Pushrods for 228r cam?
That's fine if he recommended that. We sell and install a ton of them and there seems to be a little variance in the cam cores recently. We installed the exact same cam in a car last week with stock heads that took a 7.350" pushrod and setup with .065" preload. That's why we stress so much to measure each setup!
Jon
Jon
Guys, it's pretty simple math. The stock LS1 cam has a base circle radius of .7755" and runs a 7.38" pushrod. This gives a lifter preload that offers low noise and good long term performance. When running a stock LS1/LS7 lifter, I prefer to run a preload that's the same as factory.
A 228R cam has a base circle radius of .7265". That means the 228R cam has a .049" shorter base circle radius than the stock cam. If you are trying to maintain stock lifter preload with the 228R cam, you will need to run a .049" longer pushrod than stock .7755"-.7265"). Adding .049" to the stock 7.38" pushrod length gives you a 7.429" pushrod. The 7.425" pushrod comes closest to maintaining factory preload with the 228R cam. If you run a 7.400" pushrod, it will work, but you will be running .029" shallower preload than stock. If your LS1 is at the shallower end of lifter preload tolerance, you may get some lifter noise with a 7.400" pushrod. With the 7.425" pushrod, you will have a better chance of having a quiet setup because the lifter is more in the middle of it's plunger travel (like the stock LS1).
A 228R cam has a base circle radius of .7265". That means the 228R cam has a .049" shorter base circle radius than the stock cam. If you are trying to maintain stock lifter preload with the 228R cam, you will need to run a .049" longer pushrod than stock .7755"-.7265"). Adding .049" to the stock 7.38" pushrod length gives you a 7.429" pushrod. The 7.425" pushrod comes closest to maintaining factory preload with the 228R cam. If you run a 7.400" pushrod, it will work, but you will be running .029" shallower preload than stock. If your LS1 is at the shallower end of lifter preload tolerance, you may get some lifter noise with a 7.400" pushrod. With the 7.425" pushrod, you will have a better chance of having a quiet setup because the lifter is more in the middle of it's plunger travel (like the stock LS1).
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
I understand the math. But what I'm trying to to tell you guys is we have seen some variance in base circles on the cams we have installed lately. Joseph knows a thing or two about these engines. If he comes to me telling me there is something different in the cams and the last couple he installed were different, I am inclined to believe him and I try to pass that info. along here. All I'm saying is to measure the length. At the end of the day, it's your car and you can do whatever you please. Just trying to give you a heads on something to look out for! Good luck with it!
Jon
Jon
I understand the math. But what I'm trying to to tell you guys is we have seen some variance in base circles on the cams we have installed lately. Joseph knows a thing or two about these engines. If he comes to me telling me there is something different in the cams and the last couple he installed were different, I am inclined to believe him and I try to pass that info. along here. All I'm saying is to measure the length. At the end of the day, it's your car and you can do whatever you please. Just trying to give you a heads on something to look out for! Good luck with it!
Jon
Jon
Joined: Aug 2007
Posts: 24,241
Likes: 89
From: Turnin' Wrenches Infractions: 005
I know Pat G is correct because i measured my stock cam and my TR224 that went in years ago and did the math to compare. I ran 7.425 pushrods with that and it was silent. Aftermarket cams are cut on a smaller base circle.
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TECH Apprentice
Joined: Jun 2004
Posts: 318
Likes: 52
From: Charleston, SC
I followed Pat G's logic when I put my 228R in. I got a digital caliper and measured my stock cam base circle and 228R base circle and determined that I needed 7.425" pushrods. I was pretty impressed with GM's quality control on the base circles, each one was identical.
Sorry to bring up an old thread, but I would like to pick my pushrods based on how pat g said to do it above and measure my stock cam and aftermarket cam lobes to see what I need. So how do you measure the base cicle of a cam lobe?
TECH Regular
Joined: Jul 2011
Posts: 452
Likes: 2
Measure across the top peak of a lobe to the base circle, and then subtract the lift spec of that cam lobe (depends if you measured an intake or exhaust lobe) to give you the base circle diameter. Then divide that diameter by 2 to get the base circle radius.
Do this measurement on a couple of lobes and see if you get the same answer. You should, as the base circle radius should be the same for every lobe. But be sure to subtract the lift spec for the intake lobe if you're measuring an intake lobe because intake and exhaust lobes will have different lifts.
Do this measurement on a couple of lobes and see if you get the same answer. You should, as the base circle radius should be the same for every lobe. But be sure to subtract the lift spec for the intake lobe if you're measuring an intake lobe because intake and exhaust lobes will have different lifts.
Last edited by ZeeOSix; Jul 22, 2011 at 01:31 AM.
Ok so if you have to subtract the lift spec from the cam and you have an intake lift of .598 and an exhaust lift of .650 than technicly wouldn't you need a different pushrod for the intake and exhaust sides?
TECH Regular
Joined: Jul 2011
Posts: 452
Likes: 2
So when you subtract 0.650 from an exhaust lobe measurement it should be the same as when you subtract 0.598 from what you measure when you go across an intake lobe. The cam's base circle is the same on all lobes, and all 16 pushrods will therefore be exactly the same length.
Last edited by ZeeOSix; Jul 22, 2011 at 01:49 AM.
No ... because when you measure lobe to base on an exhaust lobe it will be a larger number because the lift if larger on the exhaust lobe.
So when you subtract 0.650 from that measurement it should be the same as subtracting 0.598 from what you measure when you go across an intake lobe. The base circle is the same on all lobes, and all 16 pushrods will be exactly the same length.
So when you subtract 0.650 from that measurement it should be the same as subtracting 0.598 from what you measure when you go across an intake lobe. The base circle is the same on all lobes, and all 16 pushrods will be exactly the same length.
TECH Regular
Joined: Jul 2011
Posts: 452
Likes: 2
Better yet ... if you know who actually designs & makes the cam, then give them a call, as they should know the exact base circle and the IN/EX lift dimensions of all their cams.
lol 