Honda Spree and Elite 50 Forums

OK, got a Polini Corsa that I intend to mount to an AF16 block. Coupled with a CT Black intake manifold along with an OKO 24mm carb. Got all sorts of mods/goodies for the drive line too.

I'm going to be installing the completed AF16 block onto a 1987 Aero 50.

Can someone elaborate on the boost port that "may" need to be done to the AF16 block? That is, is it necessary to cut the engine case with the Polini Corsa? And if so, what's the gain if I do the boost port?

Basically looking for some insight about the boost port....

Also on an AF18 block, is it necessary to create/ cut the boost port?

Thanks everyone...

~Patrick

Greetings:

The Boost on the 16 is about 3x6mm. On the 18 it's closer to 6x12mm.
The case, gasket, AND cylinder have to match. If they do, just clean up the intake port and bolt the cylinder on.
Polini's done all the engineering for you, and I doubt there's much need or room for improvement.

If you try to mount a Corsa-for-16 kit on an 18 block, half the gasket will be flappin' in the breeze; a recipe for it to fail. If the Corsa kit is for an 18, you can and should carefully enlarge the 16's case boost port to match the 18's gasket.

I think he was asking more of does he absolutely need to cut the port and what gains could it potentially bring. Good info still

For the af16 you don't need to cut

Greetings:

Stated StrokedSR:

For the af16 you don't need to cut

I'm not so sure, Stroke. We've seen that the Nikasil comes in 2 versions, so perhaps the same is true of the Corsa?
Installing a small-port Polini kit on an 18 block is a recipe for disaster. The converse isn't so true, because the gasket will still be compressed on both sides. However if the cylinder has the bigger AF18 port and gasket, the tiny AF16 case port wheezing into that cavernous cylinder port surely won't perform as Signore Polini prescribed.

I recommend you check the case and cylinder, and be sure they match. Pics would be good...

The polini kits that daywot sells are for af16 blocks.

No modifications are needed. Here are a few pics of the difference between af16 an af18 parts.

(This is not actually an af18 block. This is a af16 with the boost port cut to the size of an af18)



Stock af16e

I've got several AF18 virgin blocks, and they measure 12.5 x 3mm on the boost port.

sanjuro wrote:I've got several AF18 virgin blocks, and they measure 12.5 x 3mm on the boost port.

So just wider. Not deeper?

I do not know. All of mine are af16's

Yep, they are just wider, and I've found that to be the case on five af18 motors.

that looks huge..well mine i didnt have to cut it matched right up

does anyone know if the stock SYM DD50 boost ports are smaller or bigger than the AF16??

Smaller boost port and intake port.