Is this enough piston-to-head clearance?

[ggzilla]

I'm getting my spare engine ready to install and discovered the block deck was milled, so the pistons stick up 0.025" (0.635 mm). Can I fit a closed chamber head to this? The stock gasket is supposed to be 1.0 mm installed.

 

So generally how much piston-to-head clearance is required? Say for an L16 or other engine. My engine is Datsun A14 with cast pistons 76mm bore and 77mm stroke.

 

 

I'm guessing the previous owner used an open chamber head and milled the block to increase compression. I got the engine used without the head.

[ggzilla]

I found this on Wiseco pistons FAQ page:

Steel rods in a big block usually require .045. Steel rods in small blocks require at least .036. Most imports can get by with as little as .030. Aluminum Rods generally require .010 more clearance than steel rods.

 

Now to calculate what the clearance might be with a 1.0 mm gasket and 0.025 inch pop-up...

[wayno]

You have a photo of the face of the head?

[ggzilla]

It has closed chambers (heart-shaped combustion chambers)

 

I'm thinking there is not enough clearance. The head gasket is 1.2mm uncompressed.

 

I might have to obtain an open chamber head like this.

[zed]

I'm no expert, but I enjoyed setting up the quench / clearance when I built my L18. My clearance is .035" / 0,89mm. Legendary engine builder Smokey Yunick's famous clearance figure was .040".

A tight piston to head clearance has long been recognized as one of the keys to getting best performance from a motor. I make your clearance to be 0,365mm? Which may be a bit tight. It would be a pity to put an open chamber head on your block - you will lose the benefits of squish / quench. Maybe look for a gasket with 1,2 or 1,5mm compressed clearance?

Another thought - what about knocking? Have you worked out what your compression ratio will be with this head? Have you "cc"d the head?

[ggzilla]

Thanks. I think a 1.6mm gasket would do it, but don't know where to get one except for those $100 copper gaskets. I'm trying to keep the costs down if possible.

[king bee66]

i have a "728 402" head thats surface looks identical to the 1st one you posted. the motor it came off of had dished pistons; for extra clearance i always assumed

[ggzilla]

Dished pistons is how they adjusted compression ratio in the A-series. Most of the heads have the same CCs, but different engines have different piston dish. Nearly all A-series pistons are dished except for non-USA 1000 Coupe and A12 GX hi-octane option and their Cherry counterparts. The most telling example is 1981-1982 all used the same head A12, A14 or A15, same head but different piston dishes.

 

But I see ther are no valve reliefs cut in the pistons. That might be a problem too.

[zed]

I would check valve to piston clearance with the soft solder wire method, just to get an idea. Datzenmike probably has all the answers here

[king bee66]

please keep this updated

[Master-O-Turbonics]

This is who you should use for a copper gasket. They have thicknesses from .020"(~.5mm) to .100"(2.54mm) for any gasket and they have an L series gasket.

Hussey Copper gaskets

[ggzilla]

Thanks! I was wondering about that.