Constrictor 98TA

I just wanted to run this by you guys... I'm starting to get nervous about this possible setup I plan on running.

The cam I'm going with is a Comp 228/224 .571/.568 112 LSA with 2 degrees of advance ground in. This is on Comp's XE lobes.

The heads I'm going with are 5.7L LS1 heads milled .030", with 2.02" and 1.575" valves. I didnt plan on reseating the valves or grinding in any valve reliefs. I will be using a stock GM head gasket.

I plan on installing the timing chain dot to dot with no additional advance or retard in.

What do you guys think? I purposely went with the XE lobes instead of the XE-R lobes for a little less lift. I already have the cam purchased, but not the heads. So would you recommend any changes to my head setup?

I don't have the ability or knowledge to do the clay test and just wanted your expert opinions. The .030" mill on the heads isn't written in stone, I just wanted to increase my compression ratio a little, but if its gonna make or break my motor, I will cut back on it.

mighty mex

iTrader: (3)

you need at least .001(one hundred thousandth's...did i write that in right???) of clearance to be ok.

SuperZ28

Mike, since you are running the TX speed and performance cam, you may want to just get a hold of Trevor and ask him...he's been more than helpful anytime I had a question....

his contact info is:
trevor@texas-speed.com
806-785-8408

-Alex

<small>[ March 19, 2003, 12:07 PM: Message edited by: SuperZ28 ]</small>

Jason99T/A

iTrader: (21)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by mighty mex:
<strong> you need at least .001(one hundred thousandth's...did i write that in right???) of clearance to be ok. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">.100, not .001. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

At a minimum, you would need .080" intake/.100" exhaust. You can defintely get by with less, but you are just setting yourself up for problems if you ever float the valves,etc.

Just because the XE lobes have less peak lift, doesn't mean they will clear better than the XE-R lobes with more lift. Peak valve lift occurs when the piston is a toward the bottom of the bore, so you will not have any clearance problems there. PtV clearance becomes an issues during the overlap period, when the piston is on its way up and the exhaust valve is closing and the intake valve is just beginning to open. Ramp rates, lope seperation angle, duration, adv/retard, etc. play a much more important role than peak valve lift #s. If anything, I can see the XE lobe being more of a problem with PtV problems due to its slower ramp rates compared to the XE-R.

The only way to find out for sure if it going to clear is to actually check it on your motor.

Jason

Constrictor 98TA

Well, I appreciate all the comments...I did talk to Trevor and he said it shouldn't be a problem. Like eveyrone else has said, theres really no way to know for sure unless you check it yourself.

I guess I'm just gonna have to play Russian Roulette here and hope for the best!

Thanks everyone.

AZLS1

iTrader: (2)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Constrictor 98TA:
<strong> Well, I appreciate all the comments...I did talk to Trevor and he said it shouldn't be a problem. Like eveyrone else has said, theres really no way to know for sure unless you check it yourself.

I guess I'm just gonna have to play Russian Roulette here and hope for the best!

Thanks everyone. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Are you SURE you want to do that.
I had the same attitude: https://ls1tech.com/ubb/ultimatebb.p...c;f=1;t=011752

Constrictor 98TA

AZ, I read your post, and that really sucks...

Maybe I should try the clay test.

So, all you need to do is get some clay, put half an inch thickness on any piston, then put the gaskets on, torque the heads on, turn the crankshaft by hand a couple times with the spark plugs out and then take everything apart again and measure the thickness of the valve impression?

When doing this, should I use the new head gasket? If so, will having it on for such a short period of time ruin it? Can I still use that gasket for final assembly, or will it be ruined?

When torquing the heads down for this procedure, can I just reuse the old bolts, and if so, do I need to torque them down to the proper specs, or is just getting them on hand tight sufficient for this test?

2000RATA

Mike, You should have no problem with that setup.

Constrictor 98TA

For what it's worth, I spoke to Jay at Absolute Speed yesterday and ran this by him and he said that he's done a setup almost exactly like this, and he said that @ .030" it will be very close. He said he would recommend only milling them .020" or even .025". So thats what I'll do, just cut back to .020". Thanks everyone for their feedback.

Scott McDonald

Contstrictor98TA,
As a sanity check, why wouldn't you measure the piston/valve clearance? If the motor is apart, I would go ahead and check it. I'm not a professional engine builder and I'm not second guessing the expertise of the folks that have told you it "should" be o.k., but I have built enough engines to know that all parts are built with a tolerance range and it is critical to check all your clearances. Just my .02 cents worth. It beats the alternative of firing it up only to hear the valves playing your pistons like drums.