What size TB for a 4.7 Stroker

[Bouncy]

I've been doing some reading in my spare time about TBs.

The biggest question used to be Who to buy from. Now it seems What SIZE is the real question.

Reading up on the 4.7 V8s in the grand cherokee, I see they are running a 68mm roughly.

Seems that most of the reading I come across on the internet tells of people running a 62mm TB on the 4.7 strokers.

So whats the opinion??

 

[Dr. Dyno]

If your Jeep's going to be a street machine, you can go for a 65mm or even a 68mm TB and you'll have a very snappy throttle response. If it'll be an offroad machine though, I'd advise you go for the smaller 62mm TB so that the vehicle will be less likely to jerk on throttle tip in.

 

[BBeach]

What year is it for? You can get a 5.0 mustang throttle body and mod that according to dinos site. He's got a section just on throttle bodies alone too.

 

[Steve97TJ]

If your Jeep's going to be a street machine, you can go for a 65mm or even a 68mm TB and you'll have a very snappy throttle response. If it'll be an offroad machine though, I'd advise you go for the smaller 62mm TB so that the vehicle will be less likely to jerk on throttle tip in.

What do you mean about the throttle body tipping in?

 

[jeepnuts311]

What do you mean about the throttle body tipping in?

i think he is sayin if you blip the throttle, it wont launch like its taking off the line


-Tim

 

[Bouncy]

My rig is mostly for wheeling with about 10% driving around town. 36s wont be nice on the road.

My problem is the flooding issue of the 24lbs injectors. Was wondering if the 68mm was the match for the size of the motor.

My motor will run for about 15 minutes maybe and flood out. Dumping fuel like crazy. So much so, when I removed a spark plug, it was dripping with gas.

It was suggested about spark. I am running new cap, rotor, 10.5mm firewires, new champion plugs. All that copper stuff mentioned in one thread on here. Also have a MSD coil pumping the mega voltage into the motor.

So it came down to possibly not being able to get enough air into the system fast enough. I polished my 54ish mm TB to an even 60mm below the plate. The intake was opened up to accept 63mm when I was thinking of purchasing a 62mm. Now I am wondering if Jeep put the 68mm on there to match up with the 4.7V8 for a reason.

 

[jeepnuts311]

it sounds like you are just straight up dumping too much fuel. 24lbs seems right for a 4.7L, but it sounds like your FPR (fuel pressure regulator) is shot, they also make an adjustable one, my L.A.P.S. carries the HOLLEY adjustable one, i think HESCO also makes one.

i was dumping fuel like crazy into my 4.0L. the way i found out is because it was making its way past my piston rings and i had gas in my oil.

HTH
-Tim

 

[Dr. Dyno]

What do you mean about the throttle body tipping in?

I mean throttle tip in, which is when you lightly touch the throttle pedal to move off. I have a modified '93 Mustang Cobra 65mm TB and my Jeep takes off like a bat out of hell with the smallest throttle input. Trying to crawl slowly offroad on a light throttle is quite challenging because the vehicle has a tendency to jerk, which indicates my TB is too big for offroading. On blacktop, the snappy throttle response does make driving highly enjoyable though.
Here's my TB write-up:

http://www.angelfire.com/my/fan/MustangTB.html

 

[Bouncy]

it sounds like you are just straight up dumping too much fuel. 24lbs seems right for a 4.7L, but it sounds like your FPR (fuel pressure regulator) is shot, they also make an adjustable one, my L.A.P.S. carries the HOLLEY adjustable one, i think HESCO also makes one.

i was dumping fuel like crazy into my 4.0L. the way i found out is because it was making its way past my piston rings and i had gas in my oil.

HTH
-Tim

I have a fuel pressure gauge on the fuel rail. Following the FSM, all pressures check out perfectly.

 

[badron]

Trying to crawl slowly offroad on a light throttle is quite challenging because the vehicle has a tendency to jerk
=============================
Stock of most offing.
Few have seen more then a few HP gain with over sized TB.
Any need for a OSTB depends also at what RPM range you intend to do most of you offing in. Under 3500 RPM and you can't use it at all. Plus It will spin easer.
Over 3500 and you may see some benefits. Don't bet on it. For offing the 4.0 stroking is the best bang-per-buck going.
Spend the rest of the money on beer.
If you really want more HP and don't mind a little wheel spin. Then think Nos

 

[corbinafly]

Check you map sensor and O2 sensor and vacuum lines for leaks. What year is your rig? If shouldn't dump fuel like that with 24 lb injectors unless something is wrong.

Kyung

 

[Bouncy]

I have a 90 XJ. 4.7 stroker. Ported head and intake. 2.0 intake valve and 1.60 exhaust. APN header with 3" exhaust.

New O2 Sensor. All vac lines are pretty well sealed up for swimming.

I'm running this cam from compcams. 68-232-4

Here are the specs:
Duration advertised IN/EX 250/256
Duration @.050" IN/EX 206/212
Valve Lift W/1.6 rocker IN/EX .460/.476
Lobe Sep. Angle 113 degrees

I was told the cam may be screwing up the map sensor info but not sure.

 

[Dr. Dyno]

Check you map sensor and O2 sensor and vacuum lines for leaks.

You might wanna check the vacuum hose that goes from the MAP sensor to the intake manifold. If that's cracked, broken, or disconnected, the MAP sensor won't see any intake manifold vacuum and the injectors will stay open longer dumping too much fuel. If in doubt, replace it anyway.