The V8 Owners Forum -

Hi all, I am looking for a thread that I have seen previously on here relating to head porting (some nice chap posted pictures of a ported head cut through the chamber to show what metal was removed and some flow bench info). I have done a search but can not find it, can any one post up a link, or point me in the right direction.

The reason I ask is that I have acquires a set of ported heads in a job lot of rover stuff that i purchased a couple of weeks ago and they are very different to a set of standard 10 bolt heads that came with the rest of the gear and I am wondering if they have been taken out too far to be of any use
on my 4.6.

Kind regards, Lester

Have a start with this one


http://www.v8forum.co.uk/forum/viewtopi ... sc&start=0

Oh and as you are only over in Stoke - you could always drop over with the heads and we could run them on the bench and see what figures they provide

Hi Darkspeed, thanks for the link, most kind, as to the offer of a run on the flow bench I would very much like to take you up on the offer, if you let me know when it's convenient I'll come over and bring the heads, would love to know if the heads are any good or not.

They do seem to have had a lot of material removed and after reading several post and articles on the subject I am wondering if too much has been removed and look to be fitted with standard size valves

Kind regards, Lester

Hello Lester - Will drop you a PM with contact details - date wise probably the first couple of weekends in June will be earliest - as I am away this Bank Holiday Weekend.

Will also give me time to dust the bench of and do some calibrations.

That would be great, looking forward to it very much, it will be interesting to see if the work done on them has had much of an effect either way

Kind regards, Lester

Well thanks for that, had a very informative morning. Thanks for taking the time to explain what was going on and where, shame they didn't perform any better but that's the way it goes, at least I know what's what.

You have a PM

Kind regards, Lester

I built my own bench about 6 months ago and it can be quite surprising what works and what doesn't.

I have a set of big valve heads that barely flow anymore than a decent set of stage ones that i home ported. Glad i didn't spend £1k plus on them! On the down side i can't actually work out where the restriction is on the stg3 heads.


Darkspeed, do you have any calibrated orrifice plates that i could buy/beg/borrow? My bench is currently calibrated against another home built bench which means whilst it's repeatable, the actual flow numbers are probably meaningless.

Cheers
Ben

Hello Ben,

For the plate the answer is yes and no - yes I have some but no I cannot let you borrow them as I lent then out and now cannot get hold of the guy I lent them to..

I will order myself a new set of PAP's from PTS - but then likely to not to be too keen on lending then again especially at £90 or so a set delivered.

As for finding were the heads are not flowing - measure - first off the seat/insert throat to make sure its at 90% of the head diameter needs to be at about 37mm for the RS mid valves and that this blended into the throat - make sure that the area around the valve is de-shrouded to the bore line as far as possible and as much of the valve is free at a distance from the edge of the valve equiv of about 20% valve diameter at max valve lift.

Then it's making sure that the port has a decent CSA all the way through. If its still not flowing what you think it should flow balls and velocity probe the port.

Post the figures is it low mid or high lift issues?

So having flowed all the ports it would seem some are significantly better than others on the same pair of stg3 heads





Dark blue is a stock head, light blue is a home port stg 1 jobby.

3 of the ports seem to flow well, and 4 are not much better than the stg 1 (lost the numbers for port 4 thats why there are only 7)

Is a reduction in flow after 0.4" lift on the decent flowing ports normal?

The throat diameter is 38mm rather than 37mm, and they are real steel medium valves so approx 92% of valve dia.

Flow stopping at a specific lift is quite normal - it highlights the restriction is in the port and no matter how far the valve is clear the restriction is elsewhere - flow balls - to happen at 400 on the mid valve is a bit soon as you would expect the cam used to lift past that - 430 at least so I would hope that the flow would not stall until at least 450. Drop some internal calipers in the ports and see whats going on.

I would question the 20 CFM variance you have and measure all the ports very carefully because something is odd there.

As for flow building and then stalling back at a particular lift - check your bench adaptor as that normally only happens if the valve starts to find something in the chamber.

With any odd ones like 7 and 3 - put the head on the adaptor the other way around and flow again just incase the adaptor is slightly skewed and there is bore shrouding happening left the inlet is on the left/right etc.

If you have corrected for 28" what actual depression are you measuring at or do you flow at 28" - what measuring equipment do you use?

Cheers

Andrew

Also what figures do you get for port flow without the valves fitted?

And what seat profile does it have a simple 3 angle or a radius seat? - any photo's?