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Old 04-12-2009, 04:19 PM
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New Heads,New cam: Check clearances?

Hey Guys,

Since having some valvetrain issues in my Vortec headed SBC. I decided to go in arms deep and replace everything that was suspect.

Not but just only minutes after firing her up after re-adjusting the rockers/valve lash my valvetrain sounds like a diesel again. The problem could lay with the press-in studs. Or the COMP 26918 springs with the miss-matched 774 retainers, coupled with the lift of the LT4 hotcam have wiped out the roller lifters.

So, I have in my possession new Patriot "Vortec" heads with 2.02"/1.6" valves & 185cc intake runners, screw in studs.







As well as I ordered new valvetrain components. I have a COMP XR276HR-10 cam on order, as well as COMP 875-16 lifters and COMP 787-16 retainers.

My plan is to transfer over the COMP 26918 springs from the old heads, but instead use the appropriate 787 retainers for non-LS engines. I will also reuse my Proform 1.6 ratio roller rockers.

My question: The XR276HR-10 with 1.6 rockers will spec
.535"Int/.544"
224 / 230
110

Intake open/close: 32 BTDC / 64 ABDC
exhaust open/close: 75 BBDC / 27 ATDC

with the patriot's S.S. 2.02" / 1.6" valves ( the 2.02's already sit past the heads surface while closed) , and the pistons are H345NCP-40(with 4 valve reliefs) sitting .004" @ TDC from the deck surface. I will be using a Mr.Gasket 1134 head gasket 4.13" x .028"

do any of you think I might run into a valve to piston interference issue?

Cheers ~Mykk

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Old 04-12-2009, 04:25 PM
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There is no way to know unfortunatley, without checking it. You could take the chance, but it`s just that, taking a chance. If you wish to check it, and I surely would, use play doh coated with talcum powder so the valve doesn`t stick to the play doh. My last engine sounded like a diesel, and it was due to excessive piston to wall clearence. Hyper pistons expand little, so if the bore is too big, they`ll slap and sound exactly like a diesel.
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Old 04-12-2009, 04:49 PM
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I can hear my rattles thru a screw driver touching the valve covers and not anywhere else on the heads/block, thus why I figure it was valvetrain related...

I sure hope it isn't piston slap, I miced the block & pistons before assembly late last august... there is only a couple thousand miles on the engine. (daily driver)
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Old 04-12-2009, 05:00 PM
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You can check both valve to piston clearance and valvetrain interfence on your motor with a cylinder head and gasket installed. All you need is a dial indicator and dial indicator stand. The head does not need to be torqued down to check
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Old 04-12-2009, 05:15 PM
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Quote:
Originally Posted by 04SilveradoMykk
you think I might run into a valve to piston interference issue?
Be aware that the closest valve-to-piston point does not have to be at TDC.
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Old 04-12-2009, 05:24 PM
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Quote:
Originally Posted by cobalt327
Be aware that the closest valve-to-piston point does not have to be at TDC.
The valves get the closest to the piston on the overlap when the piston is near the top 0 to 30 before TDC and 0 to 30 after TDC. Usuallly (but not always) right around 10.

Rocker arm/stud and valvespring bind occurs near peak valve lift near 110ATDC intake and 110BTDC exhaust.

A cam of that size is ususally not a problem, but its up to you to check this yourself. Do you have a dial indicator and a (magnetic) dial indicator stand
handy?
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Old 04-12-2009, 08:41 PM
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Don't use Play-Doh to check anything. It has a rebound effect due to the material used to make it and won't keep its shape. Use only oil-based modeling clay. Buy it at any craft store. Wrapped up in Saran-Wrap and kept in your toolbox, a block of it will last you the rest of your life.

Last edited by techinspector1; 04-12-2009 at 08:52 PM.
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Old 04-12-2009, 08:59 PM
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Quote:
Originally Posted by techinspector1
Don't use Play-Doh to check anything.
That hadn't occurred to me. I guess that would make it Play D'oh!

But then I admit that I never put any effort into trying to do the whole clay-on-piston thing, anyway.

I prefer to use a checking spring to know exactly when the valve contacts the piston- and at what point on the degree wheel that it's occurring.
It's actually much easier, I use a magnetic-based dial indicator that sets up in like a minute.

If there were a desire, a series of points could be graphed out to have a visual reference.
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Old 04-12-2009, 09:01 PM
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Instead of clay or play-dough, try one of the bite-sized Tootsie Rolls. Leave the wrapper on and there's no worries about contaminating anything inside the combustion chamber.
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Old 04-12-2009, 09:51 PM
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Quote:
Originally Posted by hinklejd
Instead of clay or play-dough, try one of the bite-sized Tootsie Rolls. Leave the wrapper on and there's no worries about contaminating anything inside the combustion chamber.
....Swell.
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Old 04-12-2009, 09:53 PM
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Quote:
Originally Posted by cobalt327
That hadn't occurred to me. I guess that would make it Play D'oh!

