hi all,

i recently put a new engine in my 98 sti, and had the heads cleaned and skimmed,

my question is guys i had a tapping sound caused by he shims not being the correct size / order,

i checked them and the gap is .20mm inlet and approx the same for the exhaust

GUYS is the correct gaps

.20mm (.008inch) inlet
and .25mm(.010) exhaust ????

 

when i did my old classic thats the gaps i went by.They still made a tapping noise but not excessive.Going slightly loose isnt a problem its when they go tight its time to worry

 

You might get trouble with the exhaust side if they are 0.2, newage increased the exhaust from 0.25 to 0.35 ,probably its the bigends you can hear - lol

 

no not my bigends, but thats for your advice and the newage part

 

Valve clearances should be:
Inlets 0.006~0.008"
Exhausts 0.008~0.010".

I would expect to see clearances around 0.005" larger than standard before you would be able to hear a ticking noise.

Sticking buckets in the lifter bore in the heads can cause problems/ticking noise as can noisy injectors,loose spark plugs,slight exhaust gas leaks from header gaskets etc etc.

Mick

 

I'm a bit surprised that it would take 5 thou before a noticable increase in mechanical noise was apparent? 5 thou is a massive amount! Different I know (pushrods and rockers) but I remember an increase of less than 1 thou. would result in a noticably noisier engine in a 1600 GT Capri I had back in the '70's

JohnD

 

Ahh the good old days i used to use those engines in my mk2 escorts,flat top lotus pistons and 1600e cortina chambered heads happy days

 

thank you mick, i appreciate it, i have taken the exhaust one out as they are slightly off, and i also noticed a doggy idler so will change that also to be sure. my exhaust are now at .25 so when it goes back together should be quiet as they were .20 oops,

 

Ball park figure of +0.005" is around the point you will hear an audible tick from the EJ20 DOHC 16 valve direct acting under bucket shim set up - have fitted and dialled in several sets of aftermarket cams with high lift/duration and usually combined with stainless/Inconel valves which specify a larger valve clearance than standard - at 0.012~0.014 you dont usually hear them over the usual Injector tick, any more than that they tend to sound like an old OHV Kent engine

Mick

 

Thread revival
Good info on here,I've taken of the cam cover and going to check clearance tomorrow.
What position should the cams be in to check please?

 

There isn't one position mate. It's s pita. You have to keep moving the cams by hand until you find each valves biggest gap. That is the clearance you measure.

 

Ah right,I had a quick check with the cam lobe at 90 degrees away from the bucket and struggled to get a 0.20mm in there,that would explain it then!
Cheers I will give them a proper check tomorrow

 

Just set the camshaft lobe furthest point away from the bucket ( as top left of pic on the STi V4 heads)





Mick

 

Ok thanks Mick
I will get on it tomorrow,hopefully I will find one that's out of spec otherwise my problems are worse than I think.
I've converted your specs into mm and I don't have a great range with my gauges but should have enough to tell if this is where my knocking is coming from.

 

Clearance is very tight which is not what I expected.
As I said my set of gauges are limited but should be ok to tell me if there is a problem.
I was expecting the valve train knock to be from a clearance that was to big(greater than 0.12mm out of spec)
Can anyone explain my results and what would cause the gaps to be so tight?

Cyl 2: (inlet) 0.10mm & 0.10mm. (Exhaust) 0.10mm & 0.05mm.
Cyl 4: (Inlet) 0.05mm & 0.05mm. (Exhaust) 0.10mm & 0.05mm.

Cheers
Rich

 

Rich - I'm surprised you don't have running issues when the engine has warmed up, the valves expand and you loose that small clearance.

The clearances shouldn't close up that much under normal running/mileage, so ..........

#Engine rebuilt recently/heads overhauled and clearances incorrectly set on assembly ?
#Engine has hydraulic lifters fitted so have near zero lash when trying to get a feeler blade under the heel of the cam lobe ?
#You haven't checked the clearances properly ?

Have you got any pictures of the L/H head you are checking the clearances on ?

Mick

 

Bit of a mare checking whilst engine in but I took my time and checked everything three times,even did a check with spark plugs out as I wasn't sure if this could affect readings.

It had a bottom end rebuild 30k ago but original heads used as far as I'm aware?
It's also recently had some work done,one of the jobs was rocker gaskets,new turbo&6 speed conversion. I suppose it's possible the engine came out to do these jobs and some head work was done and reshimmed?

The car has started to run pretty bad(I've only been driving on light throttle and below 3k rpm) feels hesitant with a feeling of misfire,and really bad when off throttle and coasting in gear,it revs high then drops revs intermittently,also revs stay high on gear changes(also intermittent)
Knocking noise now getting worse and more constant,could this be the noise of the piston kissing the valve top?

I have taken one pic,not very good tho so I will take some better pics tomorrow,from what I've seen from your info they are v3/4 heads,would be hard to believe someone converting the solid lifters to hydrolic but possible I suppose?

 

Seeing the pic, you do have STi 3~4 heads/cams so you can eliminate the hydraulic lifters swap ( I have seen it done in the past ) as the cam lobes would have a witness mark around the circumference of the center of the lobe where the hydraulic lifter touches.

Think you need to do a compression test to check the internal health of the engine because of the very tight valve clearances you have found.

Mick