Author Topic: ZZ4 Valve Adjustment  (Read 9789 times)

Offline Scott M

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ZZ4 Valve Adjustment
« on: April 21, 2015, 09:10:59 AM »
I have a ZZ4 in my 78 and I have a few questions regarding the valves.

from what I know I have the what you would call "base" zz4 (its not the fastburn or anything)

Ive looked on here and searched keyword "valve" and come across one tech write up regarding valve adjustment.  However I am not so positive that it is a write exactly for a steel hydraulic roller cam

Ive read all over the internet that ZZ4 are notorious for a noisy valve train.

Here is what mine was doing:

700 to about 2200ish rpm everything is normal, anything higher and there is a loud clatter that is louder than the exhaust at first I had no clue what it is then I talked to my retired mechanic neighbor and he said that the lash is set too loose or in other words there is prolly a loose rocker arm.  It is coming from the passenger side only.  I have never messed with valves or adjusted them but he said that all of them probably need to be gone over and readjusted.  The valves were adjusted by the machinist who rebuilt the motor and I am assuming there is a possibility that they need to be gone back over.

so this morning I took off the passenger side valve cover to inspect the rocker arms and there was rockers that were alot looser than others prolly 3 to 4 out of the 8.  the other 4 or 5 had minimal play.

I would like to go back through them and redo them all in order to make sure they are set right because the noise they make at those rpm are to be honest so loud its embarrassing. 

Is the only way to adjust the valves by having the motor off or can it be performed with the engine running and the valve cover off on these ZZ4 with hydr roller cam??
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Offline enaberif

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Re: ZZ4 Valve Adjustment
« Reply #1 on: April 21, 2015, 10:03:07 AM »
If you do have a roller cam then you adjust the valves using a feeler gauge.

Offline Scott M

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Re: ZZ4 Valve Adjustment
« Reply #2 on: April 21, 2015, 11:07:45 AM »
So I called up the machinist who did the rebuild and he explained to me that the best way to adjust it since it is in the truck would be to pull the valve cover off one at a time and to run the motor he then said while its running to apply a very small "light" amount of pressure on the rocker arm with the palm of your hand if it quiets the lifter then to turn the nut very slightly til the noise goes away he then said to turn it another 1/8 to 1/4 turn after it is quiet and to just run through them.  He said it will be messy but it would be the best way to do it. 

Does this seem wreckless? or would this get me to right about where I want to be?

I also am wondering if let say I tighten too tight on one what would be the procedure will running to go back to square one with that particular valve and redo the process? would it be as simple as to while its running to loosen the rocker arm nut little turns at a time till it clatters a slight bit and then start turning down on it till it quiets and then another 1/8 to 1/4 turn? The reason I ask is I blindly went in after I pulled the valve cover watched a couple of videos on youtube and I tightened up a couple of the bolts to the loose ones like 1/4 turn or a little more and now Im scared I tightened them up to much. I admit my stupidity cause I was in a hurry this morning (which is never a good scenario) and wanted to drive the truck to work. started after tightening and it ran ok till i put it in gear and had like a slight miss backing out of the driveway so I pulled it back up the driveway and (10 feet) and parked it.

With all that being said I think I will have to start it up with the valve cover off and then back them off one by one a little at a time and then do the above method if this method seems ok to do...

any advise input would be greatly appreciated.

I do have the option of hooking the tow bar back up towing it back to the machine shop (75 Miles away) and he said he would adjust them.  At the point now that if the above method will not work or it is above my head and harder than what it looks I guess Ill tow it...   
78 GMC K25 4x4 - Beach Toy
6in Suspension 2in Body
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Offline Scott M

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Re: ZZ4 Valve Adjustment
« Reply #3 on: April 21, 2015, 02:06:31 PM »
Man I hate things like this Im reading on the internet and so many swear one way and against the other and so many swear the other.  I am seeing were people recommend doing the Not running procedure and all the others saying that theyve done it to dozens of motors running and thats the only way to get a true adjustment in real time.

I pulled the valve cover back off at lunch time and backed every nut that i tightened this morning about 1/8th of a turn.  I then fired the truck up with the cover off just to see what was going on and to see how messy this procedure actually was to my suprise it was not as bad in my opinion as what people say yea little oil here and there but it wasnt like a water gun shooting up... I am going to just go home after work and tinker with it some more and enlist the help of the retired mechanic and see what we can do lol i guess... Ill report back tomorrow hopefully with no bad news knock on wood....
78 GMC K25 4x4 - Beach Toy
6in Suspension 2in Body
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46" Military XMLs

Offline gmachinz

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Re: ZZ4 Valve Adjustment
« Reply #4 on: April 21, 2015, 02:07:18 PM »
How big is your cam? You might want to verify that there aren't any pressed in studs trying to "back themselves out" due to either extreme spring pressure and/or too big of a lift on the cam. As for checking valve adjustments-a roller is still hydraulic (unless its a solid roller cam-which I doubt) so no feeler gauges required. Typically, 1/2 to 3/4 turn past zero lash is sufficient.

Offline Scott M

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Re: ZZ4 Valve Adjustment
« Reply #5 on: April 21, 2015, 02:28:15 PM »
Even though the motor is rebuilt it was rebuilt using all the stock parts listed in the list bellow so I did not put a different cam or different rockers, the machinist did have to deck the heads due to them being warped a little from over heating. he did do a valve job as well, he put new piston rings, turned the crank, new main bearings and new cam bearings he said the cam measured/looked good and used the same cam, thats all i can think of at the moment.... he has been building and rebuilding stock and performance racing motors for many of years prolly more years then I can count on my hands and toes so I do trust that he knows what he was doing and replacing....

here is a list of the original equipment that is in the motor


ZZ4 350 TURN-KEY TECH SPECS
Part Number:
19201330
 
 
Engine Type:
Chevy Small-Block V-8
Displacement (cu. in.):
350

Bore x Stroke (in.):
4.000 x 3.480

Block (P/N 10105123):
Cast-iron with four-bolt main caps

Crankshaft (P/N 12556307):
Forged steel

Connecting Rods (P/N 10108688):
Powdered metal steel

Pistons (P/N 10159436):
High-silicon aluminum with offset pins

Camshaft Type (P/N 10185071):
Steel hydraulic roller

Camshaft Lift (in.):
.474 intake / .510 exhaust

Camshaft Duration (@.050 in.):
208° intake / 221° exhaust

 
Cylinder Heads (P/N 12556463):
Aluminum; 58-cc chambers
 
 
Valve Size (in.):
1.940 intake / 1.500 exhaust

Compression Ratio:
10:1

Rocker Arms (P/N 10089648):
Stamped steel

Rocker Arm Ratio:
1.5:1

Recommended Fuel:
92 octane

Ignition Timing:
Base 10° BTDC, 32° Total

Maximum Recommended rpm:
5800

Balanced:
External
« Last Edit: April 21, 2015, 02:35:01 PM by Scott M »
78 GMC K25 4x4 - Beach Toy
6in Suspension 2in Body
Zero Rates Upfront
ZZ4/TH400/NP203
46" Military XMLs

Offline gmachinz

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Re: ZZ4 Valve Adjustment
« Reply #6 on: April 21, 2015, 03:23:26 PM »
Wow....externally balanced? That's odd. Well, I'm sure he knows what he is doing however-did he replace the rocker arm studs? If the springs are new but the studs aren't....I'd look into that. Not saying your machinist is incompetent, just trying to get a good sense of what has been replaced during the overhaul.

