The V8 Owners Forum -

Hi Chaps,

Anyone know if the little screws used to secure the throttle plate are very restrictive? (The two little screws which are split to lock them in place)

Wondering about using a shorter screw so they're flush and LOTS of thread lock

I know its game over if they come out! Just wondering if there is much restriction to flow?

Tom.

SuperV8 wrote:Anyone know if the little screws used to secure the throttle plate are very restrictive? (The two little screws which are split to lock them in place)

Wondering about using a shorter screw so they're flush and LOTS of thread lock

I know its game over if they come out

Hello Tom, I dont know, BUT I doubt very much if they cause any restriction at all.

For a start off, the only way they could affect the airflow is when the throttle plate was wide open so that the small tails of the screws were exposed the the airflow.

Even then they would only cause infinitesimal turbulence compared to all the other impediments en route to the combustion chamber.

As it happens - turbulence thereabouts could be considered an asset, promoting better mixing of the A/F mixture, prior to combustion.

For all the rest of the time when the throttle is NOT wide open the screw tails are masked from the inrushing air flow on the back of the plate, where there would be tremendous vortices set up by the plate itself making any imperfections caused by the screws totally insignificant.

As to whether it would actually be "game over" if a screw popped out, that would depend on whether the item actually made it down into one of the trumpets as opposed to falling down into the spaces between the trumpets.

Recalling my complete failure at hoop-la when I was a kid at the local fair, I think the risk is pretty low.

If for some reason you were looking at the imagined problem in order to increase the power output of the engine, you would get a lot more mileage from looking at eliminating possible power losses in the Efi system along the lines suggested her:

Stop Efi Power Losses in 15 Easy Steps.

http://www.vintagemodelairplane.com/pag ... wer01.html

By the way, I used to suffer from paranoia too, but not any more, I now know the bujjers are out to get me!

Not worth worrying about- in comparison removing half of the shaft itself so the butterfly is only held against the remaining half is much more beneficial in terms of less restriction- but even then I dont know if people bother doing it any more. Look here http://www.yellowbullet.com/forum/showt ... p?t=275928

I go to the bother of profiling butterflies, skinnying shafts and bonding in cut down screws.

A mate with a RR did some testing on AJP throttle bodied engines and the results really quite surprised me. Depends on what level of tune you have I suppose, but if you are having a larger plenum done then porting out the plenum and a few hours on the throttle seems little extra effort?

I was shown some rather nice throttle bodies at one of the race prep. centres. Instead of a butterfly they used two half moon (think Pringle) type shapes which pivoted at the top, so at WOT there was no restriction at all in the way! Surprised I haven't seen these in the after-market.

And for all out performance you use a slider instead of a butterfly so zero in the way of airflow

Ian

These lifted out of the way and formed the walls of the inlet when WOT! They were a work of art. Just goggled and can't find them! If you cup your hands together like begging and move them into a ball shape you get the principle. I think they may have been using on a touring car?

Are you thinking of roller barrels?

Typically slabbing shafts and profiling screws and the like are if you are restricted to using stock parts - if you want more airflow just go bigger.

There is always the case of every little helps but are you restricted on airflow through that part?

Andrew