1G Throttle Body re-bore/63mm or 65mm?

[sweet97]

I can have my 1G TB bored to 65mm but that would remove the thin lip that is part of the idle circuit I believe. 63mm leaves the lip but very thin. The difference can mean a 5% difference in flow. Has anyone done the 65mm bore as shown in www.throttlebodys.com pics or should I go with www.o2induction.com and the 63mm bore? Please responses from guys who have had one or the other done. thanks, mark

 

[sweet97]

throttlebodys has stopped doing 65mm bores as it does mess up the idle. I'll go with www.o2induction.com thanks, Mark

 

[BaddAssGst]

Any reason to this? I know a few guys that have gone from 2g to 1g TBs and have noticed little to no difference and we're talking 8 mm's I believe. I don't believe your going to notice any sort of difference going from 60 to 63mm. I just don't thnk that is a well spent 100 bucks.

 

[sweet97]

Yes. I am adding a JM SMIM and thought this would be a good time for a TB rebuild. Throttle shaft seals will be replaced with O-rings and the throttle body refinished to look new. They were leaking. Someone had painted the TB with some clear paint that had turned yellow. The 63mm bore is just an option that was not that much more. I'm not expecting to feel any power increase though it brings the TB to 2.5", the same as my piping. Thanks, Mark

 

[paul s]

I had my 1g t/b bored out to 63.5mm 4 years ago and along with 2g extrudehoned intake manifold it did make a small difference up top. Mostly throttle response..here are some pics:

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Stock 2g manifold vs 2g extrudehoned
stock 54mm tb, 1g60mm and 63.5mm t/b
stock runners are 55mmx28mm
extrude runners are 58mmx31mm

 

[Coup D E'Tat]

Mark, what size opening is on your JM manifold? If it's only 60mm, you're not going to help it at all.

Also, shaft seals can be replaced in 15 minutes with a $1 bag of o-rings from Home Depot.

 

[DSMraver]

No point in going bigger. I have spoken at length with one of the top 3 FWD racers in our community, and he has done pressure drop measurements with a stock 1g TB, and found about 1-2psi TOTAL pressure drop from the compressor outlet to the plenum.

Spend your money in other places, IMO.

 

[4SFED4]

No point in going bigger. I have spoken at length with one of the top 3 FWD racers in our community, and he has done pressure drop measurements with a stock 1g TB, and found about 1-2psi TOTAL pressure drop from the compressor outlet to the plenum.

At what boost level??
What type/size of intercooler??
What size IC piping??

All those are factors. If you have a factory sidemount and IC piping ofcourse a bigger TB will do you no good.
I personally made just over 500 whp @ 28psi (60-1 hybrid/TO4B) with a factory 1G TB and intake manifold. Running a Spearco 2-230 IC and 2.5" IC piping from the compressor outlet all the way to the TB. Except for the reducer couplers at the IC to adapt to the 3" inlet/outlet. With that arrangement my TB was the restriction.
I have since gone to a 3" upper IC pipe and 3" TB with a JM Fab SMIM. I have noticed huge top end(above 6000) gains and I attribute it mostly to the increase in TB size than the SMIM. Although the throttle is much touchier and once boost comes on you are basically forced to go WOT or lift due to compressor surge.

 

[larsrya8]

I have noticed huge top end(above 6000) gains and I attribute it mostly to the increase in TB size than the SMIM.

Really?

Quote from Magnus' website (in regard to their SMIM):
"Offer excellent spool up characteristics and huge top end power increases over the factory intake manifold."

 

[DSMraver]

At what boost level??
What type/size of intercooler??
What size IC piping??

All those are factors. If you have a factory sidemount and IC piping ofcourse a bigger TB will do you no good.
I personally made just over 500 whp @ 28psi (60-1 hybrid/TO4B) with a factory 1G TB and intake manifold. Running a Spearco 2-230 IC and 2.5" IC piping from the compressor outlet all the way to the TB. Except for the reducer couplers at the IC to adapt to the 3" inlet/outlet. With that arrangement my TB was the restriction.
I have since gone to a 3" upper IC pipe and 3" TB with a JM Fab SMIM. I have noticed huge top end(above 6000) gains and I attribute it mostly to the increase in TB size than the SMIM. Although the throttle is much touchier and once boost comes on you are basically forced to go WOT or lift due to compressor surge.

