Tuning issues with hoter weather

Ok those runs all look pretty similar... I did see at least one run where the rpm on the stop never dropped below 4500... the usual seems to be that it initially dropped to 42 or 43 and kinda crawled back up to 45 before kicking off.

What I have seen with my car before is sometimes air changes will affect the dead stall rpm much more than the overall horsepower.. maybe a 1000 -2000 foot altitude change has sometimes made 300 rpm difference on the stop... and that will kill et big time..

With the small cam maybe your deal is affected more at the lower rpm's..

Does your playback tach work?

The tack in not a play back. It has a shift light.

Ace

Well we went through the Trans and found no problems. So next I did a leak down and valve spring check and found #1 was 60-65% leakage! Wow pulled the heads dropped them off and will know more in the morning. Somethingl ooks a miss. The tip of the valve is not much higher than the retainer. These are out of the box 10 bolt TFS A460 heads with the 2.35 /1.88 valves. Any body know if this right? I did get this used last year


Ace

Sounds like you were very close to having one of those catastrophic   events!!!

Was there a lot of lash on that valve?....as in....had it moved since it was last adjusted? Broken locks in the retainer?

No lash problems.

Pop the retainer off yet?

The heads are at my cylinder guy. Ill know more before noon today


Ace

Update

None yet he is working in them as we speak. He is dedicating today to get these done before he leaves tomorrow for a weekend camping trip. I do know the heads have been worked on before with less than 25 passes for the same thing. Installed spring height was altered .050 to 2.050 for some reason. The installed spring pressure has been bench tested and are 190-204. Sad thing is my only choice for springs today is PSI. That's all he has in stock. I would rather have he PAC's


Ace

OK heads are in my garage ready to go back on. My head guy said who ever did the valve job has no right touching heads!!!! One angle on the valve and no back cut. I didn't understand what he said about what they did to the seat but he ended up with a a 30-45 on the valves with a back cut. and 3 angle on the seat. the last angle was very light as someone had done some pocket porting and didn't leave much for the 70 degree cut. He also used the PSI spring with a installed height of 1.990 and seat pressure of 282-288lbs and a open height of 1.190 with 768-779lbs. The cam card only calls for 240 closed and 680 open. so now we'll get this thing together friday night and get it out of the trailer and warm it up and make sure the trans is working fine and then reload and get read for the MILE HIGH NATIONALS!!!!!   

Ace

 

Well everything is done put together and back to our base line starting area and we even cleaned the cars and the trailer out and reloaded and are ready to get in line for the Nationals next week. Now I'll nave to wing my Crew Chief software for next week and hope we run as good as it did las year.

Ace

So was that you guys going out in the semi's??

dkp

Sure was. And that motor is junk kept slowing down every run. The MPH was good but we have pulled out 1.00 second on our timer .

Ace

Not bad.... 5 rounds at a national event with a junk motor... lol

Seems to me that if the motor was down on horsepower the mph would be dropping off.



I love my data logger... really helps pinpoint where the weirdness is happening from run to run...

dkp

bosshoss wrote:Not bad....  5 rounds at a national event with a junk motor... lol  

Seems to me that if the motor was down on horsepower the mph would be dropping off.



I love my data logger...  really helps pinpoint where the weirdness is happening from run to run...  

dkp

X2.. MPH should have been down and kept going down...
Is it possible that the Throttle stop is leaking air ?? Assuming it's air operated ??
OR could it be binding, causing it to open slower each time ??

last year at the july 4th race we put thing in the trailer with 3.10 in the timer and running 160mph. we pulled the converter and had it repaird from the inside as it was a bolt together unit and no other changes were made. rolled it out for the Mile Highs and it only ran 9.70 something on the 9.50 index and 156 ish on the MPH. we ended up pulling .900 roughly out of the timer to even get in the low 9.50's. So i thought it was a converter issue and tried a brand new converter and didn't know then that it was spragless so the MPH was down more and the timer had came up to 2.50ish after putting on 18 passes in late September of last year. so the converter that was repaired was send make to the maker and had them convert it from a bolt together to a weld up( was bad core to start with). so that converter was put back in the car and we started out this year with the time left in the timer 2.50 and it ran dead on the 9.50 index. so no improvements there. so we raced in May, June and july 4th and we dropped from 2.50 to 1.90. then came the Nationals and we lost even more time and we went down to 1.670. we only ran below the index one time and that was in round 3 and we broke out the least. but rally never came close on race day. after the 4th of july i pulled down the trans and checked that first( we broke a fitting in the may race in the semi final at the end of the shut down and was not able to make the final. I did't find any thing there and check the spring and they were roughly 50lbs light on the seat and then i leaked down the motor and found the #1 intake leaking 65%. so i pulled the heads and had a quick valve job done and put it back together and warmed it up and right after test the #1 again and it had 20% past the rings. by now its Sunday before the Nationals and i figured it would run slightly better but it didn't. i know it got hot and the air was 9600ft but the other car was not affected much at all.
I'm open to all suggestion and yes it air operated and the bottle has never been below 1000psi. no binding checked and lubed that on a every race day.

Ace

Sounds like its time for a refresh on that motor..  

Going to check the fuel flow and pull the needle and seat out. I have never ran a filter and have never had any junk to speak of. we also did upgrade to a larger fuel tank this past winter but other than size all the fitting and location are the same.

Ace