70 mm throttle body y not?

[M-317]

i wanted to get a 70-75 mm throttle for the mark, bluegrss and pro five o this is for you guys. I have a friend with a an 88 stanger he got a 75 mm and it took 1 sec off his 1/4 mile time. I'm not being rude but would u mind telling my y i shouldn't get the larger throttle. and doesn't it already have a 65mm? (it's a 90 lscse) thanx you guys

[gadget73]

Stock TB is 60mm on your car. You can go on the cheap for a 65mm and adapt an Explorer 5.0 65mm body to work. I've seen them sold on eBay for less than $20. requires swapping the throttle lever off your stock throttle body, but thats not too hard really.

What other work was done to the Mustang? I personally have a real hard time believing a whole second from just a throttle body on an otherwise stock engine. I'd believe it on a worked engine that really needed that extra airflow though.

[NYC LS8]

A whole second off a 1/4 mile is A LOT. A bigger TB isn't gonna do that on a mostly stock engine. Now, if this friend of yours motor was being "choked" by a small TB, then it's possible. But still, an entire second? Damn. Maybe I should bolt one on and go 12s!

[M-317]

maybe you guys are right, he did have full exhaust and some head work done. but i really want to get a 70-75 mm throttle body, please explain y i shouldn't. they're for sale in my summit mag

[cason1]

What do you have done to yours to warrant that large a throttle body??

Another thing, what are your plans for the car?? Daily driver with a bit of muscle, street/strip, strictly strip, supercharger/turbo?? This info might also help.

[ November 16, 2005: Message edited by: cason1 ]

[M-317]

I have full exhaust, headers back, i'm about to do a stage one port and polish along with getting the heads FULLY rebuilt, saving to get GT-40 upper and lower intake.

[Larry Zajkowski]

sorry to hijack, but it seemed like the right place. the guy who sold me the 65mm tb is willing to replace it w/ a 70mm tb. i should be alright w/ that right? i woulda been happy w/ the 65mm, but i'm eventually gonna need bigger anyways (car in sig)? thanks, sorry again.

[Bluegrass]

On a near stock engine in the heavy Mark, the larger area tends to lose some throttle response.
The lower intake manifold is the larger restriction. So just going larger on TB size does not get by restriction in other locatons.
In other areas, you allow more air without additional fuel richness makes the A/F ratio go leaner at WOT but may improve over time as the EEC does some table corrections.
Other areas that change is the TPS vs Throttle angle airflow vs signal to he EEC.
Normally a 65 mm TB is about as big as you could use with out making program and fuel chages on an SD engine..
These are some of the technical things that go on with this change on an SD engine.
When a blower is used the TB can offer a restriction to the ability to force air into the engine under pressure but that is another matter.
IMO anything larger than 65 can't be utilized on a stock SD engine where low end drivability is important on the street.
The basic relationship is the more air the engine "CAN" injest the larger the TB within limits. An example is a 500 +hp blown engine can use at least a 90 mm TB and Mass Air meter as long as the rest of the engine has intake, heads, cam and exhaust that will pass that much air.
As a base reference, a N/A 5L engine cannot pump more than about 500 CFM of air at 6000 rpm so installing parts that can flow more only hurts performance in the lower rpm ranges.
This is my insight on the matter so you have somthing to reference in thought.

[90LSC]

Now that Bluegrass has given the technical breakdown, let me give you a real-world, daily driver, making it to the drag strip once a year report.

I have AFR 165s, Trick Flow intake, good H-pipe,yadayada.
Last year I got a great deal on a Accufab 70mm. I had been running the stock TB on this setup and installed the 70mm a couple of hours before getting on the road to Atlanta. Ran 15.1 @ 95 MPH in the 1/4.(Was pretty certain the torque converter is the culprit of the crappy time)

A couple of months ago I got a great deal on a BBK 65mm TB. IMMEDIATE improvement in throttle response. Felt mucho better in daily stop-n-go traffic. Marginally better MPG as well.

Two weeks ago I ran 15.1 @ 95 in the 1/4.(Completely certain the torque converter needs to go!). NO change in 1/4 and it is a better daily driver.

A 65mm MAY be an improvement on a stock setup IF you go to the trouble of porting the throat of the upper to match.

[ November 17, 2005: Message edited by: 90LSC ]

[pro-five-oh]

Neither you, 90LSC, or Larry need a 70mm. You will lose low end torque and basically be slower because you have too much throttlebody.

Unless you got a stroker/nitrous/blower invested in your ride you DO NOT waste your money on a 70mm TB.

[Larry Zajkowski]

ok, so i will beat him over the head until he replaces it w/ another 65mm one then! :D

[pro-five-oh]

Course ya don't need to take my word for it, strap the car on a dyno and see the power curves with both TBs...see for yourself which one has the fattest curve. :D :D :D