Forward Cylinders req Longer Pushrods than Rear
Thread Starter
Staging Lane
Joined: Apr 2014
Posts: 74
Likes: 1
Forward Cylinders req Longer Pushrods than Rear I have a Lq4, fully machined block, that I bought from Summit Racing with 241 heads that were rebuilt. I measure the volume on the cc and they came out to 68cc. The problem I'm having is with my comp cam pushrod length checker the #1 and #8 have a .025in difference. My first measurement on cyl #1 int/exh was 7.375 @ no lash, and the #8 was 7.35 @ no lash. So then I flipped the rocker tray 180deg, now #1 is 7.3875 and #8 is 7.3625. I made sure I was on the base circle of the cam. I have no idea what to do right now.
Last edited by Lethalwx69; Feb 16, 2015 at 05:06 AM.
"heads were rebuilt".
Does this mean a valve job? Maybe the seats and valves were ground.
Sometimes, a pit in a valve seat will warrant more correction when grinding.
I have variations in mine. I can't recall the correct figures.
Does this mean a valve job? Maybe the seats and valves were ground.
Sometimes, a pit in a valve seat will warrant more correction when grinding.
I have variations in mine. I can't recall the correct figures.
Last edited by gMAG; Feb 16, 2015 at 11:01 AM.
Lay a flat edge across all the valve stems, see if you have visible gaps and measure with a feeler gauge. This will give you an idea of how different the valve depths are but can't be used for determining pushrod lengths.
Thread Starter
Staging Lane
Joined: Apr 2014
Posts: 74
Likes: 1
I swapped the driver and passenger side rocker trays, and now all cylinders except the #8 cylinder are with in .006" of each other. I don't know what's up with these rocker trays.
As for the #8 its now there's about a .011" difference. I looked at the receipt for my heads, they had ordered a new int and exh valve. So that explain why #8 requires a shorter pushrod.
As for the #8 its now there's about a .011" difference. I looked at the receipt for my heads, they had ordered a new int and exh valve. So that explain why #8 requires a shorter pushrod.
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You mean the top of the valve stems? As I recall, they are case hardened and if they ground through them you may find major issues once the car is running. If you mean the valve seat, then they will sit higher relative to the rocker.
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Staging Lane
Joined: Apr 2014
Posts: 74
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Yes, 1 new intake and 1 new exhaust valve. I had them rebuilt by a shop called Hedahls in Minot, ND. As for those rocker trays I'm definitely buying new ones, mine might be bent or something. I did double check though swapping the trays around makes for uneven pushrod lengths.
TECH Fanatic
Joined: Sep 2005
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From: NYC
I've seen many guys grind down the valve stems (ends) and it's more common than you think.
Reassure me, a hardening surface treatment is performed after machining, is that correct?
Christian
TECH Fanatic
Joined: Sep 2005
Posts: 1,584
Likes: 23
From: NYC
Does anyone know if the Rockwell hardness of the valve stem end remain at the same scale as OEM doing so?
Christian