To rebuild or not to rebuild...

[Devil Frog]

I acquired a 3FE out of an FJ62 about a month ago. The engine has 200k, and was running last year before the PO decided to part out the vehicle. Compression is above 150 psi on all cylinders. I will be transplanting into a '69 FJ40 which will be a trail toy only and maybe I might drive to work once in a while to show it off, but never a daily driver. So I would estimate I might put 5k/year on it. I will definitely rebuild the top end but am torn on whether to go into the bottom, because it is very assessable sitting in an engine stand and now would be the time. On the other hand it is a Toyota engine capable of 300-400k, compression is within spec, a bottom end kit will set me back a few hundred plus a few hundred more for machine shop labor, and the project could use the budget in other places (PS box, paint and body, suspension, lockers, Mega Squirt...), and I would like to have trail worthy sooner than later.

 

[marcfj60]

If you're getting 150 psi on all 6, I wouldn't do anything other than clean it up, desmog it and put it in the truck. Doing top end work likely won't improve anything in the valve train if you're getting 150 psi already. As you mentioned, it's a trail truck. If the motor gives out later, you have the time and space to fix it then and use the money you have now for the more immediate needs.

 

[pappy]

I say rebuild it, balance it, cam it, paint it a nice pretty blue ... but that is just me.

I think you are on the right track. It can't hurt to have the head reworked with 200K on the clock. I would probably take the oil pan off and have a look at the rod bearings since the engine is on a stand. I would also replace the front and rear seals, the water pump, and any other gaskets and hoses that would be easy now but a PITA later.

As Marc said, desmog too.

 

[marcfj60]

Isaac, keep in mind that Jon isn't married and doesn't have any kids. So there's nobody to complain about how long a project is taking or how much it is costing. But peace of mind of a fresh engine is also really nice.

Since I have no time to work on anything, I was just giving my perspective on what to do with a running motor with good compression. Although, pulling the pan off too look at the main bearings is a really good idea. I'd also replace the front and rear main seals, maybe the water pump and any other easy seals and gaskets at this point to reduce leakage.

 

[pappy]

Something else to take advantage of while the head is getting worked on. Mill the sucker. Compression on a factory 3FE is 8.1:1. I think mine is around 9:1 and I don't have any pre-det issues at factory timing. I know the 2F can take lots of milling, but I don't remember how much the 3FE can handle. Some homework should resolve the question.

Marc is also correct. I'm a SINK (or am I sinking?) Single-Income-No-Kids.

 

[Devil Frog]

I hear ya Marc.

I am leaning toward leaving the bottom end alone other that degreasing, paint, new seals and gaskets. Mill .040 off the head, clean and adjust the valves. I plan on going aftermarket ECU so I may tune. I am guessing after a complete desmog (hack the AI, EGR, O2 sensors and cats), and eliminating the constrictive Vane MAF (replace with MAP) it will not be optimal. I dont think the OEM ECU will work with a MAP sensor anyhow. Megasquirt seems to meet my requirements and budget, wish I could afford Motec though.

 

[pappy]

I don't think you will get away with running EFI with out the Ox sensors. They are not emission devices like the rest of the items in your list.

 

[Devil Frog]

I don't think you will get away with running EFI with out the Ox sensors. They are not emission devices like the rest of the items in your list.

In the stock configuration the O2 sensor is used for closed loop feedback control of the air to fuel ratio. It senses how much oxygen is in the exhaust which is proportional to the air to fuel ratio. They are used to keep the mixture lean to meet emission regs. Optimum power is achieved at a slightly rich mixture. The OEM ECU requires a signal from the 02 sensor. With an aftermarket ECU, an open loop map can be tuned, no O2 sensor. This is typically a 3d map: RPM, TPS, and MAP(or MAF) as the axes and pulse width of the injector as the dependent variable. A similar table can be tuned for ignition, same axes but spark degrees BTDC as the dependent variable. One could program the map to be slightly lean at partial throttle for best MPG, and slightly rich at full throttle for best power.

 

[marcfj60]

In the stock configuration the O2 sensor is used for closed loop feedback control ........

Show off!

Must be one of those damn engineers or something.

 

[OGBeno]

I say rebuild it, balance it, cam it, paint it a nice pretty blue ... but that is just me.

In fact, it is you!!

 

[2manycruisers]

If you are looking at increasing compression and boosting output, I'd seriously consider rebuilding top and bottom. That or do like marc said and just run it as-is. I don't have any experience with 3fes, but I recall a conversation with Hugh Phillips at Safari Ltd on the 3fe conversions he has done and said he would rather put in a high mileage motor without touching it than pull the head because warping (or maybe it was cracking?) was not uncommon. Purely anecdotal from me, though, so ignore me.

 

[alia176]

In the stock configuration the O2 sensor is used for closed loop feedback control of the air to fuel ratio. It senses how much oxygen is in the exhaust which is proportional to the air to fuel ratio. They are used to keep the mixture lean to meet emission regs. Optimum power is achieved at a slightly rich mixture. The OEM ECU requires a signal from the 02 sensor. With an aftermarket ECU, an open loop map can be tuned, no O2 sensor. This is typically a 3d map: RPM, TPS, and MAP(or MAF) as the axes and pulse width of the injector as the dependent variable. A similar table can be tuned for ignition, same axes but spark degrees BTDC as the dependent variable. One could program the map to be slightly lean at partial throttle for best MPG, and slightly rich at full throttle for best power.

