best valve spring for high boost? - Page 2

KingLT1 · 09-21-2018, 06:12 PM

Quote:

Originally Posted by oldman

I have the same spring on a stage 1 supercharger cam, TxSpeed recs the same spring upto their top stage III setup and that is a 7200 RPM cam.... The cam I have is ground by TxSpeed and suppose to be a gentle ramp. I really can't see increase in pressure causing the valve to float.
think about it piston coming up the bore intake valve starts to open, there is no issue as the pressure at best is balanced cyl to intake port, overlap event, by definition the pressure on both valves on both side are roughly equivalent since they are both open. exhaust valve starts to close as the piston is moving down the bore, there is still very little pressure difference either side of the exhaust valve head, the velocity of the end of the exhaust pulse, the valve is still open, also there is a whole lot of momentum as the exhaust valve and all the "stuff" is close to the end of travel and lifter is actually on the deceleration ramp.

So I can't see intake or exhaust pressure having any effect on valve float. I assume you are running this cam full lock?

Boost pressure definitely can float the valves. If you don't have enough spring pressure, the valves wont close.

ShizzySupra · 09-22-2018, 07:22 AM

Quote:

Originally Posted by KingLT1

Boost pressure definitely can float the valves. If you don't have enough spring pressure, the valves wont close.

^this 100%

KingLT1 · 09-22-2018, 09:54 AM

Quote:

Originally Posted by parish8

I just have the stock lt1 lifters. I replaced just 8 of them when I did the cam. If I can’t run a better spring with these lifters then I probably won’t upgrade and just short shift for awhile.

I keep the pw around 6ms. Let the port injection do the rest. I can set it where ever I need to.

I honestly couldn't say how capable the LT1 non DOD lifters are in terms of durability at high rpm. I would guess if you are running a stock or really mild cam they would be ok. I know most cam packages include a LS7 lifter as a minimum upgrade.

parish8 · 10-12-2018, 01:22 PM

I called Texas speed where I got all the parts. They are leaning toward valve float due to not adjusting the spring installed height. I did just slap them in there.

I am going to pull a valve cover and see if I can get a measurement. They said I would likely need about .050 shim OR a .050 lock that drips the retainer. They happen to sell those. Might be an easy and cheap fix.

Slowhawk · 10-22-2018, 11:14 AM

yes, shim the springs. .030 should fix it.

parish8 · 12-24-2018, 12:03 AM

Quote:

Originally Posted by Slowhawk

yes, shim the springs. .030 should fix it.

whoa, slowhawk checking in!

I did the lowering locks. they lowered the spring retainer .080 which seemed like it might be too much. I did some math and some measuring and should be .060 from bind at full lift. I called pac and they said .060 from bind is ideal.

put them in, went for a spin and now it revs cleanly. I have some other limiters kicking in at about 7000rpm but it is closing the throttle and a nice smooth limiter. I will play with that tomorrow and see if I can get it to goto 7200.

at 7000rpm it is still pulling hard. pretty sure that is still a little low.

Red Lightening · 09-15-2020, 08:29 AM

Did the shims also fix the boost issue?

laynlo15 · 09-16-2020, 10:09 AM

So, I had a .660 spring on when I bent a valve on mine. It was spinning the tires badly in roll racing at the Street Car Take over. I went to BTR .680 and then my guy that put them together shimmed them. I don't know how much but I never had an issue after that.

Tim M · 09-16-2020, 02:23 PM

Quote:

Originally Posted by Red Lightening

Did the shims also fix the boost issue?

According to the post - he didn't install any shims...it was the .080 'lowered' locks that boosted the pressure.

It does the same thing as a .080 shim in other words...

Slowhawk · 09-25-2020, 04:23 PM

spring height is a big thing with high boost. We run a 1.78" install height and no issue at 28 psi,7000rpm with reg BTR .660 springs.

Choda · 09-28-2020, 11:00 AM

Anyone find a part number for the .080 lowered locks ?

parish8 · 10-05-2020, 02:10 PM

https://www.summitracing.com/parts/MAN-13094-16 << is the box my lowering locks came in.

that says -.050

Choda · 10-05-2020, 03:24 PM

Quote:

Originally Posted by parish8

https://www.summitracing.com/parts/MAN-13094-16 << is the box my lowering locks came in.

that says -.050

Thanks Parish. I need to address a possible valve float issue with mine. It looks like every intake valve was hitting the pistons. Keep in mind, I did have vvt so I am wondering if there was an issue with that. This next combo will have the cam locked out likely using LME billet cover and single bolt cam gear.

