'75 FJ40 with original 2F... Scotty, we need more power! (1 Viewer)

[Clubtroy]

Requesting HP improvement suggestions... My engine only has 57k original miles and I am not interested in swapping out the motor but I am looking for ideas to get a little more HP out of the engine.
I see nothing in the FAQ and my searches in threads have led down many rabbit holes. I know headers are an obvious direction but how many studs / bolts am I going to break off getting the old manifold off? I would appreciate any input from all you experts and more experienced muders out there.

More info on what i have:
Weber 38
All new points, distributor cap, rotor, plugs & wires
Aftermarket igniter coil

Thanks in advance!

Troy

 

[bhsdriller]

If you don't want to lose the 2F

HI POWER 2F — MOSLEY MOTORS

www.mosleymotors.com

Won't really increase HP but adding a Sniper fuel injection can help the driveability

 

[flx]

2F should be plenty of power for a stock FJ40. If it's low on power I would check compressions... On an engine that has not run a lot, valves sometime degrade (rust on a valve let opened for a long time...).
Check also that the secondary is working on the carb, you feel the kick when it opens

 

[cruiserkev]

My first 2F was the fastest I ever saw. It had a shaved F head, flat pistons, headers and a better cam. Plenty of trail torque and would do 80 mph+ on the freeway with stock 4.11 gears and 32 inch tires.

Currently my FJ40 has a 60 series 2F, which is stock plus has headers, unfortunately it is a LOT slower by comparison, still using 4.11s but now turning 35s.

There are probably a few more options out there, if nothing else headers are an easy upgrade. Good luck!

 

[300blk]

Like others have said, make sure it’s working right, first.

Not too many significant power upgrades you can do to the engine that you would notice.

 

[Clubtroy]

Thanks guys. My issue is top end speed... my max is about 65mph on 33's. When I have it floored i get a sputtering sound that goes away when I back off the throttle. Does that point to carb issues?

 

[Clubtroy]

2F should be plenty of power for a stock FJ40. If it's low on power I would check compressions... On an engine that has not run a lot, valves sometime degrade (rust on a valve let opened for a long time...).
Check also that the secondary is working on the carb, you feel the kick when it opens

That might be my issue. Do you have a Weber 38 for dummies book?

 

[flx]

I have the sputtering at speed issue too xD

Most likely it means the fuel bowl in your carb is empty. The bowl of the carb acts like a buffer allowing to accelerate but if you stay too long at high speed the fuel delivery doesn't follow.

You can search this forum, there are dozen of topics with this kinds of issues and a lot of possible source issue :
- Needle valve from carb stay close because carb is dirty
- dirty lines limit fuel flow
- Fuel pump in end of life
- Fuel filter full of dirt
- Something in the tank blocking the outlet when too much sucking
- Bad fuel lines that let suck air
- bad spark plugs (not related to fuel this one)
...

Good luck

A few topics (in many others) I'm following currently :

1978 FJ40 2F Odd fueling issue (Solved!)

Here's a weird one! I searched the forums high and low and haven't found this issue yet, let's see if you guys have any ideas. The problem: Truck seemingly drives ok, maybe a little light on power, but overall ok. As soon as you hit 40mph in 4th gear, the truck will buck violently and not go...

forum.ih8mud.com

Carb Problems! Carb Rebuild 101 please!

Hi All: I have a problem! The Jim C. re-built carb that I got last Summer has apparently sucked some "crap" past the fuel filter. The problem is that the rig "stumbles" when the RPMs are higher that 2000 when under load (i.e. going uphill at speed.) How should I clean-up this carb...

forum.ih8mud.com

78 2f highway speed chug/cough - possible water in fuel

over the past two days ive been driving my 1978 Fj40 from Denver up to Spokane where I go to school. It’s been running fantastically other than an issue that’s starting to worry me - back story, I left my gas cap in Cheyenne at the station but didn’t realize it until a few hundred miles later...

forum.ih8mud.com

PS : a header will do noting for your issue

 

[Pitter Patter]

Mosley offers a more powerful 2F for a cool $6,000+. I can’t imagine spending that on a FJ40 motor but to each their own. If you’re up for wrenching and some machining then you could probably get close to the same thing for a lot less expense. Sounds like you just need to do some tuning because it shouldn’t sputter under full throttle. The rusted valve(s) mention is a possibility for a lack of power and you can run some tests to see what’s going on. Ultimately this isn’t a fast vehicle but a properly tuned and healthy 2F should do 65 comfortably.

