teach me something about the ls7 valve train
01-29-2018, 08:31 PM
#1
teach me something about the ls7 valve train so im trying to learn a little bit about titanium valves since thats what im gonna be running. i started to think that if my unmilled 799s are requiring a 7.3 rod, the lash caps are lowering the pushrod side of the rocker, thus shortening the length of my pushrods. im assuming the del west valves are stock height, so once i add the cap to it the valve will be taller. so i started to think, my geometry will probably off. maybe i should shim up the rocker stand somehow, but i really can't check or confirm how the geometry is using stock rockers.
so i started to think, how do the ls7s do it? they run a lash cap on the intake side, do they run a lash cap on the exhaust as well? is the titanium ls7 valve shorter than the exhaust? so once the lash cap is on there its the same height? maybe gm new the ls7 lifters could handle the extra preload on the intake side and said meh, no need for a shorter valve, pushrod etc.
so i started to think, how do the ls7s do it? they run a lash cap on the intake side, do they run a lash cap on the exhaust as well? is the titanium ls7 valve shorter than the exhaust? so once the lash cap is on there its the same height? maybe gm new the ls7 lifters could handle the extra preload on the intake side and said meh, no need for a shorter valve, pushrod etc.
01-30-2018, 07:04 AM
#2
TECH Enthusiast
On my LS7 heads I have the Xyledene Titanium valves (which have a steel tip so no lash cap required) and they are slightly shorter when it comes to pushrod length like .10-.20 so not too much. If you are running the stock lifters that preload difference is negligible. No lash caps on exhaust side on LS7 just intake (in stock form). You need the lash caps if you are running stock titanium intake valves or you will wear tips out on them.
01-30-2018, 07:06 AM
#3
TECH Enthusiast
I believe in the stock GM form the intake valve is set up that with the lash cap they are both (I and E) about the same height.
01-30-2018, 07:00 PM
#4
On both my LSX-LS7 heads and stock OE LS7 heads, the intake valve height with the lash cap is slightly shorter (~.010") than the exhaust valve height.
The LS7 lifter has .220" of travel, so it will more than accommodate the same length pushrod used on both intake and exhaust. If you're using "short travel" or "limited travel" lifters, then I would check them independently.
Cole
The LS7 lifter has .220" of travel, so it will more than accommodate the same length pushrod used on both intake and exhaust. If you're using "short travel" or "limited travel" lifters, then I would check them independently.
Cole
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02-02-2018, 11:04 AM
#11
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LS Valve Train Tech Hi Floorman, I LOVE Lash Caps ON BOTH I/E valves.
FIRST, the Rocker Pivot RELATES the stem height NOT push rod length.
NEXT, I like to DLC the Del West valves due to the dirt found in BAJA race engines.
The Ti Valve can be destroyed by seat wear in ONE Race without the DCL Face.
You will fine a GREATER contact area with Lash Cap fitment, good for Hi-Lift cams.
The method to FIND Pivot Height : Place the Valve in the head, place the Lash Cap, place the Rocker Arm tight.
Use a Felt Marker, mark the Lash CAP, move the Valve to MAX Lift AND back several time creating a wear mark on the Cap.
CENTER this mark by adjusting the Pivot Height.
You may also call me for better advice.
Lance
FIRST, the Rocker Pivot RELATES the stem height NOT push rod length.
NEXT, I like to DLC the Del West valves due to the dirt found in BAJA race engines.
The Ti Valve can be destroyed by seat wear in ONE Race without the DCL Face.
You will fine a GREATER contact area with Lash Cap fitment, good for Hi-Lift cams.
The method to FIND Pivot Height : Place the Valve in the head, place the Lash Cap, place the Rocker Arm tight.
Use a Felt Marker, mark the Lash CAP, move the Valve to MAX Lift AND back several time creating a wear mark on the Cap.
CENTER this mark by adjusting the Pivot Height.
You may also call me for better advice.
Lance
02-02-2018, 07:01 PM
#12
Hi Floorman, I LOVE Lash Caps ON BOTH I/E valves.
FIRST, the Rocker Pivot RELATES the stem height NOT push rod length.
NEXT, I like to DLC the Del West valves due to the dirt found in BAJA race engines.
The Ti Valve can be destroyed by seat wear in ONE Race without the DCL Face.
You will fine a GREATER contact area with Lash Cap fitment, good for Hi-Lift cams.
The method to FIND Pivot Height : Place the Valve in the head, place the Lash Cap, place the Rocker Arm tight.
Use a Felt Marker, mark the Lash CAP, move the Valve to MAX Lift AND back several time creating a wear mark on the Cap.
CENTER this mark by adjusting the Pivot Height.
