JD_Cravin

On a stock LS1 block...stage 2 heads and .612 lift...will I hit the pistons?

If so, what's the hightest lift without hitting the pistons?

The Emperor Of Darkness

I guess that is too much lift! I wouldn't go above .595 or even .591

XtraCajunSS

iTrader: (2)

Lift is not the main factor determining piston to valve clearance, duration is. When the valve is at max lift, the piston is already relatively far down in the bore.

Shane

The Emperor Of Darkness

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by XtraCajunSS:
<strong>Lift is not the main factor determining piston to valve clearance, duration is. When the valve is at max lift, the piston is already relatively far down in the bore.

Shane</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">yea I forgot, duration is how far down the valve goes, lift is how long the valve stays open so for duration I won't go more than 232! just my oppinion

<small>[ June 30, 2002, 06:50 PM: Message edited by: The Emperor Of Darkness ]</small>

Jason99T/A

iTrader: (21)

Actually you have that backwards. Duration is how long the valve is held open (in crankshaft degrees) and lift is how far the valve is opened (in inches).

Also, Shane is correct. Max valve lift occurs when the piston is furthest away from the valve. Piston-to-valve clearance becomes an issue during the overlap phase, when the exhaust valve is closing and the intake valve is opening.

<small>[ June 30, 2002, 07:05 PM: Message edited by: Jason99T/A ]</small>

The Emperor Of Darkness

damn then I was right the first time!XtraCajunSS tried to confuse me! I thought I read the cam lessons very well!

<small>[ June 30, 2002, 07:07 PM: Message edited by: The Emperor Of Darkness ]</small>

JD_Cravin

So with 222 deg of duration on a 112 deg LS, will I hit the piston?

Smoke_ur_5.0

iTrader: (2)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">So with 222 deg of duration on a 112 deg LS, will I hit the piston? </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Not even close..heck several of us out there have 230/230 duration cams with .030 milled heads.

AlonzoVersion 1.0

I am going 224/224 dur with .600/.600 lift on a 112 lsa and my heads are milled 30thous and I will not have any piston to valve issues.

Iron Duke

Thanks for the help guys. (JD_Cravin login at home...I am at work now <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> )

BTW: Alonzo, who is making that cam you have? 224/.600 lift...awesome!

What I am trying to do is when I get my stage 2 heads, I want to keep my car a "street machine". The C1 cam builds torque nice and early right now and as I witnessed a couple weekends ago, even moving up to a 224 duration cam, moves my torque curve UP by 500 to 750rpm. SO, I figured that by keeping the 222/222 .567 112lsa C1, adding LS6 intake, Stage 2 heads, and SLP's 1.85 rockers, I would keep my torque curve and even improve it because of the faster valve opening/closing events.

Please correct me if I am wrong. The cam would now have .612 lift with the 1.85:1 rockers...would the duration be effected by them also?

Thanks again for your help.

XtraCajunSS

iTrader: (2)

Yes, duration is also affected by rocker arm ratio.

Shane

The Emperor Of Darkness

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by XtraCajunSS:
<strong>Yes, duration is also affected by rocker arm ratio.

Shane</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">well I don't think you are right here, the only thing got affected by the ratio is lift. increasing rockerarm ratio= increase lift. duration is the degree the cam turns while holding the valve open!

Iron Duke

So one reply for "yes duration is affected" and one for "no, it is not".

Anyone care to break this tie for me? <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

I got the added lift information out of Lingenfelters book ~"Small block Chevy".

Although he did provide the added lift a given ratio will produce, he did not mention anything about duration being affected.

Here are the ratio numbers if anyone wants to check them out:

.05 added ratio will yeild .015 lift. In other words, going from 1.5:1 to 1.55:1 will net you .015 added overall lift.

So in the case of the C1 Hammercam: Going from 1.7:1 to 1.85:1 added .15 added ratio.

.015 * 3 (.15 added ratio/.05 = 3) = .045

.567 + .045 = .612 overall lift.

Colonel

Increasing the rocker arm ratio will indeed increase the duration...but only slightly. Mainly the lift is affected.

For example, a 222/222 .558/.558 would become something akin to a 224/224 .590/.590 by going to 1.8s from 1.7s.

Colonel

Oh yeah, how much exactly the duration would be affected by a rocker ratio change would also have to do with the ramp rate of the cam. Remember, when we say the duration is 222 we're not talking about from seat to seat. We're talking about time from .050 to .050. IF we were talking about from seat to seat then the duration wouldn't be affected by rocker ratio or ramp rate.

(Someone please feel free to correct me if I'm wrong.) <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Iron Duke

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">For example, a 222/222 .558/.558 would become something akin to a 224/224 .590/.590 by going to 1.8s from 1.7s.</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I see...so my 222/222 .567 going up to .612 may then become a 224 or 225 duration cam then eh?

hmmm...

Perhaps I'll need to get MTI/COMP to make me a 222/222 .600(or more) 112lsa cam then and call it the Sledgehammer! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />