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Larger throttle body vs porting and polishing?

22K views 41 replies 20 participants last post by  Cratos 
#1 ·
How much difference would it make getting a larger throttle body(85 or 90mm), vs just porting and polishing the stock throttle body? I found 85 and 90mm throttle bodies for sale on a site at $500(same price on both). Thats $500, or I think there's a guy here in the Dallas/Ft. Worth area who will port and polish mine for under $100. Anyone know said guy btw? Lost his contact info.

And if I do go larger, 85, 87 or 90mm, which would be best(considering I won't be doing more than a CAI and catback exhaust)? BMC Performance - Challenger, Charger, Magnum, 300 parts!
 
#6 ·
Unless you're going to be adding headers and hi-flow cats, the larger throttle body really isn't going to help much. Rule of thumb: Larger in, larger out. 85mm is about the largest you can go with a stock tune.

If the goal was to get more power, I think your money should go down a different path.
 
#8 ·
Well I already have a CAI, Corsa catback is one of the next things. Not sure about headers though.
 
#10 · (Edited)
The guys' name in Lewisville is Brian Sailor.

He's done hundreds of these including mine. Absolutely beautiful work and about $100 if you're associated with the DFW LX crew.

It's worth $100 but certainly not $500. I can barely tell the difference but the throttle response is better. Looks a heck of a lot better than stock but you won't see that part unless you take it apart or remove your CAI. Takes about 90 minutes and he'll do it while you wait. Very cool and he's a great guy.

You can PM me for his contact info.

The answer to "ported" or "bigger" is: ported will give you a bit on a relatively stock or mildly modded engine (exhaust, Predator). A bigger TB will be necessary as you get into big money power adders. At about that point you'll want to be working with the full time pro's like Andy at PWR. Hope that answers it definitively for you.
 
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#11 ·
According to this months mopar muscle they saw like 40HP on a 6.1 with a BBK 85mm and their CAI.??? The numbers for just the TB were about 15 HP 26Tq. about 14 & 17 on the 5.7.

Here is where I get stumped in all this: do we or do we not have a speed density system? If so we have to tune to really see any advantages. It's not like a mass air system that will somewhat adjust automatically.
 
#12 ·
I just picked up that issue this weekend and saw that as well.
I am still new to learning about some of these things but I'm very interested to hear what others say about this.
 
#14 ·
How much difference would it make getting a larger throttle body(85 or 90mm), vs just porting and polishing the stock throttle body? I found 85 and 90mm throttle bodies for sale on a site at $500(same price on both). Thats $500, or I think there's a guy here in the Dallas/Ft. Worth area who will port and polish mine for under $100. Anyone know said guy btw? Lost his contact info.


Hi, did you ever find guy here in the Dallas/Ft. Worth area who will port and polish mine for under $100. ? I live here and have an extra Throttle Body I can have him do this to.
thanks James
 
#17 ·
I have used a BBK 85mm on my 392 for several years. NO issues with codes or any other kind. However, I did port the intake inlet to just over the 85mm TB size.
If you use a true 85 or larger TB and don't port the intake, don't expect it to perform as it should.
If the ported TB still uses the OE 80mm throttle blade, as most do, don't expect any full throttle gain.
 
#19 ·
With any increase in TB outlet size, to achieve any improvement, port the intake inlet to, or to a slightly larger size.
If you don't port there is a step or ledge the air exiting the TB hits as it enters the intake.
On my 392 intake, there were some casting lines and other imperfections just inside the manifold inlet that could interrupt the airflow that I removed in the porting process.
FWIW, I stuffed a clean rag deep into the inlet and used sanding drums and grit wheels to port and clean up the inlet. I ued a vacuum cleaner to remove the dust.
 
#20 ·
ok, I'd be going from the stock 80mm TB, to an 87mm. I get they where the TB, meets the engine (manifold)... the manifold will be smaller I assume. but, what diameter is it? 80mm? 84?
also, when you say you ported the manifold, sounds like you left it on the engine....but, define "port"?...did you just clean it up, smooth the rough spots?... or did you increase the diameter to match the TB? if so, tell me what you increased it "from and to"?
for instance you opened it from 8" to 87?
thanks
 
#21 ·
As I recall, the manifold inlet at the TB was roughly 82mm. I opened it to roughly 87mm. On mine, the passage from the inlet was not full size or smoothly shaped so I ported it down several inches, opening it up as well as removing the casting lines, steps and the uneven shapes as much as possible.
Yes, on the engine.
FWIW, I had never done anything like this before, but it turned out to be easily done.
 
#22 ·
WOW, so you filed off 5mm? That's like a quarter inch! so?, I assume you did this in a way that the opening is now 87mm to match the throttle bodies 87mm, obviously by filling off 5mm.......and, it kind of funnels down in? Not sure I'm explaining correct, but obviously, the 5mm you filed off is at the opening, not the entire length?
--James
 
#23 ·
I used the BBK 85mm TB.
From the inlet in, the opening got slightly smaller for approximately 2 !/2" and then opened up further in. I opened that area to equal the 87mm inlet or slightly larger.
FWIW, the o-ring seat at the inlet is left with a very thin ridge to retain the o-ring.. If you need to port larger than 87mm the ridge may be eliminated. I personally would not want the o-ring to be unsupported.

Perhaps someone who has ported for a 90mm TB can chime in here.
 
#24 ·
I used the BBK 85mm TB.
From the inlet in, the opening got slightly smaller for approximately 2 !/2" and then opened up further in. I opened that area to equal the 87mm inlet or slightly larger.
FWIW, the o-ring seat at the inlet is left with a very thin ridge to retain the o-ring.. If you need to port larger than 87mm the ridge may be eliminated. I personally would not want the o-ring to be unsupported.

Perhaps someone who has ported for a 90mm TB can chime in here.
I guess I'm having a hard time picturing this. Sounds like you took out a lot of metal...and I'm guessing that wall is pretty thick, or you'd have to worry about "going through" it. How long did it take to get all this out?
 
#26 · (Edited)
The 392, like the 5.7 intakes, are plastic. The inlets however, are different. I have not looked into a 5.7 or 6.1 manifold, but it appears that as the inlet is straight in, the problems I encountered with the 392 manifold don't exist.
I don't recall the total time as I did it in several sessions.
All of my comments about TBs and porting still apply to the 6.1 aluminum intake, just harder to work with.
 
#41 ·
Guys I am new to all this and completely confused. I have a stock 2015 RT and would like to know what TB I have. I have zero mods right now and would like the order in which to mod my car. Like CAI, exhaust, maybe 6.1 intake, larger TB or port..... suggestions please..
 
#42 ·
with the modded one do you have to grind on the manifold, or is it just with the big ones?
 
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