2020-B1-10

Author Topic: Valve lash  (Read 186 times)

green-hornet

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Valve lash
« on: February 12, 2020, 02:24:58 PM »
I'm building my rebuild engine,pontiac 400 1976 , New hydraulic lifters comp cam,new rocker arms,new pushrods all stock,New comp cam,must do the break inn.

-Do i have to put the new lifter in oil or mount them empty?
-How do you set your valve lash?
There are so many different ways,please give your opinion and argument,and help me out what to do.

cyber104

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Re: Valve lash
« Reply #1 on: February 12, 2020, 04:25:11 PM »
Empty is fine is you prime the oil system first............

If you are using the stock Pontiac setup there is really nothing to do except tighten the rocket nuts to spec.

If you went the BBC stud with adjustable nuts like I did then here is the process.......

Grumpy's garage suggests the same method I used and may describe it a bit better:  "mark the harmonic balancer every 90 degrees starting at the timing mark,on the damper aligned with the timing tab at TDC. put the engine on #1 TDC on the compression stroke and adjust both rockers with both valves closed, then rotate the engine 90 degrees clockwise as viewed from the front and set both valves on #8. Proceed in this fashion through the firing order until you have them all set (18436572). "

The Wallace Racing website gives the following instructions - not sure if they are better or worse than the method I used - I'm going to double check mine tonight using their method to see if I get the same results.

"Number 1 piston at Top Dead Center (TDC) on compression stroke.
Adjust intake valve on #2 and #7;exhaust valves #4 and #8.

Rotate crankshaft 180 degrees clockwise and adjust intake valve on #1 and #8;
exhaust valves #3 and #6.

Rotate crankshaft 180 degrees again (TDC) and adjust intake valves #3 and #4;
exhaust valves #5 and #7.

Rotate crankshaft again 180 degrees and adjust intake valves #5 and #6;
exhaust valves #1 and #2.

Use 7/16 studs with polylocks (locking nuts with a setscrew),turn down
adjuster nut slowly while spinning pushrod back and forth with other hand until
all play is removed WITHOUT pushing lifter cup down into body.You should
JUST feel the pushrod get hard to spin.Then turn an additional 1/2-1 full
turn and lock it.
« Last Edit: February 12, 2020, 04:36:57 PM by cyber104 »
1978 TA 4-Speed W72

79T/Aman

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Re: Valve lash
« Reply #2 on: February 12, 2020, 08:20:37 PM »
just be very careful when spinning the push rod, with oil all over they can still be spun even though the lifter is already depressed,
 what rocker ratio are your new rockers?
with anything but a stock Pontiac cam you should use an adjustable valve train system, people will say you don't have to if it's under such and such lift ...that is false, it all has to do with the base circle of the cam and where the lifter is positioned.

here is another method that is easy to remember and no need to count revolutions.
as EXHAUST opens set intake, as INTAKE closes set exhaust, use a sharpy to mark the rocker as you finish it.
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79T/Aman

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Re: Valve lash
« Reply #3 on: February 13, 2020, 06:05:11 AM »
....and since you rebuilt the engine, the simplest way is to keep the intake and valley pan off and just look at the lifter and adjust as each one gets on the base circle, that is how I did my first engine at 15.
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green-hornet

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Re: Valve lash
« Reply #4 on: February 14, 2020, 02:58:44 PM »
7/16 rockerarm studs,comp cam rocker nuts.
XE262H set


« Last Edit: February 14, 2020, 03:01:29 PM by green-hornet »

79T/Aman

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Re: Valve lash
« Reply #5 on: February 14, 2020, 07:16:18 PM »
are those pics the actual engine?if so you should not use the spring shields with aftermarket springs over time they will break (Pontiac omitted them on Ra4 engines for that reason)
are the studs 7/16 top and bottom? 7/16 rocker nuts?
Are the nuts locking?
What rocker ratio? are they stock?
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green-hornet

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Re: Valve lash
« Reply #6 on: February 15, 2020, 12:13:57 AM »
Yes,that's my engine.I have o-ring seal than i need springshields,right?
Stud are top to bottom 7/16, nuts are self locking.
Stock ratio.
I have already remove the inner valve springs because the break-inn.

Fbird

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Re: Valve lash
« Reply #7 on: February 18, 2020, 08:41:46 AM »
in a stock'ish cam profile...basically any cam with less than 200 lb seat pressure ...no need to remove springs for break in...just make sure you PRIME the oil system to see oil pressure and obviously be generous with your assembly lube..prime the CARB with gas...and get it to START!!! if you have to crank carnk crank crank.... stop. First start is critical so you can get oil on the cam.
67 Firebird
1980 Turbo TA (injected 400 now :) )

Re: Valve lash
« Reply #7 on: February 18, 2020, 08:41:46 AM »
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