[gregvega]

Does anyone know what the stock head chamber cc volume is on 452 heads.

[dave-r]

It should be around 81.5cc I think but it does vary. Use that figure if you don't actually have the heads and are just trying to work out compression ratios.

They can vary not just from head to head but also sometimes chamber to chamber.

The big block open chamber heads are all in the 79cc-85cc ballpark. The only way to be sure what yours are is to measure them.

As a "near enough" measurement I just level the head and drip water in from a syringe until the chamber is full. I don't bother with the Perspex sheet and burette method. To much fuss.

[ianandjess]

cheers dave ill remember that if i ever get fussy when im porting heads it could be handy to equalise compression for a strong motor

[dave-r]

Even when I have cc'ed heads I have always still found slight differences in cranking pressure from cylinder to cylinder. I'm not sure if the gains are worth the hassle to ordinary guys like us.

But I am all for a bit of porting and mild polishing as I believe flow and heat retention in the cylinder are important. As a photo of one of my "906" cylinder heads show.

[ianandjess]

gday dave
that is a pretty sight ill bet there were a few hours on the die grinder there
heres my effort not as polished but not finnished yet its only a 318 but its all fun anyway

cheers ian

[dave-r]

I had a good start with mine as the runners and bowls on these particular heads were professionally ported by Dave Hughes. Mainly in the bowl area. I have done my own porting in the past though.

I have done only a little more on the ports and polished the exhausts (as you should). I also polish the chambers but not to a high degree. Just enough so the carbon has less grip and there is less heat transfer from the cylinder to the water jacket. Smooth and shiney conducts a lot less heat then rough and black. The less heat is transfered the more cylinder pressure (torque) you get and the cooler the water keeps.
They also steam clean up easier with just dripping water into the carb while holding the rpms up.

Don't remove material from the inside of curves in the runners. What is sometimes called the short radius. Just grind the outside of the curves. Any port matching must gently blend into the runner over a half inch minimum. More prefered.

Keep up the good work!

[dave-r]

Just noticed you have taken off that bit above the guide. It does not matter.
I don't think it makes any difference but some people like to leave that bit (see mine) as they feel it either helps flow past the valve stem or some say removing it makes no performance gains anyway so don't bother.

Swings and roundabouts.

[dave-r]

Couple more of mine.

[ianandjess]

cheers for that dave its always good to hear from someone whos had some experience with these things i was just teaching myself from pics in a book that didnt go into much detail so i just did what seemed logical
thank ian