thunderstruck507

iTrader: (18)

So I had misplaced this due to moving right after getting it and finally found it.

I had incorrectly remembered my peak being higher. I've been revving the car to 6500rpm on the 2-3 and I'm wondering now if that's why my 1/4 mph was lower than I expected.

98 ls1
2000 ls1 heads, surfaced and used Felpro gaskets and PAC 918 springs
Comp 230/224 111+3 lsa cam .572/.567 lift
lightly self ported FAST 90/90
1 3/4 longtubes to 3" duals (at the time the car had 2.25" tails after mufflers)
underdrive crank pulley
K&N cone filter rated to 850cfm to stock MAF on a 90* rubber duct to TB (recently ran it down to draw air flow from under the bumper, should help at the track)

no a/c
new plugs and wires
built 4l60e, Yank SS3600, Transgo kit, unlocked
12 bolt 3.42 gears
Chromoly steel high speed balanced driveshaft (kinda heavy)
275/50r15 Nitto 555R @22lbs

Car was heat soaked from driving to OKC, shop had been closed so it was hotter inside the building and it had just rained so it was sticky as **** outside. Previous run on the same dyno was 368rwhp but the a/f was lean. Stock driveshaft snapped that day and took out my trans so I had to come back.






Track results: (MT 325/50r15 ET radials)
60 Foot: 1.778
330 Foot: 5.062
1/8 Mile: 7.809
1/8 Mile MPH: 89.84 MPH
1000 Foot: 10.21
1/4 Mile: 12.24
1/4 Mile MPH: 110.38 MPH
Race Weight (with Driver): ~3,700.00 Lbs
DA: 1840ft

TQDrivenWS6

iTrader: (1)

Revving that high certainly looks excessive for that combo. How far do the RPM's fall when you shift 2-3?

speedtigger

iTrader: (16)

Peaking at 5900. If you have plenty of low end power, I would be tempted to back that cam up 2 degrees to a 110 centerline. Maybe it would peak at 6200 and give your some more HPs. But, I see you have a 98 motor. I have read on here that they have weaker rod bolts.

thunderstruck507

iTrader: (18)

At the time I ordered it, the cam I wanted was on back order but a friend of a friend worked at Comp. I was offered a discount and the rep said he could spec me something almost identical. It really shouldn't have had that +3 advance though, that was a mistake on his part.

I have been revving it to 6500rpm for a long time so I'm not worried about continuing to do so if the cam was retarded to put power there. I will highly consider it when I have things apart to install the 799 heads.

I'm guessing this early peak combined with the reverse split cam is why my Fast intake doesn't shine like it should have (still better than the ls1 intake by a good bit though)

sujomatt

iTrader: (7)

What made u pic those specs for the cam?

speedtigger

iTrader: (16)

That would be a good time because when you back the cam up 2 degrees you will loose some cylinder pressure and the 799s will help put that back. Are you going to mill them to bump the compression too?

thunderstruck507

iTrader: (18)

This was a few years ago and at the time I had the ls1 intake and had no intention of changing it. I did a lot of reading on here and the 224 cams were the most recommended at the time, but people also pointed to the TR230 because it was both one step up and also people were having great results with midrange torque/power and it had a very aggressive idle while still being known for a tame street cam. I was sold, it sounded like everything I wanted and needed and would keep me under my RPM limit I was shooting for since it was supposed to peak at 6300rpm but carry out a little if I wanted to keep spinning.

If I had it to do over I would have gone a different direction.

The 799s will be milled and a decent clean up port, polish the chambers/exhaust ports, and a valve job.



Last time I ran a compression check the cylinders were all 195-210 which seemed pretty decent.

thunderstruck507

iTrader: (18)

Does the fall off seem normal or should I be concerned about weak valvesprings or some other high rpm issue? Usually valve float is more jagged on a graph correct?

I know the peak is lower than expected due to the advance ground into it

s346k

iTrader: (4)

wow something is up. those are bolt-on numbers with a much peakier curve.

that cam shouldn't peak so early, especially with a ported fast 90 setup. grinding in advance will broaden the curve and ultimately push the peak farther up the band. retarding it will make the curve sharper and peak sooner.

i believe at one point chrs1313 had a very similar cam (230 230 .613 .591 lsa 111+2 copied from his dyno thread) that had a totally different curve. just search "el torro" and if i recall his thread was toward the bottom.

i assume you installed the cam dot to dot? perhaps you should pull it and degree it this time to see where it actually stands. something is up, those numbers and low and that graph looks funky. the car seems to run what the dyno represents, though, so no worries there, i guess.

thunderstruck507

iTrader: (18)

On a different day, it made right under 370rwhp on the same dyno (a/f was just near 14.1). The car runs door to door with a 2011 5.0 of the same weight or lighter from a roll and those are making 370+rwhp.

The 1/4 mph is low, but I think that is from the over revving and the cars poor aero. It take a 1 7/8" lt, 3" true dual, ls6 intake, lid, Frost tuned, m6 Z28 (at a lower weight than me) to run the same MPH the same track/day.

I've also ran a friend's 3100# z28 with 220/220 cam, longtubes, cutout, ls6 intake, udp, lid with no filter, short belt (only turning water/alternator), vig3200 stall, 3.73 gear, 26" tire, Ed Wright tuned car. He traps 1mph higher than me in the 1/8th mile but pulls 1.60 60ft so his ET are 7.4-7.5s to my 1.78s and 7.8s.



