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Valve Noise RB25DET NEO

DTT_Eruc

By DTT_Eruc,
in Engines & Forced Induction

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DTT_Eruc Enthusiast

DTT_Eruc

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Good day buddies.... So i have recently installed some Tomei Poncams(Intake 260 9.15 and Exhaust 262 9.15 lift) for my engine (RB25DET NEO).... After they were installed i never checked the shim clearance(p.s shims are above bucket type), due to it being drop in cams and my buddy who installed them never had to re-shim. Unfortunately after i started the car i heard a ticking noise from the back of the head and then investigated the reason of the noise. For a second i taught it was the body oil used(20w50) and i live in the caribbean. So i change the oil to 10w50 and the noise reduce a bit but was still there... When i pop the cam cover and check the clearances this was the results. 

*Exhaust * Numbers are in "thou" reading

1.0.019
2.0.019
3.0.019
4.0.019
5.0.020
6.0.020
7.0.020
8.0.020
9.0.020
10.0.20
11.0.20 + 0.011
12.0.018 tight or 0.017

AS Tomei recommend there clearances to be .018 thou mine reads close to Nissan specs and never did any head work....  but for when i checked the clearance on valve #11 and #12 i notice that was the problem.... What can cause that such big clearance #11 and tight clearance on #12 ....Btw this is a stock head and never done any head work as my goal was to just see how long the engine can last....  

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GTSBoy Grand Master

GTSBoy

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Just for clarity.....0.019 is 19 thousandths of an inch, right?  And 0.20 is 200 thousandths of an inch?  Is that a typo on #10 & #11?  Because the error you put after #11, or 0.011 doesn't add up.

#12 is fine.  The clearance is a tiny bit close, but not enough to cause any massive issues.  Better if you can get it right, but not going to be causing noise.

At 0.200, #11 is f**ked.  Unless you have a typo on that one and on #10..... in which case they are only a little bit wider than desired.  But they could certainly be responsible for increased clatter.

DTT_Eruc Enthusiast

DTT_Eruc

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yes everything is in thousandths of an inch so its 0.019....and 0.020 thou also....yes typo error at #10 and #11 sorry..... but with the valve clearance reading 0.020 thou + 0.011 which brings it up to 31 thou.... i havent do any compression nor leak down test just yet but will like to know what can cause such clearance... i measured the shim and bucket also checked for wares and reads within specs so am guessing its something to deal with the valve 

GTSBoy Grand Master

GTSBoy

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Oh.  30 thou.  That is definitely going to be noisy.  That is your smoking gun, and you need to fix it because that much lash will only lead to further wear/destruction.

As to the cause.....well, it can't be valve seat regression, because that closes clearances, not opens them.  Opening clearances implies either wear on the lifter or valve stem tip.  The valve seat may have a big dent in it, preventing the valve from closing completely.  This could happen if something hard went through the engine and got munched between the valve and seat.  It could also be a bent valve stem I guess, holding the valve tight just before it comes all the way up and again stopping it from seating.  Or something else stuck in the valve guide causing it to grab.

DTT_Eruc Enthusiast

DTT_Eruc

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9 hours ago, GTSBoy said:

Oh.  30 thou.  That is definitely going to be noisy.  That is your smoking gun, and you need to fix it because that much lash will only lead to further wear/destruction.

As to the cause.....well, it can't be valve seat regression, because that closes clearances, not opens them.  Opening clearances implies either wear on the lifter or valve stem tip.  The valve seat may have a big dent in it, preventing the valve from closing completely.  This could happen if something hard went through the engine and got munched between the valve and seat.  It could also be a bent valve stem I guess, holding the valve tight just before it comes all the way up and again stopping it from seating.  Or something else stuck in the valve guide causing it to grab.

One last thing am running stock(internals) at this point and knowing am going to pull off my head i was wondering if i should copper spray the head gasket cause am not willing to spend and extra dollar at this point lol  i just want the car up and running till my financial status is reading fine to do internals.... aim is just 20 to 22 psi and done 

DTT_Eruc Enthusiast

DTT_Eruc

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3 hours ago, Dose Pipe Sutututu said:

Get a Tomei head gasket, they're o-ringed. Avoid Cometic MLS unless you deck the block and skim the head.

 

already planned to and since you mention it dont think i wanna do head skimming or decking of the block just want the car back up running without having to do much... 

admS15 Grand Master

admS15

Posted
Posted
already planned to and since you mention it dont think i wanna do head skimming or decking of the block just want the car back up running without having to do much... 
If that's the case, you're better off using a factory Nissan hg. It will be much more forgiving of not perfect mating surfaces. Otherwise you'll have to at a minimum skim the head and clean the deck surface thoroughly.
DTT_Eruc Enthusiast

DTT_Eruc

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2 minutes ago, admS15 said:
1 hour ago, DTT_Eruc said:
already planned to and since you mention it dont think i wanna do head skimming or decking of the block just want the car back up running without having to do much... 

If that's the case, you're better off using a factory Nissan hg. It will be much more forgiving of not perfect mating surfaces. Otherwise you'll have to at a minimum skim the head and clean the deck surface thoroughly.

ohhhhhhh i see.... i was looking at using tomei 1.2mm and just clean the head perfect as possible and slap it on 

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

Posted
Posted
33 minutes ago, admS15 said:
2 hours ago, DTT_Eruc said:
already planned to and since you mention it dont think i wanna do head skimming or decking of the block just want the car back up running without having to do much... 

If that's the case, you're better off using a factory Nissan hg. It will be much more forgiving of not perfect mating surfaces. Otherwise you'll have to at a minimum skim the head and clean the deck surface thoroughly.

The Tomei gasket is pretty forgiving :) 

Also ditch the OEM head bolts and use a ARP head studs instead.

DTT_Eruc Enthusiast

DTT_Eruc

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1 minute ago, GTSBoy said:

Now, or in the future?

the objective tbh was to do the 600hp on stock internals and hope it last till i can afford another head and block build.... so i really didnt want to touch anything inside but now i have to clear that "valve" issue ill have no choice but to do a fresh gasket and headstud(optional for me as funds are low) lolzz 

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