DIY head porting

[Darkspeed]

OK head roughed and seats open to 36mm but no further than an inch or so into the port. and critically not much work to the short side

This initial porting increases the airflow bit by bit but the 36mm seat and blend starts to restrict the flow - this is because airflow dislikes expansion neally as much as restrictions - so this indicates that the restriction is a bit further back in the port



The seat is blended into the throat but not back into the port on the short side and the portsize around the guide area has not been increased



You can gauge this by the fact that a chubby digit will NOT go too far past the guide port into the port.

Further work removing metal all around the SSR area and blending further back into the port about 55mm is needed and a finger goes past with plenty of space

The seat has been opened up to the full 40mm valve width and I have added a 60 cut for 3 angles - (crudely)



A quick blend with a 80 grit cartridge roll



The view from the otherside showing that no other work so far



Onto the bench tomorrow to see where we are at

[ppyvabw]

Had a few sherbets, so I might get carried away.

Some nice toys there!!

I'm not going to try and do this completely blindfolded. I have some spare heads, and I found them today, so I'm going to get some blades for the bandsaw this week and carve them up to see how much I can grind and do some practicing with. (Incidently, if anyone has some knackered heads they want to exchange for good ones FOC, then PM me.)

I am going to attempt to make a rudimentary flow bench with some kind of wooden attachment similar to yours to suck through, and possibly with some attachments for the inlet manifold and exhaust that can be sucked/blown through.

I am not sure exactly what I'm going to use for a pump. I have one of those Henry vacuum cleaners which needs some new brushes in the motor, but I'd hoped for something with a bit more oomph. We have a big knackered old fridge; would the pump out of that flow more air? (I guess that'll pump more for pressure than volume) I've thought about using the compressor, but that can only blow.

I've been looking at hand-held manometers to measure the pressure drop from a plug in the spark plug hole, and to attach to a pitot tube to measure air velocity at different parts of the port to find the busy parts of the port.

Edit:

this is because airflow dislikes expansion neally as much as restrictions

I can understand that. Is that also true of the exhaust, because the hot exhaust gases want to expand, and I have noticed that the exhaust ports tend to bulge part way through then get smaller as they get to the manifold face, so might benefit from opening out there - or is that just nonsense?

[Darkspeed]

I have run the "basic" ported head on the bench this evening

At 28" 0.450" lift the flow is now up to 154CFM Which is 19.5 CFM over the stock reading. Up 14%

There are good initial lift gains due to the 3 angle and there are small gains up to mid lift and then from there on its good gains all the way.

The next job I will do is a small cut to the chamber to see if there is any flow gain due to shrouding.

Andrew

[Darkspeed]

My bench has 8 1.2kW Vacuum motors - but 4 are blocked off at present as the bench will outflow the best Rover at good depression with just 4 - I have been flowing these heads with four on a low rpm setting at present - One motor will struggle.

You need volume and pressure/suction - and only vacuum motors will do it effectively

Had a few sherbets, so I might get carried away.

I am not sure exactly what I'm going to use for a pump. I have one of those Henry vacuum cleaners which needs some new brushes in the motor, but I'd hoped for something with a bit more oomph. We have a big knackered old fridge; would the pump out of that flow more air? (I guess that'll pump more for pressure than volume) I've thought about using the compressor, but that can only blow.

[Darkspeed]

A couple more tests before I move on to some more porting on this head


An open port test - now at 165 CFM

A test with a large valve just dropped on on the existing seat

Low lift gains - and quite useful ones

No gain after .300"

154CFM @ .450"

No more for this evening but I will try and get graphs done for the work so far.

Andrew

[Quagmire]

Fascinating stuff so far, thanks!

[neal1980]

great reading Darkspeed.

I have just found myself some Buick300 heads for my Turbo project that can supposidly flow pretty well with the bigger valves installed and ported.

Fancy a porting job if I get the larger valves put it??

I was going to have ago myself but on speaking to a few people I could do more damage at home porting if I dont have access to a flow bench.

[Darkspeed]

Thanks for the encouragement and the vote of confidence guys.

I have tested the heads against some proprietary stage 3 big valve from a reputable supplier. These heads have been a concern for me from the day I tested them - the expectation was always that these great looking heads should flow better than my amatuer attempts - They dont and it made me doubt so many things with the bench and what I am seeing. Well, over the last few days I wanted to exorcise this demon and get to the bottom of it especially after doing a full comparison with the current development head.

