F8B Head mods

[fritz]

I have read other threads on head mods, but they dont answer all my questions.

Has anybody in oz actually increased the size of their valves on an f8b engine?
- The f8c has the larger valves, but isn't compatible with the f8b block. It stands to reason then that the bigger valves (in conjusnction with other bits) improve performance.

Any help appreciated.
Cheers

[hatch4play]

the simple answer would be no, it is too much work to fit larger valves into a f8b head, i looked at this route and would have had a nightmare on my hands as the f8b runs zero deck height on the block so the pistons would need the recess's machined deeper making the crown to thin for any compression or boost with forged pistons it is possible but still not easy.

jimbo

[fritz]

Would larger valves make that much difference to the amount which the valve intrudes into the cylinder?
What about raising the head (presumably using copper gasket or something) and then using dome type piston to up compression?

[Brayden]

By spacing the head to bring the valves away from the piston, you'd reverse the effect by adding domed pistons.

[fritz]

True, but by using domed pistons, surely there is more scope for shaping around the valves?
Also, if this is such an issue, surely high lift cams or cam grinds as Chris (?) had would pose problems also???

Spose I'll just have to suck it and see if no-one here really knows...

[Brayden]

A cam grind only gives bugger all extra lift, but increased duration more than anything. So valve interference shouldn't increase much at all.

Don't forget that cutting into the piston top will decrease compression too, so spacing the head will decompress, dome pistons would increase compression, then fly cuts would decrease it again!

I'm with Jimbo on this one. The amount of gain you would make on the larger valves would be proportionate to the size of the shitfight you'd create in the process.

[niiko]

just put a twin cam head on it

actually i think you still have to dish the pistons

[fritz]

If anything, I'd say the restricting factor will be lack of room to increase the size of the valves, but then this is only my opinion...
Once I get the cam sorted , I'll take the lot to a head specialist and let them deal with it...

Twin cam would be great, but then you'd be stuck with cams designed to work with a turbo.

[Gladier]

just bore it out ...

actually i read something a long time ago - porting your head gives you LESS power than streamlineing (adding more material) ... someting to do with flow rates....

the engineering behind it backs it up too

[stevan_istheman]

Yeah, i've heard that too.
I'm told the more turbulence that's in the intake, the better mixture you get. Which would be right when you think about it.

I still say EFI fixes everything.

[fritz]

All very confusing...
Do the Braydens & Cols of this world agree that porting will result in reduced power?

[pony-tail]

To find out if porting would be of benefit you would need to get flow tests done - Whether porting is of benefit or hinderence depends on the actual design of the head .
Over porting will decrease torque and shift the power up the rev range thus reducing engine flexability and driveability .
Sizeable increases in horsepower do not come cheap .
My suggestion is to get a good rebuild (using quality components) on your F8B get your ports matched to the manifold and do the Charade turbo conversion (with maybe a small top mount intercooler )
Best person to ask about this would be "Colin"
My turbo experience is all on 4G63 /4g93 Mitsubishi motors - and not all good - I have a Car in my garage right now with a destroyed motor (due to detonation which wrecked the piston crowns and holed two combustion chambers ) So you definately need someone better at it than I am to instruct you !

[hatch4play]

i agree that porting will not increase power, as suzuki heads always flow good from factory, + the size,length and passage of the ports to the valves are very well designed. If anything porting will just shift power in the rpm range!

jimbo

[fritz]

My suggestion is to get a good rebuild (using quality components) on your F8B get your ports matched to the manifold and do the Charade turbo conversion (with maybe a small top mount intercooler )

Pony-tail, I'm not really into turbos. - In fact there is a lot I dislike about them. I know bang for your buck they'r going to give me much more power, and I respect other peoples choice to have them on their boys. Personally however I prefer a revvy N/A engine anyday (not that a stock f8b is that). Hopefully I can make it that though.

I was quoted $150 per port and a decent amount for new valves. I think making a jugement on value is going to be a difficult call.
I think Josh and maybe Col has their engines ported, so it'd be interesting to hear their opinions on this subject.

It may also come down to whether or not I can find a suitable cam as well. Head mods are possibly wasted with a stock cam.

[Colin]

a simple port and polish never hurts theres no need to go over board removing heaps of metal make the ports flow better by removing casting burs and bring the openings out to suit the gaskets them port match the manifolds to suit the gasket