F4R port and manifold dimensions

[Andrew Cooke]

I thought I'd start a thread where owners of the various F4R engines could post dimensions they've measured. I've got a couple of bits measured so far, so I'll start the ball rolling. Note that there is a fair spread port to port, so at best these numbers will be +/-0.25mm.

PH1 172 and PH2 172 upper inlets at the face where they join the lower inlets, they're much the same at:
25mm x 46mm
note that the upper manifolds are tapered down to this size, and easily opened out to match the RS lower.

PH2 and RS lower inlets, they are not the same as each other. Note that where the manifold bolts to the head the mounting face is not true to the port direction, I've tried to measure the size of the port rather than the 'gasket' size. (it'll make sense when you look at yours, honest...)
PH2 lower inlet manifold 25mm x 46mm (1050 sq mm)
RS lower inlet manifold 27.2mm x 47.9mm (1144 sq mm)
note that the cross section of the lower manifolds are approximately parallel.

PH2 172 cylinder head inlet port is 29.6mm x 49.8mm (1286 sq mm) at the manifold face, but soon closes down to 2x 25.6mm (1030 sq mm) round ports.

Even though the inlet ports are CNC'd they look a bit crappy on my engine, and not especially consistent port to port. I might be wrong, but I imagine a good cylinder head would bring more power to a standard inlet/ECU engine than a pair of cams.

Over to you lot, plenty of variants to measure, as well as exhaust ports

[Scoff]

You did well to find an RS lower bit, I'd like one too Thanks for measuring too, I had no idea how they compared. I could measure a phase 2 plenum if you hadn't already.

[Rob@Backyardracing]

You did well to find an RS lower bit, I'd like one too Thanks for measuring too, I had no idea how they compared. I could measure a phase 2 plenum if you hadn't already.

Isnt the Jam-sport lower the same as the RS, i fitted one a while ago for a lad to replace is RS one to find both manis looked identical from memory, it was a few years ago

[Andrew Cooke]

Isnt the Jam-sport lower the same as the RS, i fitted one a while ago for a lad to replace is RS one to find both manis looked identical from memory, it was a few years ago

The RS says RS (see pic), and has the bigger port all the way through. Jamsport port stuff out, so I guess you may get an RS back, or something else, who knows... The question is, do they port the non RS inlet all the way through, or just match the ends up and call it good. I've seem matched stuff where only the ends are opened up.

[Spooky]

Seems like a good modication for the 172.

If I was keeping the standard inlet plenum on my R5, I'd source one myself but I'm using throttle bodies

[Andrew Cooke]

Seems like a good modication for the 172.

If I was keeping the standard inlet plenum on my R5, I'd source one myself but I'm using throttle bodies

fit what you like, as long as you measure 'em

[Spooky]

Bugger that, get your vernier warmed up, I'll bring it to you and you can get cosy

You can measure the one already on my 172 as well if you really want to

[Rob@Backyardracing]

Sorry Andy im confusing you, the mani i got didnt have RS on it, it was to replace the RS unit he had thinking it was going to be larger, but it wasnt from looking at, looked exactly the same and from memory the port wasnt just matched sure it was all the way, wish i messured cc at time to see and to give idea, did cross my mind...

[Andrew Cooke]

just measured an exhaust port, no idea what flavour of F4R head it is.. (Steve?)

Anyway, it's much nearer to rectangular than the oval inlet.

22.7mm x 40.8mm

[SP33DY]

Not sure mate I only bought it to strip and make sure I had all the tools to do the full engine strip and rebuild with the forged internals.
I'll ask Andy to see if he still has the block, but I fear it was badly damaged when a piston went at rockinham.