 

[Mark Jennings]

But Captain, I’m given ya’ all she’s got....

F and 2F with 4:11 gears is one step up from tractor....ain’t meant to go fast, meant to pull at full throttle from idle in top gear. When I drive my 68.....it’s all about ‘slow cruising’ and ‘stump’ pulling torque!

 

[Living in the Past]

Did you check the compression? Adjust the valves? Check the timing? When you say max speed of 65 MPH is that using a GPS to check your speed or the stock speedometer? Speedodometer reads low with 33" tires unless you have switched out the speedometer drive and driven gear at the back of the transfer case. Or some other means to correct the speedometer.

 

[mrboatman]

I never had any luck with the weber get a Holley Sniper set up you will do 70+ with it. I can go 70+ with a F and 33`s but try to keep it between 65 and 70 on the highway

 

[brian]

get rid of the weber, thats likely half your problems....non usa oem carb.....my 75 will easily and happily do 75-80 all day long with 33s and 3:70s.

 

[TEQ]

Sniper FTW.

I'm super happy with mine on my '78 2F, esp at Utah (SLC+) altitude. My motor is pretty tired and the Sniper breathed new life into it.

I also looked at "built" 2Fs. I'm now convinced if I ever did a non-2F transplant and was going to spend that kind of money I'd do the Cummins R2.8.f

 

[Dizzy]

I'd bet that there is an oil leak at the valve stem. Low miles, but, too many years. It keeps the intake valve caked up with crud. Results in low vacuum, not an rpm's friend.

Start with the engine itself, then, make sure there are no vacuum leaks, then, work on the carb and the spark.

Pull your spark plugs, and post up an in-focus, detailed, pic, with them labeled 1-6.

 

[Catching Neutral]

You guys have me wondering if something isn’t quite right with mine . 78 desmogged 2F. I have had it up to 67 mph and comfortable isn’t a word I would use to describe it. Felt like 67 was pushing it. 45-54 feels comfortable.

 

[1911]

You guys have me wondering if something isn’t quite right with mine . 78 desmogged 2F. I have had it up to 67 mph and comfortable isn’t a word I would use to describe it. Felt like 67 was pushing it. 45-54 feels comfortable.

Because the F-series motors have timing gears instead of a chain or belt, and flat valve tappets, and a 40-series has no insulation or sound deadening to speak of, they sound worse than they really are. It is very eye-opening to put a cheap tachometer on the steering column; it will show you that what you thought was "about to fly apart" was actually only modest rpm. A 2F in good trim will turn 3,000 rpm for a long time, but it sounds like it is really screaming.

I guess it's possible that a previous owner put lower-geared differentials in yours - you could count drive shaft versus wheel revolutions to figure that out. The '79-on U.S.-market 40's came with slightly higher-geared 3.70 diffs. Mine (with 33" tires, i.e. "rubber overdrive") is moving 65 mph at 2,500 rpm; comfortable to do all day (I've driven mine 750 miles in a single day). At 3,000 rpm it is doing 75 mph or close to it. The steering on these short-wheel base vehicles starts to get scary about then.

 

[FJ40Jim]

Thanks guys. My issue is top end speed... my max is about 65mph on 33's. When I have it floored i get a sputtering sound that goes away when I back off the throttle. Does that point to carb issues?

Yes. The tiny carb is not helping, possibly combined with a tiny air filter.
Is the carb throttle(s) wide open when the pedal is on the floor?
Is the auto choke is fully open when the engine is warmed up?
Is the stock ignitor still operational?
Is the stock distributor still in place?
Is the vac hose connected from ported vac to the dissy retard?

Post the results/answers, pleez.

 

[greenbeasty]

You might want to listen to @FJ40Jim , he definitely knows a thing or two about a thing or two!

 

[Clubtroy]

Yes. The tiny carb is not helping, possibly combined with a tiny air filter.
Is the carb throttle(s) wide open when the pedal is on the floor?
Is the auto choke is fully open when the engine is warmed up?
Is the stock ignitor still operational?
Is the stock distributor still in place?
Is the vac hose connected from ported vac to the dissy retard?

Post the results/answers, pleez.

Hi Jim,
I'll be able to go work on the 40 tomorrow and will post all responses. I do have a clarification Q for you so I know what I am doing.
I'm not sure what the ported vac to the dissy retard is. Can you help me out on this one is I can respond accordingly.
Thanks!