reuby,

I have done this in much the same way as described with a couple of exceptions. I assembled the head to the block with no head gasket and set the rocker to valve "lash" at 0. I then turned the engine over and made sure that there was no contact between the valve and the piston. Once I was convinced that there was not and I had run the engine through a couple of cycles I removed the head and measured the clay on all four cylinders. (I know, overkill, but what if?) As long as I had between .008 and .012 I figured that all would be OK. (Head gasket compressed thickness and valve lash were not in the measurement here so that is why I figured that would give me a margin of error.

hmm righto, its a lot more complicated than I thought i would be, but then it always is.

I dont have the paperwork with me right now ( I am at work doh!) and wont be home for a while. From memory the block was shaved a little to level the boy out, then a 1mm shim has been installed to bring the compression back down to 8.8:1. Will have to do some more research into this, or perhaps I should just order them, fit em, and sit back and enjoy. The change from 1.5 to 1.55 ratio is not much extra lift and I already have a 1mm shim and the extra lift isnt too much.

hmmm.....

Hi Reubs, The valve clr is the rocker to valve setting not valve to piston. To check valve to piston clearance, Man it,s pretty involved.. Prob best off to google "checking valve to piston clearance",Just to make sure what I,ve said is correct I,ll give it my best shot anyway. With your bottom end fully assembled an camshaft installed in the position it will be used in, either advanced, retarded or heads up, [Thats what degreeing the camshaft in is about] place some plasticine or modeling clay on top of the piston lightly oil top of plasticine or clay so valve doesn,t stick to it when it touches.Place light valve springs in cyl you wish to check. {They must be able to shut valve & also be soft enough to be opened by finger pressure, Install head torqing it down to spec, now with the piston at top dead centre take valve height measurement with valve closed then open, there is your valve to piston clearance.Depending on the lift of your cam and the timing of it ,how much yr block is shaved, if yr head has been shaved, the height of yr head gasket, it all goes into the combination.Just don,t valve bounce it cause it all goes out the window then LOL!! When you got the cam did you say I want this cam or did you tell them about your motor an they offered this 1?? Forgot to check WIKI before I posted this whats the factory cam got for lift?

Sorry i forgot to explain fly cuts

This is a pic of the B-Project's piston. They have the valve relief [fly cut] cast into the crown of the piston already. The end result is similar. You get the idea...

Flycuts = cutouts in the pistons to allow more compression or lift without the valves hitting the pistons.

Ahh yeah if i didnt make it clear, yes I want to install some roller rockers.

and fly cuts???

I take from the info in your post, that you thinking of installing roller rockers?

Yella Terra ? Even though thay list two ratios, from memory I think they only have the 1.55 for sale these days. BTW the std ratio is 1.5 from memory.

Fly cuts are the answer to you problem, unless you already have them.

image of the spec sheet incase I have translated it incorrectly.

Folks

I need some help working out this cam specs sheet for my motor.

The cam is from JTS Performance with the following specs

Profile - 104CB
Actuation - Flat Tappet
R/Ratio - In 1.5 Ex 1.5

Cam Lift
In - 282
Ex - 281

Duration Adv.
In - 274
Ex - 271

Duration @ 050
In - 212
Ex - 212

Valve Clr
In - 0.013
Ex - 0.013

Valve Lift
In - 0.4092
Ex - 0.4077

Cam Lift tdc
In - 044
Ex - 038

Phase <)
In - 110

Timing Adv
Open
Ex - 66.5
In - 28

Close
Ex - 24.5
In - 66.5

52 Deg Over-lap


Timing @50
Open
Ex - 37
In - -2.5
Close
Ex - -5.5
In - 35

-8 Deg Overlap

Trying to get information from most performance shops is hard at the best of times, but once you mention datsun, or you dont want to part with your cash right now, they become very unhelpful

I rang Neil and got some good advice and called Jeff Taylor from JTS who built the engine, and got conflicting results.

JTS say dont bother, but everyone else says they are great. After much deliberation and thought, I plan to get some, but now i just have to decide the ratio to order. They come in 1.55 and 1.65 with standard bieng 1.44 I believe.

I used an online calculator hererocker calc

to see if what I can do is possilbe and it seems that its not going to happen if i am reading my cam sheet right.

The valve clr or clearence is the distance from the valve at max lift to the piston which is 0.013

according to the calculator, if i change to 1.55, I will gain 0.0138 lift.
With only 0.0130 valve clearence my valves will hit the pistons.

Is my intepertation correct??