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I have experienced valve float and it was not noticeable in 1st gear at all, but 2nd it came on strong. But this was with a TH400 not a glide. Very curious what your installed height is as well.
it doesn't look like your getting a good connection on that cylinder with the dull oxidized end i would either change that wire or try to tighten up the connector in the boot and add some dielectric greese
What cam lobes are they? 6200 rpm is a real common area for valve float on ls cars. You want atleast 160-170 lbs of seat pressure. If your map reading bounces around quickly under high load it's valve float. Spark blow out is also very possible, how much dwell are you running on those coils? It helps alot to run them up to 4-4.5 msec.
What cam lobes are they? 6200 rpm is a real common area for valve float on ls cars. You want atleast 160-170 lbs of seat pressure. If your map reading bounces around quickly under high load it's valve float. Spark blow out is also very possible, how much dwell are you running on those coils? It helps alot to run them up to 4-4.5 msec.
Coils are at 4 ms. No idea what lobes are on the cam. This is it.
That's open pressure not seat pressure. I may have missed it but what rockers are you running? I was running the yella terra ultralights and it was causing valve float on my setup. Simply by changing to stock rockers my back half mph went from 27 to 30. I'm running the same turbo as you but its the billet s476 T6 with 92mm exhaust 1.1 a/r.
Here is my dyno graph on 15 psi with valve float from the yella terras. In 3rd gear the car felt like it hit a wall and I could hear the engine fluttering going down the track.
Last edited by Nitroused383; 09-27-2016 at 05:19 AM.
Nothing changes the set up but shims under the springs. If you get this right the open pressure should be around 400 with seat between 150-170, this should keep the valve in control near 7000rpm with most street type lobes and steel valves.
Kurt
Originally Posted by Forcefed86
Ah, I see. So after looking at the actual cam card it's .612. So a .038 shim should get me back in the general area of acceptable. The 7.35 push rods would make it even worse. Add the thicker LS9 HG in there and who knows what kind of actual valve lift I'm getting... I'll chk the push rod length and shim them up.
-thanks
Also noticed my #2 plug wire end is discolored. Looked like it was firing on the business end,but I don't recall ever seeing that dull discoloration. Plugs were .025 which appears to be what the new set I installed are gapped at out of the box. Dropped them down to .019.
You can't just blindly throw shims at it. You need to measure valve spring install height with a valve mic. Not every intake and exhaust will take the same amount of shim to get with in .050" of coil bind.
Last edited by Nitroused383; 09-27-2016 at 09:37 PM.
You can't just blindly throw shims at it. You need to measure valve spring install height with a valve mic. Not every intake and exhaust will take the same amount of shim to get with in .050" of coil bind.
Its a factory untouched head on an untouched factory valve train, retainers and all... with a beehive spring. Isn't the installed height 1.8?
Think all they were getting at is I was shy of the advertised open pressures because of my lack of lift. So shimming the difference in lift is a good start. With only .015, .030, .060 options it's not like I can get very exact anyway?
This is a pretty mild cam and low RPM setup anyway. if I could get it to rev clean to 6500 I'd be thrilled, and thats more RPM than I'll even use in the 1/4 with my current gearing/tire.
Last edited by Forcefed86; 09-27-2016 at 10:38 PM.
There is too many variables to say it's at 1.8 now though. What if your retainers and keepers put you at 1.750 and you throw a shim in it. You could coil bind your springs and wreck alot of ****. I just prefer to know what's exactly going on. It's not a bad idea to measure the springs and see if they are still holding good pressure. PAC nitrided springs are very good and mine only lost 10 psi on the seat after 15,000 miles.
I would guess it will be very close to 1.8 now, but I would look at your springs stack number before buying shims as the .060 might fit better. If you have calipers you can do a simple test for making sure everything is safe. If your cam has mild ramp lobes you're probably already safe, but some low duration stuff is very fast aggressive ramps that cause issues.
Kurt
Originally Posted by Forcefed86
Its a factory untouched head on an untouched factory valve train, retainers and all... with a beehive spring. Isn't the installed height 1.8?
Think all they were getting at is I was shy of the advertised open pressures because of my lack of lift. So shimming the difference in lift is a good start. With only .015, .030, .060 options it's not like I can get very exact anyway?
This is a pretty mild cam and low RPM setup anyway. if I could get it to rev clean to 6500 I'd be thrilled, and thats more RPM than I'll even use in the 1/4 with my current gearing/tire.
09-26-2016 | 08:39 PM