Offline Scott M

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Re: ZZ4 Valve Adjustment
« Reply #7 on: April 21, 2015, 03:36:44 PM »
That is a good question, I will call him up sometime and ask him, I know I should know this but I don't know all I really know is what I stated not much more or less. the mileage on the motor before being rebuilt was unknown but according to him it was in pretty good condition.  the reason I took it to him in the first place is when checking the tolerances on the main bearings One of the bearings had a what i want to call a scar were a piece of metal had must have got in there so I decided to take it in and have it completely gone through...  I will ask him.  I need to pull the receipt with all the parts he ordered first and see if I can get a answer myself before calling.
« Last Edit: April 21, 2015, 03:38:47 PM by Scott M »
78 GMC K25 4x4 - Beach Toy
6in Suspension 2in Body
Zero Rates Upfront
ZZ4/TH400/NP203
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Offline enaberif

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Re: ZZ4 Valve Adjustment
« Reply #8 on: April 21, 2015, 03:48:30 PM »
Externally balanced? Usually only on a 383 or 400 ... Not a 350.

Offline Scott M

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Re: ZZ4 Valve Adjustment
« Reply #9 on: April 21, 2015, 03:55:58 PM »
that list of specs is just what I got off of gm performance the official website, this is an older model ZZ4 (prolly more than 5+ years old) I dont know if they have changed from what they say now
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6in Suspension 2in Body
Zero Rates Upfront
ZZ4/TH400/NP203
46" Military XMLs

Offline Scott M

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Re: ZZ4 Valve Adjustment
« Reply #10 on: April 24, 2015, 10:30:07 PM »
Ok so i have maybe a new theroy that might make sense, ive looked up a lot of stuff on this and it seems to be very common, i believe that this problem i am expierencing is what is called pinging....anybody have expierence with that? From what ive read it seems very similar to what im expierencing but i have no idea what my timing is set to or how to do any of that, i have zero expierence with that and my time was set by having the motor at what would be called tdc stabbed the distributer where it was facing number 1 and then by sound of the motor retarded it or advanced it but no measurements were taken

I am expierencing a ping clatter type noise at about 2300-2500 rpm and then after running for awhile i expierence what i believe to be a little kick back from the starter i believe not 100% but starts good when cold could this be my problem, also my current setup has the vacuum advance on the dizzy going to the appropriate carb vac, some people suggest going to a. Manifold vac on the zz4 and doing a canister or something i dont believe i have that on my current setup and say there is an advance regulator i have no knowledge really about any of this.  Is there a way to trouble shoot?
78 GMC K25 4x4 - Beach Toy
6in Suspension 2in Body
Zero Rates Upfront
ZZ4/TH400/NP203
46" Military XMLs

Offline Scott M

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Re: ZZ4 Valve Adjustment
« Reply #11 on: April 27, 2015, 08:33:34 AM »
I went out of town this weekend and when I got into town I decided to mess around with the truck a bit.  I first retarded the timing just a hair, I then went and put octane booster in the tank and let the truck warm up.  After it was warmed up I romped on it a little bit and the ping was reduced.  I believe it is still a timing issue and plan on getting a timing gun this week to see exactly where we are.  I then  hammered on it to about 4000 rpm took it home and then changed the oil for the first time.  I am going to open up the filter since this is the first oil change since break in. prolly about 100 miles on the oil

thanks for all the replies!
« Last Edit: April 27, 2015, 08:35:08 AM by Scott M »
78 GMC K25 4x4 - Beach Toy
6in Suspension 2in Body
Zero Rates Upfront
ZZ4/TH400/NP203
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Offline Scott M

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Re: ZZ4 Valve Adjustment
« Reply #12 on: April 28, 2015, 12:10:31 AM »
Alright i have seemed to somewhat have fixed my problem, i started just retarding the time from where i have it set currently i got to a point where i eliminated the ping while also gaining alot of power, seems that the timing was way too far advanced still plan on putting a gun to see exactly where im at but i do know im awhole lot closer than ever now, the motor has alot of power between the 2500 to 4000 rpm it scoots my big truck alot better than the old 350 i still think there is more to be had out of this zz4 though but it close
78 GMC K25 4x4 - Beach Toy
6in Suspension 2in Body
Zero Rates Upfront
ZZ4/TH400/NP203
46" Military XMLs

Offline enaberif

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Re: ZZ4 Valve Adjustment
« Reply #13 on: April 28, 2015, 04:35:08 PM »
You need a timing light... Timing should be around 8-10 BTDC for a stock setup. You can go higher as long as you don't hear those "pings".