge Triumph 6
C MGA Fuel gauge question MG 8

Similar threads

Top