Issues with 4AC swap in a 1981 DLX

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ErickC
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My tercel:: 1981 DLX, 1982 STD

Issues with 4AC swap in a 1981 DLX

Post by ErickC » Thu Jul 11, 2019 6:16 pm

Hi guys,

So the 3AC in my 1981 Tercel decided to throw a rod last October - I don't know why, I took pretty good care of it. Either way, I had a freshly-rebuilt 4ALC available in a 1987 Corolla that I had given to my best friend some years ago, which, unfortunately, has been eaten up by rust. He suggested that we just use that engine (my original idea was to use the engine out of the '82 STD I have lying around, since the non-availability of aft lower control arms and general rustitude has turned that car into junk).

Anyway, the swap went relatively smoothly, but we've had some issues:

1.) I need to find a timing belt cover that will fit the lower cover on the 4ALC, because there's no way we're going to be able to get the harmonic balancer off. I'm broke, and that bolt is more than our cheapo Wal-Mart impact wrench could handle. The obvious solution is to cut away the flange around where the Corolla's engine mount would go (since the alternator belt runs across it) and patch the hole with scrap plastic. The original 3AC cover won't fit the lower cover, and I don't know if an AE86 cover will fit, either.

2.) The engine runs... barely. We have to advance the timing 45 degrees just to get it to start, and it barely develops any power. I've checked the cam timing about a dozen times, and it's correct, so I'm wondering if it's a vacuum problem, or some kind of carburettor problem. I did use the original carburettor, as the plugs on the 4A ones we have lying around are completely different. Could this be the problem? Should I Frankenstein one of those carbs to use the 3AC electronic parts? I have otherwise followed the vacuum diagram precisely, and the vacuum tubing is all new as of a couple of years ago, with questionable lines having been replaced last week.

3.) Complicating matters is that it's a California-spec car, so I don't actually have a functional carburettor that's correct for it. The original one is in pieces in a box in my garage somewhere. I bought a rebuild kit when I replaced the original (it had issues), thinking that it might be interesting to teach myself how to rebuild it. It quickly became apparent that rebuilding a carburettor is black magic for people with abilities well beyond mine. I can't really remember what was different on that carb, so I've been judging by the differences between vacuum diagrams on this car and my '82 STD. The main difference seems to be that the California-spec diagram has no lines going to the dashpot on the aft side of the carb (throttle positioner, I think? I can't remember), so I'm presuming that carb lacked the dashpot.

I'm really at a loss for ideas here. I'm also kind of getting tired of bumming cars off of friends while my car is out... so any help would be appreciated. I'm super tempted to just plug every vacuum line that isn't absolutely essential and start from there... the problem being that I have no idea which lines those are. I'd guess the vacuum advance, PCV, and brake booster, but I have no idea.

Oh, yeah, some idiot (not me) cut the wire to the oil pressure sensor. I'm at a loss as to what to do about that, since it looks like it was cut on both sides of the harness, so I have no idea where the wire would have gone. I yakked the terminal from the Corolla (since it's scrap anyway), but I really don't have the patience to disassemble the dashboard... I'm presuming that the car somehow ran low on oil (how? I have no idea, it was fine when I had checked it last, and it hadn't been driven much since then) and that's why it threw a rod, so I'd bet good money that I wouldn't be in this jackpot if this sensor had been working.

Also, if anyone wants a 1982 Tercel with rusted-out control arms... that car runs great. You just won't be able to drive it anywhere, since the springs have punched holes through the aft control arms. It's also getting pretty rusty. It would make a good beater for someone with the money to have new control arms made. That person is, unfortunately, not me, since, as I have previously indicated, I'm broke. :P

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Petros
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Re: Issues with 4AC swap in a 1981 DLX

Post by Petros » Fri Jul 12, 2019 3:15 am

Hi Eric,

welcome to the forum!

1. I would not cut anything open just yet. easiest way to get the front bolt off the balancer is to find a way to hold the engine from turning and use a big breaker bar on the bolt (this is actually better than using an impact wrench) First, remove #1 spark plug and push into the combustion chamber soft cord to fill up the space, leave the end of the cord hanging out so you can retrieve it (verify the valves are closed or on the compression stroke or you can bend a valve), and than rotate the engine until it locks up against the cord in the #1 cylinder. Apply a big breaker bar to the front bolt, with a cheater pipe over the handle if necessary, until you get the bolt to break free. if it is really stuck apply heat to the head of the bolt (protect the harmonic balancer from the heat so the rubber stays bonded, those are valuable). Usually that will get the front bolt out, than you can take a large soft mallet and knock the harmonic balancer back and forth, and outward. that usually is enough to break if free of the crank and you can wiggle it off by hand.

this has always worked for me except in one case where there was a lot of rust between the balancer and the front of the crank (that one took a puller, but this is not usually necessary). the key is to break it loos

If you do not have a large bearker bar wrench handle Autozone has a free tool lending program, some other auto parts stores do as well.

2. I would double check the distributor is installed properly, consider that you have to get the rotor pointing at the correct cylinder spark terminal, as well as have the housing positioned properly. not easy to line up both at the same time when installing it. sounds like the rotor is off several teeth on the gear. Also, double check the vac routing, and all the vac lines are good. look for any sources of vac leak in the manifold, carb, vac operated components, etc.

3. you should be able to make the federal carb work okay on the California emissions equipped car. I have owned several of both, and they are not that much different. mostly the routing of the air intake for the catalytic converter is different, and should not affect the carb. there may be a few vac ports in different locations, but you can fake that by adding a T or similar to find a vac source.

these are all fairly easy issues to fix, but finding the problem may be a challenge (and often frustrating), but once you find the problem, the fix is usually easy.

