Patrick G

iTrader: (14)

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?

TAQuickness

iTrader: (28)

I'm running 7.240 ish with my combo. Safest bet would be a PR length checker.

Patrick G

iTrader: (14)

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.

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 = .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

SideStep

7.240??? What are your mods????

moeZ28

iTrader: (7)

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?

SideStep

Oops.. you are right I changed the above post... everything else is correct..

Patrick G

iTrader: (14)

What do you mean you went to the garage to measure the cam? I thought that bad boy was already in your car, LOL.

GuitsBoy

iTrader: (4)

assuming the heads are not milled...

776 - 728 - 15 = 33 less preload according to my math...

redtail2426

iTrader: (10)

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.

GuitsBoy

iTrader: (4)

All the comp cams ive seen were all in the 1.45x range

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....

GuitsBoy

iTrader: (4)

Okay, I really need to learn to read the first post

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.

SideStep

Yupper, we do get nuts over the numbers... 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....

Tony Mamo @ AFR

iTrader: (13)

Jeeeeez Pat.....That looks like a "noob" question

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.

redtail2426

iTrader: (10)

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 Mamo @ AFR

iTrader: (13)

I have found no difference in power with less preload but noticed that the valvetrain was a little quieter with more preload. Keep in mind we are talking about actual preload at the lifter, not just the amount of preload by figuring turns of the bolt and the thread pitch which is less (that distance gets multiplied by the rocker ratio which equals the net preload on the lifter I am quoting above).

Tony

redtail2426

iTrader: (10)

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.

Bo White

iTrader: (59)

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.

HavATampa

iTrader: (49)

Good info Tony! Thanks for showing us how to make this necessary chore a lot easier.