calc pushrod length
Thread Starter
Burning Brakes
Joined: Jan 2007
Posts: 833
Likes: 2
From: Boca FL
calc pushrod length
I have 8 turns on the checker to get 0 lash. How do you calc length?
I have Z06 LS6 heads, no milling, Cometic .040, and Comp 232/236 598/602 112 +2 cam. I was using the 7.35 rods before with the TSP228R and it was pretty quiet.
I have Z06 LS6 heads, no milling, Cometic .040, and Comp 232/236 598/602 112 +2 cam. I was using the 7.35 rods before with the TSP228R and it was pretty quiet.
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Not sure which one you are using, but the Comp Cams one starts at 6.800". Each turn is 0.050" so you have:
6.800 + 8 X 0.050 = 7.200 zero lash length. You need to add preload too this number.
Calculating the other way, 7.385" (stock length) - 0.052 + 0.040 (head gasket change) + .050" (assumed base circle change) = 7.423"
Something doesn't appear to be right.
6.800 + 8 X 0.050 = 7.200 zero lash length. You need to add preload too this number.
Calculating the other way, 7.385" (stock length) - 0.052 + 0.040 (head gasket change) + .050" (assumed base circle change) = 7.423"
Something doesn't appear to be right.
Last edited by vettenuts; Mar 28, 2009 at 08:40 AM.
Pro
Joined: Oct 2005
Posts: 733
Likes: 0
From: Vanceboro NC
The best thing you could do is lock the nuts on you pushrod checker and take it to a machine shop and ask them to measure it for you. That is if you don't have a 8" dail caliper to measure it with. I would not trust counting the turns to be very accurate.
Whatever the meassured lenght comes up to be add .020 to .040 to it and call http://www.mantonpushrods.com/ for a set of 11/32 pushrods. You can check with Comp as they have some of the 11/32 pushrods in stock for a little cheaper, but the Mantons are deff. well worth the money.
The 7.200 is probably close to being right, as the stock 7.400's are normally to long.
Whatever the meassured lenght comes up to be add .020 to .040 to it and call http://www.mantonpushrods.com/ for a set of 11/32 pushrods. You can check with Comp as they have some of the 11/32 pushrods in stock for a little cheaper, but the Mantons are deff. well worth the money.
The 7.200 is probably close to being right, as the stock 7.400's are normally to long.
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
No, but if the lifters have just been installed and the trays are new they tend to stick to the top. If you push down you will hear it clink against the cam. Just double check your measurements, if you only milled and are using stock rockers with no shims for some reason you seem a little short.
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Whatever the meassured lenght comes up to be add .020 to .040 to it and call http://www.mantonpushrods.com/ for a set of 11/32 pushrods.
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Thread Starter
Burning Brakes
Joined: Jan 2007
Posts: 833
Likes: 2
From: Boca FL
Well I checked it again on #1 8.5 turns int/exh, went to #6 and the samething. Now when I bought the heads I was told they were untouched, they must have been milled; how much? I do have the hollow stemmed vales in the heads (Z06) which may acount for some. I come up with 6.8+(8.5x.050)=7.225 + .050 preload = 7.275 When I took the eng apart this time I had 1 1/4 turns removing rocker bolt to 0 lash.
Last edited by coanan; Mar 28, 2009 at 06:55 PM.
Drifting
Joined: Jan 2004
Posts: 1,419
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From: Alamosa CO
I had the exact same cam in my 346 with worked LS6 heads, they were however angle milled for 59cc chambers to get the SCR up to 11.5
to 1. with the stock MLS gaskets I ran 7.350" comp pushrods and they worked well. Never bothered using a length checker because my cylinder head guy, Pete Incaudo, who also spec'd the cam supplied the pushrods with the package, and he surely knows what he's doing!
hope this helps.
Jimbo
to 1. with the stock MLS gaskets I ran 7.350" comp pushrods and they worked well. Never bothered using a length checker because my cylinder head guy, Pete Incaudo, who also spec'd the cam supplied the pushrods with the package, and he surely knows what he's doing!
hope this helps.Jimbo
Pro
Joined: Oct 2005
Posts: 733
Likes: 0
From: Vanceboro NC
Well I checked it again on #1 8.5 turns int/exh, went to #6 and the samething. Now when I bought the heads I was told they were untouched, they must have been milled; how much? I do have the hollow stemmed vales in the heads (Z06) which may acount for some. I come up with 6.8+(8.5x.050)=7.225 + .050 preload = 7.275 When I took the eng apart this time I had 1 1/4 turns removing rocker bolt to 0 lash.
Makes one wonder why company X recommends 5/16 7.400" pushrods for all cam packages.
Thread Starter
Burning Brakes
Joined: Jan 2007
Posts: 833
Likes: 2
From: Boca FL
Thread Starter
Burning Brakes
Joined: Jan 2007
Posts: 833
Likes: 2
From: Boca FL
With pushrod checker;
(I come up with 6.8+(8.5x.050)=7.225 + .050 preload = 7.275)
Should I be using the 7.300?
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
That will work if the indicator is over the pushrod and you loosen until zero lash. If you keep loosening the rocker may move around or come up with the bolt some and throw off the reading.
Thread Starter
Burning Brakes
Joined: Jan 2007
Posts: 833
Likes: 2
From: Boca FL
Pretty sure I did it right, matches the pushrod checker with in .005. So the 7.300 rod should work? Around .075 preload
Thread Starter
Burning Brakes
Joined: Jan 2007
Posts: 833
Likes: 2
From: Boca FL
Now measure that pushrod checker with a dial caliper add .020" to .040" to the length. Why would you trust counting the turns on something that is so critical in you valve train geometry? 7.225 really doesn't sound that short I've had some shorter than that.
Makes one wonder why company X recommends 5/16 7.400" pushrods for all cam packages.
Makes one wonder why company X recommends 5/16 7.400" pushrods for all cam packages.