4AGE Head swap - making the impossible into the possible

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JDNightFox
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4AGE Head swap - making the impossible into the possible

Post by JDNightFox » Thu Oct 18, 2018 9:58 am

I am currently gathering information to see how possible this would be.

Since the 3A and 4A have the same head design, and head bolt pattern (as far as I can tell) this should follow the same process as the Jeep 4.0 MPI swap which I have successfully completed. Online sources say the 4A and 4AGE will NOT have valve clearance issues if swapped

Pros: (over doing a complete engine swap) no need to frankenbuild the bottom end to fit the transmission, instant fuel injection, MPG+HP upgrade, anyone can do this

cons: sourcing all the parts for a price that doesn’t cost as much as a complete engine, interference with parts fitting (exhaust, distributor, mounting points for extra hardware)

So far what I think I would need:

Complete wiring harness including all the sensors and ECU
Crank timing gear (are the shaft diameters the same on the 3A and 4A?)
Timing belt
tensioner
timing dust cover
THESE are because it looks like the 4AGE has a different cam gear profile. Although the 4AGE silver top / black top look like they have an identical cam gear profile then the crank timing gear may not be necessary (if someone has more info on this let me know)

4AGE complete head and valve cover
4AGE head gasket
Distributor
Spark plug wires
Intake manifold
Exhaust manifold
Airbox and piping
Vacuum lines

Things that need to be accounted for:
Crank sensor mounting
Redirecting exhaust manifold
Fuel pump

Like I said before, I converted a 4.2L Jeep carbureted engine to mopar multi port injection using this same process, so I have experience with what needs to be accomplished for it to work. This is if the head bolt pattern is identical and the oil /coolant ports match up for the most part (the Jeep 4.0 head has casting holes that are open to the air when mounted on a 4.2 block, the process accounts for this, in case the 4AGE head has the same issue)

I would need good measurements of both to see where everything lines up and what head holes are necessary

teranfirbt
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Re: 4AGE Head swap - making the impossible into the possible

Post by teranfirbt » Thu Oct 18, 2018 1:43 pm

The bottom end, other than pistons, of an early (85 to 86) 4AGE is identical to a 3A and 4A. I built a 4AFE out of a 3AC block bored almost 3mm over to fit 4AFE pistons. The easiest path would be to find an early 4AGE out of a Corolla GTS, MR2, or FX16 and swap the crank from the 3AC in place. This gives you the 4AGE head with 6 bolt crank needed for the Tercel flywheel.

None of the distributor 4AGEs got crank sensors for timing, it's all in the distributor. Unless you find a Corolla GTS intake, you'll need to modify an MR2 or FX intake to put the throttle on the front. A custom header is almost certainly a requirement due to steering rack geometry.

Note that the later 4AGE bottom end got bigger rod journals, this is everything 87 and up, which won't swap straight over.

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Petros
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Re: 4AGE Head swap - making the impossible into the possible

Post by Petros » Thu Oct 18, 2018 3:07 pm

that is likely possible, but why bother? There is no simpliflying benefit to a head swap. the early 4age will take a the 3ac flywheel from the tercel, bolts right up, as well as all of the other hard point mounts. it is a simple bolt up swap.

The single biggest problem, and cost, is to make a custom built exhaust header fit, and find a way for the intake manifold to work in the Tercel engine compartment, in addition to installing the EFI fuel sytem. you still have these issues with just the head vs. the whole engine swap.

In addition to that, with the 3ac short block, you have the problem of figuring what timing belt set up and tensioner will work reliably, as well as swapping out the pistons so you have four valve relief cut outs in the top of the pistons (for the 4 valve combustion chamber 4age head), rather the the 3ac two valve cut out configuration.

I highly recommend you keep the 4age as a complete and matched engine. it has already been sorted out by the factory (who has a multi-million dollar R and D department) and has many millions of miles of proven reliability. With the 3ac/4age head, you are on your own to work out the problems, many of which can not be anticipated, and will likely be discovered after the fact, and it will be a costly lessons learned in the process.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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JDNightFox
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Re: 4AGE Head swap - making the impossible into the possible

Post by JDNightFox » Thu Oct 18, 2018 5:45 pm

Yeah that’s the info I was looking for. The head swap would be more ideal for those who can’t / don’t want to move an entire engine, or those that paid for a rebuild and have low miles on their 3AC

