whats the go with the valves in the sohc? how big is to big, i want bigger valves to go with the fresh engine but i just dont know how big i can go...

or would it be best to just get a tickford head?




any info would be great, cheers

hey mate

i went bigger valves in my head...they are 2.5mm bigger on zorst side and .5mm bigger intake side...

most ppl work on 80%...so watever u get in u want to get 80% out

Get a ticky head cause they are bigger. Not sure how much by but they are still bigger.

Tickford head exhaust valves are 2mm bigger (41mm vs 39mm) but intake are the same.

look.....ive just had my head done....

it cost me 18 a valve for each side...so about 200 odd bucks and ive got a head that "is should breathe better then an tickford head"...

now ive looked on the net at the cost of a ticky head v a standard one....

heres the cost.....
head $50
overhaul 400
valves 216
cam 270
srpings 140


so it depends on wat u want...as i want a bigger cam it cost a little more...but if u dont..or already have one i dont see splashin out on a ticky head that may need overhauling and has already cost 500-700 when a stocky head cost me not even that to get done to the same...if not better specs

yea i new the tickford valves were bigger, but i wanna go a bit bigger then that, im goin a big cam so i need a fairly decent flow, i no ill have to spend over a grand on the head so i may as well do it right from the bigging, correct?


im just wanna know physicaly within reason whats the biggest/best size to go?


an thanks guys for the replies

$270 for your cam? nice one, what sort is it?

ill need to spend a bit more then that on my head, iv been told that theres a fair chance that the lobes of the cam will kiss the head so it's goin to need some work

I have std sized valves for a tickford head and it flowtested 380hp with a 73% split. You are going to need to build a very serious engine to justify bigger valves.

see now that there, thats what i was sort of unsure of, wether or not i would actually have to go bigger, i dont know what the std or tickford valves with a decent bit of head work would be flowtested like

so stockstandard you recon that the tickford valves would be fine for any sort of n/a rebuild

i just went an r6 cam from rpd.... its isnt that big but if u look at wat the xr;s got compared to the stock falcons...it is a diff...valves on zorst side and the comp...

so the for them to make the valves bigger would have some point to it...

it cost me about 1200 all up for my head

I dont believe so. I certainly wouldnt bother putting bigger valves in unless they fell in my lap for free.



How many CFM did it make with the bigger valves?

hasnt been flowed

i talked to a few engine builders up here and thats one thing they suggested from their experience

well i think i might start looking around for some oversized valves

intake valve area is directly realated to the power potenial of an engine.
the size of the intake valves in the ford OHC I6 is the main reason people have trouble reaching the 400fwHP mark.


exhaust valve size is realated to intake valve size and stat of tune of the engine.

if we take the stock I6 with 39mm exhaust valves take into acount the state of the stock tune the 47mm intake valve is not a bad size.

if we move onto higher tuned engines with more compression longer duration high lift cams the area ratio changes and it is common for the tickford 41mm exhaust valve to be used.

using the 41m exhaust valve upwards of 11:1 compression and long durration cams the size of the intake valve neededs to increase.
in this case a 50mm intake would be beter.

obviously simply fitting the valve is pointless the port needs to modified to use the valve.


somthing els that might be of interest is total valve area Vs power potentail of and engine.
if we take the the stock 47mm intake we get a total intake valve area of all 6 valves of 10404.3mmsq wich gives us potential of close 350hp.
remember these are not exact figures but it is quite close when compared to the peak power alot of engines make when highly tuned.
the power numbers are from what i can see worked out from the posible air flow through the valve window a given valve size will create.

that 350hp potential also shows up when we look at alot the higher tuned I6s around these and other forums with many strugling to reach 180rwkw.

no look at the potential of the 50mm valve. we get a total area of 11775mmsq and a power potetial of around 392hp


a few things to consider with the falcon head.
can you fit the valve in the space you have to work with.
and can you modify the port to use the valve area.

i'm sure there will be a few people that might disagree or be interested in where this info came from and calculations used. so shoot me a pm