Valve groove help!

[VIN18M]

So when I pulled my build motor apart the CP pistons had 4 grooves for valve clearance. The larger grooves were on the exhaust side/front of the motor (oil filter side). I've since had about 15 thou taken off the block when I had the bores done.
Today I put the pistons back in and put the head on to check clearances without a head gasket and the valves are hitting. Surely the head gasket thickness wouldn't make that much of a difference? It's only 1.8-2mm.
I'm thinking the larger groves should be on the inlet side but they werent like that when i opened her up and the motor spun fine then?
Can anyone confirm this?

 

[caged]

Put the head gasket back on and it will be fine, but do recheck.

 

[4piknup]

And the arrows on the pistons point towards the front of the engine? Ie not the flywheel end.

What makes you think they are not in backwards?

They might be 3g pistons in a 2g. I was looking at the asymmetrical pistons but thought the valve cutouts would be on the wrong sides as you suggest.

Dummy assemble your engine with the used gasket and clay your valve/piston clearances

 

[VIN18M]

It's a 4g93 so they are definitely correct pistons.
I dummy fit it with the head gasket and spins fine now, although I haven't torqued the head down yet. Ill be getting some clay this week to test next weekend hopefully.

 

[4piknup]

Bluetak will do it.
Sorry I thought we were talking about 63t engine.
Although I think the 93 was released in opposite direction...

 

[khubner1]

hmm i never clayed mine when i rebuilt it just made sure she spun freely.

 

[CYBORG-X]

i always do clearances without headgasket. i suggest 60thou clearance, but also check your valve timing as this has a major part.
now measure the headgasket and use 50% crush as your spec. now with some basic math you can work out your clearance..
i normally dont see any issues when building 4g93 engines as the valve pockets are ratherly deep... it only at 305 deg cams and hi comp pisons you have issues

 

[VIN18M]

Well the cams I'm running are 290's but that shouldn't affect clearance as far as I know as it only affects duration.

When I did the clearance test with the head gasket in I also hooked up the timing cover, water pump harmonic balancer, belt etc and had everything top dead centre before testing.

Whilst rebuilding I also found that rod #3 had the piston on the opposite way to the other three pistons so the oil grooves on the bearings were on the opposite side. I've now fixed that and they are all in and torqued up, crank is in, girdle is in, just need to get some clay this week and check the valve clearances to be safe and get the head back on.

Things are progressing well with it so far anyway, I'll start a build thread shortly.

 

[4piknup]

Absolutely it will affect clearance. A longer duration cam will have more overlap. So it opens the intake valve earlier before tdc. So it will be closer to the closing exhaust valve and to the rising piston.

Pick your piston to valve clearance and clay your engine.
If you have adjustable cams gears. Give the cams as much overlap as your safety clearance allows. This will allow you to move the cams later on the dyno and know how far is safe

 

[VIN18M]

When I did the test I had the cam gears set at 0. So advancing or retarding the timing may give me valve clearance issues during tuning then?

How do you avoid this?