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70mm thottle body
- Thread starter sdryde
- Start date
- Location
- WA state
Not sure about the TB you are talking about. But strokedjeep.com has 64mm bored TB's.
cruiser54
NAXJA Forum User
- Location
- Prescott, Az
O-Gauge Steamer
NAXJA Forum User
- Location
- Colorado Springs, Colorado
When I built the stroker for my 97, I used the TB from the 4.7L V-8. There are two, one is 65mm the other is a 68mm (found on the Magnum engines). I built a simple 1/2" thick aluminum adapter to go from our four bolt mount the the three bolt mount used on the TB. As the V-8 uses an o-ring to seal the TB and I did not want to attempt to groove my adapter, I just made a gasket.
Electrically, you need to make a "hydrid" IAC from both your existing IAC and the one on the 68mm TB. Just swap the plunger from the 68mm and bolt it in.
Total cost was $40.00 including shipping the TB. I just looked at car-part.com and a TB from a 2000 V-8 can be had for as low as $16.00.
Oh, yah. You also need to open up the intake manifold. As I was converting to the 99+ manifold, I modded that one and installed manifold an TB as an assembly. Obviously, make sure all chips are removed from the manifold prior to install. I stuffed rags into the plenum and then flushed with solvent.
Electrically, you need to make a "hydrid" IAC from both your existing IAC and the one on the 68mm TB. Just swap the plunger from the 68mm and bolt it in.
Total cost was $40.00 including shipping the TB. I just looked at car-part.com and a TB from a 2000 V-8 can be had for as low as $16.00.
Oh, yah. You also need to open up the intake manifold. As I was converting to the 99+ manifold, I modded that one and installed manifold an TB as an assembly. Obviously, make sure all chips are removed from the manifold prior to install. I stuffed rags into the plenum and then flushed with solvent.
Last edited by a moderator:
Talyn
NAXJA Forum User
- Location
- Radford, Communistwealth of Virginia
The throttle response is going to be pretty touchy with a 70mm throttle body.
Thats kind of what I was thinking... Just going by the volume of air needed to for a 4.0, seems like overkill to me. Maybe for a stroker, but for a 4.0 I doubt you will get much of a performance gain compared to a 64mm TB.
Talyn
NAXJA Forum User
- Location
- Radford, Communistwealth of Virginia
I think it would even be overkill on a stroker. I know that Dino has a 65mm TB and he says its a bit too touchy and doesn't recommend it. My 63mm is a pretty good match with out being overly touchy.
Are you talking about a stroker application? I would guess so by looking at your sig?
I was planning on a 63 as well for my 4.0 , intake, exhaust.
- Location
- San Bruno, CA.
I run a 62mm J&C TB with my 4.7 and it's groovy.
O-Gauge Steamer
NAXJA Forum User
- Location
- Colorado Springs, Colorado
Depends on the displacement. In my case I was feeding the 4.7 stroker with the TB from a 4.7 V-8 (68mm). How is this too much? Total airflow is a function of displacement, the formula is:
CFM=(CID*RPM*VE)/3456
where:
CID= Cubic Inch Displacement
RPM= Revs/Minute
VE= Volumetric Efficiency
Assume 80%to 85% VE. TB flow rates are typically rated at 28"Hg Vacuum which is a theoretical value as none of us get that. Here at 7,000', I idle at 16.5"Hg. When I lived in California (Moss Beach, on the coast south of SF), I saw 23"Hg as a fairly normal value depending on the current Barometric Pressure.
It makes no difference if it is 1 cylinder or 10...
Here is a TB calculator: http://dairally.net/daihard/chas/MiscCalculators/DaiThrottle.htm
CFM=(CID*RPM*VE)/3456
where:
CID= Cubic Inch Displacement
RPM= Revs/Minute
VE= Volumetric Efficiency
Assume 80%to 85% VE. TB flow rates are typically rated at 28"Hg Vacuum which is a theoretical value as none of us get that. Here at 7,000', I idle at 16.5"Hg. When I lived in California (Moss Beach, on the coast south of SF), I saw 23"Hg as a fairly normal value depending on the current Barometric Pressure.
