91-95 69mm TB prototype

[SappySE107]

Im gonna meet up with john this weekend hopefully to have it tested out. Im also gonna try to find a shop to do the overbore since it was so much fun to do by hand....

Anyway, here is a pic of how the prototype turned out. not perfect but i think it will do ok for the IAC to deal with for idle. Guess we will find out

[dykz34]

Should be interesting... I can see gaps around the perimeter. How much of that can the IAC compensate for?

[grandprix34]

how much??! I'll be a prototype tester!

[Anonymous]

That looks good dude, I hope it works out.

[SappySE107]

The flash actually makes it look like there is more gap. After I took that pic I looked again and it doesnt have a lot of that gap (but there are 3 small areas that do). Im hoping its ok like this at least to see if its worth doing anyway. John is testing it out for me this weekend hopefully. I wanna make sure it works first.

Pricing...well it sucks ass to do that all by hand so im gonna ask around to see what it costs to have a shop to do it. The shop I go to all the time wont do it so thats 1 down.

[grandprix34]

hey man what if i port it? I already have it bell shaped plus some mild runner work. I can finish off the rest of the TB, ship it to you for the final porting within the TB throat (or i could do that too) and you just install the new plate

[SappySE107]

Thats what I was talking about, the bell shaping is simple, but porting out the entire TB 5 mm takes a long fricken time.

[RacerX11]

What did you use to bore it out? I was planning to use a cylinder hone on mine.

Marty

[SappySE107]

cylinder hone would take you about 2 weeks straight to finish, and about 50 sets of stones. I used that to do a little but it was just too damn slow. I ended up using carbide bits going around and round and yes it took a long time as well. I measured the diameter with a telescoping gauge to measure the diameter till it was real close, and then i tried to slide the plate in. Once the plate would fit, I put the shaft back in and then the plate and saw how far it would turn. Then I marked it and used sandpaper rolls to open it up where it was hitting till I could get it to close all of the way.

[RacerX11]

Ouch. I guess I won't bother with the hone. I guess a lathe won't work on the integrated TB.

The finished product definitely looks good for being hand done. The setup time is the biggest cost to have a shop do it, so if you can get several done at a time, it might not be too bad.

Marty

[SappySE107]

Ive got 2 or 3 i can do at once but its a matter of finding a shop that can deal with it being at an angle. I dont mind doing them by hand but it isn't worth my time to do it for cheap. I do bellmouth the opening and open up the plenum area behind the plate to smooth the transition...which no one else selling these things does. I wish the cylinder hone worked faster but it kills the stones and they are all uneven after a bit of use since the TB isn't straight bored stock.

[Lyle's GTP]

Why not bore it out, rather than port it? Isn't that what RSM does? That way you would be able to get a perfect cylinder. Then you could go in and clean it up with a flap wheel. Plus, doesn't RSM go to 72mm?

Lyle

[pocket-rocket]

They can't physically go to 72 mm without running into the coolant jacket, or was it the shaft bearings? They acually run theirs to 69 mm also. So technically anyone with one can sue for false advertising. So what were the differences in the powerband with the RSM units? Top end better, less low end or what? If no one remembers, I guess Ben, Oldskoolgp, and I will find out this weekend.

[Lyle's GTP]

So, that means that there is as little as 1.5mm of material left before you are where you are not supposed to be? That's cutting it kinda close isn't it?

Lyle

[SappySE107]

RSM bores them out 69.4mm, which is not what they claim (70). I can't bore it out, what would I bore it with? I think I explained everything above. There is plenty of metal left between the blade and the bearings with 69mm. I dunno what max is, im just doing 5mm over stock because it is safe and effective.