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Old 07-25-2020, 01:16 PM   #1
69 customcamper
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396 experts need help

Hey Guys,

I rebuilt my 396 which is a 69 block. Have the Camaro Heads with a Melling MT6 RV Cam. I ended up Putting Poly locks as the replacement Rocker nuts kept coming loose. Factory ones stayed tight. It has 20-50 oil with Zinc additive and 50 PSI oil pressure at idle with a mechanics oil gauge hooked up. Sounds great when cold. Once it hits 185 - 190 degrees , it idles a little rough and sounds like lifters clacking. Done valve adjustment 10 times. I used 3/4 turn. Tried 3 different oils........ If I missed one of the oil plugs for lifter galley on front of motor behind the timing gear , Would I still have 50 psi ? (Doubt it !) . Plugs are staying white so I am thinking it is also lean. Compression is 150 psi all 8 cylinders.......... What else ? Almost ready to yank it and build another motor. I pulled the Bypass valve this morning and it seems good. No gasket although I do not think that would change much other than possibly mixing a tiny bit of unfiltered oil with filtered oil ?
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Old 07-25-2020, 01:29 PM   #2
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Re: 396 experts need help

Why such a thick oil ?
Most guys i know run 10/40 or even 5/30

20/50 is a diesel truck oil

Do you have headers?
Are they loose

Have you used comp cam lifters i have heard there fairly noisy
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Old 07-25-2020, 01:35 PM   #3
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Re: 396 experts need help

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Originally Posted by gmc684x4 View Post
Why such a thick oil ?
Most guys i know run 10/40 or even 5/30

20/50 is a diesel truck oil

Do you have headers?
Are they loose

Have you used comp cam lifters i have heard there fairly noisy
I tried 5/30 and oil pressure dropped to 25 when it got warm.

I have cast manifolds and yes I hear a slight exhaust leak which I am going to address this weekend. But that should not make it idle rough as the noise increases or am I wrong ? Bolts are very tight.

Standard melling brand Hydraulic lifters. Started with a chinese brand which I swapped already as at first a few would not pump up.
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Old 07-25-2020, 01:50 PM   #4
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Re: 396 experts need help

Is your 50 psi idle oil pressure reading with the engine and operating temperature or cold? What is the oil pressure hot at cruise rpm?

Steve weim55 Colorado
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Old 07-25-2020, 01:54 PM   #5
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Re: 396 experts need help

Have you tried 10/40 ?

Did you check for coil bind on the valves?
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Old 07-25-2020, 02:04 PM   #6
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Re: 396 experts need help

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Originally Posted by 69 customcamper View Post
I tried 5/30 and oil pressure dropped to 25 when it got warm.



Standard melling brand Hydraulic lifters. Started with a chinese brand which I swapped already as at first a few would not pump up.
Nothing wrong with 25 psi hot idle. You only need 7-10 per 1000 rpm.

When you changed lifters did you try to break the cam/lifters in again.
Sounds a lot like a cam getting wiped.
Big blocks are notorious for wiped cams.
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Old 07-25-2020, 02:35 PM   #7
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Re: 396 experts need help

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Is your 50 psi idle oil pressure reading with the engine and operating temperature or cold? What is the oil pressure hot at cruise rpm?

Steve weim55 Colorado

It is 50 psi weather cold or hot . So cal has not been to cold in the mornings lately. It will go up to 55-65 depending on speed.
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Old 07-25-2020, 02:36 PM   #8
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Re: 396 experts need help

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Nothing wrong with 25 psi hot idle. You only need 7-10 per 1000 rpm.

When you changed lifters did you try to break the cam/lifters in again.
Sounds a lot like a cam getting wiped.
Big blocks are notorious for wiped cams.
When I removed the lifters the cam looked fine. Also it is not noisy until you drive it and it warms up . When it got to 25psi It was even noisier.
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Old 07-25-2020, 03:04 PM   #9
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Re: 396 experts need help

Of course the cam looked fine. Lifters and cam wear in togethor.
Changing the lifters likely changed that.

Pop the valve covers off and check all the rockers are moving the same.
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Old 07-25-2020, 03:15 PM   #10
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Re: 396 experts need help

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Of course the cam looked fine. Lifters and cam wear in togethor.
Changing the lifters likely changed that.

Pop the valve covers off and check all the rockers are moving the same.
Ok . I will look when the motor is hot to see if I can spot the change. I cut window in a pair of valve covers for purposes of valve adjustment.
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Old 07-25-2020, 03:33 PM   #11
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Re: 396 experts need help

Did you have machinist check valves for your cam lift for binding issues ?
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Old 07-25-2020, 03:50 PM   #12
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Re: 396 experts need help

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Did you have machinist check valves for your cam lift for binding issues ?
All new springs and stainless steel valves. He said they were good for a much more aggressive Cam. Mine is just one notch up as I just wanted low end torque.
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Old 07-25-2020, 04:03 PM   #13
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Re: 396 experts need help

That is a big check mark of not an issue valve binding can wipe the cam as well

Did the machinist check the new spring rates match the cam too heavy a spring can be hard on the cam too
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Old 07-27-2020, 08:35 AM   #14
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Re: 396 experts need help

I'm a bit confused on the time line of events. You rebuilt the motor with Chinese lifters and then you couldn't get them to pump up and so you replaced them.
Was that before you fired the engine for the first time and broke the cam in?
When you said they wouldn't pump up what exactly do you mean?
What is the part number of the new lifters?
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Old 07-27-2020, 10:34 AM   #15
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Re: 396 experts need help

When you tighten the set screw on poly locks it acks the initial adjustment off. If you tight them up without the set screw sufficiently backed off it will crack the poly lock. Poly locks on hydraulic cams are a pain in general
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Old 07-27-2020, 01:00 PM   #16
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Re: 396 experts need help

I would just verify your procedure for adjusting the valve lash is correct.