It makes no difference if it is 1 cylinder or 10...
Here is a TB calculator: http://dairally.net/daihard/chas/MiscCalculators/DaiThrottle.htm
Dr. Dyno
NAXJA Forum User
- Location
- Al Ain, UAE
On my old 4.0 I've tried the stock TB, stock TB with taper removed (60mm), and a 62mm TB. With full external bolt-ons and a DIY ported head, the 60mm TB was sufficient and I saw no difference with the 62mm.
On my 4.6 stroker I initially used the 62mm TB and later swapped it for a heavily modified Mustang 65mm TB. I also tapered the TB spacer bore from 65 to 62mm to give a smooth transition to the intake manifold. The 65mm TB made throttle response sharper and it's fun driving on the street, but it's also challenging when driving offroad at slow speed while feathering the throttle 'cause it can sometimes become jerky. The 62mm TB is well balanced for a mild 4.6 stroker.
On my 4.6 stroker I initially used the 62mm TB and later swapped it for a heavily modified Mustang 65mm TB. I also tapered the TB spacer bore from 65 to 62mm to give a smooth transition to the intake manifold. The 65mm TB made throttle response sharper and it's fun driving on the street, but it's also challenging when driving offroad at slow speed while feathering the throttle 'cause it can sometimes become jerky. The 62mm TB is well balanced for a mild 4.6 stroker.
So with a 4.0 engine, would you say the best bang for your buck is to just take the taper out of your own TB and save the money of buying a more heavily bored one?
Assume 80%to 85% VE.
====================
True: But Max VE do not happen at max RPM as some may think. Max VE happens at ABOUT max torque or real close to it. That's why torque start to fall of above that RPM because VE starts to drop even with RPM going up.
If you want to know how big a TB you will need at SAY 6k RPM or so drop that VE to 55~65%. That's with a catback system and a funny looking cone air cleaner.
Now with a bad ass cam, some real head work, headers, OPEN headers that is and/or some kind of blower. Real VE numbers can change.
A 70 MM TB is good for bragging rights and little else. But go for it. Over size TB are a lot easier to live with on a DD. Then over carb was.
====================
True: But Max VE do not happen at max RPM as some may think. Max VE happens at ABOUT max torque or real close to it. That's why torque start to fall of above that RPM because VE starts to drop even with RPM going up.
If you want to know how big a TB you will need at SAY 6k RPM or so drop that VE to 55~65%. That's with a catback system and a funny looking cone air cleaner.
Now with a bad ass cam, some real head work, headers, OPEN headers that is and/or some kind of blower. Real VE numbers can change.
A 70 MM TB is good for bragging rights and little else. But go for it. Over size TB are a lot easier to live with on a DD. Then over carb was.
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cruiser54
NAXJA Forum User
- Location
- Prescott, Az
Probably best bang for your buck is to get a bored TB with the corresponding size replacement butterfly in it from www.strokedjeep.com for less than $100 exchange.
hubs97xj
NAXJA Forum User
- Location
- Fort Wayne, IN
I spent $5 for the drum sanding kit I used to remove the taper from my two. I'd like to run a larger TB to see if it would make any difference, but I'm basically just too cheap to do that.
cruiser54
NAXJA Forum User
- Location
- Prescott, Az
I've done that in the past. The larger bore with the bigger butterfly is way better.
Dr. Dyno
NAXJA Forum User
- Location
- Al Ain, UAE
Yes.
cruiser54
NAXJA Forum User
- Location
- Prescott, Az
I should mention that I've only done this mod on Renix Jeeps, where the TB is bored from 52mm to 60mm, probably a more noticeable difference than going frm 58 mm to 62 mm on an HO.
