Venom Snake

I've been knocking my brains out to get this issue resolved but no hope and I'm still getting a valve float at high RPM according to my tuner. I don't know what's causing this really. I've even changed the valves, springs and also lifters - all racing and better. I used to have the same issue even before when my tuner said it had to do with the valve springs but unfortunately it is not. At the dyno the map wasn't getting up to 100 and was stuck around 95 only. It's not getting enough into the intake seems to be.

Could it be because I'm running the stock throttle body while I've got the 102 intake on? Should I replace it with the NW one that I have? Or is it because I haven't changed the stock rockers yet? Is this a tuner faulty? Please help. The previous owner of the car had to replace the stock GM throttle body because it was causing some issues to the car while he had the NW one on.

If you guys are gonna ask for my dyno sheet and see it by yourself, here you go then...

FYI car running on full boltons only no heads or cam. Is it actually a good idea to have racing springs for a non-cammed car?

Bill Dearborn

As far as I know the choice of intake doesn't have anything to do with valve float other than permitting the engine to run at a level where it occurs. It is totally a mechanical problem. Weight of valve train, rpm, cam profile, valve springs are what you need to look at. What rpm are you encountering valve float?

Bill

Dan_the_C5_Man

You say you've replaces some parts.

Please post EXACTLY what you changed / what valves, springs, push-rods and lifters you are running.

And this sort of "breaking up at high RPM" is often tied to ignition issues.

But give us the history and maybe some "diagnosis via the Internet" magic will happen.

olddragger

just to clarify---are you saying your map readings are lower than expected due to a valve float problem? If so at what rpm are you experiencing the float ( as bill posted)
506 rwhp is ok for a bolt on engine---guess depending on what all is bolted on...

Undy

Maybe your tuner is floating and not your valves? I just can't believe valve float on a stock cam. It could be tire spin due to hard rubber. If it would me I'd try a different dyno.

Michael_D

Something smells funny......

Need more info. Also need to know why you think you have valve float. Nothing on that pull looks like float to me.

Venom Snake

I don't know I thought maybe it could be from the stock GM throttle body where the NW should be replaced in its place. If the intake has nothing to do with the valve float, then what is causing the issue here? I checked with my mechanic and he said there is absolutely no fault from his side. Maybe my rockers could be damaged or else? Take a look at the last 2 dyno sheets I posted above, you can clearly see I'm having a valve float at 6,500 RPM and higher.

I did not replace anything big to the car. OK let me be straight here. I got the car from the previous owner as a full boltons and did not change or added more horsepower since then. The only thing that I've done last week was to go for my safe side to the engine which is changing the valves, springs and lifters. Oh and even the head gasket for a little higher compression. The funny thing is, I did not get face this issue when change the parts, I had it since the first day I got the car I suppose until I had it on dyno later. So the issue was still there when I got the car in my hands and even until now. I'm running Pack 600 for the springs, as for the rest I'm not sure I'll have to ask the dealer and get back here.

Yes, that is correct. It is stuck at 95 where it should be at 100 or around I believe. At 6,500 RPM is the float, please check the last 2 attachments above you should be able to see it in the dyno sheet. Car is running on fast 102 intake, stock TB, Haltech filter, ARH headers xpipe, B&B exhaust, MSD wiring.

My thoughts exactly. I don't think so its tire spin because I'm having Envo on them. I have thought of trying another dyno though.

What more info do you need here? I don't think, that's what the tuner said to me. Take a look at the last 2 attachments I posted above.

Unreal

That dynograph shows no signs of float.

For your mods, that looks like a normal curve, in the normal power range. I strongly suggest finding a new mechanic/tuner.

olddragger

concur. 2nd opinion is called for

C5 Hardtop

It isn't your car thats the problem, its your tuner. Don't give him another dime.

Venom Snake

Are you saying my tuner is bluffing? Find a new mechanic? Why is that?

What? Please try to be more specific here.

I had a good feeling that it has to do with my tuner. But the problem here is, we don't have many good tuners in the Middle East.

olddragger

I understand.
the dyno curve posted really doesn't have any signs of valve float that I am aware off.
a dyno curve showing valve float on a n/a engine would have a more abrupt and sharp decline in power than what is shown. Yours doesn't show that---it is showing the gradual decline that we all see after a certain rpm.
How is the car driving? any lost of power noticed?
95-96 map reading is Ok at WOT

Venom Snake

I'm not a tuner and I'm kinda new to this so I wouldn't understand pretty much when it comes to tuning. But as long as you and others are saying there's no float in the graph, I'm happy to hear it. Car driving seems to be great and in fact, I have even gained 2 HP more (506HP now and 504 before) in a timid hot weather at 105.

vertC6

Are those PAC 600's dual? If so that's your problem. I would just run the PSI 1511 at 1.8 height with the Ti retainer. Much lighter than stock and won't bounce at all. It's also possible your coil bind clearance is not set where it needs to be and many cause the bounce, ideal is .060 to .080 coil bind.

vertC6

Are you running the PAC 1218?

Venom Snake

No it's actually PAC 600 single but racing. Are you saying the springs have been misplaced somehow?

No, PAC 600 single racing.

Unreal

Float and bounce are different things, and once again, graph shows no issues. Why springs were replaced makes no sense.

Sounds like a shop just trying to sell you parts.

Dan_the_C5_Man

I think we are getting off track here.

The OP's complaint is clear to see in the dyno graph - he is pointing out the jagged lines present starting at around 6,400 RPM.

IF the the parts the OP says we're replaced are the STOCK intake and exhaust valves and lifters, AND the cam is stock as claimed, pretty much any decent spring will work (to the OP - NO, you do NOT need "racing springs" for the stock cam and valves - GM's set up has been tested as stable up to 7400 RPM).

I think the issue is the "problem" in the graph is most likely not valve float, despite what the OP's tuner claims.

Unreal

A lot of graphs look like that if you turn smoothing off. That is why people run SAE smoothing 5.

C5 Hardtop

The engine may be hunting for the right timing near the 6500 RPM mark. Maybe its getting some knock? The air/fuel seems kinda lean in one case at 12.78. You should ask him for the data logs of the dyno runs and post that up. You should have things like timing advance, knock retard, knock, RPM, fuel trim and so forth.
Note the power numbers are STD and not corrected. Only the corrected factors should be compared across other dyno HP/TQ results to see who has the bigger shlong.