You may also call me for better advice.
Lance
FIRST, the Rocker Pivot RELATES the stem height NOT push rod length.
NEXT, I like to DLC the Del West valves due to the dirt found in BAJA race engines.
The Ti Valve can be destroyed by seat wear in ONE Race without the DCL Face.
You will fine a GREATER contact area with Lash Cap fitment, good for Hi-Lift cams.
The method to FIND Pivot Height : Place the Valve in the head, place the Lash Cap, place the Rocker Arm tight.
Use a Felt Marker, mark the Lash CAP, move the Valve to MAX Lift AND back several time creating a wear mark on the Cap.
CENTER this mark by adjusting the Pivot Height.
You may also call me for better advice.
Lance
i never thought of the larger contact surface, thats def a good benefit in lash caps.
i can't use wipe pattern as im not using a roller tip rocker. I've searched this and many times have read that ur not goona be able to get an "ideal" wipe with stock rockers.
02-04-2018, 08:47 AM
#13
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Pivot Height Hi Metal/Pedal, I have MARKED stem tips using LS OEM Rocker arms for 20 YEARS with the above stated method.
THIS IS the best Rocked arm to use re-fitted with CHE's.
THIS WILL HAVE THE BEST PATTERN as the diameter of the small end is MUCH larger than ALL Roller Tip Rockers.
The HIGH LIFT camshaft "rules" ARE CHANGED when LASH CAPS are fitted.
THUS the Solid Roller AND OEM Rocker Arms can work will TOGETHER.
I also use a 8mm/10mm "stem stud" 1.5" long. (VW Tech)
NOW : The ABSOLUTE WORST METHOD of getting the Valve Train correct IS the believe the Push Rod is used the adjust Valve Lash.
AS STATED the Pivot/Stem Tip relationship determined by the pattern IS the CORRECT METHOD.
Lance
THIS IS the best Rocked arm to use re-fitted with CHE's.
THIS WILL HAVE THE BEST PATTERN as the diameter of the small end is MUCH larger than ALL Roller Tip Rockers.
The HIGH LIFT camshaft "rules" ARE CHANGED when LASH CAPS are fitted.
THUS the Solid Roller AND OEM Rocker Arms can work will TOGETHER.
I also use a 8mm/10mm "stem stud" 1.5" long. (VW Tech)
NOW : The ABSOLUTE WORST METHOD of getting the Valve Train correct IS the believe the Push Rod is used the adjust Valve Lash.
AS STATED the Pivot/Stem Tip relationship determined by the pattern IS the CORRECT METHOD.
Lance
02-08-2018, 03:51 PM
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It seems like such a simple solution to potentilly greatly improve rocker geometry. Why is this not practiced more often? I've never heard or read of anyone doing this, and it makes complete sense to do so. I'm still baby lift at .625" but some of these other guys at .660"+ need to explore this...
02-09-2018, 10:33 AM
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LS Valve Train Tech HI All, thanks for the kind words.
I should add that the ability to SHIMM/MACHINE the CHE Rocker pedestal does exist. (correct pivot height requirement)
I have done this with LS engines, taught by work done on Pantera Ford 351-C Valve Train assembly.
SO I STATE : Use this method when a Solid Roller Camshaft is fitted/Solid Lifter, the Lash Cap for valve lash adjustment ?
This IS the method most engines use OR a Puck.
I have seen/assembled engines the use the Crower Shaft Rocker assembly at a cost of $1400.00, a good bit of kit.
This is ONE method of Valve Adjustment when a Solid Roller is fitted.
Imagine HOW EASY it would be to fit a Solid Roller Lifter, same Hydraulic Cam. (commonly named a "tight lash" camshaft)
This lifter IS lighter AND will NOT collapse due to Spring Nose Pressure/Valve Weight.
This type of Lifter will "pump up".
Lance
I should add that the ability to SHIMM/MACHINE the CHE Rocker pedestal does exist. (correct pivot height requirement)
I have done this with LS engines, taught by work done on Pantera Ford 351-C Valve Train assembly.
SO I STATE : Use this method when a Solid Roller Camshaft is fitted/Solid Lifter, the Lash Cap for valve lash adjustment ?
This IS the method most engines use OR a Puck.
I have seen/assembled engines the use the Crower Shaft Rocker assembly at a cost of $1400.00, a good bit of kit.
This is ONE method of Valve Adjustment when a Solid Roller is fitted.
Imagine HOW EASY it would be to fit a Solid Roller Lifter, same Hydraulic Cam. (commonly named a "tight lash" camshaft)
This lifter IS lighter AND will NOT collapse due to Spring Nose Pressure/Valve Weight.
This type of Lifter will "pump up".
Lance