.

We will start with something like this, it doesnt need to be a GT head, a standard one is fine, in some instances even better, it depends what your trying to achieve. The important thing is to find a good casting without cracks and minimal corrosion.

after we've cleaned the head, we'll check for casting damage then start working with a die grinder to open up the ports, valve throats and chambers.

Once the ports are nearly there we get the seats cut roughly for the new valves, this will be a 'first cut' and will then allow us to open the port out more accurately round the throat and to match the valve seat.

 

Once the seat are cut and blended we'll use a dummy valve to protect it and make a start on the combustion chamber, this is the tricky bit, you can only unshroud the valves so far out because of the bore of the cylinder and head gasket, equally, the more you remove, the lower the compression ratio, we can get some of this back by skimming the head later but there is a limit. Once the chambers are complete we will recheck the valve seats, finish the porting and check our work on a flow bench, what we're looking for is a good smooth curve showing air flow in, and out of the chamber right from the moment the valve lifts off the seat and smoothly increasing all the way up to maximum valve lift, again this is all variable depending on engine capacity and valve size, and the kind of result your looking for.

The chamber and valve throats showing a 3 angle finish and bronxe guides

One piece stainless steel valves we stock several different types of valves, from standard to Full race on piece narrow stem for FJ/MAE and 1500-1650 precrossflow, we also stock lightweight steel ratainers and collets and full race spring sets

Heads are finally skimmed to acheive the required compression ratio, we will fit bronze guides if and when necessary, which is 90% of the time, and hardened unleaded seats for general road use with unleaded fuels.

Depending on final useage we will also machine and or shim the valve spring seats to correct the installed length of the springs (If your using uprated and or double springs for example)

Finally we'll degrease, clean and assemble, oh, and a lick of paint doesnt go a miss !

One of the things we don't do is polish, polish and more polish, we have seen many heads which look like works of art, but by and large they are exactly that, works of art! If anything a mirror polish can be detrimental to a homogenised flow of fuel/air mix, people do argue that it helps stop build up of carbon deposits, but again this is negligible.

 

Please feel free to contact us for any head or valve requirements road or race, we do keep some stock, but complete heads are usually prepared to order

 

 

 

If you would like more information about the team, please email us : info at throbnozzle - racing.co.uk
Thanks.