What are your mods???? 
Comp XE-R lobe base circle vs. stock
Thread Starter
Joined: Nov 2001
Posts: 8,246
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From: Victoria, TX
Comp XE-R lobe base circle vs. stock Does anybody know how much smaller the base circle of the Comp XE-R cams are compared to stock?
If one was running a .050" shorter height from head milling (.034") and thinner head gaskets (.040" thick), what pushrod length would be considered ideal with an XE-R cam?
If one was running a .050" shorter height from head milling (.034") and thinner head gaskets (.040" thick), what pushrod length would be considered ideal with an XE-R cam?
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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.
Thread Starter
Joined: Nov 2001
Posts: 8,246
Likes: 34
From: Victoria, TX
Pushrod checker is not the answer I'm looking for. I'm looking for the base circle cam dimensions of a Comp XE-R cam and how that compares to stock. Even more importantly, how that base circle dimension change affects pushrod selection, if at all compared to stock.
TECH Fanatic
Joined: Mar 2003
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Hey Pat,
I just went to the garage and measured my factory LS1 cam and my new XE-R 226/230 cam...
LS1 base diameter was 1.552 ish /2 = .776 base circle
XE-R base diameter was 1.457 /2 = .7285 base circle
Soooo.. by my math, assuming your factory PR measured 7.385 (and mine do, checked on several different calipers) you need a 7.3825 PR to be equal. Assuming you are using 7.4s currently. That would give you .0155
more preload compared to factory, hypothetically speaking. Should run quiet...
What is up???
Good luck,
Scott
I just went to the garage and measured my factory LS1 cam and my new XE-R 226/230 cam...
LS1 base diameter was 1.552 ish /2 = .776 base circle
XE-R base diameter was 1.457 /2 = .7285 base circle
Soooo.. by my math, assuming your factory PR measured 7.385 (and mine do, checked on several different calipers) you need a 7.3825 PR to be equal. Assuming you are using 7.4s currently. That would give you .0155
more preload compared to factory, hypothetically speaking. Should run quiet...
What is up???
Good luck,
Scott
Last edited by SideStep; Feb 18, 2006 at 09:58 AM.
Originally Posted by SideStep
Hey Pat,
I just went to the garage and measured my factory LS1 cam and my new XE-R 226/230 cam...
LS1 base diameter was 1.552 ish /2 = .7285 base circle
XE-R base diameter was 1.457 /2 = .776 base circle
I just went to the garage and measured my factory LS1 cam and my new XE-R 226/230 cam...
LS1 base diameter was 1.552 ish /2 = .7285 base circle
XE-R base diameter was 1.457 /2 = .776 base circle
so what does this mean with the pushrods?
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Originally Posted by moeZ28
you got the numbers mixed up. .776 should be for the stock cam diameter and the .7285 should be the comp.
so what does this mean with the pushrods?
so what does this mean with the pushrods?
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Thread Starter
Joined: Nov 2001
Posts: 8,246
Likes: 34
From: Victoria, TX
Originally Posted by SideStep
Hey Pat,
I just went to the garage and measured my factory LS1 cam and my new XE-R 226/230 cam...
Scott
I just went to the garage and measured my factory LS1 cam and my new XE-R 226/230 cam...
Scott
__________________
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.
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Originally Posted by SideStep
That would give you .0715 more preload compared to factory, hypothetically speaking.
776 - 728 - 15 = 33 less preload according to my math...
I believe each cam base circle is a little different.If his Xer cam is a certain diameter,then it doesnt mean that yours will be the same,a cam with close to the same specs will probably be pretty close,but i always mic new cams to see for myself what they are.I would think if you get someone with close to the same specs to measure theirs that you would be alright.
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Originally Posted by GuitsBoy
assuming the heads are not milled...
776 - 728 - 15 = 33 less preload according to my math...
776 - 728 - 15 = 33 less preload according to my math...
Also, I just measured another XE-R cam 228/232 and came up with the same dimensions....
Last edited by SideStep; Feb 18, 2006 at 10:16 AM.
Originally Posted by SideStep
His heads are milled.... and I am assuming the PRs he is using currently are 7.4s and his factories were the same as mine... and he started with a factory composite has gasket, .054ish... many things changed... The way this looks to me is if he started with 7.385 PR then milled heads, used thinner gaskets and smaller base circle he would need a 7.3845 PR to keep the same approximate preload as before. I THINK Pat is using a 7.4 which would have an extra .0155 preload compared to using a factory PR.
Also, I just measured another XE-R cam 228/232 and came up with the same dimensions....
Also, I just measured another XE-R cam 228/232 and came up with the same dimensions....
Remember that .0155 is ten-thousandths. I dont think you need to go to that detail, so lets round it up to 016 thou.
Stock cam radius - comp radius - pr length diff - mill - gasket diff
.776 - .728 - .016 - .034 - .016 = -.018
that means .018 more preload on your lifters. this should be within the accepable limits.
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Originally Posted by GuitsBoy
that means .018 more preload on your lifters. this should be within the accepable limits.
I am going to experiment with a slighly longer PR (.025) and see if it cuts down on the noise, after I see how loud this latest cam is.... 
Originally Posted by Patrick G
....what pushrod length would be considered ideal with an XE-R cam?
Assuming heads are in place with the proper headgasket (or the same thickness shims during mock-up), the following is a quick rundown to check and measure for proper pushrod length:
Install an adjustable PR initially set too small (makes sure cam is on the basecircle of the lobe you are checking)
Bolt down the factory rockers....
Set the adjustable pushrod to zero lash and remove
Measure pushrod, then add .050-.100 to that figure which now represents your pushrod preload into the lifter and the total length of the pushrod your engine requires. This is obviously quickie instructions for a factory rocker arm set-up (pedastal mount).
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Guys....pushrod length/valvetrain geometry is critical to power output and reliability. "Internet Tech" may or may not give you the proper information for an optimal combination, or one that even runs for that matter.
Sorry Pat....couldn't resist the "noob" comment.....LOL
Tony M.
Originally Posted by redtail2426
i thought .030-.040" was good,.050-.100 seems like a lot compared to what people have told me ,was i misinformed on my preload figures??
Tony
interesting info,thanks for clearing that up.Your pushrod measuring method for stock rocker arms is very good and i dont know why i didnt think of doing it that way,instead of using that online calculator to get "close".Your method seems very accurate and simple to do.
Thats how I used to do Ford 5.0's and the way I would do the LS1 . I have found that more preload controls the heavier roller hyd. lifters at higher rpms compaired to the older flat tappets that I use less preload.
. I have found that more preload controls the heavier roller hyd. lifters at higher rpms compaired to the older flat tappets that I use less preload. 