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Old 04-12-2009, 05:19 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, 05:25 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, 05:49 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, 06:15 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, 09:41 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 09:52 PM.
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Old 04-12-2009, 09:59 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, 10:01 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, 10:51 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, 10:53 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 11:06 PM.
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Old 04-13-2009, 02:50 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, 05:24 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 05:30 PM.
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Old 04-18-2009, 12:23 AM
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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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Old 04-19-2009, 09:19 AM
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Didn't get as far as I would have liked, I stopped at about 1:30a while I was still thinking clear before I started making mistakes.

Heads assembled & torqued down with 26918 springs & 787 retainers.



valvetrain is adjusted per comps instructions using their 875 lifters



Those spectre "fabbed" aluminum valve covers do look pretty mean





...here is to show the difference between the Comp 787 vs 774 retainers on the 26918 when installed on gen IE vortec heads

787 on the left.....774 on the right





The comp 26918 springs, 787 retainers & proform 1.6 ratio aluminum roller rockers

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Old 05-03-2009, 04:14 PM
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A little video, after switching to a Speed Demon 650cfm


http://www.youtube.com/watch?v=D7vtulnfwPU
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