Wilka_SS · 04-16-2021, 01:29 AM

Bump, did the locks change your install height and get you what you needed? I keep getting float issues above 6600 ever sense the cam was new and has less than 2k miles on it, if easy enough ill change the locks to help with installed spring height, to my knowledge there are 2 retainer designs, the more bell shaped and the flat ones, I have the older flat ones.

10-12-2018, 01:22 PM	#18
parish8 Drives: 17 SS a8 Join Date: Feb 2010 Location: omaha Posts: 1,678	I called Texas speed where I got all the parts. They are leaning toward valve float due to not adjusting the spring installed height. I did just slap them in there. I am going to pull a valve cover and see if I can get a measurement. They said I would likely need about .050 shim OR a .050 lock that drips the retainer. They happen to sell those. Might be an easy and cheap fix. __________________ dropped a valve in the 6.2. now running a drop in rods and piston 5.3 best et 5.83@121 with the 5.3 http://www.camaro6.com/forums/showthread.php?t=465472

09-16-2020, 10:09 AM	#22
laynlo15 Drives: 2022 Lt1 A10 Join Date: Nov 2015 Location: clark, mo Posts: 8,860	So, I had a .660 spring on when I bent a valve on mine. It was spinning the tires badly in roll racing at the Street Car Take over. I went to BTR .680 and then my guy that put them together shimmed them. I don't know how much but I never had an issue after that. __________________ 2022 Lt1 6.2 A10, Maggie 2300, THPSI Port Inj/10 rib, Rotofab, E, Nickey, SCOL, Griptech, RC Bandits, Hoosiers/MT 9.80@142.96 1.44 60ft, 6.34@112 707/669 RWHP/TRQ. 16SS Maggie 2650 9.41@147 1.35 60ft, 5.99@119. 16 C7 A8 10.90@128 Bolt on stuff

09-28-2020, 11:00 AM	#25
Choda Drives: Turbo 6.2 Join Date: Feb 2019 Location: Buffalo Posts: 702	Anyone find a part number for the .080 lowered locks ? __________________ 2016 Turbo Camaro SS - 800hp/900tq 9.7@146 2018 LTZ Z71 Redline Silverado - 381hp/420tq 13.8@100

10-05-2020, 02:10 PM	#26
parish8 Drives: 17 SS a8 Join Date: Feb 2010 Location: omaha Posts: 1,678	https://www.summitracing.com/parts/MAN-13094-16 << is the box my lowering locks came in. that says -.050 __________________ dropped a valve in the 6.2. now running a drop in rods and piston 5.3 best et 5.83@121 with the 5.3 http://www.camaro6.com/forums/showthread.php?t=465472

10-22-2018, 11:14 AM	#19
Slowhawk Drives: 1999 Trans Am Join Date: Jul 2009 Location: Bridgewater,Ma Posts: 2,017	yes, shim the springs. .030 should fix it.

09-15-2020, 08:29 AM	#21
Red Lightening Drives: 2016 SS Camaro Convertible Join Date: Nov 2018 Location: CO Posts: 19	Did the shims also fix the boost issue?

09-25-2020, 04:23 PM	#24
Slowhawk Drives: 1999 Trans Am Join Date: Jul 2009 Location: Bridgewater,Ma Posts: 2,017	spring height is a big thing with high boost. We run a 1.78" install height and no issue at 28 psi,7000rpm with reg BTR .660 springs.

04-16-2021, 01:29 AM	#28
Wilka_SS Drives: 2016 Nightfall Metallic Grey 2ss Join Date: Oct 2017 Location: New Orleans, LA Posts: 121	Bump, did the locks change your install height and get you what you needed? I keep getting float issues above 6600 ever sense the cam was new and has less than 2k miles on it, if easy enough ill change the locks to help with installed spring height, to my knowledge there are 2 retainer designs, the more bell shaped and the flat ones, I have the older flat ones.

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