99 Black Bird T/A

iTrader: (4)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by NB99Z:
I went out and measured my Comp Cam and its 1.493 base circle. So centerline to heal would be .7465
I'm going to mill my heads .030 so I guess I will use 7.40 push rods. Before reading this post I was going to use 7.35. Thanks for the info.

Kevin[/QB]</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">So that would mean: 7.40 for .030 heads with the Comp Cam

What if NB99Z was using heads that were milled .055 instead of .030?

.055 - .030 = .025 difference due to head milling

so

7.40 - .025 = 7.15

so

Would 7.15 push rods be right for the Pace LS6 heads that are milled .055 if the cam had a base circle the same as NB99Z?

thanks

<small>[ July 14, 2002, 11:34 AM: Message edited by: 99 Black Bird T/A ]</small>

Tin Indian

[Quote] 7.40 - .025 = 7.15
_________________________________________

Your zero's are a little off.
7.40" - .025" = 7.375" (correct)

Thats exactly half way between the stock 7.40" rods and the shorter 7.35" (50 thousands shorter)rods that are avail

I guess you could use either size. Remember, there is a variance for preload in your stock lifters so it don't have to be exact.

Ideally, you would need rods that are .025" (25 thousands) shorter than stock = (7.375")

99 Black Bird T/A

iTrader: (4)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Kimchee and Rice:

Your zero's are a little off.
7.40" - .025" = 7.375" (correct)

QB]</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Thanks.

Reason I ask is the Pace sells CNC'd LS6 heads for about $2000 no exchange, but the heads are milled .055 and they said push rods might be an issue.

Tin Indian

Like I said... You should be right inbetween the stock 7.40 and the shorter 7.35 as long as you are installing the cam too (if in fact your Comp Cam's base circle is the same as NB99Z's cam).

You may just want to use stock length rods.
On another thought, I have heard that Norris sells rods that are .025" shorter than stock. That would be ideal for your head/cam setup.

With .055" milled heads alone (with stock cam), I would use the shorter 7.35 rods.

<small>[ July 14, 2002, 04:49 PM: Message edited by: Kimchee and Rice ]</small>

99 Black Bird T/A

iTrader: (4)

If I did those heads yes I'd want to do a cam too.

I'd really have to buy the cam and measure it before being able to tell about the push rods wouldn't I?

Tin Indian

edited my post....

You could always measure the base circle of the cam after you got it. Thats accross the area of the lobe where there is no lift.
You need to cut that distance in half. That number will then be the distance from the cam's certerline to the heal (backside) of the lobe.

DriveATransAm

i too have a comp cam with a 563 lift though. ive taken 0.050 off my stock heads- i was going to exchange the stock length pushrods with shorter pushrods. is that correct <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> its hard to get a clear answer from anyone.

Tin Indian

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by DriveATransAm:
<strong>i too have a comp cam with a 563 lift though. ive taken 0.050 off my stock heads- i was going to exchange the stock length pushrods with shorter pushrods. is that correct <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> its hard to get a clear answer from anyone.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">NB99Z measured his cam ... [Quote] "I went out and measured my Comp Cam and its 1.493 base circle. So centerline to heal would be .7465"

If that is what your cam measures at (who knows for sure), then your cams base circle (actually centerline to lobe heal) is .030" less than stock. But you milled .050" off the heads. that changes things. Combining the two specs, you would need rods that are .020" (20 thousands shorter than stock) to have the EXACT preload as you did when it was stock.

Comp Cams pushrods only come in increments of .050", so you would be better off with stock legnth rods (7.40")

Real simple;
1. Mill the heads - you need shorter rods
2. Smaller base circle of the cam means a shorter distance from cam centerline to lobe heal - you need longer rods
3. If you have a cam [and] head package, you need to combine the two in order to determine what length rods you need.

You need to use a set of machinist's calipers to measure the base circle. Half that distance is the cam centerline out to the lobe heal. Thats the important distance, because it determines lifter preload.

