DOHC TB RE-Modified! :edit:

[z34Phoenix]

Well. after 5 hours of grinding and polishing, my TB is done (again)

 

about a year ago, i had an extra TB and intake manifold, so i went about for my first time port matching and polishing them. i also spent time reworking the inlet and exhaust sides of the TB to smooth it out and work in the cuts that resulted from matching the TB to the Intake arm.

 

Well since it was my first attempt at it, there were some area's that had room for improvement. so today i took the time to redo the TB. on my first attempt, the mouth of the TB had a bevile on the lip and then it was pretty much stock until after the throtle plate. behind the throtle plate, is where i did most of the orignal work.

 

On this new attempt i now did away with the bevile and have a perfict cone from the mouth lip to the throtle plate! and although it isnt as polished as my first attempt, it is nice and smooth and very slick! I also took the time to shave the extra off the bolts on the throtle plate... Yes I know all this seems and probably is overkill for my engine, but it was a fun project.

 

 

[TeeJay3800]

Damn. Looks awesome!

[chadz34]

You are good with that stuff man!

[Crazy K]

nice!

 

Tips on how to do?

[dohcfiend]

don't tighten the screw on your intake tubing too much

[z34Phoenix]

yeah it looks kinda thin huh? the picture makes it look thiner then it is. that first 1/4 inch probabl is weak but the rest is fine. i took the car out this morning... when my exhaust cutout is open, the car pulls NICE. once i get my UD pulley friday...and find the time to install it. i'll be in heavin.

[slick]

Thats what the one I sold looked like. Mirror shine and all.

[19Cutlass94]

Looks pretty damn good!!!

[per0781]

looks good. has anyone tried the throttle shaft mod?

before

 

after

 

http://www.geocities.com/wilwaxu/throttlebody.html

[z34Phoenix]

No not yet... i have shaved the bolts on the plate thought....

 

i like that site... i never saw that before, I am going to try that shaft mod. but i think im going to leave about 1/4 in on each side to better help hold the plate. but sand and taper it.

[RedGTP]

euhmm .. stupide question ... What it is ?? what the difference with this ???

[Crazy K]

does it make any noticable difference and how did you do it?

[patgizz]

with all that work, did you bore it out and put in a larger plate? you'll only move as much air into the motor as the bore of the TB

[z34Phoenix]

well, as a mater of fact, the bore isnt the desciding factor on how much air can make it thru. Remember air is compressable. so if you can make distance/duration of the restriction (throtle bore) as small as posible, then you can squeeze! (yes squeeze) air past this restriction.

 

also smoothing the inlet and exhaust reduces turbulence. this reduction in turbulence will also increase flow. but no i have not changed the throtle plate.

 

It does make a seat of the pants diff. i dont have the luxury of a dyno, but on the highway the car has a lot more pull.

 

i did some basic calculations tonight. i was comparing Throtle plate/bore area's between the stock(64mm), modified (calc to be equivelent of 67mm), and 70mm RSM TB. here is what i found

 

(edit #'s prior calc used 65mm as factory bore and not 64mm as it has)

the factory TB had a bore area of 2577mm

the factory TB with the throtle arm cut has a bore area of 2897mm (12.5% over stock)

the 70mm RSM TB ($400) has an area of 3148mm (22% over stock rsm quotes 12+ HP gain)

 

after figuring out those calculations, i am deffinatly going to mod that arm tomorrow morning! should only take about 2 hours of work if not less.

 

for info on the steps, either read that link above, or pg 6 of my WWW. when i complete this final step tomorrow i will get more pics to update my WWW. For specific questions, I welcome PM's

[dohcfiend]

i was going to ask you that. if you had plans on boring the arm opening?

[z34Phoenix]

Well it took more then 2 hours today! In the process of cutting the bar, i acidentally nicked the TB itself... a few times!... so i ended up resanding the entire TB. and it took another 5 hours.

 

I was shocked, i was able to open up the bar even more then what that LS1 site shows. that bar is pretty stiff. so after cutting off the top part, i shaved the lower to about half its original height.

 

i recalculated the bore area for what i ended up with. and i was within 1/2 of the total area of what a 70mm TB would be.

 

here are my calc:

 

my TB = Total bore area - bar area = [ Pi ( 64mm/2)^2 ] - [ 2mm x 64mm]= 3090 and with Sig fig's it is 3100

a 70mm TB= [ Pi (70mm/2)^2 ] - [ 10mm x 70mm ] = 3148 also with sig fig's it is 3100.

 

now, i know they arent going to flow exactly the same, but they should flow within a reasonable amount of each other. and my TB will deffinatly out flow the stock hands down. but enough talk here are the pics:

 

 

[per0781]

now that's looking good on LS1's, ported tbs result in a 5-10 hp gain. I'm interested as to the hp gain on yours.

 

p.s porting tbs on the side can get you some nice pocket change. 8)

[z34Phoenix]

Well then... Im at the boards service! any one what to be my first client?

 

again there seems to be a noticable diff in the car. but this time i am much lighter on the peddle. so it must have made a diff. RSM quotes +12 hp from a 70mm tb. and if that ls1 site says 5-10 is possible then, i'll just take a stab at it and say its probably about +8 hp over stock, IMO.

 

the only problem i have found, is that with out the bar it was hard to center the throtle plate. i have to try and recenter it tomorrow, it seems like it is grinding ever so slightly when closed. This is deffinatly best when paired with exhaust. once i crack that cutout open. the car comes to life! i just cant wait to get my new alt and UD pulley in this thing.