Another idea I was thinking of would be some type of fuel injection adaption to our current engines, if the distributor from the newer models can bolt in

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Re: 4AGE Head swap - making the impossible into the possible

Post by Petros » Fri Oct 19, 2018 3:19 pm

there is an ancient thread about someone that adopted a throttle body injection system off a Suzuki (if I recall correctly) to the Tercel. the throttle body assembly has all of the sensors built into it, and you just have to make an adapter for the carb/intake manifold. Looked like a good way to go.

there is another thread with someone (from Pesscott AZ) that adapted four motor cycle carbs to the Tercel, they cut the intake manifold and used rubber hose to make four intake runners. That was a slick set up. I thought that was a great set up, lots of cheap parts available for it. there also may be motor cycle EFI that is easier to adapt.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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JDNightFox
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Re: 4AGE Head swap - making the impossible into the possible

Post by JDNightFox » Fri Oct 19, 2018 7:37 pm

Petros wrote:
Fri Oct 19, 2018 3:19 pm
there is an ancient thread about someone that adopted a throttle body injection system off a Suzuki (if I recall correctly) to the Tercel. the throttle body assembly has all of the sensors built into it, and you just have to make an adapter for the carb/intake manifold. Looked like a good way to go.

there is another thread with someone (from Pesscott AZ) that adapted four motor cycle carbs to the Tercel, they cut the intake manifold and used rubber hose to make four intake runners. That was a slick set up. I thought that was a great set up, lots of cheap parts available for it. there also may be motor cycle EFI that is easier to adapt.
Yeah I've got his kit right now. It uses a microsquirt system but I need to buy the computer hardware and getting that stuff from microsquirt costs almost as much as a used 4AGE on ebay

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Petros
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Re: 4AGE Head swap - making the impossible into the possible

Post by Petros » Fri Oct 19, 2018 9:32 pm

that is why it is much cheaper to go with factory ECM and figure out how to adapt it to the non-EFI car. likely factory toyota EFI components are far more reliable than aftermarket anyway, not to mention lots of spare parts and info on the system.

if you can come up with an inexpensive way to go distributor-less, than adapting the 4AFE engine, or head, might be a better alternative. the head is lower and more compact, and should fit under the hood easier. shopping for a crank fired ignision system at picknpull is far less costly than magasquirt.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

teranfirbt
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Re: 4AGE Head swap - making the impossible into the possible

Post by teranfirbt » Sat Oct 20, 2018 7:17 am

Factory ECU 4AGE will be much easier than a 4AFE since the distributor is on the side of the head instead of the back. Fuel system isn’t bad, but you’ll want to run a surge tank in the engine bay since the Tercel fuel tank isn’t baffled, which can lead to fuel starvation on an EFI pump.

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JDNightFox
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Re: 4AGE Head swap - making the impossible into the possible

Post by JDNightFox » Sun Oct 21, 2018 1:18 pm

teranfirbt wrote:
Sat Oct 20, 2018 7:17 am
Factory ECU 4AGE will be much easier than a 4AFE since the distributor is on the side of the head instead of the back. Fuel system isn’t bad, but you’ll want to run a surge tank in the engine bay since the Tercel fuel tank isn’t baffled, which can lead to fuel starvation on an EFI pump.
What does this mean exactly? I might need to do that to the Jeep too

It's running fine as is but what exactly do the baffles do

teranfirbt
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Re: 4AGE Head swap - making the impossible into the possible

Post by teranfirbt » Sun Oct 21, 2018 3:45 pm

The internet will do a better job than I:
https://www.streetmusclemag.com/tech-st ... t-baffled/
The baffles keep fuel at the pump inlet when the tank is lower and you're cornering. This isn't an issue for the carb setup because the carb has its own built in surge tank (float bowl). Even if the fuel pickup gets air, you still have enough fuel in the bowl for a few seconds of running.
An EFI pump requires fuel at the pickup 100% of the time or else it will fill the rail with air and starve the injectors. This isn't the end of the world, put fuel back on the inlet of the pump and it will return fuel to the injectors, but air through an EFI pump for extended periods of time is a bad idea.
The setup on my 4AFE swap uses a lower pressure electric carb pump back at the tank to fill a ~1 gallon surge tank in the engine bay. That surge tank feeds an EFI pump for the rail.
Realistically 1 gallon is a lot for a surge tank, you could use a quart surge tank on a small engine like the 4AGE and be fine.

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