This is on a car that makes over 700WHP+, 2.5" IC piping, big bar-plate FMIC, and 30psi+ boost, that's the car that was tested.

 

[OB1]

I just went with a 1G non turbo throttle body. 65mm and idles like a champ.

 

[4SFED4]

Really?

Quote from Magnus' website (in regard to their SMIM):
"Offer excellent spool up characteristics and huge top end power increases over the factory intake manifold."

I used the 1G TB with an Extreme SMIM and noticed no signifigant diiferance. I did notice a slightly quicker spool, most likely due to the smaller plenum and runner area to be filled. I don't make any comparisons between the Extreme SMIM and the JM because I couldn't use the 3" TB on the Exterme piece to make my findings accurate. The TB limitation was the main reason to buy the JM. I just recently purchased a BJs SMIM I can use the 3" TB on and I plan to do a comparison between it and the JM.

One signifigant differance I noticed using either SMIM unrelated to the TB is how the cylinders burn. With the factory manifold #1 and 2 cylinders always seem to run leaner than #3 and 4. With both SMIMs I noticed the plugs reading more evenly. Both SMIMs were used with a ported 95 manifold on the exhaust side.
Some people claim an equal length header will resolve that problem. I just recently tested that theory on my street car. With a factory 1G intake and equal length header, #1 and 2 cylinders still showed a signifigant diiferance in burn as with the stock exhaust manifold.

DSMraver I didn't intend to sound nasty, just wanted to know under what conditions those results were found. Thanks for the feedback.

 

[sweet97]

I just went with a 1G non turbo throttle body. 65mm and idles like a champ.

Is this a simple plug-n-play mod? If not what did you have to do to make it work with the turbo wiring? Also it seems you are using the stock 2G intake, correct? If so how did you open it up for 65mm? Yourself with a grinder or did you take it to a machine shop? looks like it flows 17% more than a 60mm 1G and a huge amount over a 2G. All the nipples and such on that NT TB? Thanks! mark

 

[sweet97]

I used the 1G TB with an Extreme SMIM and noticed no signifigant diiferance. I did notice a slightly quicker spool, most likely due to the smaller plenum and runner area to be filled. I don't make any comparisons between the Extreme SMIM and the JM because I couldn't use the 3" TB on the Exterme piece to make my findings accurate. The TB limitation was the main reason to buy the JM. I just recently purchased a BJs SMIM I can use the 3" TB on and I plan to do a comparison between it and the JM.

One signifigant differance I noticed using either SMIM unrelated to the TB is how the cylinders burn. With the factory manifold #1 and 2 cylinders always seem to run leaner than #3 and 4. With both SMIMs I noticed the plugs reading more evenly. Both SMIMs were used with a ported 95 manifold on the exhaust side.
Some people claim an equal length header will resolve that problem. I just recently tested that theory on my street car. With a factory 1G intake and equal length header, #1 and 2 cylinders still showed a signifigant diiferance in burn as with the stock exhaust manifold.

DSMraver I didn't intend to sound nasty, just wanted to know under what conditions those results were found. Thanks for the feedback.

The Extreme SMIM has "smaller plenum and runners" than the stock 1G? The 1G has a tiny plenum compared to the JM. What prompted you to go and buy another SMIM, the BJ's, after you have the JM and 3" TB running so well?
Sent you an email for info on the 3" TB but you can answer here for everyone if you like. I find this topic interesting since it does seem to be overlooked by many. Thanks, Mark

 

[OB1]

Is this a simple plug-n-play mod? If not what did you have to do to make it work with the turbo wiring? Also it seems you are using the stock 2G intake, correct? If so how did you open it up for 65mm? Yourself with a grinder or did you take it to a machine shop? looks like it flows 17% more than a 60mm 1G and a huge amount over a 2G. All the nipples and such on that NT TB? Thanks! mark

It bolts right up exactly the same way a 1G turbo one would. Your TPS and ISC bolt up with no problems either. I was using the stock 2G intake and just used a die grinder to bore the opening out in the intake to 65mm. All the nipples are there but pointing in the opposite direction than the 2G throttle body. Just replace the vacuum line with longer ones and your good to go.