All at 28"

Test head

Thou lift - CFM
50 - 20
100 - 48
150 - 75
200 - 104
250 - 130
300 - 140
350 - 148
400 - 154
450 - 158

Stage 3 head

50 - 21
100 - 48
150 - 68
200 - 88
250 - 108
300 - 129
350 - 148
400 - 157
450 - 162

The loss of mid flow lift between .150" and .350" is quite unbelievable and it has taken me absolutely ages to find out where in the port the mistake has been made - however I had a breakthrough today and its now so obvious I cannot beleive I missed it - It was all from reading a comment I made earlier in this thread that made me think.

I now need to do a bit of work to make sure I am on the right track but it would be good to have a few guesses from you guys as to what the problem is/was.

I will post a load of pictures here in a minute of the head.

Bear in mind that this head is from a reputable porting company - Not JE, JED, or Burrell I hasten to add.





Big valve and modified standard valve





The Stage 3 head and inlet port work carried out - it's a very nice looking job and one would assume that there would be an increase in performance and the flow rates be head and shoulders above the flow of the roughed out develpment head.

The figures go to show that looks can be very deceptive and its easy to make small errors that destroy flow.









The roughed out F development port







Next bit of work will be further back in the port and some more detail around the guide and the SSR to see if I can get the standard valve to outflow this stage 3 at all lifts. I will have trouble at the very low lift because thats down to valve diameter - Tt already outflows during mid lifts so its left to see if I can get the higher flows up. Running the numbers it is possible as a 40mm valve should in theory be capable of beating those flows quite easily.

Andrew


Andrew

[Baracus]

I don't know if it's just a trick of the camera but this dimension looks very narrow given the size the bowl area's been hogged out to compared with my stage 2 NCK/TVR heads.


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[sean]

Send him one of the TVR heads and I am sure he would be happy to do a flow comparison. More data can't do any harm. Those stage 3 heads look pretty on the face of it, but the figures do seem to suggest otherwise when it comes to the actual performance.

[goodsy1968]

Sounds like the stage 3 heads needs a better seat job doing, due to thier losses at mid lift. Also the chambers need modifying due to valve shrouding.

[ppyvabw]

My bench has 8 1.2kW Vacuum motors - but 4 are blocked off at present as the bench will outflow the best Rover at good depression with just 4 - I have been flowing these heads with four on a low rpm setting at present - One motor will struggle.

You need volume and pressure/suction - and only vacuum motors will do it effectively

I won't be able to flow that much air, but having read some articles by Dave Vizzard, some guys make mini flow benches and then calibrate them to whatever the standard pressure is; 28" H2O? So if your mini flow bench with your hoover and a u shaped tube full of water pulled 40" H20, you could look up on a chart and it would give a CFM value at 28" or whatever...

All interesting and useful stuff you've posted Andrew! Thanks!

[Wilts289]

Just to say how much I am enjoying this thread, and how it has solved my Chrissy Present List. Every year it's the same thing... "must be something you want for the car" (Hawk 289 with 4.2l Rover) but asking for new Wire Wheels or Big Brake Kit or pair of Stage 3 heads seems a bit greedy! However since this thread started it's been easy: Cylinder Head Stand, Porting Kit, digital vernier, small heater for the garage, so come Boxing Day off to try basic work on a pair of Vitesse heads. Pointless asking for the Bible i.e. Des Hammil V8 power tune , so now totally reliant on the V8 forums band of experts. So Merry Christmas and thanks to everyone and I am following this one to the end! Roll on another 25 BHP

[Pocket rocket]

Pointless asking for the Bible i.e. Des Hammil V8 power tune ,

Strangely there's one on Ebay ATM http://www.ebay.co.uk/itm/DAVID-HARDCAS ... 3a6d69c0d9 [NTDWM]

[Wilts289]

Hi Pocketrocket,

already have the Hardcastle book - didn't realise they are so valuable! Very useful as a starting point, but no specifics on headwork, whereas I understand the Hammill book has lifesize pictures of what to aim for re ports and combustion chambers. Anyone confirm that or prepared to post up photos?