Builds Project Pikachu: 1977 FJ40 (1 Viewer)

[Dizzy]

I've been tooling around with some different carburetor jet combinations as well. Although my spark plugs look great, I'm looking to maximize power here at 9,100' in elevation. I started off stock of course, which is a 1.44 primary jet. Then I jumped to a 1.14 jet, which was too lean. My next high-altitude size is a 1.38 primary jet and I'm going to run this for a while and see if there's any noticeable increase in power or MPGs. Runs great, but I can't tell a whole lot of difference from stock just yet. The sweet spot would be great to have the 90999-41124 1.24 primary jet, but it's no longer made.

Ideally, I'd re-jet the secondary and power valve as well, but it's nearly impossible to find much data on this, much less the NLA high altitude jets themselves.
View attachment 2694523

One thing that I have considered is soaking a jet in salty vinegar to remove oxidation, then using lead solder to plug the hole, and drilling it out to the smaller size. I mentioned it on Mud, and got the general disapproval.

I'm running a 138, in a non-USA Aisan, at altitude. Spent a good amount of time running up to 10,300' The best was 15mpg on my worn-out 2F. The times when I experience lean conditions is during cold weather. Running a header, so no heat from the manifold.

 

[Pura Vida]

One thing that I have considered is soaking a jet in salty vinegar to remove oxidation, then using lead solder to plug the hole, and drilling it out to the smaller size. I mentioned it on Mud, and got the general disapproval.

I'm running a 138, in a non-USA Aisan, at altitude. Spent a good amount of time running up to 10,300' The best was 15mpg on my worn-out 2F. The times when I experience lean conditions is during cold weather. Running a header, so no heat from the manifold.

If it work, it works. I say YOLO.



Tech question? Listen to mud


opinions from mud? Ignore at all cost heheheh

 

[Dizzy]

@Pura Vida Best to listen to Mud 'gurus.' They have turned more wrenches. Like cbmontgo mentions, the secondary and the power valve isn't something that you can tune, so even a smaller main jet can only result in an overall inbalance. Plus there are the slow jets, etc.

Tuning for altitude doesn't make much sense, to me. The basic principle of the carb is speed of air from the bottleneck at the throttle plate and venturi; well, just because the air, at altitude, is less dense, doesn't mean that it is moving any slower. I started with a smogerator that was intended to be in balance with EGR combined with fresh air, a vac retard spark, dino fuel. Plus the whole thing was lightly caked with some kind of mineral deposit and/or metal oxidation. I thought that installing an O2 sensor would let me read the exhaust, but results from three different O2 sensors was wildly inconsistent, enough to no longer entertain the idea of TBI. Ultimately, I installed a new non-USA carb, got better performance, gas mileage, and got rid of a carb drool that lowered the level in the float bowl when it sat parked. Runs better now.

 

[middlecalf]

@cbmontgo do you have the octane adjuster on your dizzy? If so isn’t that another potential altitude adjustment tool?

 

[cbmontgo]

@Pura Vida Best to listen to Mud 'gurus.' They have turned more wrenches. Like cbmontgo mentions, the secondary and the power valve isn't something that you can tune, so even a smaller main jet can only result in an overall inbalance. Plus there are the slow jets, etc.

Tuning for altitude doesn't make much sense, to me. The basic principle of the carb is speed of air from the bottleneck at the throttle plate and venturi; well, just because the air, at altitude, is less dense, doesn't mean that it is moving any slower. I started with a smogerator that was intended to be in balance with EGR combined with fresh air, a vac retard spark, dino fuel. Plus the whole thing was lightly caked with some kind of mineral deposit and/or metal oxidation. I thought that installing an O2 sensor would let me read the exhaust, but results from three different O2 sensors was wildly inconsistent, enough to no longer entertain the idea of TBI. Ultimately, I installed a new non-USA carb, got better performance, gas mileage, and got rid of a carb drool that lowered the level in the float bowl when it sat parked. Runs better now.