I'm snickering because I have yet to see an aftermarket DFI system that's turn key - in my limited exposure to these things. Meaning, once you've installed a non oem FI ECU, you then spend the rest of your life continuing to "tweak" it - playing with maps, adjusting dependencies, etc. Of course, that may trip your trigger but sorta takes the fun out of simply driving the beast IMHO

 

[Cruisergreg]

I'm snickering because I have yet to see an aftermarket DFI system that's turn key - in my limited exposure to these things. Meaning, once you've installed a non oem FI ECU, you then spend the rest of your life continuing to "tweak" it - playing with maps, adjusting dependencies, etc. Of course, that may trip your trigger but sorta takes the fun out of simply driving the beast IMHO

Ash has it exactly right - a Megasquirt or any other "tweakable" ECU will drive you crazy (BTDT) unless your ulterior motive is tinkering. My experience has been that tweaking one parameter in a 3D map will throw off something in the other two dimensions. I now prefer "plug 'n' play". And then there's the altitude issue. Older ECUs have a fairly limited ability to compensate for thin air and even though it's hunting for the magic 14.7 to 1 ratio that engine is (was) probably running rich (all my EFI stuff does) and pushing that mixture farther may produce diminishing returns. The car companies have had engineers working thousands of hours coming up with the best compromise in maps in all driving conditions and us shade tree guys don't have those sort of resources to get driveability "right on". That said, you have a strong understanding of EFI and if you want to experiment, go for it, but it'll probably extend your trail worthiness much longer than just leaving schit alone. Again, BTDT.

 

[Devil Frog]

Ash has it exactly right - a Megasquirt or any other "tweakable" ECU will drive you crazy (BTDT) unless your ulterior motive is tinkering. My experience has been that tweaking one parameter in a 3D map will throw off something in the other two dimensions. I now prefer "plug 'n' play". And then there's the altitude issue. Older ECUs have a fairly limited ability to compensate for thin air and even though it's hunting for the magic 14.7 to 1 ratio that engine is (was) probably running rich (all my EFI stuff does) and pushing that mixture farther may produce diminishing returns. The car companies have had engineers working thousands of hours coming up with the best compromise in maps in all driving conditions and us shade tree guys don't have those sort of resources to get driveability "right on". That said, you have a strong understanding of EFI and if you want to experiment, go for it, but it'll probably extend your trail worthiness much longer than just leaving schit alone. Again, BTDT.

I totally agree that a tunable ECU can lead to countless hours of tweaking. From my experience once you build a proper fuel and ignition MAPs, using the right tools, a dyno and wide band A/F logger, you will unlock 98% of the performance potential. Racers and Hot Rodders will kill themselves to get that last 2%, but for trail use a good baseline tune will be great for a modded engine.

I am guessing the Jon could unlock another 15% in both power and torque with a properly tuned ECU. The porting and desmogging will definitely flow better, and at lower RPMs the stroking (2f bottom) will draw more air. My guess is that with a stock ECU, that purdy engine is running lean.

 

[pappy]

I am guessing the Jon could unlock another 15% in both power and torque with a properly tuned ECU.

Probably. There is no doubt there could be more potential. But, I'm happy with it and don't feel I need to tweak out more.

The porting and desmogging will definitely flow better, and at lower RPMs the stroking (2f bottom) will draw more air. My guess is that with a stock ECU, that purdy engine is running lean.

Why?

 

[Devil Frog]

Why?[/QUOTE]

Jon,

The fuel delivery on the stock ECU is designed to meet emissions on the 3FE, with ability to compensate with feedback over a small range. Your engine has the ability to draw more air over its rev range. A 2FE will not rev as high due too its longer stoke, but on the same interval from idle to its redline it will flow more air than a 3FE. The 3FE does not have an advantage until it is revving higher that a 2FE is capable. Since the ECU was for the 3FE the fuel delivery will most likely saturate for the flow you are able to achieve, resulting in a lean condition. Of course this is speculation.

I saw a few months ago that you did some dyno pulls, did the dyno by chance make a plot of RPM vs Air:Fuel? A plot like this would answer the question immediately. 13.5:1 would be a good baseline.


If your engine is meeting your expectations I wouldn't even bother. You can spend a fortune chasing that last 2%. I am lean towards a Megasquirt becuase I can get into one under $400

 

[alia176]

I read somewhere that the 3FE heads can take a .030" shave before having to go to premium. You still retard the timing a tad to compensate for the extra compression though.

 

[Devil Frog]

After pulling off the head, I think I going to overhall the bottom end too.

 

[BionicCruiser]

answered that question didn't it?!

 

[Devil Frog]

I say rebuild it, balance it, cam it, paint it a nice pretty blue ... but that is just me.

I think I will go with a red and black theme though