Engine rebuild and power mods

[jims-terrano]

I was sooooo wanting to pass comment on the plywood head gasket :lol

Hat off to ya Pete, you really have gone above and beyond with the engine.

 

[makeitfit]

Cheers guys, but fat lady ain't singing yet :lol

 

[macabethiel]

This link will help calculate the effect.

Is there a DIY method of calculating the reduced compresion ratio ? Obviously by removing some material the CR will go down a bit but is it significant ?
Thinking more boost but harder starting as Luke suggested :nenau

https://en.wikipedia.org/wiki/Compression_ratio

If you work on the basis of an average / new Nissan diesel compression ratio the only unknown quantity you will have will be Vc - clearance volume.

The clearance volume will include not just the cylinder head total volume but also the area that is not swept by the piston, head gasket, piston tops etc. When you calculate this and then subtract the volume you have recessed (that will be the area you have machined out (pye r squared x depth) you will arrive at the slightly greater value of Vc.

Then do the calculation again where the compression ratio is unknown but other values are. This will give you the new compression ratio - you will then compare that to the first figure you used. This can then be used to give you a % change in compression ratio.

If the maths defeats you PM me with the dimensions you have cut out & I will give it a go for you. Dont forget if it has been rebored the swept volume will be greater.

 

[macabethiel]

https://en.wikipedia.org/wiki/Compression_ratio

If you work on the basis of an average / new Nissan diesel compression ratio the only unknown quantity you will have will be Vc - clearance volume.

The clearance volume will include not just the cylinder head total volume but also the area that is not swept by the piston, head gasket, piston tops etc. When you calculate this and then subtract the volume you have recessed (that will be the area you have machined out (pye r squared x depth) you will arrive at the slightly greater value of Vc.

Then do the calculation again where the compression ratio is unknown but other values are. This will give you the new compression ratio - you will then compare that to the first figure you used. This can then be used to give you a % change in compression ratio.

If the maths defeats you PM me with the dimensions you have cut out & I will give it a go for you. Dont forget if it has been rebored the swept volume will be greater.

Where I said subtract you add of course to get the marginally larger value of Vc

 

[Lazy-Ferret]

I think I would just cheat, fill a syringe with Diesel, and see how much it takes to fill the cut out... there you have, how many CC's more than original. :augie

 

[macabethiel]

I think I would just cheat, fill a syringe with Diesel, and see how much it takes to fill the cut out... there you have, how many CC's more than original. :augie

That works but don't forget the meniscus effect when measuring what is "fill".

 

[makeitfit]

Fill your boots time !

Had a job cancel last minute so found myself in need of some spanner action.
Time to pocket these ruddy pistons
Duct tape to seal up as much as I could prior to cutting.

Template bolted down to the block . I had to open the bolt holes a little so I could accurately position the template . Used the vernier and a hammer to get it all spot on then tightened up the bolts :thumb2

Cut a bit, hoover a bit, cut a bit, repeat.....

I had to climb IN the engine bay to do No4

Template off and remove tape. Clean and retape, then refit template as above.

Here's the last bit I got to today. Finishing the pocket with a bit of emery .

Maybe tomorrow I'll get to dummy build it again. Fingers crossed.
Onwards

 

[solarman216]

Very interesting Pete, I like the array of spacers for the head bolts, lets hope this all works, Rick

 

[Davey Boy]

This is so interesting Pete.....carry-on! :thumb2

 

[weedave]

I'm gobsmacked!!!! very very nicely done!!!

I cant imagine the butterfly stomach when doing this, you are a braver man than me sir :thumbs

Keep er lit!!

Dave

 

[makeitfit]

Did the dummy build . Turned over by hand and I'm happy to say clearance is secured
Tried at .20mm on inlet and .30mm zorst
Too cold to continue tonight but will check my plasticine clearance blobs tomorrow.One final dial gauge check and then rebuild time :clap

Onwards

 

[luke1987]

Well done Pete, Can't wait to see the outcome with the cam dialled in.

 

[solarman216]

Mmmmm nice one Pete, just out of interest my Lister engines require a small piece of solder, wire to be placed on the piston to check bump clearance, I just wonder if your Plasticine may just expand a little after compression so possibly giving a false reading, especially if the surfaces were clean and dry possibly sticking to the two surfaces, just a thought, but worth checking, Rick

 

[Davey Boy]

Solder... That's a good idea.
In my old Pajero manual, they used to use Plasti-Gauge during the engine re-build. A crushable strip marked out in increments.

 

[RJL Services]

found them on ebay item number 173609836432:thumb2

 

[luke1987]

Ive used plastigauge once and it was a thou out which in engine building terms is a no no. Can't beat a proper micrometer they're not that much these days.

 

[Davey Boy]

A thou out....jeeese!

 

[makeitfit]

You won't like it but plasticine did the job lol I'm sure Not as accurate as plastic gauge but I got 1.1mm clearance on zorst and 1.6 on inlet. Pics tomorrow

 

[luke1987]

Good job Pete, I think people have got a bit confused here with what plastigauge is used for. Its actually used for sizing crank bearings up the idea is you put a piece on the crank and tighten a main or big end cap down then measure the squish to show the size of bearing needed like so.



But its no where near as accurate as it should be. Using plasticine to measure valve clearance to a piston however is exactly what I would have done it just works

 

[makeitfit]

Here you go, plasticine evidence blobs are squished but not too far

and on the zorst valve

Here it is on the thicknessometer :lol

and the inlet

During the dummy build I used the old head gasket to get as near the end result as possible.
I also dialled in the cam again, I just had to be sure I've done it right.
Turned over again again and confirmed the cam hi point on inlet lobe. From there I reset the cam cog and one tooth is the amount that gets it as good as spot on . So this is where I am.

Please Luke, if you think I've dropped a bollock , let me know :thumbs
Then after a little clean up the pockets clean up nicely

Hope to get a few hours tomorrow night to bolt down the head for I hope the last time :bow
Onwards