Check my valve lash math?
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Check my valve lash math? this sound right to you guys?
2006 TrailBlazer 5.3 PCMofNC Rob Style Cam with LS7 lifters
11 turns @ 0.05 = 0.55
0.55 + 6.8= 7.35
7.35 + 0.090 = 7.44
7.450 = Comp Cams P/N 7639-16 = 0.091 pre-load
2006 TrailBlazer 5.3 PCMofNC Rob Style Cam with LS7 lifters
11 turns @ 0.05 = 0.55
0.55 + 6.8= 7.35
7.35 + 0.090 = 7.44
7.450 = Comp Cams P/N 7639-16 = 0.091 pre-load
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Well I have been hearing mixed things. I think its mainly due to everyone having a different setup. but I have heard a lot of guys run pre-load in the .090s to keep the valve train quite down..
right now I have 7.400 pushrods and the noise sucks to listen to after a cam swap.
I dont really want to buy two sets of push rods so I went on the higher side. Keep in mind this is a daily driver..
right now I have 7.400 pushrods and the noise sucks to listen to after a cam swap.
I dont really want to buy two sets of push rods so I went on the higher side. Keep in mind this is a daily driver..
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But isn't spec for LS7 lifters .080 to .100 ? and in my math I come up with .091 pre-load.
I used a Comp Cams 7702-1 Pushrod Length Checker and at 10 turns I still wasn't at zero lash... Same on both the intake and exhaust..
I used a Comp Cams 7702-1 Pushrod Length Checker and at 10 turns I still wasn't at zero lash... Same on both the intake and exhaust..
I used the math you have in post 1
11 turns x .05 = .55
.55 + 6.800" = 7.350"
So you should have been 7.35 @ zero lash
7.45 would be .100 more giving you that preload
And .050-.080 is the norm for ls7 lifters, .100 is high..
Not saying it won't work, but I've never seen anyone recommend it
11 turns x .05 = .55
.55 + 6.800" = 7.350"
So you should have been 7.35 @ zero lash
7.45 would be .100 more giving you that preload
And .050-.080 is the norm for ls7 lifters, .100 is high..
Not saying it won't work, but I've never seen anyone recommend it
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okay so let me ask you this then... if I know I'm at 7.350 for zero lash and I'm running a 7.400 PR.... that means my current preload would only be 0.050 ? and this would cause the noise. So bumping the pro-load up .025 should make it less noisy and closer to stock?
I'm use to old school SBC's this is my first LS engine :-)
I'm use to old school SBC's this is my first LS engine :-)
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okay so let me ask you this then... if I know I'm at 7.350 for zero lash and I'm running a 7.400 PR.... that means my current preload would only be 0.050 ? and this would cause the noise. So bumping the pro-load up .025 should make it less noisy and closer to stock?
I'm use to old school SBC's this is my first LS engine :-)
I'm use to old school SBC's this is my first LS engine :-)
Bumping up preload can help but it might not be the cure..
The noise can be a combo of the whole valvetrain
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Crap the Cam spec card is at home and I'm at work.... going off memory is a .601 .610 lift and a 114 LSA but I forget the duration I will check once I have the cam card in hand.
the springs are ProMaxx Performance 8401
Max. Valve Spring Lift: .650"
Coil Bind: 1.090"
Spring Pressure Closed: 135 lbs @ 1.800"
Spring Pressure Open: 375 lbs @ 1.150"
LS7 lifters
Stock PR's
Stock Rockers
the springs are ProMaxx Performance 8401
Max. Valve Spring Lift: .650"
Coil Bind: 1.090"
Spring Pressure Closed: 135 lbs @ 1.800"
Spring Pressure Open: 375 lbs @ 1.150"
LS7 lifters
Stock PR's
Stock Rockers
How many miles have you put on it after the cam swap?
Stock PR's are probably pole vaulting..
Find out what lobes that cam is ground on, if they are aggressive you might want to bump up preload and run a 11/32 OD PUshrod from manton pushrods..
Stock PR's are probably pole vaulting..
Find out what lobes that cam is ground on, if they are aggressive you might want to bump up preload and run a 11/32 OD PUshrod from manton pushrods..
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I have about 50 miles on the engine since the swap. but lots of idle time. I have only spun the motor up once to 6,200 rpm. until I have the pre-load right I have been driving it like a grandpa. no higher then 3,000 rpm
I will post the cam spec card in about 45mins when I get home.
I will post the cam spec card in about 45mins when I get home.
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ok cam card says
gross valve lift intake .606 exhaust .610
Duration @ .006 intake 269 exhaust 273
Duration @ .050 219 intake 223 exhaust
lobe separation 112.0
Grind# LS1 13015R / 13016r HR112+4
this all the info you need?
gross valve lift intake .606 exhaust .610
Duration @ .006 intake 269 exhaust 273
Duration @ .050 219 intake 223 exhaust
lobe separation 112.0
Grind# LS1 13015R / 13016r HR112+4
this all the info you need?
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and had to get it running for work... planing on picking up the replacements and installing them this weekend.
so it sounds like 7.425 is the way to go with .075 pre-load...
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FYI.. this is where i got the idea to run a 0.091 ish pre-load
https://ls1tech.com/forums/generatio...6-091-a-2.html
https://ls1tech.com/forums/generatio...6-091-a-2.html
The dual springs you have should be able to hold it
I would get some better pushrods, here's a few options.. Budget depends on you but the 11/32 are top of the list at $180 and go down from there.
Check out Briantooley racing for other pushrod options..
1. 11/32 manton PR's
2. 5/16 chromoly PR's (.105 wall)
3. 5/16 chromoly PR (.080 wall)
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I'm going to go with the Brian Tooley 5/16 chromoly PR (.080 wall) since its just a daily driver... and they should handle a little bit of fun here and there.
PCMofNC has them for $101.00 shipped to me so that sounds like a good price.
Thanks for all your help!
PCMofNC has them for $101.00 shipped to me so that sounds like a good price.
Thanks for all your help!
Let us know how it turns out
I went through the same thing when I had the LS7 lifters. I started with .057" preload and it was loud. I then went with a .025" longer pushrod (.082" preload) and it got quieter. This was on XE lobes. If I remember correctly, the LS7 lifter has about .160"-.180" total plunger travel so they are a little more forgiving when it comes to setting preload. For street applications I was told to shoot for the middle of the total travel.