ROGERSPERF.

When you see a dip in the TQ that way weather its a chassie dyno or engine
it has to do with one or two things.Ex. gas reversion or valve train hormonics.
You mentioned you changed the cam but did you change the springs for the cam.If the closing ramp is to wild for the springs the valves will bounce and you will get a dip in TQ. and if you added heaver rocker arms that will also cause the valve train not to be able to control the closing.Did you dyno the car before if you did look at that graft to see if the dip is there.




mike

offaxis

iTrader: (19)

Hey Verbs

I just recently switched from the tr230 Reverse spit to the R1 standard split. I was driving the car around for a while andit felt good. I brought it in for a retune and found I was making 390/360 through an unlocked converter. I was about to go crazy. After alittle tuning I was up at 431/422 unlocked. I have a friend that made the simular switch and the same thing happened to him. Go for a tune. I think with very minor adjustments you may find what you are looking for.

blk~2000~Z28

Looking at the graph you can see that the 2 pulls were very similar in their results. Both start to go screwy at exactly the same spot. Maybe the dyno it self was all messed up? Something is definently not right though and I hope it is a small fix, b/c personaly I think you should have landed 470HP with those mods. Good Luck.

BB

iTrader: (7)

Damn Verbs! I am having to fix the same problem you had and I had the same setup. Except my valves didn't bend. I sure hope I don't have as much of a problem.

If it were me I would be thinking about putting the valve train back to the same size PRs, and remove the shims and just see what happens. I would take TEAs advise and just torque to spec. It is apparent from the graph that your valve train falls apart at high RPM.

BTW, I dumped my YTs right away. I am going either with adjustables or throwing stocks back on until I get the setup right and dyno. I know the last thing you want to do is throw more money at this thing. Any chance you got the stock rockers you can throw back on? You can probably get a set for ~$20 to $60 here or on ebay. To me it would be worth a test because we know they work - I am not saying leave them on just put them on to test.

I know many folks do fine with the YT but you and I didn't. And in my opinion the mix and matching of PRs and shims have screwed your valve train up. Or you got a head that sucks/damaged.

These were TEA heads right? You should have sent them back to them. First thing Brian told me was don't let someone else mess with these cause they will mess them up.

Hope this helps.

verbs

The tuning should be dead nuts on. My A/F ratio on the dynograph is perfect, I have a buttload of timing, and no knock retard/detonation. I can't see where I'm going wrong.

I did change the valvesprings to Crane 832's and they were installed per the recommended height per Crane. The Crane 832 double springs are capable of handling .650 lift so I'm told. I've had the YT rockers on for a while even with my TR 230 cam, and the only big problem they ever caused from what I can tell was valve float above 6500rpms.

Here is my dyno graph from the same shop a year and a half ago without the Yella Terra rockers on.



Strangely, here is a dyno (it was 35 degrees hotter outside for this dyno) at a notoriously conservative dyno, and this would be after the Yella Terra rockers (notice the valve float). I figured that my #'s were down because it was over 100 degrees outside and everyone was seeing poor #'s (everyone was down about 15rwhp), plus I had switched from 3.73 gears to 4.10 gears. This may have been before or after I started bending valves, I'm not sure.

https://ls1tech.com/forums/attachmen...achmentid=2292

I still have the stock rockers, and those will be going back on the car Monday to see if that makes a difference. Stock pushrods too.

The only adjustable rockers I considered were the Comp 1.75 adjustables, but I think that would increase my lift too much. I'd be at like .635-.640 lift on the exhaust side.

BB

iTrader: (7)

I hear you about the 1.75 ratio. I haven't done the math yet but I am hoping 2cc reliefs will give me the right clearance.

I think Mike is dead on with his analysis regarding the valve train.

CHRISPY

You mentioned .004-0.018.

The .004 preload on those few cylinders is too little preload.

Are you noticing any clicking sounds from the top end from the rocker area?

Also dump the YT's, put in stock rockers and try out a new MAF.

You need a full LS1edit tune with the new cam by an experienced shop. I would also look at a Comp 977 or the 921 spring. Something is whacked there for sure.

Also check your plugs and wires. If you have an intermittant miss on a cylinder it can look like that too. Did you clay and check PtoV clearance? Did you flycut the pistons?

JZ'sTA

iTrader: (23)

Something is defentially wrong. Are you sure you have enough P/V clearence?

verbs

I can't hear any clicking sounds. I don't see how .004 preload can be too little since that is what Comp specifies as proper preload (.002-.004 preload is preferred).

I have the best LS1 edit man on my side to give me a hand with the tuning, but I don't quite think its that; my A/F is still dead nuts on. I have not retuned the car since I got the new cam. I don't see how these springs could be the problem. I'll dump the YT's first and take some stress off of them though.

P/V clearance is .90 on the intake and I forgot what the exhaust P/V is, but it should be fine.

The plugs looked spotless per the shop, but I'm going to Ohm out the wires and coilpacks just to be sure.

GrannySShifting

iTrader: (10)

looks to me liek a vlavetrain issue. might be compounding at high rpm (yella terras etc), but just too tight beforehand maybe?

Hits a brick wall like Ive seen valvetrains that were just to tight, just much earlier than normal. Hows the springs?

GrannySShifting

iTrader: (10)

Turn all your misfire codes back on, misfire detection etc, and see if anythign loads up on soem cylinders.

MAF readings are goiggn to be low, because it isnt making any power.

P Mack

iTrader: (6)

Your cam's not a tooth off is it? I would guess not since your P/V is fine, but I have heard of people having low power even with a perfect tune for this reason.

verbs

If my cam was a tooth off I'd think I'd have some serious P/V issues.

ROGERSPERF.

Idon,t no if you have anought time on this new set up or not take the rockers off and look at the tip of the valves you should see at straight line across the middle of the valve tip if you see an x patteren your valve train is out of control.





mike

GrannySShifting

iTrader: (10)

color the tip of the valve, see if its walking or staying centered on the stem?

verbs

Well, I tested the spark plug wires tonite and their resistance varied quite a bit. On the driver side, one cylinder was at 159 ohms, two were at ~187 ohms, and one was at 210 ohms. On the passenger side, one was at ~159 ohms, one was at 220 ohms, and on the the back two plug wires, the metal inside the boot was stuck to the plug after I took em off so I couldn't ohm them.

I replaced the plug wires so that I now have all 8 plug wires' resistance at 156-159ohms. SSonYourSix and I each did separate before and after test drives, and I felt that after the plug swap it stumbled a lot less down low, picked up some power down low, and it seemed to be a bit faster. SSonYourSix seemed to think its a lot faster and noticed it stopped stumbling too.

Using a Predator (since my laptop w/ ATAP is FUBAR), we were able to tell that the MAF readings were climbing steadily as we went to WOT, so it seems the MAF was working.

Maybe the plug wires being bad caused the problem, so I'm going to re-dyno on Monday first thing to see if that's the problem. I'm going to check for valve float again, and if it's there, the stock rockers are going back in.

Jason99T/A

iTrader: (21)

Trust me Matt, put the stock rockers back on.

Chicago Crew UnderBoss

iTrader: (1)

I'D listen to JASON if i were you as he has been there and DONE THAT!!!

Mike K.

I am interested to see what happens with the stock rockers as well.

Jason you have never seen a setup be able to go above 6500 rpms with they YT's? It kinda sucks to have jumped on the bandwagon for these things and it turns out they are becoming a hinderance performance wise to our motors

66ImpalaLT1

I dont think its simply the YT's, the problem started at almost 4000rpm. Its worth trying the stock rockers because its an easy swap.