CJ OUT at Indy!!

[442OLDS]

If they tossed a couple CJ cars,then how can the other ones be fine?Aren't they all the same except for weight and transmission type?



Sorry,this question has already been asked.


And it sure does seem silly to worry about what kind of pistons a car has when it has a supercharger on it.

[Rich Biebel]

In the old days.....ALL class winners got torn down and if they were found illegal the r/up got torn down...and if they were found illegal......there was no class winner! Been there and done that as the saying goes....If a car is not torn down it's obvioulsy considered legal......

[Mike Voth]

Al - good point. We got tossed at the KC National Open last fall b/c after we reset our GTE record, two combustion chambers measured incorrect. One by a meer .4 of a cc also. Sent the heads back to Dave Layer and he said they checked fine. The short of it...we have heads that make us SHORT on power just so they will pass NHRA inspection. It DOES matter what equipment is used.

[Jeremy]

I posted on this burette problem earlier this year and it didn't get much attention.
I checked two of NHRA's burette's against mine and all three were different. NHRA's high dollar/quality burette's had a differents of point eight cc's on a 100 cc's which is alot when your checking 150-200 cc port volume.
I googled on the internet and it says class A burette's (best) only have to be within one cc to be with in spec's.
Thanks
Jerry

[bill dedman]

>>>"class A burette's (best) only have to be within one cc to be with in spec's"

"within one cc" when measuring what size volume??? That is the defining criterion...

[Jeremy]

"within one cc" when measuring what size volume??? That is the defining criterion...
__________________
Bill

Within one cc on a 100 cc's or 1 percent.

[RJ Sledge]

I've used a burette that I got from PMS (Pudgy Pendergrass) in San Antonio, Texas 210-681-2405 for over 20 years, and I swear it checks the same as any NHRA Tech burette. I have been through teardown numerous times and have never had a problem. Give him a call if you want the real thing. Its tough enough to do this stuff without having a SNAFU with the measurements.

RJ

[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 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.

Pete is pretty much dead on with his comments. I worked in a Navy calibration lab for over 18 years up until I retired. There are tolerences involved in precision equipment and they NEED TO BE CHECKED at intervals. I always made sure my stuff was correct as I brought my own checking equipment with me to the races. I did NOT rely on IHRA's tools. How many have been bounced over the years for .001 of an inch ? A dial indicator tolerance is plus or minus .001 in its self. The moral of the story is you HAVE to allow some amount over or under depending what engine part and spec your dealing with for heat build up, "pilot error" (the tech guy), and not build these things to the "enth degree" or dead on. Its the responseability of the racer/engine builder to make certain the head is allowed enough "wiggle" room for C.C.s or the valve diameter is correct, enough deck height is allowed for wear and tear, rod streach (they do streach a small amount with duty cycles) or enough room is allowed for any other engine part. NHRA and IHRA always had problems with valve springs being at or under the correct pressure back when the stockers had to run the factory specs. Pete is also correct in that the plastic burettes are JUNK. Buy a glass one that is certified from someplace like Fisher Scientific or another precision tool supplier. I remember when I was cutting some heads for C.C..s (428 CJ) and had them all at 68.2 to 68.4 C.C.s for a good engine builder (Ford guy) here in Md. I gave them back and about a day later he screamed that I ruined them. Well he had used a plastic burette to check them and they showed up being a full c.c. short with his burette. I knew better because my burette was glass and I checked it at work when I was working for the Department of Defense (Navy). I proved it to him and his customer went on to win the Gatornationals stock eliminator that year in his Orange 428 CJ Mustang. It passed tech with flying colors. Moral of story....use certified tools and allow wiggle room. Its YOUR responsability.