Combustion chamber volumes
 

I had a set of EAB heads milled 0.015 - 0.020" to clean up the gasket surfaces and then painstaking relieved the dome areas to get a minimum clearance of 0.040" with the pistons. The combustion chamber volumes cylinders 1-8 are


68
70
69.5
67
66
69
70
68



How close should these be to each other?? I will have to grind a little out of the valve area on #5 since the clearance is borderline: 0.307/0.315 without a head gasket installed and my cam lift should be about 0.350. Others seem OK at 0.330-0.380 (without the gasket).


Here's my jig for measuring the piston clearance. For valve clearance, I installed the heads, valves and guides and measure how much I could move the valves up and down between the head and the seat, with a dial indicator on the valve stem tip.

https://live.staticflickr.com/65535/...21323a38_b.jpg93FE453B-D999-45C0-9447-774440828BC3 by kenhenry_06268, on Flickr

https://live.staticflickr.com/65535/...8ee9dfef_b.jpg38F8D6AC-7705-4287-A7F1-267781AE84BB by kenhenry_06268, on Flickr

Re: Combustion chamber volumes
 

Since you appear to be a guy that likes the details, why not match the chamber volumes to within 1cc? That is what I'd do.

On the valve issue, keep in mind that the valves are not perpendicular to the deck, they are canted, so the only real area you'll need to clearance is up at the top of the "eyebrows" of the chamber. I use a carbide cutter with a "flame" tip to do this work - then polish with a sandpaper roll.

You can always clay the top of the valves, put the head on without a gasket, push the valve up (compressing the clay) until you hit the head and you'll see what I mean.

Also, it is not a bad idea to check the valve clearances (on all of them) with clay and the cam in the engine - so you're sure you are not hitting the head without the head gasket. If you don't hit the head without the gasket, then you'll be good to go.

Re: Combustion chamber volumes
 

Thanks! For just general purpose relieving the chamber of the material in cases where there is no valve contact issue, where should it come out from? I suppose it might not matter much though obviously not from the dome area. Ken

Re: Combustion chamber volumes
 

Many ways to get the job done for sure....my preference is to apply bluing to the piston crowns and the valve heads(from 10 o'clock to 2 o'clock). Wth the head hanging on three studs.I turn the motor over 5 or 6 times and see the interferance witness marks the bluing has left on the chambers. 6 to 8 hours per head easy to relieve the chambers.


Charlie ny

Re: Combustion chamber volumes
 

Charlie, Is this with a head gasket installed or with the head directly on the block?