Valve Float or Tuning Issue?
Thread Starter
Pro
Joined: Jun 2008
Posts: 672
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Valve Float or Tuning Issue?
Hello all,
Just got my recently built 404LS2 on the dyno for some tuning. It is a Livernois 404 with 243 heads (330cfm, 240cfm), Pat G spec cam 239/247 .623 114+2 on LSL lobes, ported FAST and supporting mods. She pulls nice and steady and is making 498rpm right about 6200 while still climbing then all of a sudden it hits a wall and nose dives. From 498rwhp at 6200 to about 400rwhp at 6800. Tuner thinks it is valve float. I have Patriot springs in there. With the cam sheet it called for a 7.40 in push rod, but with a 7.35 the geometry was right on. Do you all think it is the valve float due to weak springs?
Thanks
Just got my recently built 404LS2 on the dyno for some tuning. It is a Livernois 404 with 243 heads (330cfm, 240cfm), Pat G spec cam 239/247 .623 114+2 on LSL lobes, ported FAST and supporting mods. She pulls nice and steady and is making 498rpm right about 6200 while still climbing then all of a sudden it hits a wall and nose dives. From 498rwhp at 6200 to about 400rwhp at 6800. Tuner thinks it is valve float. I have Patriot springs in there. With the cam sheet it called for a 7.40 in push rod, but with a 7.35 the geometry was right on. Do you all think it is the valve float due to weak springs?
Thanks
Last edited by Slwsvt; Jun 14, 2009 at 12:09 AM.
Safety Car
Joined: Jan 2008
Posts: 4,711
Likes: 3
From: Middle of No where AK
Check your lift on the springs. Also it is always recommended to change springs when you upgrade to a different cam regardless of lift.
Safety Car
Joined: Dec 2005
Posts: 4,157
Likes: 37
From: North Carolina
St. Jude Donor '07-'08-'09-'11-'12
Patriot Performance Gold .650" Dual Spring Kit Technical Specs:
Install Height: 1.800"
Max. Valve Spring Lift: 0.650"
Spring Pressure Closed: 135 lbs. @ 1.800"
Spring Pressure Open: 375 lbs. @ 1.150"
Coil Bind: 1.090"
Retainer Material: Titanium
Patriot Performance Xtreme .660" Dual Spring Kit Technical Specs:
Install Height: 1.800"
Max. Valve Spring Lift: 0.660"
Spring Pressure Closed: 155 lbs. @ 1.800"
Spring Pressure Open: 410 lbs. @ 1.140"
Coil Bind: 1.090"
Retainer Material: Titanium
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Thread Starter
Pro
Joined: Jun 2008
Posts: 672
Likes: 1
Patriot Performance Gold .650" Dual Spring Kit Technical Specs:
Install Height: 1.800"
Max. Valve Spring Lift: 0.650"
Spring Pressure Closed: 135 lbs. @ 1.800"
Spring Pressure Open: 375 lbs. @ 1.150"
Coil Bind: 1.090"
Retainer Material: Titanium
Patriot Performance Xtreme .660" Dual Spring Kit Technical Specs:
Install Height: 1.800"
Max. Valve Spring Lift: 0.660"
Spring Pressure Closed: 155 lbs. @ 1.800"
Spring Pressure Open: 410 lbs. @ 1.140"
Coil Bind: 1.090"
Retainer Material: Titanium
Safety Car
Joined: Dec 2005
Posts: 4,157
Likes: 37
From: North Carolina
St. Jude Donor '07-'08-'09-'11-'12
Wait...do you have 4.10s installed? If you do, there is a secondary rev limiter that kicks in 500rpm before the final rev limiter. It's in the "RPM Limit Accel Thresh vs Accel" table using HP Tuners. If you have 4.10s and this wasn't adjusted in your tune, it's more than likely the problem.
Thread Starter
Pro
Joined: Jun 2008
Posts: 672
Likes: 1
Wait...do you have 4.10s installed? If you do, there is a secondary rev limiter that kicks in 500rpm before the final rev limiter. It's in the "RPM Limit Accel Thresh vs Accel" table using HP Tuners. If you have 4.10s and this wasn't adjusted in your tune, it's more than likely the problem.