Yeah, tuning for altitude is tricky, but maximizing horsepower and not fouling plugs are my two targets. I fly a lot at high elevation airports and leaning an aircraft engine properly is key to the two things i mention above. But maybe for an FJ40, as JimC said one time, “if it runs well, leave it alone”, or thereabouts.

I’m just tinkering at this point because I like messing with carbs and looking for stuff to do with it. Since the spark plugs look fine, I’m not too worried.

@cbmontgo do you have the octane adjuster on your dizzy? If so isn’t that another potential altitude adjustment tool?

Yes. I advanced timing to about 14 degrees, and also have the stock vacuum advance on the distributor. I believe some of the older 40s had a manual advance adjustment knob on the distributor, but my ‘76 and ‘77 do not.

 

[Dizzy]

For my info purposes,
what is your carb?
what is your vacuum at idle, and rpm?
do you have current dry compression numbers?

 

[cbmontgo]

For my info purposes,
what is your carb?
what is your vacuum at idle, and rpm?
do you have current dry compression numbers?

Stock, original carb with partial desmog. I’d have to get back to you on vacuum, but it was amazingly close to factory spec (minus hg for elevation) last time I put a gauge on it.

I’ve never run compression numbers.

 

[cbmontgo]

Boys night out. Had a great time at the local pub in Divide.

 

[middlecalf]

What’s the drinking age in Colorado?

 

[cbmontgo]

Friday evening grocery store run.

We’ve had a good bit of rain lately, and it’s got the wildflowers blooming and has kept the dust at bay on the back roads. This old 40 is running great, as always.

 

[cbmontgo]

Did some more tree work with the luxury tractor yesterday. This is a 17’ tree trunk that I hauled to my future cabin site for milling (eventually).

Thinking about tractors. When I was a kid, I learned to drive, mud ride, and back a trailer on an old mid-1960s International Harvester. This got me going down memory lane and I found a pic of one identical to ours from the 1980s/early 1990s online. My brother and I spent some time reminiscing about this last night. I miss those simple days from childhood in Mississippi.

Funny, it is yellow and white.

 

[G-Cat]

Nice!

 

[JVZii]

I’ve been searching for a good condition 1977 cluster for a while. There are some subtle differences for the year range and these aren’t very easy to find. Nearly all of them are corroded around the gauges too.

Amazingly, @JVZii had this one come up for sale with gauges in perfect original condition. Even the mileage matched mine, which is kinda crazy. The wear and tear on the besel even matches the dash. Very happy.
View attachment 2624875

I was just catching up on your thread (while I pretend to work a few more hours before the long weekend).

The cluster looks fantastic. Looks like it was put there in 77. Very glad it worked out for you.

 

[cbmontgo]

It was a nice 53 degrees this morning for some errands in town.

 

[wngrog]

Can’t like those temps for jealousy. It’s miserably hot here

 

[cbmontgo]

Can’t like those temps for jealousy. It’s miserably hot here

You can make me jealous in a few months, when it is 70 on Christmas Day.

 

[Catching Neutral]

You can make me jealous in a few months, when it is 70 on Christmas Day.

I’m getting in on that as well

 

[DPV7070]

Not sure how I missed this thread, but I've enjoyed the hell out of it over the last two days. Makes me really want to explore life in CO after dental school. It's a good thing you're doing for your kids, not that you need me to tell you.

-Another Ole Miss alum, pilot, 40 owner, etc., etc., etc.

 

[cbmontgo]

Not sure how I missed this thread, but I've enjoyed the hell out of it over the last two days. Makes me really want to explore life in CO after dental school. It's a good thing you're doing for your kids, not that you need me to tell you.

-Another Ole Miss alum, pilot, 40 owner, etc., etc., etc.

Thanks for that. Wow...very cool that we have so much in common. I'm going to send you a PM.

 

[G-Cat]

You two should go out to the garage and do karate!