16 replies to this topic

[rsg]

When porting the exhaust side of a cylinder head, I've heard some conflicting info. Some say to open up the exhaust ports by scribing round the gasket and removing the required material, while others say leave a step to the manifold for the pressure pluse flows, i.e the head ports are smaller than the manfold tube ports. I've just had a call from Piper (as i'm writing this) saying my manifold is ready so will be getting the dremel out in a coupe of days.

Vocky, I think you matched the ports on your sand cast head.

SA guide here says not to.

What are peoples thoughts on this?

[Duncan VXR]

Good read dare I say it but it may be worth asking some of the tuners who work on our cars. They must have played and should have some RR figures to back up the work and confirm your question specific to our engines. I want to pull the head off my engine and play now LOL

[vocky]

that thread is based on a carb'd V8 engine, especially the bit about quite rough inlet ports, the z22se intake ports don't help mix the fuel as the injectors are aimed directly at the back of the inlet valves, a carb'd engine needs the inlets to be quite rough to help mix the fuel. I port matched both the head ports and exhaust manifold to the exhaust gasket opening size on my z22se and saab cylinder heads. Seems to work very well, Joe589 has my original z22se cylinder head and he was very happy with the bhp increase

[Winstar]

you should have the exhaust ports slightly smaller than the size of the runners to stop reversion. But the gasket should be smaller than the runners

[vocky]

good point Winstar the exhaust runners were mostly larger than the gasket opening, I just tweaked a few spots

[rsg]

thanks Winstar/Vocky . Let the dremelling commence..... Duncan, looks like you've done everything else so give it a go!

Edited by rsg, 13 January 2009 - 05:42 PM.

[The Batman]

Seems to work very well, Joe589 has my original z22se cylinder head and he was very happy with the bhp increase

I was very happy with the outcome

[FLD]

I started out reading Vizards book 'theory and practice of cylinder head modification'. Bit out of date now but still a good starting point for practical stuff. For a theoretical view 'introduction to internal combustion engines' is a good read but again doesnt cover all the maths and stuff. After this I got into the proper hardcore stuff of venturi valve throats and port volumes etc that I can only just get my head round so dont ask for an explanation.

[rsg]

I started out reading Vizards book 'theory and practice of cylinder head modification'. Bit out of date now but still a good starting point for practical stuff. For a theoretical view 'introduction to internal combustion engines' is a good read but again doesnt cover all the maths and stuff. After this I got into the proper hardcore stuff of venturi valve throats and port volumes etc that I can only just get my head round so dont ask for an explanation.

Yeah i've been reading 'Four Stroke Permance Tuning' By A. Graham Bell and that took a similar view to the SA internet guide. I'll look out for Vizards book though

[FLD]

Here you go although looks like some availability issues (66 quid used!!)

http://www.amazon.co...y...5853&sr=1-1

http://www.amazon.co...r...5747&sr=8-1

[Treble]

that thread is based on a carb'd V8 engine, especially the bit about quite rough inlet ports, the z22se intake ports don't help mix the fuel as the injectors are aimed directly at the back of the inlet valves, a carb'd engine needs the inlets to be quite rough to help mix the fuel.

I port matched both the head ports and exhaust manifold to the exhaust gasket opening size on my z22se and saab cylinder heads.

Seems to work very well, Joe589 has my original z22se cylinder head and he was very happy with the bhp increase

How much have'd you done on that head? Bhp increase how much?

[snowwhite]

you should have the exhaust ports slightly smaller than the size of the runners to stop reversion.

I would definitely keep a step from the head to the exhaust to discourage reversed flow at lower engine speeds

Yeah i've been reading 'Four Stroke Permance Tuning' By A. Graham Bell and that took a similar view to the SA internet guide. I'll look out for Vizards book though

I have that and the Forced Induction equivalent sat next to me right now, both very good starting places My dissertation is exhaust design, so I have been doing a lot of reading

[slindborg]

you should have the exhaust ports slightly smaller than the size of the runners to stop reversion.

I would definitely keep a step from the head to the exhaust to discourage reversed flow at lower engine speeds

Yeah i've been reading 'Four Stroke Permance Tuning' By A. Graham Bell and that took a similar view to the SA internet guide. I'll look out for Vizards book though

I have that and the Forced Induction equivalent sat next to me right now, both very good starting places My dissertation is exhaust design, so I have been doing a lot of reading

If your conclusion dosent include "Cherry Bomb back boxes are wikkkkid" I will be most dissapointed

[Winstar]

I have that and the Forced Induction equivalent sat next to me right now, both very good starting places My dissertation is exhaust design, so I have been doing a lot of reading

OT ish
what aspect of exhuast design? good books to read if you can get them are:

Theory of engine manifold design: wave action methods for IC engines by Winterborne & Pearson
Design techniques for engine manifolds: wave action methods for IC engines by Winterborne & Pearson

They are both out of print now but I worked with Pearson when I was at Lotus and he really knows his stuff.

[siztenboots]

what makes the old wah wah wah noise from an old morris traveller , is it baffles, manifold, valve or cams, the system itself is really tiny ID

[snowwhite]

what aspect of exhuast design? good books to read if you can get them are:

Theory of engine manifold design: wave action methods for IC engines by Winterborne & Pearson
Design techniques for engine manifolds: wave action methods for IC engines by Winterborne & Pearson

They are both out of print now but I worked with Pearson when I was at Lotus and he really knows his stuff.

I am designing a whole new system, basing a lot of it on a 2D engine model in Ricardo Wave. Has been done for the last few years, the engine model itself is reasonably accurate and ties in with dyno testing, so we are just messing around with CAM profiles, inlet manifold and exhaust manifold designs.

Uni library has copies of them both and I have read those as well They came highly recommended by my IC engines lecturer as well

[vocky]

that thread is based on a carb'd V8 engine, especially the bit about quite rough inlet ports, the z22se intake ports don't help mix the fuel as the injectors are aimed directly at the back of the inlet valves, a carb'd engine needs the inlets to be quite rough to help mix the fuel.

I port matched both the head ports and exhaust manifold to the exhaust gasket opening size on my z22se and saab cylinder heads.

Seems to work very well, Joe589 has my original z22se cylinder head and he was very happy with the bhp increase

How much have'd you done on that head? Bhp increase how much?

not really sure what bhp increase the head gave, it has +1mm wasted stem valves and piper cams too

it suited the higher flowing 2.4 inlet manifold perfectly

this thread shows it's replacement saab head