396 experts need help

[69 customcamper]

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 ?

[gmc684x4]

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

[69 customcamper]

Originally Posted by gmc684x4

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.

[weim55]

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

[69 customcamper]

Originally Posted by weim55

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.

[geezer#99]

Originally Posted by 69 customcamper

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.

[69 customcamper]

Originally Posted by geezer#99

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.

[gmc684x4]

Have you tried 10/40 ?

Did you check for coil bind on the valves?

[geezer#99]

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.

[69 customcamper]

Originally Posted by geezer#99

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.

[Ironangel]

Originally Posted by geezer#99

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!

[69 customcamper]

Well turn out I had a mess. I took things apart again and wonder if this was the case the first time and I just did not notice it ....... 5 Broken valves springs. Broken on the outter spring so the valves were still closing. Also noticed the Valve guides were too loose. I bought these heads ready to go from someone on ebay. They were beautifully cleaned and had all new hardware. Crappy job ! So I am getting new guides and cleaning them up again and getting the correct springs for MTC6 Melling Camshaft. I am thinking they were not the right springs. I should have looked closer but I have never had a broken spring in all my years of automotive since 1992. I have probably worked on 30 different engines of various types LOL. Oh also the valves were all Snow white on the bottom. Lean condition........

Mike

[gmc684x4]

Did you have machinist check valves for your cam lift for binding issues ?

[69 customcamper]

Originally Posted by gmc684x4

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.

[gmc684x4]

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

[HO455]

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?

[JMac11]

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

[69 customcamper]

Originally Posted by HO455

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 .

[j_cst_10]

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.

[kwmech]

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

[Boog]

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.

[j_cst_10]

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.

[69 customcamper]

Originally Posted by j_cst_10

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.

[gmc684x4]

Did you re break in the new lifters after you changed them ?

[Ironangel]

Originally Posted by 69 customcamper

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 ?

20w-50 is overkill for a fresh rebuild! I'm going to guess your using off the shelf Valvoline VR1 right? Great oil, wrong viscosity! I break all my motors in with 30w only! For two reasons, ring break in and cam break in. Cams only get oiled by the splash and oil slung around by the crank and windage. That's why 2000+ rpm is suggested. The thicker oils wont flow or sling readily until hot and with tight clearances on a fresh rebuild that oil don't get to the critical areas as fast or readily as the thinner oils. Poly locks on a hydraulic cam and lifter is again overkill that can create more problems than they're designed to prevent. Use a quality NEW rocker nut and your done, mark them with a sharpie or paint stick so you can visually verify if they back off or not. A loose poly lock will always back off where a questionable used lock nut wont in many cases. Your not spinning that motor up to 8K and beyond so loose the poly locks! Poly locks also require torqueing to 20 ft lbs, did you torque yours? Use the "EOIC" method to set your valves and give the nuts 1/2 turn. If the valve train is making noise after warm up, you most likely didn't get the rocker nut within the preload range of the lifter. Nothing wrong with adjusting one or two lifters with the motor running but how in the world can you hear the one with the whole gang clattering? What else, oh, drilling a 1/16" hole in each oil galley plug at the front will relieve air trapped in the end of each galley and drip oil on the timing set, BBC's are notorious for oiling issues up front. If Thad Harms and David Vizard drill their plugs, that's good enough for me, I'll spare you the details...I use Valvoline VR1 10w-30 after break in, order it online because the Chinese auto parts stores don't stock it...After re-reading your post, I'm questioning the integrity of the rocker studs...Are they worn out 3/8" studs? New 7'16" Studs are cheap insurance, install them using red permanent Loctite...I have had studs come loose on the older cast iron heads...What is a "Camaro head?" I guess my 69 290 heads are Vette heads? No, they're 3964290's...