Valves for 300 heads??

unstable load · Post by **unstable load** » Tue May 28, 2013 5:57 pm

OK, I'll bite.... what are flow balls??

DaviesDJ · Post by **DaviesDJ** » Tue May 28, 2013 8:03 pm

Small light spheres on the end of cotton or a very thin wire to indicate direction and nature of flow (laminar vs turbulent etc) I believe - nit used them yet. Unless I have just exposed myself for the bull-sh***r I am;-)

Darkspeed · Post by **Darkspeed** » Wed May 29, 2013 9:29 am

The are balls/beads of various diameters on the end of stiff wire that are fed into the port you move them around the port and watch the numbers - if there is a significant fall in a particular area you know thats the area that may need some material removed.

You mark the wire with graduations typically coloured that gives you the gauge of how far into the port the ball starts to infuence / restrict the flow.

Bits of string on the end of stiff wire also have a use with finding turbulance but thats more difficult to quantify as it will depend on port velocities and thats reletive to the amount of air your bench can flow

My bench is over 12kW /16 HP at full power - which is not too far off the power developed by an average 3.5 engine 16x8 = 128BHP

DaviesDJ · Post by **DaviesDJ** » Wed May 29, 2013 10:40 pm

Wow, is that a custom/purpose built item? Would love to see something like that in action! Do you have a seedi in your garage also?

Darkspeed · Post by **Darkspeed** » Thu May 30, 2013 7:57 am

DaviesDJ wrote:Wow, is that a custom/purpose built item? Would love to see something like that in action! Do you have a seedi in your garage also?

Do a search there are plenty of pictures of it - see the thread about heads a few below this one.

Here's one

And this is the motor block

No Serdi in the garage but I have access to radius seat cutters but I do my "playing" with a couple of old Black & Decker valve and seat grinding machines - crude but they do the job.

The bench is a full digital PTS home build job and works very well.

DaviesDJ · Post by **DaviesDJ** » Thu May 30, 2013 6:20 pm

Wow, kick ass! Bit of a cheak to ask, but once I have finished develing my own heads on my cheapie floating pressure set up, would you be willing to test the set for formal figures?? Sorry to ask mate, but looks such a nice setup:-)

Darkspeed · Post by **Darkspeed** » Thu May 30, 2013 7:43 pm

No problem at all, be happy to. The offer to run any RV8 head, or any other head for that matter, on the bench is open. Would just need to sort out a suitable adaptor for non Rover

I hardly ever use it to be honest, built it because I wanted one. But I am just too busy with building cars and playing with bikes - Best thing I did with it was fit it with casters

DaviesDJ · Post by **DaviesDJ** » Fri May 31, 2013 1:01 pm

Great, thanks mate:-) Will look forward to bringing my rover / 300 heads eventually - really kind mate. Just out of interest whats the best you have seen flow wise on rover heads, and did that involve lifting the intake floor?? (I keep banging on about this;-))

Darkspeed · Post by **Darkspeed** » Fri May 31, 2013 2:49 pm

I have not tested any really big valve Rover heads on my bench the best flow has come from the Real Steel heads but they stalled due to port size - the figures are on here somewhere.

Any filling of the port will very likley stall flow as the head is port restricted and I dont think you will change the port shape without losing CSA.
When you start fitting big valves and get the flow up you need to open up the ports a fair bit and the casting ends up pretty thin.
Any filling in to raise the floor will IMHO just lose flow bit time

You can get a big valve in the head and open the seat and bowl up to match quite easily but the port is hard work which is why good heads cost so much.

It will certainly be interesting to see what numbers 300's are capable of.

Blown v8 · Post by **Blown v8** » Fri May 31, 2013 3:43 pm

I'm watching this very closely !
I've stripped my 300 heads,and in the process of ordering the big valves,
Good luck,and keep posting !

DaviesDJ · Post by **DaviesDJ** » Fri May 31, 2013 7:09 pm

Great, finished the chambers valve seats and valves in the next week or so:-) I will do some measuring of he ports - according to my reading the port for 2-2.5 valve diameters should be about 0.7-0.8 valve area in cross section, if it is less or equal to this then I think you are right on these heads. Although the angle milling I plan will tilt the port up an simulate filling the floor 2-3mm without sacrificing cross section

DaviesDJ · Post by **DaviesDJ** » Sat Jun 01, 2013 7:58 am

The port area on the standard 300 heads is about 0.75 of the valve diameter which is about right, but with 1.77 inch inlet this would be cut significantly. So I will need to enlarge this via the roof and cylinder wall side.

Darkspeed · Post by **Darkspeed** » Sat Jun 01, 2013 8:09 am

The 0.7 0.8 is a figure dependent up the amount of valve shrouding and I have never seen figures as low as 0.7 used - typically 0.8 is the lowest figure used and a completely unshrouded valve - as in a Hemi head using 0.84 reducing to 0.8 for bath tubs - also remember that a square port does not flow as much as a round port for the same CSA you around 10% more area and to be increasing the CSA all the way back out the port.

As the push rod pinch point is the real restriction in the port I would start the design of the port there and see what CSA can be accommodated. That is where sectioning a head for wall thicknesses and taking a port mould is very useful.

Any big valve head for a small bore RV8 will be shrouded the large bore offers some significant benefits from being able to unshroud the valves - its not much but it makes good flow improvements.

The big valve stage 3 head I have actually flows better with a smaller valve due to shrouding and poor chamber work. All the hard work in the ports and on the seats all undone by the chamber which would have been the easiest work to do with making up a simple card template.

DaviesDJ · Post by **DaviesDJ** » Sat Jun 01, 2013 4:47 pm

Yes, bore shrouding is a problem, particularly as it looks like i will have to stick to 94mm as my con rod small end is too small for anything other than a ford modular piston (0.866 inch). still, i thought of that and hence plan to angle mill and move the dowels approx 2mm to bring the heads further over, my manifold allows me total flexibility as it is 2 separate components so i can do this. would this not make up for this by reducing valve shroud? the angle mill will be about 0.1-.012 inches up on the spark plug side, corresponding to a degree or two i beleive.

DaviesDJ · Post by **DaviesDJ** » Sun Jun 09, 2013 9:30 pm

Ok guys, on my day off Tuesday and plan to do the following, going to wedge skim my 300 heads with 0.1 inch tilt to aid compression and move the valves slightly more to the midline, also plan to move the dowels a mm or two, and ovaling the bolt holes and oil ways etc. the plan is obviously to refuse shrouding. BUT I am nervous about ovaling the bolt holes, am I going to meet fresh air as I grind, how will all this effect my oil feed and water etc, has anybody done this (on rover or 300 heads) and do you think it am just end up ruining a good pair of heads (which is my worry)

Looking forward to your opinions guys.

Dave