O.K Back by popular demand, here's the spring story,
When I was with Nickens one of the biggest issues was valve springs (it still is). The life expectancy of an intake spring was maybe three runs if all went well and the driver didn’t over-rev the thing. Exhaust was a little more forgiving, but not much. At the time we were trying to shift at 9500. The HEMI ran more RPM then the wedge stuff at that time. If the driver ran it to 9600 in any gear the eight intake springs would be junk. At 9750, just get out a box, because you didn’t even need to check them, all 16 were going in the trash and you would be beating the retainers loose. Anybody who has ever been around high RPM engines knows exactly what I mean by that.
Even when the car ran well and the driver hit all the shifts on time we would come back and find two or three springs that needed to be changed. Now assuming that they didn’t wear out while the car was being towed back from the far end, when did the springs give up? Third gear? Or forth? Or as the car crossed the stripe? If you can figure that out, you are better than I am. It seemed pretty obvious that if we could keep the springs up to pressure that the valves would stay under control and there had to be some performance that was there for the taking if only we had better springs.
One advantage that we had was that we were the factory MOPAR team and Chrysler was one of the principles in Ilmor. If you haven’t heard of Ilmor they are an engineering firm in England they are involved with Formula 1 and with Penske on his Cup stuff. Racing is their whole world and we’re talking about some really smart guys. Initially we sent them all of the valvetrain components that we were running at the time and explained that we couldn’t keep springs on the thing. The answer that they came up with was that no one in their right mind would use these parts in any engine much less trying to race this stuff. Keep in mind that a F-1 engineer has probably never seen a push rod-LOL So they sent a couple of guys to Houston to check out first hand what we were doing and try to find a better way. One of the guys had a PHD in mechanical engineering and the other was right there with him in the brains department. They had spent some time working on Cup stuff for Penske so they had a little understanding of the type of engine we were running but when they saw the first Pro Stock HEMI they were blown away. We explained to them that a new spring would lose 40 lbs or so on the first run. They told us that if a Cup spring lost 8 lbs after 500 miles they would be fired. We had the right guys work on this now.
Step one was on the Spintron. I was the Spintron operator, if you’re not familiar with that machine is has a 75 HP electric motor and it will spin the valvetrain components without worrying about blowing up an engine. So you can check stability, valve float and bounce and any number of things. If you drop a valve on the Spintron you will be down about ten minutes. So it is the perfect tool to find the limits of stuff. The valve movement is tracked in real time by a laser in the cylinder. Just Google them if you want more info. One of the toys they brought from Ilmor was a load cell that goes under the spring (we machined a deeper pocket to accept it) and would tell us spring seat pressure IN REAL TIME with the valvetrain spinning at 9500 RPM. It was cool! And really enlightening. What we learned was that the spring was so out of control above about 7200 you couldn’t tell what was going on. There was a lot of room for improvement and they believed that they could help us. I jokingly told them that all we wanted was a spring that would run to 10,000 RPM and last for a season. His response was “Why would you change them after only one season?” We were on the same page. Two and a half days of trying to wear out the Spintron and Dyno and they had the information that was needed to go build us springzilla. They contacted us a couple of weeks later and said that after analyzing the data from the tests the main problem was that the camshaft was so aggressive that when the engine was running at high RPM the valve was being pushed open so fast, the first coil of the spring would smash into the second coil before it could move out of the way. The second coil would then be sent flying into the third coil and so on. Now just for kicks, get yourself a valve spring and try to get the first coil to touch the second one without the second one moving. They had an answer, they could build us a new spring that would stand up to what we were trying to do with it. We couldn’t wait.
They came back to the states a few weeks later with the new spring. It didn’t look much different but they assured us they would cure all of our valvetrain issues. It was time to fire up the Spintron. With the old springs if I took it to 9800 RPM the spring would break almost immediately and I do mean in seconds, before you could even get a reading. I put one of the new springs on and ask where do you want to start (8000 was the usual point). He said it didn’t matter I couldn’t break it. I love a challenge so I set the machine for 10,000 and ask again, he ask what I was waiting for so I hit start! At ten grand the valve was as happily under control at it used to be at 8000. I couldn’t believe what I was watching. After about thirty seconds at 10,000 he told me I could probably take my hand off the emergency stop button, because his spring wasn’t going to break. We spent most of that afternoon doing more testing on the Spintron and this spring was magic. It controlled the valves as good as the old springs at lower RPM and didn’t wear out. The first spring lost 10 lbs after ripping on it all afternoon. It was now Dyno Time.
The next morning we put one of the race engines on the pump, warmed it up and made a baseline hit. Then we changed the springs. We made four or five pulls and it was within a half a horsepower. Changed springs back and it repeated perfectly. The next race was Reading and we couldn’t wait. Those guys wont know what hit them. We had the magic springs. We had found the cure for the biggest problem we had and couldn’t wait to unleash it on them.
Reading didn’t go quite like we had planned, both cars qualified bottom half and lost first round. We just never got a handle on it. We also made ten runs (five with each car) and never had to change a spring. Back at the shop the engines went back on the pump and were fine, right where they should be. We checked the cars, and couldn’t find any problems. It was just a bad weekend. Off to the next race, the cars were still slow. No reason, nothing we could find wrong, just slow. We went testing when we got back and couldn’t get the cars to run, finally after exhausting everything we could think of David ask what’s different? We had changed ignition boxes, batteries, carbs. You name it we changed it. The only thing left was the springs, but we knew they were good, we could check them and they were fine.
The next day at the track testing we opened up with a 6.86 199 not very good. Second run 6.87 199. David ask if we had any of the old springs, yeah, there were still some in the trailer. Lets change them. O.K. you’re the boss, but the springs aren’t the problem, they are fine.
New (old) springs, back to the line 6.80 202 That’s more like it. Back at the trailer two springs down 100+ lbs and one with a broken inner. Replace three springs, back to the line 6.79 202 but it still can’t be the springs, can it? We put the magic springs back on and ran 6.86 198, change to the old springs and made one last hit for the day. 6.79 203 and wiped out four springs.
When we called the Ilmor guys and explained it to them, they decided that you just can’t help some people. I have still never found anyone that can explain it to me and if I hadn’t been there and lived it I’m not sure I would believe it either, but they springs wouldn’t go down the track. We started changing 3 or 4 springs every run and being fast again.
And that’s the spring story, next time we’ll talk tires………
Alan
