High boost valve float - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

CGbambam · 01-09-2018, 02:05 AM

So what would be the next step up from PAC 660 lift springs?
Anything under 20 psi it’s fine but once past that i just valve float
Personally always heard bad things about pac’s but it’s what came with my TSP long block. Still hydraulic lifters, can’t seem to remember exact cam specs off the top of my head, but I’ll find them. Long block is maybe 6 months old, less than 5k miles on the springs

For reference it’s a 427 lsx on twin 67/66 precision’s with prc 260cc heads hollow steam. Was considering BTR 685 lift springs but want to hear what everyone is using. (Picture below for attention)

frankwjr · 01-09-2018, 09:21 AM

need cam specs..and if I was you I be on the phone with PAC or PSI...they are the experts.

BTW - who set the valve train up originally? they did do all of the check/verify right? sounds like premature spring wear..they should last about 10k, right?

Slowhawk · 01-09-2018, 09:44 AM

Pressure can be changed by spring height. I shim them for more seat pressure on boosted app's.

AGP Turbo · 01-09-2018, 01:52 PM

More cam, more valve spring, more RPM= more problems
It's a pushrod motor. Optimize without boundary's that the engine is good at.
25psi with everything else within the correct boundary's is way more reliable and faster than a sketchy 20psi with a big cam and over stressed valve train.
You say more spring, I say less cam.

CGbambam · 01-09-2018, 02:46 PM

Well I kind of need a big cam, so it can carry up to a 7500/7800 shift and not fall on its face.

BiggFoot · 01-09-2018, 04:36 PM

Wish I could help you but I am just not pushing that sort of boost yet. Guess this issue is something I will have to look forward to when/if I do go up in boost.

PLEASE keep us posted on how you fix this and good luck. I will try to inquire of my shop how they would handle but boost is AGP's life blood so there must be merit in his reasoning. Just saying

CGbambam · 01-10-2018, 10:22 AM

Cam specs are 239/259 629/629 116+5
Will do i'll keep y'all posted

bayarea408 · 01-10-2018, 11:42 AM

sub'd

AGP Turbo · 01-10-2018, 01:27 PM

Something is telling me this is spark blow out. What's your plug gap now? Stock coils?

CGbambam · 01-10-2018, 02:17 PM

br8's at .020 and yes stock coils

i thought it was spark blow out also but on the log at WOT my rps we steadily increasing and then drop a bit and increase back up, back down and then up

stevieturbo · 01-14-2018, 01:00 PM

Simple solution...speak to your cam supplier and have them spec the springs to suit your application, your valvetrain, rockers, valves etc..

They should have the experience/knowledge to know what you need from all that info and their cam.

And you say valve float occurs at 20psi...that statement doesnt make sense. It will vary with load and rpm, not just boost pressure.

01-09-2018, 02:05 AM	#1
CGbambam Drives: 2011 Camaro 2SS Join Date: Sep 2015 Location: Houston Posts: 410	High boost valve float So what would be the next step up from PAC 660 lift springs? Anything under 20 psi it’s fine but once past that i just valve float Personally always heard bad things about pac’s but it’s what came with my TSP long block. Still hydraulic lifters, can’t seem to remember exact cam specs off the top of my head, but I’ll find them. Long block is maybe 6 months old, less than 5k miles on the springs For reference it’s a 427 lsx on twin 67/66 precision’s with prc 260cc heads hollow steam. Was considering BTR 685 lift springs but want to hear what everyone is using. (Picture below for attention) Attached Images

01-09-2018, 09:21 AM	#2
frankwjr Drives: 2010 SS 2SS M6 Join Date: Aug 2016 Location: Smithsburg, Md. Posts: 2,445	need cam specs..and if I was you I be on the phone with PAC or PSI...they are the experts. BTW - who set the valve train up originally? they did do all of the check/verify right? sounds like premature spring wear..they should last about 10k, right? __________________ 2010 SS 2SS M6 - Tune by RDP dynoSteve!(Woot) - Daily Driver - *150K!* - All work by me...

01-09-2018, 04:36 PM	#6
BiggFoot Drives: 2010 Camaro (M6) 1000+ HP SBE Join Date: Jun 2011 Location: Houston Posts: 1,391	Wish I could help you but I am just not pushing that sort of boost yet. Guess this issue is something I will have to look forward to when/if I do go up in boost. PLEASE keep us posted on how you fix this and good luck. I will try to inquire of my shop how they would handle but boost is AGP's life blood so there must be merit in his reasoning. Just saying __________________ F-1X, Cog Drive, ATI Super Pulley/Sprag ~ 19 psi Blower Cam Brodix BP BR 3 Heads Kooks LT Headers and full 3" exhaust Fore Triple Pump Fuel System with ID 1700X Injectors - E85 conversion DSS 9” Conversion (1400 hp axles, driveshaft, pumpkin) & Strange 3.70 gears McLeod RXT Twin HD Clutch & Upgraded Slave RPM Level VII TR6060 BMR Drag Suspension Package w/Strange shocks Carlyle 15" and M/T ET Street R radials 10.1 @ 143 mph 1/4 mile

01-09-2018, 09:44 AM	#3
Slowhawk Drives: 1999 Trans Am Join Date: Jul 2009 Location: Bridgewater,Ma Posts: 2,017	Pressure can be changed by spring height. I shim them for more seat pressure on boosted app's.

01-09-2018, 01:52 PM	#4
AGP Turbo Drives: All things Turbocharged Join Date: Dec 2010 Location: AZ Posts: 1,199	More cam, more valve spring, more RPM= more problems It's a pushrod motor. Optimize without boundary's that the engine is good at. 25psi with everything else within the correct boundary's is way more reliable and faster than a sketchy 20psi with a big cam and over stressed valve train. You say more spring, I say less cam.

01-09-2018, 02:46 PM	#5
CGbambam Drives: 2011 Camaro 2SS Join Date: Sep 2015 Location: Houston Posts: 410	Well I kind of need a big cam, so it can carry up to a 7500/7800 shift and not fall on its face.

01-10-2018, 10:22 AM	#7
CGbambam Drives: 2011 Camaro 2SS Join Date: Sep 2015 Location: Houston Posts: 410	Cam specs are 239/259 629/629 116+5 Will do i'll keep y'all posted

01-10-2018, 11:42 AM	#8
bayarea408 Drives: T Join Date: Mar 2015 Location: CA Posts: 803	sub'd

01-10-2018, 01:27 PM	#9
AGP Turbo Drives: All things Turbocharged Join Date: Dec 2010 Location: AZ Posts: 1,199	Something is telling me this is spark blow out. What's your plug gap now? Stock coils?

01-10-2018, 02:17 PM	#10
CGbambam Drives: 2011 Camaro 2SS Join Date: Sep 2015 Location: Houston Posts: 410	br8's at .020 and yes stock coils i thought it was spark blow out also but on the log at WOT my rps we steadily increasing and then drop a bit and increase back up, back down and then up

01-14-2018, 01:00 PM	#11
stevieturbo Drives: it changes Join Date: Nov 2010 Location: Norn Iron Posts: 1,126	Simple solution...speak to your cam supplier and have them spec the springs to suit your application, your valvetrain, rockers, valves etc.. They should have the experience/knowledge to know what you need from all that info and their cam. And you say valve float occurs at 20psi...that statement doesnt make sense. It will vary with load and rpm, not just boost pressure.