Valves are 38 inlet and 33 exhaust
I can't remember what they were off... but they were too long and I cut them down to suit
I then run a hardened lash cap on top to stop the chance of them mushrooming the non hardened tip
Doubt the roller rockers ever would do that... but that's what I did anyway

are those bigger valves than normal ? look different to mine, and mine have the nissan logo on them...

hmm ok, keen to hear what the clearance measures at when you pull it apart. I'm hoping to check mine soon as I'm going to rebuild in the next few months.

I'd say I'm just lucky... but... I'll be rechecking all the clearances once the engine comes apart and let you know
Chambers look like this

your not an Idiot... just learning, better to learn and find out than to have to rebuild it again.... well done...

OK, i'm an idiot... repeat after me.. "it is only by doing that you learn"..


Following Neils Post i decided to take a step back and recheck everything i have done... well, due to me being 'sure it was like this' when i built the std engine 3 years ago i had the cam about 180 degs out with the crank.
Now I aligned it properly as to the picture in the Wiki i get 3.5 and 3.3mm clearance .
So ive continued with the pistons just as flat tops.

With 30cc in the head, 1.2mm HG (6cc) and the step on one side of the mazda piston (est 1cc) i get a CR of 10.3... Camtech recommended a minimum CR of 9.. i run 95 octane petrol, so i think all should be good.

Quote:

How the hell have you not had valve clearance issues? Are your valve seats sunken deeper in to the chamber and head face not planed down at all?
I ran flat top mazda pistons at zero deck height, 0.6mm off the head face and had to cut pockets in the pistons tops for clearance.
I have been told you can run as little as 1mm clearance on inlet valve and 2mm on exhaust, sometimes even less. Have also seen pistons with evidence of valve contact as well though.

Hi Neil,
According to your cam spec you have .309 lift at the lobe, with 1.65 rockers that gives .309 x 1.65 = .509" lift = 12.95mm

My cam spec(camtech 621) has .399 valve lift with 1.5 ratio rockers, this calculates back to .266 lobe lift. I'm using the std rockers at 1.44 ratio, so my lift should be .266 x 1.44 = .383" = 9.72mm..
So you have about 3mm more lift than me.. i would be hitting the pistons for sure... yet you have no problems...?i must have someting different somewhere, maybe its to do with the cam timing ?

I wonder if my head has been skimmed in the past... I cc'd the chambers and got about 30ml which according to tech wiki is correct...so i asssumed not.

Something to consider there pointed by Neil is the rocker geometry in case you change to roller rockers or similar higher ratio rocker, cam or other in the future. Doing it now leaves some scope for the future and safety margin.

Depending on the compression you can just mill them 1.5mm etc but notching for valves is not expensive.

Something to consider there pointed by Neil is the rocker geometry in case you change to roller rockers or similar higher ratio rocker, cam or other in the future. Doing it now leaves some scope for the future and safety margin.

Depending on the compression you can just mill them 1.5mm etc but notching for valves is not expensive.