9.57 is much better...

2 hours ago, Home Built by Jeff said:

I shaved 1mm off the head and I actually stuffed up the calculation, as I didn't add the combustion chamber volume to the swept volume, so it is more like 9.57:1.

459 + 53.5 = 512.5

512.5 / 53.5 = 9.57

 

Getting better but you also need to factor HG volume which brings it down to 8.6:1 ratio.

 

Another important factor is "squish". Which is how close the flat piston top comes to the flat chamber bottom.  For your set up it will be ~ 1.1mm space.  Ideally it should be less than 0.7mm but how close you bring them is balancing return with risk.

 

You can bring the two closer and up the compression by offset grinding the crank to fit 1mm larger rod bearings or you can shave the top of the block 0.5mm.

 

btw the 53.5cc volume you measured is very close to stock value.  You can shave more off the head to bring up the compression.

Edited April 13, 20186 yr by 240260280

Absolutely, but I really don't want to go crazy with it. I am only looking at giving this engine a quick freshen up, not going to town, otherwise I would have replaced the valves, recut the seats, and done a lot more porting.

This week I have got myself some extra valves to replace the dodgy ones I had previously, so I get them lapped to fit and then move on to more body work.

 

 

This week I have got myself some extra valves to replace the dodgy ones I had previously, so I get them lapped to fit and then move on to more body work.   [/url]  

Hey Jeff,

Been watching your videos for awhile now. Not sure if it’s already been mentioned about your cylinder head seats. I found out the seats are bronze and soft which would get pitting and damaged since there’s no lead in fuel nowadays. Have you gotten your valve seats changed to account for unleaded fuel now?


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No, I am just giving this a light freshen up. I am not going to town. That said, the seats all look to be in pretty good condition. There is definitely no pitting in them, and they actually seem quite hard compared to the valves when I was doing the lapping. The valves would wear much quicker than the seats with the lapping paste. I know I should get the seats re-cut and then lap the valves to match, but I have checked the seal on them with bearing blue and they all seat well so I am happy.

I believe you could check the seats with a magnet...

This week I have chosen to have a big swing at getting the bodywork on the Z finished.

 

 

Great morning!  F1 practice in Baku and new video from Jeff!

This week it was time to start cleaning up the engine block and paint it up ready for the rebuild.

 

 

Jeff

 

Edited May 5, 20186 yr by Home Built by Jeff

Yikes!  Your engine rebuild is passing mine!!  And you are restoring a car too. 

I spend at least one day each week on this car, so to me it still feels super slow!