Taper or straight bore for TB

[allbottledup]

Which is better to do? And what size should I do. I have a B18B.

 

[MikeBergy]

Venturi that baby!!!

If your induction system is untouched, it probably will only hurt performance. I'd stay anywhere from 62-65 mm. Get some head work done, and that might justify droppin the bones on a new TB. Otherwise just save your money.

 

[allbottledup]

i have a friend whos going to bore it for me I was just wondering if I should taper bore it or straight bore it. Its not costing me a penny. I didnt plan on going bigger than 65mm anyway. Im going to port match the intake manifold. Also port out the runner a bit.

 

[JDMilan]

taper, your opening to your IM and the TB gasket is only so big.

 

[allbottledup]

thanks...i think im going to go 65mm - 62mm

 

[JDMilan]

yup,

 

[allbottledup]

and then port match the intake manifold to 62mm?

 

[pills_PMD]

yes.. but the next question is.. do you trust him? does he have the correct equipment to make the new throttle blade.. its not an easy thing to get right without precise equipment

 

[JDMilan]

yeah, usually a new throttle plate should be made, if you look online there are some decent placed that don't charge an arm and a leg for TB boring, most cost like 200 bucks plus yours and you get a new plate with screws, tapering, and your ready to go.

and yes it's wise to match the end of the taper to the entrace of the IM.

 

[allbottledup]

Well im in the military and in my platoon we have a full machine shop and weld shop so I can fabricate about anything. I got 37 days left so i gotta get on it.

 

[vpSPOONsol]

yea, in my squadron we have a metals tech shop too, im tryign to get the guys to mill my head for me

 

[allbottledup]

marines will do anything for some beer so im set!

 

[MikeBergy]

Just make sure they drink the beer AFTER they ream out your TB. I would have guessed to taper the TB out from 62-65mm rather than the other way around, to slow down the flow into the plenum. You want the flow to all the intake runners to be equalized, and the closer to zero the velocity at the inlet of the plenum is, the better.