MrDavid

iTrader: (11)

Well, the general consensus is that what i'm having is a valve spring issue. I have a forged 347 LS6 with stock 6.0 heads, a custom grind blower cam from TSP, and D1SC with FMIC and SNOW stage II meth kit. 7.4503 Chromoly pushrods, Manley dual valve springs and Manley valves, LS7 lifters, LS6 intake and stock TB. All components are brand new with the exception of the intake and TB.

Cam specs are 228/234 .571/.576 114+2 LSA on a 112 Centerline

Had the car on the rollers last week for some tuning and to make a long story short, the car pretty much fell on its face right at 5800 rpms. It pulls like a train all the way to 5800 making 620hp/610tq, but within the next 500rpm's after 5800 the engine loses 80rwhp and gets very rich (in the low 10's). It did this same thing for several pulls, after adding timing and pulling some fuel up top.

Is anyone else running Manley springs on their forced induction car? If so, have you run into an issue of not having enough closed seat pressure with these springs when in the upper RPM band making 12psi or more of boost?

I'm trying to find out the correct route to take to address this issue before replacing valve train parts. Hoping to get a subject matter expert who might have run into this problem before. Any advice is appreciated.

MrDavid

iTrader: (11)

I guess everyone is running PRC duals.....?

Boo"SS"t

iTrader: (2)

You'll have to look at your spring rate.

Avengeance

iTrader: (4)

Thats what I run and a custom cam with more lift than you have..... I have no valve float issues... stretching all the way to 6500rpm.

Jimmy P

iTrader: (177)

Who installed the valve springs on the heads, and did they know it was going to go on a boosted setup? Normaly you need to run a little more spring pressure.

tomz28

iTrader: (20)

PRC all the way to 6800rpm. but that was on a smaller cam ZO6 cam

ss.slp.ls1

iTrader: (36)

I assume Patriot Extreme duals will work just as well as the PRC duals?

Bob@BruteSpeed

iTrader: (16)

What spark plugs are you using, and at what gap?

Are you sure you are not getting any blower belt slippage? A new belt needs to tightened again after the first half an hour to an hour of use. Bob

MrDavid

iTrader: (11)

I bought the LS6 as a longblock about a year ago from a guy on this forum. It was originally intended for a APS twin turbo setup. It already had the oil drain holes drilled in each side of the oil pan, so it was definitely intended for boost.

Belt slippage was the first notion that we had also, but the graph is as smooth as butter all the way up to where it falls off a cliff at 5800. I will post the graph today sometime when I get a hold of it. If the belt was slipping, the graph would get pretty choppy where the slipping occurs. Plus, the belt it tightened all the way down. It has no play in it at all. 8 rib setup as well.

I am using TR-7 plugs which i'm pretty sure are gapped .030. At 12lbs of boost, the spark shouldn't be getting blown out that easily.

I don't know the spring rate either. I did have a machinest measure the installed height, coil bind, closed seat pressure, and open pressure yesterday.

Installed height was 1.66"
Closed seat pressure 130lbs
Open 350
coil bind was .100" beyond my max cam lift

AFASTYZFR1

iTrader: (55)

Might want to pull plugs and just check them....I run NGK BR7EF gapped at .030 and don't blow spark out at 16 psi

MrDavid

iTrader: (11)

If the problem was in the plugs how would it pull great till 5800 then fall off? You suggesting the spark is getting blown out around that rpm range and then its loading up with fuel?

MrDavid

iTrader: (11)

Not exactly sure how the Winpep 7 software works so this was the best image I could produce.

AFASTYZFR1

iTrader: (55)

I doubt spark is getting blown out if they are 7's gapped at .030 but I am just saying to pull plugs to check for any signs......running rich, lean, detonation, if your plug is the right heat range.....I just found some articles on google on how to properly read plugs and it helped me in the past.....It would just be a good starting point to check plugs if you have no idea about whats going on

MrDavid

iTrader: (11)

We pulled a plug when it was on the dyno and the tip was kinda white, or maybe a little yellowish. Thought maybe it was the methanol. Its not running rich or lean, which we could actually tell from the real dynograph which had A/F ratio and psi reading. IDK why the one they sent me has only HP reading.

There was no detonation or spark knock.

Boo"SS"t

iTrader: (2)

There's your problem, @ 130lbs you're just bleeding off your boost, not enough pressure to keep the valves closed. I had the same issues with my AFR 225's w/ standard springs which were rated at 135lbs closed seat pressure, I ended swapping the springs for their optional higher rate springs and solved all the valve float problems.

Bob@BruteSpeed

iTrader: (16)

Methanol - are you using pure methanol or a mixture?

MrDavid

iTrader: (11)

This is the post I was looking for. Thank you for your input.

And i'm running a 50/50 meth/water mix.

Bob@BruteSpeed

iTrader: (16)

Get rid of the 50/50 mix, that is putting out your flame. We found that with boost you generally need to run 100% methanol. Bob

Boo"SS"t

iTrader: (2)

Just so you know, my dynograph started falling off the cliff big time @ 4200rpm with 11lbs of boost. Good luck and keep us posted!

MrDavid

iTrader: (11)

I believe i'm going to change my springs to PRC Gold Dual Xtreme's in about 2 weeks. I planned on running 100% methanol when I ordered the kit, but my tuner said I needed 50/50 so thats what I did. Seemed to work very well dropping intake temps 40+ degrees and he added a good bit of timing.