I have often mentioned the necessity of using calibrated measuring tools when assembling/testing an engine. For the V6 build, I ordered and got from Speedway a valve spring tester and I checked and paired the new Arricambi springs I got. The readings were good, but a bit high compared to the published specs (~12-15lbs higher). It turned out that with the available installed height (IH) I have, spring pressure would be too high. Visions of worn cam lobes, had me scouring for alternate springs and I did find a set with the correct pressures. Long time ago, I had measured another V6 sring set again from Arricambi and it was smack on spec. Curious about this, I took two springs to work and measured them on two of the calibrated testers we have there. Brought the curves home and sure enough, my tester was reading high. I used the correct curves to adjust it so it now reads the same with the others. Well, the previously 'unsuitable' springs are ok for use with std weight valves and if trick retainers are used (allowing for more IH) their pressure can be lowered for use with lightweight valves.
The moral of the story is to use calibrated tools/gauges and if not, to know how 'wrong' your tools are. Compression gauges, torque wrenches, spring testers and all car instruments-speedo, tach, oil press. gauge, water temp gauge. All these can be calibrated, some in conjunction with their senders. I really want to know my true speed and laugh when other guys can't decide whether its their speedo, tach or both that are wrong! Maybe I'm paranoid, but I had to recalibrate the speedo when I switched from 15 to 16" wheels (from 205/50-15 to 205/50-16) Maybe its 'trivial pursuit' but press. gauges that read zero at idle are a sore sight I'm sure!
Jim K.
Except for the speedo (who needs a speedo anyway 
), you are right.
The problem is you don't know how accurate your stuff is if you don't have anything (which IS accurate) to check with. Also, some cheap stuff is not possible to calibrate except by making your own compensation (which again is a source for error and confusion).
I found a tire pressure gauge I have was 0.3-0.4 bar off when I checked it against my new accurate one. Shit like that is not worth keeping even for spare.
), you are right. The problem is you don't know how accurate your stuff is if you don't have anything (which IS accurate) to check with. Also, some cheap stuff is not possible to calibrate except by making your own compensation (which again is a source for error and confusion).
I found a tire pressure gauge I have was 0.3-0.4 bar off when I checked it against my new accurate one. Shit like that is not worth keeping even for spare.
Funny you should mention it Micke, I spent a small fortune (relatively speaking) on a correct/calibrated tyre pressure meter last spring.
It has found me some time around the tracks.
(repetability is the key here)
It has found me some time around the tracks.
(repetability is the key here)Mats Strandberg
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-
GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-
GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
Most people will fall for the 'new = accurate' reasoning. Its really an eye-opener to be able to visit a calibration department in a large company and get a whiff of 'primary', 'secondary' standards and so forth. Anything that measures anything has to be calibrated at certain intervals (from 6 months and up depending on type)
Hah, when was the last time your track timing equipment was calibrated? How about the speed radar gun that hit you? We have had people get away with speeding here, because the cops couldn't produce valid radar calibration certificates in court, heheh!
I'm just trying to bring up the importance of calibration in all car-related things that affect our sick
hobby. Mats'tire pressure example is on the nose. You may laugh, but I have a very accurate tire press gauge, one of those penlike things with the scale that pops out the back! I take this to work and check it yearly. Another thing I had calibrated (it was off by ~5%) is the tire shore meter, very handy to have.
Jim K.
Hah, when was the last time your track timing equipment was calibrated? How about the speed radar gun that hit you? We have had people get away with speeding here, because the cops couldn't produce valid radar calibration certificates in court, heheh!
I'm just trying to bring up the importance of calibration in all car-related things that affect our sick
hobby. Mats'tire pressure example is on the nose. You may laugh, but I have a very accurate tire press gauge, one of those penlike things with the scale that pops out the back! I take this to work and check it yearly. Another thing I had calibrated (it was off by ~5%) is the tire shore meter, very handy to have.Jim K.
One last thing: a very interesting pictorial representation concerning accuracy and precision (are they different??) can be found here:
http://www.flatsurv.com/accuprec.htm
Jim K.
http://www.flatsurv.com/accuprec.htm
Jim K.
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Sporttunergtv6
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ahh yes... recalling one of the many joys in chemistry class- the distinction between accuracy and precision. that was right before i learned about stoichiometrics (funny, that was also right around when greg gordon published his tech article on ljet... and it all made sense!)
vittorio
ps: here here on calibrated properly working tools, sears loves it when i show up with a box of tools that need to be replaced.
vittorio
ps: here here on calibrated properly working tools, sears loves it when i show up with a box of tools that need to be replaced.