18RG 88253 porting?

[Shifty]

Guys

I have an 88253 head that I'm considering fitting a set of 44mm throttles to. However (and I forgot to measure this morning before leaving home) the intake ports look WAY smaller than 44mm... how much can these buggers be ported out?

It's not worth the trouble of fitting 44s if there will be a brick wall behind the throttle plate.

[river]

Hi,

40s are fine for the 18R-G, even if it's been bored/stroked to 2.4litre, unless you got some massive plans and mods for it.

I doubt you'll get any benefits going 44, except costing you a lot.

seeyuzz
river

[Shifty]

Short-term plans are limited to some porting and a moderate set of cams, but longer-term probably get a bit more serious with it. As I already have the 44mm setup (throttles, injectors, linkages, TPS, etc) and am planning to get more serious with it later, I figured now is as good a time as any to fit the 44mm setup rather than doing it twice.

As a side note if anyone is interested in the 44mm EFI setup, I may consider selling or trading for 40mm carbs in good working order.

[Rodger]

Without getting into technical details, the idea is to taper the port sizing from filter entry point all the way to the valve seat.
So match the bore of the manifold to the throttle bodies then taper through to the head, matching the head to the manifold.

The head certainly does not need to be cut to the same size as the throttle plate and would be impossible on any OEM head.

Regards

Rodger

[Shifty]

Hi Rodger

Thanks for your reply, you've confirmed what I expected. I'll get a small amount of porting done but make up most of the different by tapering the runners down from the throttle plate to the port.