Direct swap larger throttle body M20?

[Dagamus(NM)]

Not likely, but I may still have pics of one that happened to a while back on one of computers.

Anyways, I am going to with an adapter just because I want to see how the throttle response is with one of them.

[digger]

What is this now?

Its a M20 throttle body bored out to accept an M30 butterfly works out to be +3-4mm or so.

[digger]

Not likely, but I may still have pics of one that happened to a while back on one of computers.

Anyways, I am going to with an adapter just because I want to see how the throttle response is with one of them.

BBTB have been done for donkeys years on the M20 never heard of problem unless you start going more than 65mm. Establish that a 63-64mm butterfly is too small before you start adding in more complexity than you might need.

[rvaughnp]

Its a M20 throttle body bored out to accept an M30 butterfly works out to be +3-4mm or so.

That sound like the way to go.:p

I will look up a supplier for the plate off the M30. Or just a salvage yard.
Then you would keep the vac lines and etc. as stock. Cool.
Thanks Digger.

[nando]

yeah, it really is the simplest and most direct way to do it. I haven't put mine in yet, need to have my intake manifold tanked and blasted, I already cleaned up the TB inlet and matched it to the new TB and gasket matched the outlets.

[rvaughnp]

Just put in an "order" for a M30 butterfly valve on different boards. Hopefully I can come up with one. Being I will be getting the Miller MAF, why not open it up as much as possible?
I looked around on multiple sites, no one seems to sell it individually.
I'll keep looking.

[rvaughnp]

Does anyone have specs on the plate? I wonder if i could get a local water jet company to cut one?

[nando]

I know it's 65mm.. don't know the thickness.

[rvaughnp]

Thanks Nando,
I will pull the one out of the M20, it should be the same thickness and measure it. then try to make some phones calls this week.

[Luis325]

Let me know! im interested in this as well...
What cars can you find the bigger tb?

[whodwho]

Does anyone have specs on the plate? I wonder if i could get a local water jet company to cut one?

The problem with making one is that the edges are angled. It looks like the ones from an M50 are the same as a M30. I have an M50 one next to me with a M20 TB apart waiting to be machined for it.

Couple pics to see the diff on the two

[rvaughnp]

OK, the M20 butterfly plate is:
Round - roughly 60mm (it is really an egg shape more than a circle by about .25mm, just fyi)
Thick - 1.95mm

The throttle bore is more of a venturi shape. Meaning the inlet and outlet are roughly the same size but the center at the rod where the plate attaches is narrower.

The inlet is roughly 63.5mm
The outlet is roughly 62.25mm
The center is roughly 60mm

So... by machining, we are taking roughly 1.5mm out of the ends and 5mm or so out of the center.

To the think of the edge... if we were to machine a straight bore, we wouldnn't have to worry about the edge. For that matter, you would want a flat edge like the stock M20.

[nando]

you want to keep the venturi though.. especially with a 5mm bigger plate.

[rvaughnp]

Is that something a machinist can perform? Its one thing to drill a hole, its another to drill a tappered hole.

[nando]

it's definitely possible. It looks like the one I have was done by hand though.