This lifter preload deal dont have to be exact. Like I said before, there is a certain margin (give or take) with hyd lifters. Maybe .040" either way. I dont know exactly, but your .020" would be well into being within limits with stock length rods. Closer than with the shorter 7.35" rods.

Ron,

<small>[ July 14, 2002, 09:03 PM: Message edited by: Kimchee and Rice ]</small>

DriveATransAm

hmmmm. so IF my base is smaller than stock, it will be ok <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> . I gotta talk to izzo now cause i asked if i could swao rods.

DriveATransAm

any other opinions? izzo emailed me saying that he has put stock pushrods on 0.030+ heads with no problems. i cant get through to ask about type of cam and exactly how much was off the heads.

edit: got through to izzo and hes gonna see about getting some inbetween rods made by manly. he said he has put stock length with a comp cam...which makes sense then.

<small>[ July 15, 2002, 01:13 PM: Message edited by: DriveATransAm ]</small>

LIL SS

iTrader: (9)

Here is my take so far..

Stock setup: .7756" (Cam Base) + 7.4" (Pushrods)= 8.1756

To get things back to stock preload, all numbers must = stock of 8.1756.

So If you had your heads milled .055" and had a cam with a base of .7465 things would loook like this: 8.1756" (Stock Setup) - .055" (Milling of the heads - .7465" (New Cam profile) = 7.3741" push rods..

A = Stock setup
B = Head milling
C = Cam profile
D = New push rods

A-B-C=D

Another hypathetical: If I were to use stock heads and regrind a stock cam. If the cam were to come back with a .64 center, I would need 7.5" push rods.

<small>[ July 15, 2002, 01:58 PM: Message edited by: LIL SS ]</small>

Tin Indian

LIL SS...

[Quote] Another hypathetical: If I were to use stock heads and regrind a stock cam. If the cam were to come back with a .64 center, I would need 7.5" push rods.
_____________________________________________

The stock centerline to heal is .776"

There is no way an regrind LS1 cam would have a .640" centerline to heal.

Thats .136" smaller than stock! (hundred and thirty six thousands)

But, just for talk, [IF] that was the case, you would need some real long 7.536" rods! Thats still another .036" (thirty six thousands) longer than the 7.50 rods that you said you would need.

Since the aftermarket rods are made in .050" increments, you would be closer with 7.55" rods in your hypathetical situation.

Ron,

Of course, you could also mill .136" off the heads. Then you could use the stock 7.40" rods.

Of course, you wouldn't have anything left of the heads! <img border="0" alt="[jester]" title="" src="graemlins/gr_jest.gif" />

<small>[ July 16, 2002, 12:00 AM: Message edited by: Kimchee and Rice ]</small>

LIL SS

iTrader: (9)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Kimchee and Rice:
<strong>The stock centerline to heal is .776"

There is no way an regrind LS1 cam would have a .640" centerline to heal.

Thats .136" smaller than stock! (hundred and thirty six thousands)

But, just for talk, [IF] that was the case, you would need some real long 7.536" rods! Thats still another .036" (thirty six thousands) longer than the 7.50 rods that you said you would need.

Since the aftermarket rods are made in .050" increments, you would be closer with 7.55" rods in your hypathetical situation.

</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I see your point about the rods being made in only .050" and having to go with a 7.55" rather than a 7.5" in my hypethetical situation.

However, I still don't agree with you on the re-grind issue.. I can't think of any other way to increase the lift on a cam besides reomving material off the bottom of the cam. I suppose you could add material to the top and grind it down, but I don't know how well that would work.

I'm 99% sure of this, as I talked to someone that works with Dema Elgin (Elgin Cams) He is a local cam grinder. In order to increase the lift with out changing duration just grinding off the bottom, if you want to increase the lift by .1" you would have to cut .1" off the bottom. If you wanted an extra .1" in lift and more duration, you would first have to cut the duration then figure out how much to cut off the bottom to achieve your desired lift. He put it in terms I could understand <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />