Placcy inlet mainfold

Rich H · Post by **Rich H** » Tue Dec 19, 2006 4:45 pm

Just swapped the inlet manifolds back to the placcy one. Makes sod all difference except for a different noise, possible a bit deeper. Seems to make no difference to the power delivery. In short, despite what the salesman says (Shug!

) don't bother with a VVC manifold on a non VVC car.

Might actually swap it back as the port matching in better on the VVC as I cut them to match the gasket and the land between the coolant and No 1 & 4 inlet is pretty small now... Ah well. Another 3 hours or so...

Might even fit the PRRT, but then again....

Sanjøy · Post by **Sanjøy** » Tue Dec 19, 2006 4:58 pm

Mine was put on my car by Mike Satur when he built it.

Post by **Shug** » Tue Dec 19, 2006 6:19 pm

As I said at the time

it'll only make a wee percentile difference at the top end.

As you are a self-confessed pussy with the throttle, how would you know?

Post by **campbell** » Tue Dec 19, 2006 9:30 pm

The story goes that VVC cast metal inlet is good when you need the higher airflow on tuned engines...but as a result, sacrifices torque at lower engine speeds. And this is particularly magnified on a standard engine, where the lower volume of the std placcy inlet means air shifts faster at those lower speeds and volume isn't needed at higher ones cos the engine can't use it anyway.

There's a bunch of physics to explain it, Robin will be along in a minute if anyone wants the detail.

But suffice to say, as part of a wee upgrade I am about to undertake with my cylinder head, I will NOT be changing the plastic inlet manifold (other than cleaning up some plastic offcut, if I can reach it!)

Campbell

Rich H · Post by **Rich H** » Tue Dec 19, 2006 11:17 pm

I have become a mite less forgiving with the throttle I'll have you know, but still not got back on track as yet.. .

I'm going to have to change it back I reckon anyway, I'm pretty sure it's leaking water

Loads of steam for ages on startup, could just be condensation but it's sipping coolant again (It is overfull a bit)

FYI the gasket to the head was in pretty poor shape with the rubberised bits flaking off

Proper Rover jobbie too.

robin · Post by **robin** » Wed Dec 20, 2006 10:18 am

Shug wrote:As I said at the time it'll only make a wee percentile difference at the top end.

The VVC head has a wider inlet port to match the alloy plenum; just bolting the plenum onto a head with standard ports will present a step change in radius to the airflow and basically isn't a good idea.

The 135 heads have been tapered out so that at the inlet port they are the same radius as the plenum. In the end the valves are the same size, but the air flow doesn't have to pass the step.

If you haven't done anything to the port diameters you don't want the alloy plenum.

If you have widened the ports out to meet the alloy plenum you probably don't want to revert to the plastic plenum because the air flow will then slow when it crosses from the narrow plastic pipe to the (now) wider port.

Cheers,
Robin

Rich H · Post by **Rich H** » Wed Dec 20, 2006 1:26 pm

Yes i did widen the ports and that (I think) is what is causing the leak. Going to swap it back when I can be bothered to get a new gasket.

robin · Post by **robin** » Wed Dec 20, 2006 2:44 pm

RICHARDHUMBLE wrote:Yes i did widen the ports and that (I think) is what is causing the leak. Going to swap it back when I can be bothered to get a new gasket.

If you widened the ports you cannot swap back to standard plenum, can you? Won't the rubber gasket of the standard plenum end up overlapping the ports now?

Cheers,
Robin

Rich H · Post by **Rich H** » Wed Dec 20, 2006 4:14 pm

Not quite but it doesn't leave much of the placcy on the inside edge. I widened both the VVC manifold and the head to the gasket and checked the placcy to the same before fit and it should be ok.... but obviously isn't (Or I've blown the head gasket, one or the other...!)