The cam was installed dot to dot with a ls2 timing chain. I used 7.4 pushrods which I plan to check soon. The engine is a little noisy but not excessive, it got louder with the Fast intake. Could I have bad lifters? They were purchased as "GMPP lifters with 35k miles on them" from the tech section here and all looked perfect. Would there be a good way to tell without pulling the heads?

Does anyone else agree with s346k? Back a couple years ago when it first went together I felt the car was down on power but it kept running decent and I looked at everything short of pulling the cam back out or the heads back off and found nothing wrong. So I just accepted it for what it was.



Chris1313 said it looks like valvetrain instability. Maybe due for new springs?

thunderstruck507

iTrader: (18)

Any other ideas or opinions?

I checked my pushrod length and came up with a pretty normal 1 1/2 turns past zero lash to 22 ft/lbs so I think they're good to go. I'm all out of ideas. Only thing I haven't done is a leak down test.

s346k

iTrader: (4)

i don't know, man. i can only compare your car to the ones i've had and the ones i've helped with and ran at the track. i don't think the aero is that big of a deal given those speeds. i only know a few things, the rest is speculation:

i know that graph is not right.

i know that car should trap more than what it does.

shifting sooner will help for sure, but how much who knows. i think 115 mph is feasible out of that combo. i do not think you'll see 5 mph by shifting sooner, though.

thunderstruck507

iTrader: (18)

I agree with you on both counts. The car could weigh more than I think, but I doubt it. 3700-3750#s should be extremely close (based on what it weighs with my sub, tools, etc in it).

If the shifts pick up anything it will help. But another hindrance was the air filter being right behind the radiator sucking in even worse air than what we had outside.

This trip I will have it routed to where air flowing under the bumper with pass directly onto the filter to both reduce IATs by an easy 15-20* (and likely more depending on ambient temps that day) as well as mildly force air into the filter. This should take care of the retard I was getting on the hit last time, if not I might need to rework the timing to come in later.

Are you considering DA into your opinion? DA that day alone robbed me of 2-3mph.

speedtigger

iTrader: (16)

Did I read earlier that you had 2 1/4 tail pipes during that dyno session? If so, I must say a restrictive exhaust and a reverse pattern cam is not a happy combination at all. Have you ever opened the exhaust up at the track?

thunderstruck507

iTrader: (18)

Yes during that session the tails were on the car still. I cut them off a couple months ago and the car sounds better, idles better coming to stops (less surge), and no longer shows any noteworthy gains by opening the cutouts.

With the tails the car would trap 86-87mph closed cutouts and 88-89 open (depending on DAs).

So I do know it would have shown a little better power open but he said it was better to tune the way the car would be driven the most. He offered to let me open them and lock the converter for a "glory pull" on the dyno, but I did not want to chance another run.

(The car broke a tailhousing in 08 on the dyno and the trans/driveshaft on my first trip to XP) I had since adjusted pinion angle properly and installed a high speed balanced driveshaft, but didn't want to test my luck

XtraCajunSS

iTrader: (2)

I see classic valve float here. Those Xtreme RPM lobes are fairly aggressive and if the springs aren't up to the task or aren't shimmed right, that's your problem. If you look closely at the graph, the problem starts at approx 5375 RPM.

Regardless, in my opinion, that graph shows valve float.

Thanks,
Shane

s346k

iTrader: (4)

i had a 71 ss chevelle. it weighed 3800 on the nose with an iroc 355 & iron 041 heads on it, with a th400 and 12 bolt. very clean car and i didn't have anything extra in the car except floor mats, trunk included.

i'm assuming a da of somewhere around 2k', as that seems to be the most popular here through summer and most of fall. my lid muffler car went 87.9999 in the 1/8 on a day the da was above 2500'. my bolt-on a4 car had its best pass on a day the da was ~2250'. i wasn't smart enough to wait on colder weather and try for a better pass, i always seemed to have better things to do.

thunderstruck507

iTrader: (18)

Thank you, I was under the impression these lobes were actually less aggressive than the Thunder Racing lobes, I was writing off some HP loss from that alone over yall's grind.

Like I said I have the duals which could go on, or I could try to have these shimmed (if they are still up to par, they have a lot of miles on them...car was daily driven from 08 until fairly recently).




I scaled mine at 3820# a while back. Me in it, amp/sub, tools, and a box of extra parts. I remove the tools, sub, and parts at the track. Sub is 40#, tools are ~15-20, and parts box was ~10#. I also try to run with less fuel. I also removed the sound deadening from under the carpet which I weighed at a little over 30#s on a bathroom scale.


For comparison purposes my old dyno sheet is below, details: same combo as above minus UDP, stock ls1 intake/ported tb, stock driveshaft, mail order tune, restrictive air filter (2" neck), cutouts open, WOT all the way to fuel cut at 6500rpm on blue line, red graph shows me letting out because I saw smoke from tailhousing leaking fluid onto exhaust

XtraCajunSS

iTrader: (2)

That graph shows valve float as well, just a little later starting just over 6K. It's really hard to say if those lobes are more or less aggressive. There's so much more to it than just lift and duration. I do feel that if you retard your cam 3 or 4 degrees and fix the spring problem, you should make some killer power.

Thanks
Shane

kinglt-1

iTrader: (26)

I agree with shane, definately some valve float going on....and wouldnt be suprised if thats costing you 15whp or so. I run 918's with stock cam/1.85 rocker setup. Definately put the duals in or atleast a pac1518.