But then I admit that I never put any effort into trying to do the whole clay-on-piston thing, anyway.

I prefer to use a checking spring to know exactly when the valve contacts the piston- and at what point on the degree wheel that it's occurring.
It's actually much easier, I use a magnetic-based dial indicator that sets up in like a minute.

If there were a desire, a series of points could be graphed out to have a visual reference.
Ya still need it to check oil pump pickup to pan clearance. And ya need it to check intake manifold to head front to back and top to bottom. And yeah, I guess if someone were paying me to do it, I'd graph the PV clearance. Heck, I might even pad the job and graph it straight up, advanced and retarded.

Last edited by techinspector1; 04-12-2009 at 10:06 PM.
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Old 04-13-2009, 01:50 PM
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I am able to borrow a magnetic base dial indicator for this project and I hope to tackle it this weekend.

Some one walk me through what/where I need to measure with the indicator

Cheers ~Mykk
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Old 04-13-2009, 03:30 PM
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Using my simple Go-No-Go clearance test method all you do is adjust the cylinder #1 valve train to 0 lash, valves closed with no hyd lifter plunger preload. Then rotate the crank so that the #1 cyliner is at TDC fireing. Then mount the dial indcator on the intake valve spring retainer. Make sure there is some preload on the Dial indicator plunger (.150 or so) and 0 the gauge. Then from the 0 lash point tighten the rocker adjustment nut so that the hyd lifter plunger compresses and the valve opens by .060" as indicatoed on the dial gauge mounted on the retainer. Move the dial indicator to the exhaust retainer (valves closed TDC firing) and do the same thing to it. (tighten the rocker until the valve is open .060")
Now both vaves are held off seat +.060" when the valves would be closed (cam on base circle) Now rotate the crankshaft slowingly by hand 2 complete revolutions. If you can rotate without bind or resistance then you have a minimum of .060" valvetrain clearance at full lift and at least .060" of VTP clearance. Next rotate the crankshaft again by hand slowly until #1 cylinder is on the exhaust stroke (exhaust valve is closing, piston is rising) until approx 60 BTDC on the exhaust stroke and stop. (piston is half way up the bore on the exhaust stroke.) Now remount the dial indiator on the intake retainer with at least .100" plunger preload and 0 the dial. Now tighten the rocker so that the valve opens a additional .040". Do the same to the exhaust valve. Now both valves have been adjusted .060" +.040" or .100" tigher than 0 lash. Now slowly by hand rotate the crankshaft to TDC and past TDC to 60 ATDC and stop. Do not go further beyond 60 ATDC on the intake stroke. Stop. You now have swept thru the critical overlap period when both valves are open and the piston and valves are closest. And if it did not jamb, you have at least .100" VTP cleanance.
All you need to do to test for VTP clearance is sweep the overlap past TDC with the valves adjusted +.100" further open than 0 lash.

Loosen off both rocker completely to allow the hyd lifter plundgers to rise in the lifter bodies and then reset the valves lash as you normaly would with valves closed.

This will tell you that you have at least .060" of valvetrain/rocker/spring clearance at full valve lift. And at least .100" VTP clearance.
No play doh. No light checking springs required.
Do not force the crank shaft. Turn by hand slowly. If it stops It means you have found interferience.
rocker/stud/springcoil bind/pushrod/guide slot interference will be at or near 110 BTDC and 110ATDC
respectively for the intake and exhaust valves. and piston/valves clearance/interferience point is +/-30 either side of TDC on overlap.


You need only mount the 1 cylinder head with gasket and snug down a few head bolts to do this.
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Old 04-13-2009, 04:24 PM
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Remove the spark plug. Even with the head just snugged down, you could possibly generate a little cylinder pressure as the piston comes up on its compression stroke and make it more difficult to "feel" interference in the valvetrain and piston/valve. You wouldn't necessarily have any VP problems on the compression stroke because the closest near miss will be at overlap, but just take out the plug and make the motor easier to turn over.

Last edited by techinspector1; 04-13-2009 at 04:30 PM.
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Old 04-17-2009, 11:23 PM
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Got started, a couple hours worth of work.





LT4 Hotcam is out. There is an obvious wear pattern on the cam from the rollers... but the lobes are not getting worn down at all. I'll put a mic on it and see if it's in spec before throwing it up on EBay.



The green oil is due to the UV die I had in there to help locate a leak.

The COMP XR276HR-10 cam is lathered in black moly and stabbed in place.



Tomorrow eve I'll (with a ton of help from a friend) finish her up, transfer the valve springs over to the new heads with the new retainers and get her back together for the drive home.

Cheers ~Mykk
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