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Cylinder Head Dynamics NZ

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Selwyn
Cylinder Head Dynamics NZ

We are a small machine shop specializing in cylinder head development, over 30 years in the race engine industry with multiple world championships.

Our cylinder heads and development work is supplied to engine builders & racers through out NZ. 🏁

24/10/2026

1) - Good first outing Saturday night for the 9E Modified (Arapere/Pottinger) team at Stratford's opening meeting. Sheldon getting in 3 solid races which then put him on the front row for the feature with Sheldon leading it from start to chequered 💪🏁

2) - Also good first meeting for Matt Goddard in the 68E Six Cylinder sprintcar, winning the South Island title CTRA at Ellesmere Speedway. 💪🏁

3) - And good to see Toby Walker in the Mean Machine powered stockcar running one of our cylinder heads getting 3 wins from 3 starts and fastest lap time of the night at Eastern States Speedway opening meeting! Great work Walkers Racing. 💪🏁🏁🏁

Everything - no exceptions!
Measured - ✅️
Calculated - ✅️
Tested - ✅️
Repeated - ✅️
Guessed - ❌️❌️

18/10/2026

Positive start for the Eathorne 3nz Stockcar at Nelson Speedway on Saturday night for their opening meeting.
The 3nz Stockcar running one of our heads this season on top of the engine by Tony & his team at Mean Machine Nelson.
Nice to see Riley take out 1st place overall for the Trackman Trophy 🏆 💪🏁

Also good to see Kerry Walker picking up the 🏁in the first race, running one of our heads on top of the engine by Mean Machine💪, another good positive start to the season ahead.

📷 - BM Photography

Everything - no exceptions!
Measured - ✅️
Calculated - ✅️
Tested - ✅️
Repeated - ✅️
Guessed - ❌️❌️

16/10/2026

How good does the 3NZ Stockcar look!! , running one of our cylinder heads on top of the rebuilt engine by Mean Machine. 💪🏁🏆

16/10/2026

Ford Intech engine we've just finished for Matt Goddard (68E Ellesmere).

Sounds cool for a 4.0ltr 6 cylinder & "nearly" tips 400 ftlb torque! 💪🏁

14/10/2026

Tech tip: Valve spring rates

If we measure a valve spring on our Romac 1000 lb tester and it equals
- 255 lb @ 1.950
then we measure it again at 1.650 (-.300)
= 395 lb @ 1.650
Now we can actually work out the "spring rate" of that valve spring like this

Difference in pressure 395 lb - 255 lb = 140 lb
Difference in height 1.950 - 1.650 = 0.300 inches

Spring rate = 140 / .300 = 466 lbs per inch

Now we can also calculate over the nose pressure (total lift)

Seat pressure = 255 lb
Valve lift = .718 (the engine these springs belong to)
Spring rate = 466 lb718 x 466 = 334.5 lb (added to seat pressure)
- 255 lb (seat) + 334.5 lb (calculated) = 590 lb over the nose

Our Romac tester is first calibrated for correct height with the attached DTI, next is the pressure with the calibrated test spring.

You will see the actual measured pressure over the nose is correct with the calculated.💪🏁

Everything - no exceptions!
Measured - ✅️
Calculated - ✅️
Tested - ✅️
Repeated - ✅️
Guessed - ❌️❌️

11/10/2026

Been a big long project this one , however today was dyno day & to hear the note was awesome.
From the (custom CHD) carb at the correct cfm demand through to the headers the program we use was spot on!!
Throttle response is good and sounds crisp , the HP is good with the torque getting close to tipping 400 foot pounds!!!! (540 nm!!)
Different project doing a 4.0ltr Intech engine to run on alcohol & looking forward to seeing its performance on track. 💪🏁😎

Track feedback:
"It's got s**t loads of power & f**kin awesome off the turn" 😎👌

📷 on track pic - Dirt Diaries NZ.

Everything - no exceptions!
Measured - ✅️
Calculated - ✅️
Tested - ✅️
Repeated - ✅️
Guessed - ❌️❌️

28/09/2026

💪🏁🏆

Hey everyone

Bit of a upadate with the first practice at Woodford Glen for this season done and dusted last Saturday we are pleased with the car showing good speed right out of the box with only being 0.200 seconds away from the lap record which we are very happy about, this weekend we look at doing our first proper meeting for the season at Ashburton speedway. Below is my confirmed meetings so far with the potential of a few new meetings.

Massive thank you to everyone who has helped this season be possible Dad, Mum, Shakaia, Jason and everyone else.

Thank you to these sponors without yous this wouldn't be possible
Cranford Outdoor Power & Equipment Centre
Stonelay Stonemasons Ltd
Thumbtip Designs
Cylinder Head Dynamics NZ
Cando fishing
Wright Automotive
Rust repairs
United steel

Cheers Nik

26/09/2026

Hey team
Anyone out there thats got a set of headers 1 7/8 to suit Holden VN 5.0ltr head, just after a set to use on engine dyno.
Maybe someone has a set they have made etc 🤔

PM if you have anything or know of a set.

📷 for attention.

Cheers.

24/09/2026

NZ Champions 💪🏁🏆

28/08/2026

Something a little different, Aussiespeed Performance Products intake manifold, ported, port matched including spacer to plenum, burr finish💪, going on an Intech Ford for 6 cylinder sprintcar on alcohol.

Looking forward to dyno.💪🏁

Have a good weekend team 🙏

Everything - no exceptions!
Measured - ✅️
Calculated - ✅️
Tested - ✅️
Repeated - ✅️
Guessed - ❌️❌️

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Selwyn

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