Head Flow Figures

[zebra]

A thread for those with Ported heads.

I am keen to know what figures in CFM you are getting from both intake and exhaust ports.

Hopefully there are enough people on here with ported heads to keep this going.

So follow this proformer thingo

Head Type: (eg RB20DET, RB26DETT etc)

Porting Type: (eg CNC, backyeard job, Pro head guy etc)

Valve size: (eg standard, 1mm over size etc)

Flow at x lift: (eg 200cfm at .450thou or 130cfm at 8mm etc)

Manifolds fitted: (eg none, stock exhaust manifold etc)

Power/turbo/boost: (eg 300rwks, GT3076, 18psi etc)

Comments:

Port Photos: (Not asking to give away any secrets or anything like that)

Cheers

Andrew

[zebra]

Head Type: Cast Iron Ford Cleveland 2V (small port)

Porting Type: Cleaned up/Port matched by me

Valve size: Standard 2.04" Intake 1.56" Exhaust

Flow at x lift:Intake 197cfm at .450", 203cfm at .550" (tells me there is no point going any larger than 500thou lift) 175cfm Exhaust at .500" (flows a little more at .550 but like the intake its not worth going that big)

Manifolds fitted: None

Power/turbo/boost: Will flow just under 400hp at the crank

Comments: Pretty good for near standard heads with un-touched chambers, Has cemented my decicion to run it at 309 cubic inches instead of 351 or 383, due to the fact that the bigger capacity will cause I big drop off in power in the top end, as well as limiting revs.

Port Photos: To come

[PM-R33]

Cool idea

I don't have all the specs on mine though but will still add.

Head Type: RB25DET

Porting Type: Lewis Engines (Adelaide)

Valve size: Standard

Flow at x lift: 265cfm at .400 on intake

Manifolds fitted: Stock exhaust manifold and stock intake runners (Plazmaman plenum)

Power/turbo/boost: Last dyno tune on old Microtech 263rwkw on BP98 at 18-20psi on HKS GT-RS

Comments: Head was ported, polished and had the valve seats cut by Lewis Engines. Installed all new valvetrain gear along with Performance valve springs and Tomei 256 camshafts.

On the road difference, very large gain in midrange power, not much gain in peak kw figure due to limit of HKS GT-RS.

Currently retuning it myself and will have new dyno sheet next year.

Edited November 24, 2010 by PM-R33

[zebra]

^^ The 25 heads flow more than I thought!!!

[PM-R33]

Yeah we got very good results out of it

Normally he ports them out to around 250cfm but my head was with him for a long time so he spent a bit more time on it and went a bit beyond to what he normally goes for the price I was charged.

[zebra]

Cool

Heavily ported 2v cleveland heads will flow about 260-270cfm, Interesting when you consider the RB head has 4 valves per cylinder and is 30 years newer than the Cleveland. They were designed for a 5.8L v8 though compared to a 2.5L turbo six

[The Dan]

You forgot to add

What car is used for: Street/Drag/Track

Very important in port selection. And 265cfm is nothing for an RB25 head. We have made 480hp at the wheels on a stock head with pon cams.

I'll try to get more information on flow etc for Noels head if Marty White will give them to us.

It is also important that the flow specs are checked properly. Some people incorrectly check flow at the cylinder head face. 2 inches of tube should be added on the exhaust side to get correct flow on an RB cylinder head

[zebra]

Dan, not sure if you know, but is there any difference in flow between a 25 head and a 26 head? I guess the larger 26 valves will help flow a little

[PM-R33]

And 265cfm is nothing for an RB25 head. We have made 480hp at the wheels on a stock head with pon cams.

Ohh I didn't mean it to sound like it was a huge amount or something, I know you can get a lot more

It's a street car and the porting was only done since the head was off to get the valve springs put in. Figured while it was off to give it a bit of a port.

Edited November 24, 2010 by PM-R33

[fatz]

i think any head would have to be flow tested independanty to get a real idea of whats good

[PM-R33]

Any way, less chat, more figures and specs

Edited November 24, 2010 by PM-R33

[The Dan]

Ohh I didn't mean it to sound like it was a huge amount or something, I know you can get a lot more

It's a street car and the porting was only done since the head was off to get the valve springs put in. Figured while it was off to give it a bit of a port.

nah I know, was moreso replying to what Zebra said

[JonnoHR31]

i think any head would have to be flow tested independanty to get a real idea of whats good

they're talking about cylinder heads you dirty old man

[t_revz]

Rb25

Pro head guy

Standard size ferrea valves

234 at .500 before porting

245.5 at .400 intake after

253.3 at .500 intake after

135 at .300 exhaust before

137 at .500 exhaust before

157.7 at .300 after

161.6 at .500 after

No manifolds

Ss2 hypergear will be fitted

Mostly street with occasional track work

Most of the work done was on the chambers with 4-5 hours done on the ports. Will try get photos up later. Also tomei springs and poncams fitted