Re-Jetting for Re-chambered head??

[Alan 4Runner]

Thanks!
I used a small boring bar for the combustion chamber at about 80° so nearly perpendicular to the head gasket sealing surface and have since gone a bit deeper to increase the volume to ~23cc

I will go measure it up and get a new picture later on but at a guess, the near perpendicular cut is about 1/2" deep before a radius of about 1/4" and a flat section around the spark plug!

After seeing more pics I'm keen to get my cylinder back off and work on the intake side as well as more on the exhaust!

All I've used for my port work is a dremel

 

[wwholden]

Yeah I cut mine at 60 degrees. How you getting this radius at the bottom before the flat area around the spark plug?

And Ive been using a dremel too. What type of cutter you using to get back that close in the corners on those transfers?

 

[Alan 4Runner]

Just using the round bit with the rough cutting edge, it takes a little while and you need to unclog the bit every few seconds but it gets there! I found that filling the chamber with a bit of water and running the tool slower helps with the clogging as long as you can still see what you're doing..

 

[Alan 4Runner]

Here's the pics of my second cutting of the chamber.. Measures about 44mm diameter and about 3/8" deep before radius in the corner of the combustion chamber relief!

 

[Blaaster]

Just using the round bit with the rough cutting edge, it takes a little while and you need to unclog the bit every few seconds but it gets there! I found that filling the chamber with a bit of water and running the tool slower helps with the clogging as long as you can still see what you're doing..

Metholated Spirit is the recommended cutting lubricant for Aluminium.

 

[Alan 4Runner]

Metholated Spirit is the recommended cutting lubricant for Aluminium.

Cool, thanks for the tip I:I

 

[Blaaster]

Another tip tools should be sharpened as if cutting mild steel, it has the same working properties a aluminium.

 

[best]

Alan, my son (Triplecrown) is running a 22cc (I believe, sheesh, age and memory, there is a problem there but I forget what) chamber with no problems and good power. We decreased it from somewhere like 28cc bit by bit and still no detonation at all. Running about 1mm squish at the moment, a pretty good value to strive for as optimum. We will be trying an 18cc chamber, JoeAK47 and others assure me can 18cc run on pump premium gas.

Part of the secret to doing this is a slightly increased exhaust duration.
Our present cylinder has an exhaust port raised 1mm over stock.
Neil and I feel this is a bit too much with the stock base gasket, but others differ.
It all comes down to where you like your power and how high you want to rev it.
More revs can mean more power at the cost of reliability, all things being equal.

You can raise your exhaust port with a second basegasket as a test before you grind.

Steve

 

[Alan 4Runner]

Steve, when I first cut my head down it measured 18cc but I hadn't had it on a lathe at that point (I work away and the "toys" are at work!) so had just removed most of the head gasket lip and used a dremel to remove a little material around the spark plug.. Still had a large and somewhat deep squish area so the main difference was the CCR which was up from ~6.6:1 to ~7.6:1..

It was noticably torquier and didn't seem to change to the top end. Was running claimed 98 octane pump fuel and had no issues with detonantion. Like you I have raised my exhaust port approx 1mm and am running 1 base gasket so I guess I can agree with joeAK47 that premium pump juice is ok for higher compression!

I'm really keen to see how my head goes in it's new state of machinedness! Shame I have to wait another 2 weeks before I can test it out!!!

Cheers blaaster for your little tips mate, every bit helps