Forum » Off Topic Discussion » How far out can valve clearance's be before it impacts performance/idle quality?

How far out can valve clearance's be before it impacts performance/idle quality?

Off Topic Discussion

If it's not really about tuning or wiring. Then it belongs in here.

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Hey all,

I had my Subaru EJ255 heads reconditioned at a local cylinder head specialist shop. I checked my clearance's and found they were all out of spec.

Honestly looked like they hadn't done any work to them at all, I called up the shop and questioned them about it.

They said the clearance's were all OK and they would run them without issue - "It doesn't matter if they are a thou or two thou out" is what I was told...anyway I accepted there answer as I have not been doing it for 30+ years.

None the less here is what I recorded (cam lobe base on the bucket was when my measurement was taken).

Factory Spec according to the manual is

Intake: 0.20mm+0.1mm or -0.03mm

Exhaust: 0.35mm +-0.02mm

My results were...

(See attached)

The shop told me they did them at 0.010 to 0.011 thou - so 0.254mm to 0.2794mm - Factory spec calls for 0.35mm.

The car runs ok, but the idle has a bit of a miss to it everynow and then. The engine shakes a tad while on idle.

Could this be why ?

I have been told that the factory sets the clearance's pretty loose to cater for everyone's climates - living in australia I am told that I can run tighter clearance's not only to reduce valve train noise but have slightly more lift. (Which makes sense)

But are my readings too far out?

My initial thoughts were they just couldn't be assed machining down the factory buckets or purchasing new ones.

Attached Files

While I wouldn't be super happy with the machine shop if I'd asked them to set my valve clearances to the factory specs and they didn't follow through, what they've set them to is fairly reasonable, and I don't think would be causing your slight miss at idle.

I don't think the image upload worked - I have reattached it now