Corsa piston build with throttle bodies

so what are the stem lengths neil ?
and you only need to concentrate on the exhausts imo, open the inlet ports to the same size as the inlet valve throats, and open the exhaust valve throats to the same size as the ports
 
Cg 95.7
Qg 94.7
Ga 92.6


6fc1c354d3b76b95addd55badbf20782.jpg


But the recess for the collets between the qg and ga are the same height........but then the tip of the qg valve will stick out further


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pork said:
So would the caps still go under the buckets?


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Click to expand...
yes the caps are a lot lighter than 2 shims eh, you could cut the seats to suit the caps and then shave a tad from the stems to get the clearances bang-on
 
Went to a head shop today, just for some info.

He said these are too big for the standard seats and would need new seats which is about £700 plus the new valves

What he did say was he can open the seats up as much as he can, then turn down the new valves to match it

Says il gain just over 1mm in each valve......not sure if it’ll be worth it

Only way to increase valve size without spending silly money I guess


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definitely worth it on the exh neil, and some porting on the throats to maximise the extra 1mm, i would probably use the longer cr inlet valves turned down, with buttons and no shims
 
I take it all cr inlet valves are the same?

And use the qg exhaust valve still?


Bloke said to do all the polishing/porting first before he has a go........save me wasting my money if I mess it up I guess


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depends how big you can get the ports neil, they are the inlet bottleneck, and shimless will mean less valvebounce

PICT0264.JPG
 
Just been cleaning the head......just seen these

2a95ce5ee34611e70a9a06a013dbde2c.jpg

28356de15d56d52df25235a9959118b6.jpg



Only a 1mm deep, and will be giving the head a couple mm skim......should be ok?


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Had a quick go at the Combustion chambers, left the old valves in as i didn’t want to damage the seats, (putting new valves in anyway )

Before

a2197384b5cc659951594a9a8e0ab7fa.jpg


After........think I can get it more of a mirror finish

2fca0b6ec9ec07ae477cb993a2ce31d2.jpg





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Cool, will do.

I’ve had a go at blending in the seats to take off the lips/steps

Quite sharp edges really


This is gunna take ages!


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i would use a sharpened masonary drill for opening the seats neil, and very coarse emery (24 grit) wrapped around a rollpin for the alloy ports
 
What about this edge here.....should I blend the it in to get rid of the step?

aea8cb1f3bd0c448496615d633ccf004.jpg



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pork said:
I take that as a no then
Click to expand...
You can deck the block a bit to tighten up the quish zone they provide to improve compression and det resistance. My measurements said I could take 17 thou off the block, but that was before I went with CG10DE pistons, so if my calculations are correct it will be a high 12.5: 1 or so compression ratio. If I remember correctly others have run higher though so should be ok and I'm running 98 octane.
 
fuzzy-hair-man said:
You can deck the block a bit to tighten up the quish zone they provide to improve compression and det resistance. My measurements said I could take 17 thou off the block, but that was before I went with CG10DE pistons, so if my calculations are correct it will be a high 12.5: 1 or so compression ratio. If I remember correctly others have run higher though so should be ok and I'm running 98 octane.
Click to expand...

I’ve already done that with mine, have to with using these corsa pistons


Just thought I’d ask before I went too crazy with the dremmel


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How much of a mirror finish should I be getting?

I can get it smooth to the touch, it’s almost feels soft it’s that smooth......but I can still see sanding marks


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From what I've seen, the inlets; smooth out imperfections and smooth to a brushed look, I can't remember what grit but not too fine, like 80? The exhausts and combustion chambers as much as you like as it will help stop carbon build up and hotspots in the combustion chamber.
 
fuzzy-hair-man said:
From what I've seen, the inlets; smooth out imperfections and smooth to a brushed look, I can't remember what grit but not too fine, like 80? The exhausts and combustion chambers as much as you like as it will help stop carbon build up and hotspots in the combustion chamber.
Click to expand...


I’ve got them like this so far, feels silky smooth

0b0885f3245bca73927c9e077d8daa20.jpg


The combustion chambers are almost mirror finish, they’re a lot easier to get to obviously


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whats the dia of the ports now neil ^ ? and the dia of the seats/throats ?
and the rough finish mainly applies to carbed inlets
 
I’ve just concentrated on cylinder 1 ports for now, see what it measures at once I’m happy enough with it, then copy over to the others.

I’ve taken out quite a bit of metal so far just by removing cast marks and blending stuff in.

The exhaust valve, I’ve opened up the throat some, it’s tight getting a decent tool in there.

But being I’m gunna that bloke to cut in the cr12 valve (said he will be able to cut the seat an extra 1mm) I thought I’d see what else can be taken away after that


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pork said:
I’ve just concentrated on cylinder 1 ports for now, see what it measures at once I’m happy enough with it, then copy over to the others.

I’ve taken out quite a bit of metal so far just by removing cast marks and blending stuff in.

The exhaust valve, I’ve opened up the throat some, it’s tight getting a decent tool in there.

But being I’m gunna that bloke to cut in the cr12 valve (said he will be able to cut the seat an extra 1mm) I thought I’d see what else can be taken away after that


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Click to expand...
You can also cut my middle between the pair of valves to create a smoother path

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Got a head gasket to see what I can remove around the valves........not much is there?

3c2ea09bfdc29aee77d0bbef315cbed6.jpg


3bbae61f35c2a158d6371a7a47df0b37.jpg



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Just Bought all the cr12 valves and 2mm lash caps.

Gunna take head of current engine this week , and see what’s going on with the massive amount of blow by that’s going on.


just need rings bedded in more

......more than likely I’ve broke it already


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I did.

I did a leak test yesterday and it wasn’t great, so either my rings ain’t bedded in, or I’ve broke all 4


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