An easy way to do it quickly is mark the distributor body with a marker where each terminal is on the cap. Verify your at #1 TDC with the rotor pointing at the correct terminal. Adjust both rockers on #1 for 1/2-3/4 turn after zero lash. Remember with poly locks to go the half turn or so, back off an 1/8 of a turn and seat the set screw and then turn the rest of the way.

You can mark your balancer with a mark every 90 degrees as well and run through the same procedure.

Then repeat going through the firing order using your distributor body as reference.
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Last edited by j_cst_10; 07-27-2020 at 01:07 PM.
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Old 07-30-2020, 10:34 AM   #17
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Re: 396 experts need help

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Originally Posted by j_cst_10 View Post
I would just verify your procedure for adjusting the valve lash is correct.

An easy way to do it quickly is mark the distributor body with a marker where each terminal is on the cap. Verify your at #1 TDC with the rotor pointing at the correct terminal. Adjust both rockers on #1 for 1/2-3/4 turn after zero lash. Remember with poly locks to go the half turn or so, back off an 1/8 of a turn and seat the set screw and then turn the rest of the way.

You can mark your balancer with a mark every 90 degrees as well and run through the same procedure.

Then repeat going through the firing order using your distributor body as reference.
I cut a window into a valve cover and adjusted them with engine running. Anybody oppose ? I have tried with running and without. Does not seem to change anything.
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Old 07-30-2020, 10:48 AM   #18
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Re: 396 experts need help

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I'm a bit confused on the time line of events. You rebuilt the motor with Chinese lifters and then you couldn't get them to pump up and so you replaced them.
Was that before you fired the engine for the first time and broke the cam in?
When you said they wouldn't pump up what exactly do you mean?
What is the part number of the new lifters?
So the first lifters I ran 100 miles. It was only 2 or 3 that would not pump up. So I replaced all 16 with Melling JB817 which are usually the ones I use but they were not available locally and I did not want to wait.

When I say they would not pump up , I mean you remove valve cover while motor is warm and you are able to lift the rocker arm on the valve with the bad lifter and collapse the plunger. New ones all pop up except what I notice now in the morning after the motor ran last making the noise, the lifters (Not sure how many) are loose and tap for 20 seconds or so. So I think the lifters are not getting enough oil. I really believe this .
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Old 07-30-2020, 11:37 AM   #19
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Re: 396 experts need help

Did you re break in the new lifters after you changed them ?
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Old 07-30-2020, 11:38 AM   #20
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Re: 396 experts need help

I would adjust using the procedure I outlined so you know exactly where they are. Move the pushrod up and down and tighten until you feel zero lash. Then 1/2-1 turn after.
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Old 07-30-2020, 11:48 AM   #21
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Re: 396 experts need help

That sounds an awful lot like the lifter issue the early 454's had. After warm up lifter clack appeared and this was with a stock engine. Oil pressure was good but it clacked after warm up. Usually it was on cylinder #1. The GM fix was to drill a small hole in the lifter galley plug at the front of the block next to #1 cylinder to let the hot oil out and fresh oil into the lifters. Dad and I drilled his to cure his lifter clack after having replaced those lifters several times. No more problems. There was a service bulletin back then so this information came from GM in the early 70's.
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Old 07-30-2020, 11:50 AM   #22
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Re: 396 experts need help

I have the same issue with my 454 with the nuts not holding adjustment and slowly backing off. I just bought a new set of nuts and will swap them out and adjust this weekend. I think the ones that came with the rockers may be junk chinese who knows. I have the comp cams roller tip rocker set
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Old 07-30-2020, 02:15 PM   #23
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Re: 396 experts need help

I wish I could give you some sound advice but honestly itís so difficult to discern these issues without actually being in front of the engine and hearing it. I can tell you what my recent experience is although itís a bit discouraging. I will no longer do any engine rebuilds for customers anymore. I have done More small and big block Chevyís then I can count for decades prior without issue but in the last five years replacement parts in the supply chain have become so bad and unreliable I can no longer put together an engine I can stand behind because of it. I can think of 4 engines in the last five years I have had a hand in that have the exact problem you are speaking of. Noisy lifters when the engine is hot. In my personal opinion I really believe it is defective lifters in every case but I do not have definitive proof.

Steve weim55 Colorado
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Old 08-01-2020, 04:40 PM   #24
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Re: 396 experts need help

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I wish I could give you some sound advice but honestly itís so difficult to discern these issues without actually being in front of the engine and hearing it. I can tell you what my recent experience is although itís a bit discouraging. I will no longer do any engine rebuilds for customers anymore. I have done More small and big block Chevyís then I can count for decades prior without issue but in the last five years replacement parts in the supply chain have become so bad and unreliable I can no longer put together an engine I can stand behind because of it. I can think of 4 engines in the last five years I have had a hand in that have the exact problem you are speaking of. Noisy lifters when the engine is hot. In my personal opinion I really believe it is defective lifters in every case but I do not have definitive proof.

Steve weim55 Colorado

The chinese and taiwan parts are total Garbage. That is correct.
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Old 08-02-2020, 08:31 AM   #25
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Re: 396 experts need help

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Originally Posted by geezer#99 View Post
Of course the cam looked fine. Lifters and cam wear in togethor.
Changing the lifters likely changed that.

Pop the valve covers off and check all the rockers are moving the same.
This! And I'll add checking with your eyeball is a crude method, use a dial indicator to measure the lift! Only then can you rest assured that all lobes are good, it only takes one bad lifter to wipe out it's lobe. I've had out of the box lifters that failed to pump up because they were failing to collapse presenting zero preload! The Asian machining processes are questionable at best and should never be trusted!
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