Z-RATED94

iTrader: (6)

Anyone ever have a set of 918s go soft? The last few times to the track were very disappointing. Down about 4-5 tenths and 5-6 mph. The only thing that comes to mind about the lastest runs is that the motor seems like it might be lagging right before the shifts again. It did this a few years back with the 987 springs, which were not up to the job from the get go. I find it hard to believe they wore out in less than 2k, but we'll see tomorrow as it goes back on the dyno. If it is valve float, it looks like a set of Patriot Gold Extremes will be the next choice.

1989GTA

I have. When I originally put them in they were only around 115# on the seat. However they ran ok. Then after some miles were put on the motor I begain experiencing power loss. Suspecting the springs I took them off and they measured between 95 and 100#.

I replaced the springs with Manley beehives and the power came right back.

wrd1972

iTrader: (12)

Those dudes are shot.
918's at 1.800 install height are 130# new.
918's at 1.750 install height are ~138# new.

You can expect springs to lose up to 5# in a few thousand miles from what I have been told. Nature of the beast. If you are measuring ~100#, then thats barely better than stock LT1 springs. Chances are you are floating valves. Time for new springs.

96capricemgr

iTrader: (1)

Depends on the lobes of the cam, there are popular cams capable of destroying the 918s in just 2k miles as wrd1972 found out the hard way last spring. Other more responsibly setup packages can get 15K+ out of them.

https://ls1tech.com/forums/lt1-lt4-modifications/889759-355-le-dyno-tune-friday-guess-my-numbers.html
Few sets of springs and a new cam later and it seems to be all fixed though.

ulakovic22

iTrader: (12)

If you put them on and they only had 115# you were screwed from the get go. Once you lose the initial 5-7% on start up if you lose anymore you lose control of the valves all together and wear the springs out quicker. Since you never had enough to begin with I bet you'll pick up a nice boost in power with new springs. Good luck.

Edit: How long have you had the springs on the heads. You have a Joe O. cam so I'm guessing it's been a while?

Z-RATED94

iTrader: (6)

As mentioned, about 2k on the beehives. The car doesn't get driven much. In a few more hours we'll see what the dyno might tell us.

Greaseymec

iTrader: (9)

A set of PAC springs are in my near future. Cryo treating has been known to slow spring tension loss. My 292XFI cam will zap a set of springs fairly quick. With that in mind I will be cryo treating my next set. FWIW.

Mec

BlackScreaminMachine

iTrader: (17)

It isnt just the 918's ANY spring, if beat up enough with AGGRESSIVE cam lobes will degrade a spring.

Depending on the set up, and if the motor sees HIGH RPM fequently, the springs should be checked every season, and if your removing them, then of course replace them. I am running new Comp 918's w/o issue. PAC makes a great spring.

Z-RATED94

iTrader: (6)

Well it seems I might be hitting the limiter (6500). Soooooo I'll send the computer off to Ion to have that fixed. Plus send my spare in for the same tune with slightly lower shift points for the nitrous. Thanks for the help guys.

flame

iTrader: (13)

I had 10,000 miles and over 100 1/4 passes on my 918's with a BRE cam (not sure what lobes) and only 3 springs were down on pressure over the rest. I just replaced them because I sold the motor and wanted to be sure the new owner didn't run into problems.

NightTrain66

iTrader: (7)

Z-Rated,

are you thinking the springs might be good now and the problem was the rev limiter the entire time?

Did the dyno runs look good at high RPM?

Lloyd

Z-RATED94

iTrader: (6)

Hi Lloyd, yeah the pulls looked pretty good. Motor peaked at 6k and lost very little hp by 6400-6500rpm. At 6500 it did sound like it hit a limiter although I thought it was set higher. I'm no expert looking at the graph, but I'm getting better. With the 987s the rpm fell off quickly after 6k. With the 918s the motor loses around 5-10hp over the next 4-500 rpm after 6k. Shift points are set at 6400. Yesterdays chart looked like it wanted to shut off at 6500. You could here it popping, but sounded good up until that point.
The only thing I'm doing different this year is putting the car in OD instead of 3rd. It doesn't see OD during the run, but I was told there is more line pressure this way. The 2-3 shift was having a problem with the nitrous last year. I believe it's shifting better this year, but maybe the shift point changed just a hair using OD and it's touching the limiter right as it shifts.

LS1 SPEED

iTrader: (22)

did Ion confirm what the rev. limiter was set at yet?

There are 2 things we see it being as mentioned Tuesday...

-low rev limiter

-opti/ignition issue

let me know what Ion says when you speak with him

BTW : post the graph I sent you

Z-RATED94

iTrader: (6)

Larry, could you post it for me? When I talk to Ion I'll get back to you. Thanks

LS1 SPEED

iTrader: (22)

Z-RATED94

iTrader: (6)

Thanks Larry. Anyone want to take a stab at why this car is down half a second and 5-6 mph? I'm all ears.

NightTrain66

iTrader: (7)

do you have any dyno pulls from the car when it was running faster?

Lloyd

Fixxer99TA

iTrader: (5)

Yeah, something to compare to will help ALOT...

Z-RATED94

iTrader: (6)

I'll have to ask Larry to post them up if he has the time. Ion did get back to me and the rev limiter is at 6900.

LS1 SPEED

iTrader: (22)