CJ OUT at Indy!!

[Pete Beau]

The first thing that must been done in any measurement system is calibrate it! For anyone in the barn today, check for calibration stickers on the measuring equipment being used. If there is none then the gage is suspect. However, that also means that all gages being used by anyone must be calibrated in order for everyone to be on a level playing field. As an example, I have been in some garages/ shops and the guys are using calipers that are decades old and look like they have been through hell; let alone been calibrated.

The second thing in a measurement system is Gage R&R (gage repeatability & reproducibility). Basically it is a method of determining the amount of variation that a measurement system has in relation to the specification/ tolerance of the feature being measured. The end result is given in the form of percentage of error in relation to the tolerance of the specification. What is the tolerance that NHRA assigns to combustion chamber or piston volumes? The specification is a minimum value; you can be bigger, not smaller. How much bigger or what is the high limit of the specification? From that point you can determine what the gage error can be.

Just some food for thought.

[Bill Harris]

Did they pull a rod a piston out of these engines? If not, how can they accurately measure the CCs of a dish in a piston that is sitting at a 45 degree angle in the block?

[X-TECH MAN]

Originally Posted by Bill Harris

Did they pull a rod a piston out of these engines? If not, how can they accurately measure the CCs of a dish in a piston that is sitting at a 45 degree angle in the block?

It can be done....I did it all the time. I checked the winner of the quick 32 S/S at the US Class Nationals several years ago and my measurement was "Dead on" the manufacurer spec. and matched the engine guide in the car at a 45 degree angle while leaning over the fender. If I remember correctly it was Randy Manns car. It was an Olds engine in a Camaro or Firebird (cant remember which) SS/GT car. It even surprised him.

[Jeremy]

RJ you said your burette checked the same as NHRA Tech's burette. The NHRA Tech's burrette's (2) I checked from our Division did not check against each other as I said there was a .8 cc differance.

I tried to call you when I was in Pipe Creek, I have the wrong phone number.

Jerry

[X-TECH MAN]

The given tolerance for a burette is 1%. On a 100 C.C burette that is 1.0 (one point zero) C.C.s. Reason alone to allow some wiggle room when milling your heads. Not only the burette is involved but the medium usuallly used is alcahol and is tempature sensitive. A hot cyl. head will not check the same as a head at room temp. The alcahol will expand when the head is hot and give you a smaller reading. Some go so far as putting the head into a cooler full of ice to bring down the temp of the head. 1/2 or even a full C.C over the spec. will not slow down the car. The engine will never know it.

[Pete Beau]

Originally Posted by Jeremy

RJ you said your burette checked the same as NHRA Tech's burette. The NHRA Tech's burrette's (2) I checked from our Division did not check against each other as I said there was a .8 cc differance.

I tried to call you when I was in Pipe Creek, I have the wrong phone number.

Jerry

So, if we allow 10% G R&R the minimum tolerance that that system could measure would be 8 cc's!! Now that may seem ridiculous but that’s the results of the calculations. So how much error do you want to allow in the system? If the tech. stated that your combustion chamber was .5 cc small then that measurement was within the error of the two gages.

Also keep in mind some features are more difficult to measure than others. The most difficult are visual attributes or specifications. One persons course finish is another’s fine. A color (one of the most difficult) may look light blue to one person and medium blue to another.

The budget for the measuring system plays a big role. Like anything else, you get what you pay for.

[Mike Taylor 3601]

I was reading post and going to make basically same statement as you Terry.It does'nt matter what your
burett or mic's or caliper shows the tech man goes by their tools reading it's our responsibilty to leave
room in our measurements for difference in gauges,just like lbs per cubic inch classes it's your responsibility to claim correct cubic inches.I had customer truck pulling406'' limit so everyone built400sbc
30 over he got pumped 406.7 would'nt pass so I had to destroked cranks to 3.735 stroke deck block.007
rebalance actaully ran better then because crank had stroke&index equalized then.
I heard of some Dodges that got bounced at Indy several years ago few minutes later truck owner supposedly came up on golf cart w/ the updated specs that had been faxed to him from mopar so they were legal.Has anyone else heard that story before?
Mike Taylor 3601

[Chad Rhodes]

Originally Posted by Mike Taylor 3601

I was reading post and going to make basically same statement as you Terry.It does'nt matter what your
burett or mic's or caliper shows the tech man goes by their tools reading it's our responsibilty to leave
room in our measurements for difference in gauges,just like lbs per cubic inch classes it's your responsibility to claim correct cubic inches.I had customer truck pulling406'' limit so everyone built400sbc
30 over he got pumped 406.7 would'nt pass so I had to destroked cranks to 3.735 stroke deck block.007
rebalance actaully ran better then because crank had stroke&index equalized then.
I heard of some Dodges that got bounced at Indy several years ago few minutes later truck owner supposedly came up on golf cart w/ the updated specs that had been faxed to him from mopar so they were legal.Has anyone else heard that story before?
Mike Taylor 3601

I would have thought that if it was a specs mistake that ford would have gotten them reinstated by this morning. It may have cost them a few GT500's for Compton's kids or something but I figured it would have been done. I would think that a manufacturer advertising and selling a "stock eliminator legal" car that didn't pass tech would be opening the door for a ice class action lawsuit. If they don't get the spec changed, then all of these motors have to be taken apart to check for legality. If I were NHRA, I would not change the spec without a reevaluation of the HP rating

[stefan callender]

Originally Posted by Chad Rhodes

I would have thought that if it was a specs mistake that ford would have gotten them reinstated by this morning. It may have cost them a few GT500's for Compton's kids or something but I figured it would have been done. I would think that a manufacturer advertising and selling a "stock eliminator legal" car that didn't pass tech would be opening the door for a ice class action lawsuit. If they don't get the spec changed, then all of these motors have to be taken apart to check for legality. If I were NHRA, I would not change the spec without a reevaluation of the HP rating

How does anyone know If these motors were opened up and played with??

[X-TECH MAN]

Originally Posted by Mike Taylor 3601

I was reading post and going to make basically same statement as you Terry.It does'nt matter what your
burett or mic's or caliper shows the tech man goes by their tools reading it's our responsibilty to leave
room in our measurements for difference in gauges,just like lbs per cubic inch classes it's your responsibility to claim correct cubic inches.I had customer truck pulling406'' limit so everyone built400sbc
30 over he got pumped 406.7 would'nt pass so I had to destroked cranks to 3.735 stroke deck block.007
rebalance actaully ran better then because crank had stroke&index equalized then.
I heard of some Dodges that got bounced at Indy several years ago few minutes later truck owner supposedly came up on golf cart w/ the updated specs that had been faxed to him from mopar so they were legal.Has anyone else heard that story before?
Mike Taylor 3601

The problem with a P&G pump is its not that accurate (dead on). Cranking speed of the starter/voltage of the battery and the cam shaft over lap has a little to do with the reading not to mention the temp allowance used. Normally if one is used correctly and all othe varibles are there (cranking speed, etc.) the P&G pump will show a little UNDER the actual cubic inches. It all depends on the person using the pump and his/her experience. Not all P&G pumps measure the same either.