Mod Guide: Throttle Body Half Shafting
#1
08-29-2016, 11:10 PM
Join Date: Apr 2010
Location: Mentor, Ohio
Posts: 12,156
Throttle Body Half Shafting
I have done this with my L67 throttle body that is adapted to my l36 (3800). I now did this to my LA1 (3400) on my '04 Grand Am.
I'm going to focus on the LA1 throttle body. Even though I did this for a 2004 Grand Am, it also applies to a 3400 powered Monte and any other GM 3400 vehicle. Please note, if you decide to get a donor throttle body for the 3400, GM made minor changes through the years. This link has some 3100/3400 info about the throttle bodies and other items:
https://wot-tech.com/94-99-3100-large-port-swap.html
On this throttle body, I did more then just half shafting. About a month ago when I did numerous services to my cooling system, I bypassed the coolant connections to the throttle body with a piece of hose (no coolant flows in/out of my throttle body. That being said, I opted to cut off that section on my project piece. Allows that bypass hose to rest a little better, not so cramped.
In the pic below (photo found on the Internet) you can see marks of what I wanted to cut.
In my project piece, I removed the throttle plate (I found it would have been handy to mark it's orientation prior to removal, it seems to only fit one way). Before I removed the throttle shaft (which holds the plate), I marked off were I wanted to cut. You want to cut only the side that has the heads to the screws. I also did not cut as tight as I could to the edges. I did this so I could still have a complete shaft protecting the bearings of the throttle body.
Removing the throttle shaft took a small smack with a hammer and it slide out.
Before I performed any grinding on the throttle body housing, I taped off the bearings for the throttle shaft (I did not want metal debris getting in to them).
Using the Dremel, I feathered down any steps or rough castings in the air flow path (not many). I uses a metal cutting disc to cut a section of the throttle shaft out. I used an angle grinder and removed the coolant passage.
When I re-installed the throttle plate, I used a dab of red loctite on the screws. Once installed, I grinded off the excess.
Below are various project pics. Once completed, I installed into the Grand Am.
So far I have been very happy with the results. I have improved throttle response, a little more pep. Watching fuel trims on my Scanguage II, not much has changed, but the car would benefit from being completely re-tuned (right now it's mostly a factory tune short of some transmission changes).
The work to mod and install this throttle body was very brief compared to other mods I've done and cheap (free if I wanted to mod the throttle body that came with the car).
I'm going to focus on the LA1 throttle body. Even though I did this for a 2004 Grand Am, it also applies to a 3400 powered Monte and any other GM 3400 vehicle. Please note, if you decide to get a donor throttle body for the 3400, GM made minor changes through the years. This link has some 3100/3400 info about the throttle bodies and other items:
https://wot-tech.com/94-99-3100-large-port-swap.html
On this throttle body, I did more then just half shafting. About a month ago when I did numerous services to my cooling system, I bypassed the coolant connections to the throttle body with a piece of hose (no coolant flows in/out of my throttle body. That being said, I opted to cut off that section on my project piece. Allows that bypass hose to rest a little better, not so cramped.
In the pic below (photo found on the Internet) you can see marks of what I wanted to cut.
In my project piece, I removed the throttle plate (I found it would have been handy to mark it's orientation prior to removal, it seems to only fit one way). Before I removed the throttle shaft (which holds the plate), I marked off were I wanted to cut. You want to cut only the side that has the heads to the screws. I also did not cut as tight as I could to the edges. I did this so I could still have a complete shaft protecting the bearings of the throttle body.
Removing the throttle shaft took a small smack with a hammer and it slide out.
Before I performed any grinding on the throttle body housing, I taped off the bearings for the throttle shaft (I did not want metal debris getting in to them).
Using the Dremel, I feathered down any steps or rough castings in the air flow path (not many). I uses a metal cutting disc to cut a section of the throttle shaft out. I used an angle grinder and removed the coolant passage.
When I re-installed the throttle plate, I used a dab of red loctite on the screws. Once installed, I grinded off the excess.
Below are various project pics. Once completed, I installed into the Grand Am.
So far I have been very happy with the results. I have improved throttle response, a little more pep. Watching fuel trims on my Scanguage II, not much has changed, but the car would benefit from being completely re-tuned (right now it's mostly a factory tune short of some transmission changes).
The work to mod and install this throttle body was very brief compared to other mods I've done and cheap (free if I wanted to mod the throttle body that came with the car).
#4
08-31-2016, 07:29 PM
Join Date: Aug 2008
Location: London, Ontario
Posts: 5,611
Nice work Jason!
