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 ? |
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 |
Re: 396 experts need help
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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. |
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 |
Re: 396 experts need help
Have you tried 10/40 ?
Did you check for coil bind on the valves? |
Re: 396 experts need help
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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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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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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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Re: 396 experts need help
Did you have machinist check valves for your cam lift for binding issues ?
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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 |
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? |
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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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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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 . |
Re: 396 experts need help
Did you re break in the new lifters after you changed them ?
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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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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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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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Re: 396 experts need help
I wish I could give you some sound advice but honestly it’s 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 it’s a bit discouraging. I will no longer do any engine rebuilds for customers anymore. I have done More small and big block Chevy’s 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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The chinese and taiwan parts are total Garbage. That is correct. |
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Re: 396 experts need help
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 |
Re: 396 experts need help
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Re: 396 experts need help
Got it all back together with the correct valve springs and sleeved valve guides so everything is tight. Not getting enough oil to driver side valve train. It chatters . Oil pressure is 50 psi cold at idle. I just realized something......... The HEI distributors I have been using do not have the 3rd ring up high on the shaft like the original points type distributor I had. Could this be letting oil out of the galley ??
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Re: 396 experts need help
Please post a pic of the shaft where you believe ye 3rd O ring is located....
The lower section of the distributor body is a slip fit into the bore above the cam. As the engine heats up, the aluminum body of the distributor expands, closing up the clearances. Question...when you rebuilt the engine...did you drill small holes in the plugs that go into the front of the oil galleries? The holes, one in center of each plug, are 1/16" usually...to allow trapped air out of the galleries....air lock is a common issue with BBC engines.... :chevy::chevy::chevy: |
Re: 396 experts need help
I would put a cam in it. You will be on lifter set number 3. The cam stands little chance of survival. The new cam and new lifters need to be broke in together. You cant mix the order if you take the lifters out for some reason. In 45 years I have not seen good results with a used cam and new lifters. After you head experience I would review your entire build.
Jimmy |
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