I don't run any emission components nor the stock intake anymore though. I run the throttle body on a Magnus intake now. Bolts up just fine.

One more thing, I remember picking up 4 new bolts (longer I believe) because the lenght of the throttle body bolt shafts are longer. Also you can't use your 2G throttle body elbow because the N/T throttle body uses a rubber coupler to connect to the uper intercooler pipe. One more thing, change the shaft seals before you install.

Let me know if you have any other questions.

 

[4SFED4]

The plenum volume of the Exteme intake is about equivilent to the 1G. It does however have much shorter and slightly larger runners(port matched to the ported head I also bought at the time). I had to port the JM manifold when I recived it.
Before I bought the JM SMIM my original intent was to get a BJs intake, but unfortunately I was one of the victums of that mess with him. I found a used BJs manifold and decided to buy it and do a comparison since I wanted one in the first place.

I change things on regular basis on my car. I figure if I don't try different things how am I gonna go faster. After I finish my SMIM testing, I am goint to do an exhaust manifold comparison. I just recently installed a DNP-55 header, I want to compare with a SBR cast manifold utilizing a manifold mounted external gate with both. I have Tial 38mm and 44mm gates, but I will msot likely get the adapter to use on the SBR for the 44mm gate, the DNP is already flanged for it.

 

[CanadianTSi]

I just went with a 1G non turbo throttle body. 65mm and idles like a champ.

The 1g Non Turbo necks down to 60mm on the manifold side...

 

[OB1]

The 1g Non Turbo necks down to 60mm on the manifold side...

Forgot about that.

Regardless its a huge improvement over the 2G both in flow and throttle response.

 

[stevemonroe]

The 1g Non Turbo necks down to 60mm on the manifold side...

Hi All,
Just stopped in to mention that I have a new machining service for those considering the NT throttle body. Send me your 1G NT throttle body and I'll clean, beadblast, machine the bore to 63mm, install new gaskets & seals and modify the shaft for $100 incl shpg. With the 1/2 shaft mod I do on these, the flow will equal a 65.5mm TB. No problems with the shaft mod and it's been done on several hundred Buick GNs with no failures. (and we don't run BOVs)

View my DSM service at http://throttlebodys.com/

Thank you for reading. All questions answered and all feedback is appreciated.

Steve
[email protected]

 

[4SFED4]

With the countless failures of Accufab and other Mustang style throttle bodies believed to be associated with the use of a half-shaft why weaken a factory piece. I can't see the flow increase being signifigant enough to take the chance of damaging the engine.

www.dvdtfab.com did and extensive artilce on their site about the half shaft problems.

 

[stevemonroe]

I didn't find the article on that link but I did see a Mustang TB bolted to their fine looking custom intake manifold and it had the 1/2 shaft mod on it. Pic is Here The intake is supposed to be a new offering from them so maybe they do use the shaft mod now (?)
In addition to all the Buick GNs with no BOVs and smaller throttle shafts running this type of shaft, I've also done about 100 DSMs and none have broke. Any damage to the engine if one did break would be if the throttle somehow jammed in the WOT position and the driver did not think to turn off the key. The chance of parts being injested by the motor are slim to none IMO. I know some here don't agree with that but I can only rely on my 40 years of automobile experience and nearly that much machining background.
Bottom line is 5% flow increase is a significant amount but if a customer requests a full shaft, I'll provide that also. My thoughts are to offer the most flow possible without compromising the TB wall thickness.
Thanks.
Steve

 

[90blacktsiawd]

Steve, are you they same guy selling the bored out throttlebodies on ebay?

 

[stevemonroe]

Steve, are you they same guy selling the bored out throttlebodies on ebay?

Yes that would be me. If signatures were allowed in some detail here I would also link to my popular DIY Alky instructions page.

 

[90blacktsiawd]

Ah i see. So your also the guy who doesn't do 90 throttlebodies correct?

 

[stevemonroe]

Ah i see. So your also the guy who doesn't do 90 throttlebodies correct?

Yes I'm sorry I can't do those too. I don't like to turn down anything but the 90 model TB can't be done to my satisfaction b/c the non-removable fiav section would fill with cutting chips when it's machined and there's no practical way to prevent that or be sure they're all cleaned out after the work is complete.
But..I'm open to any suggestions..
Thanks
Steve