I've never heard of "half shafting". To be honest, I wouldn't think that it would make much of a difference, but cleaning everything up would certainly help. You'd know better than I. Did you invent this idea? That tb looks a little thin walled to bore out more - have you tried? You may have yourself a nice little niche market - it seems customers are lining up already.
Great job of photo documenting. This is always such a useful step for everybody else, but requires significantly more patience to do. Thanks for sharing.
I've never heard of "half shafting". To be honest, I wouldn't think that it would make much of a difference, but cleaning everything up would certainly help. You'd know better than I. Did you invent this idea? That tb looks a little thin walled to bore out more - have you tried? You may have yourself a nice little niche market - it seems customers are lining up already.
Great job of photo documenting. This is always such a useful step for everybody else, but requires significantly more patience to do. Thanks for sharing.
#5
09-01-2016, 12:52 AM
Join Date: Apr 2010
Location: Mentor, Ohio
Posts: 12,156
Thanks for the kind words. I did not invent the half shafting idea. I saw bonneville guys do it to the 3800 and when you dig deeper people have done this to numerous other cars for years.
But the concept makes sense. It is essentially allowing a small amount of more air in. So in terms of throttle response, it would behave as if you had your foot into it a little more and at wot, it simply give a little more air. When you look at larger bore throttle bodies, many times they are not larger by much, possibly the same amount of air flow change as half shafting.
I have done this to both my Monte 3800 and now my Grand Am 3400 and I have been happy with the results.
As for boring it out, supposedly there is room to enlarge the bore, but I lack the equipment to do it (I would want solid precision and I don't have the tools for that).
But the concept makes sense. It is essentially allowing a small amount of more air in. So in terms of throttle response, it would behave as if you had your foot into it a little more and at wot, it simply give a little more air. When you look at larger bore throttle bodies, many times they are not larger by much, possibly the same amount of air flow change as half shafting.
I have done this to both my Monte 3800 and now my Grand Am 3400 and I have been happy with the results.
As for boring it out, supposedly there is room to enlarge the bore, but I lack the equipment to do it (I would want solid precision and I don't have the tools for that).
#6
01-30-2019, 08:35 PM
Thanks for the kind words. I did not invent the half shafting idea. I saw bonneville guys do it to the 3800 and when you dig deeper people have done this to numerous other cars for years.
But the concept makes sense. It is essentially allowing a small amount of more air in. So in terms of throttle response, it would behave as if you had your foot into it a little more and at wot, it simply give a little more air. When you look at larger bore throttle bodies, many times they are not larger by much, possibly the same amount of air flow change as half shafting.
I have done this to both my Monte 3800 and now my Grand Am 3400 and I have been happy with the results.
As for boring it out, supposedly there is room to enlarge the bore, but I lack the equipment to do it (I would want solid precision and I don't have the tools for that).
But the concept makes sense. It is essentially allowing a small amount of more air in. So in terms of throttle response, it would behave as if you had your foot into it a little more and at wot, it simply give a little more air. When you look at larger bore throttle bodies, many times they are not larger by much, possibly the same amount of air flow change as half shafting.
I have done this to both my Monte 3800 and now my Grand Am 3400 and I have been happy with the results.
As for boring it out, supposedly there is room to enlarge the bore, but I lack the equipment to do it (I would want solid precision and I don't have the tools for that).
#7
01-30-2019, 09:08 PM
Thanks for the kind words. I did not invent the half shafting idea. I saw bonneville guys do it to the 3800 and when you dig deeper people have done this to numerous other cars for years.
But the concept makes sense. It is essentially allowing a small amount of more air in. So in terms of throttle response, it would behave as if you had your foot into it a little more and at wot, it simply give a little more air. When you look at larger bore throttle bodies, many times they are not larger by much, possibly the same amount of air flow change as half shafting.
I have done this to both my Monte 3800 and now my Grand Am 3400 and I have been happy with the results.
As for boring it out, supposedly there is room to enlarge the bore, but I lack the equipment to do it (I would want solid precision and I don't have the tools for that).
But the concept makes sense. It is essentially allowing a small amount of more air in. So in terms of throttle response, it would behave as if you had your foot into it a little more and at wot, it simply give a little more air. When you look at larger bore throttle bodies, many times they are not larger by much, possibly the same amount of air flow change as half shafting.
I have done this to both my Monte 3800 and now my Grand Am 3400 and I have been happy with the results.
As for boring it out, supposedly there is room to enlarge the bore, but I lack the equipment to do it (I would want solid precision and I don't have the tools for that).
#9
09-28-2019, 10:38 PM
Join Date: Apr 2010
Location: Mentor, Ohio
Posts: 12,156
Right now I have too much going on to take on extra projects at the moment (and it's most likely going to be that way for a few months).
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