valve info maybe usefull

[pulsarboby]

we're building an engine for someone at the moment who had a major valve problem on the rollers not to long ago.

anyway whilst trying to sort out and lap some valves for the ported head being fitted i came across something that i for one had not been aware of before and this could cause people major probs with engines they are building, so well worth taking note.

below is a picture of 3 valve heads (3 different type of valves which all appear similar other than markings on the bottom, same lengh / diameter and they will all fit perfectly in valve guides)

top left 3 exhaust valves

as said they will all fit ok but be warned as there are differences!
here is a pic of the side view of the ones to the left and right

if you look at the top of valve stem where the collets fit you will see that the head of one valve will sit higher than the other.
now in laymans terms this will cause a compressed spring rate on that particular valve, it will also cause a prob with regard to shimming as the shim will fit higher on the stem.

the centre valve in the first picture is different again as the lead on that valve is higher than the other two so will sit proud of the seat.

so for anyone attempting to build there own engine this info is well worth taking into account and could save you a whole heap of probs with regard to head troubles
on inlet valves they should all be marked 54c with a nissan logo on bottom
exhaust valves should all be marked 5c with logo on bottom

i almost got caught out with this today was only by sheer luck that i noticed the differences on the top, i just originally thought that they had possibly have been a paten type/make valve fitted, but thats clearlly not the case

 

[pulsarboby]

valve info maybe usefull

maybe not:lol: perhaps i was the only one who wasnt aware of that:mong:

 

[Trondelond]

I hated this post. Made me think that maybe I need to whip the head off. But I won't.

Well done!

 

[pulsarboby]

aaaah thanks trond, i feel all that typing was worthwhile now:-D

 

[fubar andy]

aaaah thanks trond, i feel all that typing was worthwhile now:-D

Looky, looky, bendy, bendy...

 

[GTIR-LOZ]

surley if its shimmed correctly it wont matter as the gaps would still be right

 

[pulsarboby]

it matters a lot loz as if you fit valves with different leads then the displacement of the combustion chamber and swirl will be affected.
secondly if you fit the one with the different valve stem lenghs from collet to valve stem tip then that spring will be under far greater compression than the others which in theory could cause thrown rockers and excess head noise even if its shimmed correctly.

its quite important that all valves are matched!

 

[shroom]

sounds very interesting bob tbh thats not something I would have ever thought of looking at,

thanks for sharing this as im sure some day something like this will be a problem for someone and if they are graced with the ability to search then just maybe they might find an answer

 

[GTIR-LOZ]

i agree with the faces of them being different, they should all the the same but a surely few fractions of a mm isnt going to make much difference on the shimming and spring tension or is that a bad picture im looking at?

 

[williams]

did you find out why there are valve differences? are they from different manufacturers or is it a manufacturing error?

 

[gtirx2]

I have seen the design of the 2 on the right before but i have not seen the one on the far left before.
I always thought that the middle valve was off the early heads and the 5c one on the right was off the later heads?
If you buy a new valve from nissan you will get the design on the far right with the 5c marking.
Are you sure the valve on the left is a genuine gtir valve?
Also how do the middle and 5c valve compair height wise?

 

[pulsarboby]

i agree with the faces of them being different, they should all the the same but a surely few fractions of a mm isnt going to make much difference on the shimming and spring tension or is that a bad picture im looking at?

its not fractions of a mm but around 2mm difference and that will make a big difference if you have springs which have different compressions scattered throughout the 16.

Are you sure the valve on the left is a genuine gtir valve?
Also how do the middle and 5c valve compair height wise?

rich..... tbh im not sure what its from, the valves were handed to me in a bag but its a perfect fit both lengh and width ways.

the middle valve and nissan 5c valve are both the same height and the stems are the same but the lead on the middle valve is higher than the nissan one so it sits rather proud of its seat, this will then make the valve short at the other end which will once again give a different spring compression rate.

 

[darkyGTI-R]

I think I understand?If I was building an engine which i'm not lol usefull info though Bob thanks for that,so as long as all valves are the same no problems!?