GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Nikkormat · Post by **Nikkormat** » Sat Feb 13, 2016 1:16 pm

OK, I've got three questions for you FI guys...

#1 - Can I use a GM throttle body on my divided front and rear Offenhauser Dual Port. The primary and secondary runners are divided all the way to the head. So I can't see a practical way of adapting the GM and not killing flow. I've got a two barrel IH intake but doing an intake swap is a pain in the rear. Especially with the big cast iron high rise that weighs north of 80 pounds.

#2 - My Jeep has the ultra high tech 37 amp motorla alternator. Swapping it out adds $150 bucks to my budget and might make this swap out of reach. Is 37 amps enough for headlights, blower, wipers, running lights, TBI, fuel pump, and battery charging?

#3 - My exhaust leaks a little between the pipe and manifold on the drivers side, and a whole lot on the passenger side. Would this need to be addressed before TBI could go on?

csuengr · Post by **csuengr** » Sat Feb 13, 2016 8:52 pm

The best thing you can do with the Offenhauser is pull it off and sell it for scrap. That is all they are pretty much good for.

Secondly, IH is short for International Harvester. I am pretty sure a IH intake won't fit. A two bbl AMC intake will work better than the future beer cans you have now.

Any reason you can't put a bigger alternator from a later year FSJ?

You don't NEED to fix the exhaust leaks. You should, just because they are very annoying. It won't screw with the O2 readings.

Nikkormat · Post by **Nikkormat** » Sat Feb 13, 2016 10:41 pm

The intake is from an IH application 401. It's the stock 72-74 four barrel with two big bores machined in the middle for a 500 cfm holley two barrel. The carb flange is full four barrel size, so I should be able to just drill and tap for the GM throttle body.

FSJ Guy · Post by **FSJ Guy** » Sat Feb 13, 2016 11:35 pm

I don't see how the Offy would HURT. It might not be the best, but it would certainly work. You just wouldn't have any benefit of the "efficiency" primary runners. It would always be running with both. If that's what's already on your truck, run with it.

TBI ECM won't draw much, and neither should the fuel pump. i'm going to guess, 10 amps max, and most of that for the fuel pump. But you probably want to upgrade yours eventually.

FSJ Guy · Post by **FSJ Guy** » Sat Feb 13, 2016 11:37 pm

Oh, and yes, ideally you should have the engine running well before a FI swap. Fix those exhaust leaks. They'll only get worse.

Nikkormat · Post by **Nikkormat** » Sun Feb 14, 2016 12:37 am

How would I get fuel to both sets of runners? The TBI adaptors I've seen are for open plenum or split plenum...

FSJ Guy · Post by **FSJ Guy** » Sun Feb 14, 2016 11:22 am

Most adapters set the throttle body in the middle. Either way, there is probably enough space for both runners to be exposed. Hard to say without seeing the adapter on it.

Bill usn-1 · Post by **Bill usn-1** » Fri Feb 19, 2016 8:40 pm

#1 - Can I use a GM throttle body on my divided front and rear Offenhauser Dual Port. The primary and secondary runners are divided all the way to the head. So I can't see a practical way of adapting the GM and not killing flow. I've got a two barrel IH intake but doing an intake swap is a pain in the rear. Especially with the big cast iron high rise that weighs north of 80 pounds.

Not all adapters are created equal. Mine are designed to feed all bores equally.
Yes IH did use the AMC 401 for about 2yrs when the Unions shut down the IH engine plant. So any amc engine that will interchange with the 401 can use that manifold.

#2 - My Jeep has the ultra high tech 37 amp motorla alternator. Swapping it out adds $150 bucks to my budget and might make this swap out of reach. Is 37 amps enough for headlights, blower, wipers, running lights, TBI, fuel pump, and battery charging?

TBI will only add a little more then if you ran an electric fuel pump with the carb.
All power for the system should be directly from the battery thru a power relay.

Code: Select all

#3 - My exhaust leaks a little between the pipe and manifold on the drivers side, and a whole lot on the passenger side. Would this need to be addressed before TBI could go on?

ABSOLUTELY fix it.
The O2 sensor reads the amount of oxygen remaining in the exhaust. If you have any vacuum or exhaust leak it will allow unburned oxygen into the exhaust. that will affect the feed back and the corrections the ecm makes to the fuel being delivered.
If you can't afford to perform basic vehicle maintenance like fixing exhaust leaks, you should not install EFI.
You can not take short cuts like running 5/16" fuel line or cheap carb fuel hose and expect the system to work correctly.

Again....you should read and follow the instructions on http://www.binderplanet.com

Nikkormat · Post by **Nikkormat** » Sat Feb 20, 2016 4:01 am

Bill I've spent hours reading your posts. It's where I've gotten most of my information.

My exhaust leaks stem from improperly supported plumbing and fatigued studs. The weight of the exhaust system stretches the manifold to pipe studs as you drive and they can't be tightened any further. It's not the cost of the repair, I just haven't gotten around to it as I was going to replace the whole system.

Nikkormat · Post by **Nikkormat** » Sat Feb 20, 2016 4:02 am

If everyone says go 3/8, I'll go 3/8.

Bill usn-1 · Post by **Bill usn-1** » Sat Feb 20, 2016 10:59 am

If the exhaust is weighing on the manifolds then I recommend a flex joint near the engine.
http://www.summitracing.com/parts/sum-6 ... /overview/

3/8 on the feed is not what everyone says, it's what GM did from the factory.
It's how the system was designed to operate correctly.
Your install should mimic the factory install as close as possible.
Pump in or near the tank and 3/8 feed, 5/16 return.

Nikkormat · Post by **Nikkormat** » Sat Feb 20, 2016 12:24 pm

Do you object to using nylon hard lines?

Bill usn-1 · Post by **Bill usn-1** » Sat Feb 20, 2016 12:41 pm

Nikkormat wrote:Do you object to using nylon hard lines?

For feed, yes.
The wall is thicker so the ID is smaller. Right back to 5/16 or 1/4"
And there is no real good way to make a secure connection on each end to hold up to the fuel pressure.
You can use a compression fitting with a ferrel in the end to give it some strength but then that reduces it more.

Do it right and do it once.
There is no need to short cut.
The steel brake line is less than $10.

Nikkormat · Post by **Nikkormat** » Sat Feb 20, 2016 5:20 pm

Bill usn-1 wrote: The steel brake line is less than $10.

Not up here, sadly. The last 6 foot section of 3/8 I bought was $17.

What are your opinon on aluminum?

csuengr · Post by **csuengr** » Sat Feb 20, 2016 7:57 pm

It depends on how you were going to fasten the nylon tubing. I would not recommend hose barbs. They do make fittings specifically for nyplon tube that you just push the tube in and the fitting secures it. Good for 100 psi and better and the tube can easily be removed. Might be out of your budget, but I have no idea what they cost. The ID of the nylon tube isn't an issue. It's been used on vehicles for over 20 years now.

Aluminum doesn't play well with ethanol, or so I heard. I did use aluminum on my CJ without any issues, other than trying to find 5/16" fittings.

csuengr · Post by **csuengr** » Mon Feb 22, 2016 8:24 am

These are what I am referring to.

http://www.mcmaster.com/#push-to-connec ... s/=118ify5

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GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.

Re: GM TBI on Offenhauser Dual Port, is my alternator big enough, and O2 sensors with leaky exhaust.