Good luck
'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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Re: Issues with 4AC swap in a 1981 DLX

Post by irowiki » Fri Jul 12, 2019 11:56 am

My guess is you developed an oil burning engine. One of my first Tercels burned a quart every 100-200 miles!
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ErickC
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Re: Issues with 4AC swap in a 1981 DLX

Post by ErickC » Sun Jul 14, 2019 8:19 pm

I knew it burned oil (It's a Toyota A engine, after all), but at the rate it burned oil it should have been fine. It hadn't been driven much since the last time it was topped off. That said, we did see signs of a major leak between the #3 and #4 cylinders where the head meets the block that I don't recall being there before. Since I've heard that 3A heads aren't particularly suited to the rigors of being mounted to a running engine, I suspect there may have been some kind of cascading failure that caused the engine to hemorrhage oil.

Anyway...

Yes, the spark timing is off a few teeth. The engine won't start with any less than 45 degrees of advance. With the stock 5 degrees, it just sputters and otherwise does nothing. This leads me to believe that something is really wrong with the carburettor - maybe it's running way too rich? I think I read that a mixture that's too rich can cause this kind of problem. I know that the Corolla carb worked fine, so that's why I wanted to know if I could just swap out the electronics and call it good. That would be the least-stressful solution, I think.

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Re: Issues with 4AC swap in a 1981 DLX

Post by irowiki » Mon Jul 15, 2019 12:51 am

You should probably start with timing the distributor properly, double check that you have the number one cylinder at top Dead center, then make sure when that happens that the crankshaft pulley is in line with zero, and the mark on the camshaft is at the proper place: You're able to look into a little hole On the camshaft pulley and see a triangle, that means the bottom end is top dead, the top end is top dead and you're looking inside the cylinder hole for number one and making sure it's the one at top dead center.

then you remove the distributor cap and then the distributor align the rotor with the number one spark plug position and stick it back into the engine button it all up and it should run at that point.

In my opinion you're chasing the wrong demons at this point.
Former Tercel Enthusiast (not a practical family car anymore but they still have a place in my heart)

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ErickC
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Re: Issues with 4AC swap in a 1981 DLX

Post by ErickC » Mon Jul 15, 2019 5:17 am

I did all of that several times. Having changed the timing belt on an '87 Corolla with a 4AC in it, and having also pulled the distributor on the same car to replace the when it went bad, I'm pretty familiar with the process (out of necessity, of course!). It was absolutely in the right place, but still wouldn't fire at all (by the by, my 45 degree figure isn't an estimate, it comes from the timing light). That's what's really puzzling me: in my experience (I've had four cars with carburetted A engines total), these engines are usually pretty tolerant of screwy carbs and vacuum leaks, that is, they'll usually still start and run. It just doesn't make any sense.

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Re: Issues with 4AC swap in a 1981 DLX

Post by NWMO » Mon Jul 15, 2019 10:48 am

Erick,

You are getting good advice from Petros and irowiki. I don't think there is a lot to add, but I will make a couple of comments.

I've never experienced it with Toyota, but I did have an old Ford where the harmonic balancer started allowing the center to spin inside the outer ring. Never enough to notice by eye, but it of course made timing with the marks impossible.

As Petros stated, you should be able to get the harmonic balancer off and use the correct covers. With the lend-a-tool programs, it's more about elbow grease than $$.

45 degrees BTDC (if accurate) only leaves a few options. I am quite confident, no amount of carb or vac problems would create this scenario. It is far more likely (even if you have checked a thousand times) that the timing belt placement is slightly off, the distributor is not in correctly or lastly, your plug order is incorrect.

It might be best to concentrate on getting the harmonic balancer off and then return to the timing issue with fresh eyes. The other suggestion would be to get a second set of eyes to check it with you, there have been times I was amazed at what I missed when I was sure everything was correct.

Chris
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ErickC
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Re: Issues with 4AC swap in a 1981 DLX

Post by ErickC » Wed Jul 17, 2019 10:08 pm

Guys, I appreciate your advice, but the only way it's a cam timing issue at this point is if the lower sprocket has ground down or broken the crankshaft key and is being held in some other position by friction. While this is a distinct possibility (it has happened to me before), given that this engine was purchased as a long block from JIS in 2013 and had fewer than 2,000 miles on it in the Corolla, I don't think that it's likely.

Anyway, about the camshaft and distributor. We took our time and worked slowly, spending two whole days transferring parts, verifying that there was no play in the timing sprockets (I am paranoid about the crankshaft's key), and verifying that the camshaft was set up per the Corolla's FSM (since the Tercel's FSM is for a 3AC, obviously). At no time were any fewer than two people working on this engine. The distributor was mounted to the engine while it was in the stand with the valve cover off, after we had manually cycled the engine a few times to ensure that the camshaft was indeed in the right place (which it was). Only then did I put the distributor in, with the marks aligned per the FSM, and we're certain that the shaft didn't move because we had the valve cover off and watched it go in. When the engine was finally installed, and did not want to run, we made two assumptions:

1.) The timing belt skipped or was otherwise incorrect

2.) The distributor was placed in the engine incorrectly

I decided that there was no use in frustrating ourselves, so I called it a night. The next day, we manually cranked the engine two full revolutions to ensure that the timing belt had not skipped a tooth or otherwise wasn't in the right place. It was fine. To be sure, we did it again. It was still fine. Then we pulled the distributor, re-aligned the protrusion on the shaft with the dimple on the stator (per the advice in the FSM, we did not mistake the pins for the mark), held the assembly so that the #1 and #4 terminals were vertical, and slid it in. The shaft did not move, and the distributor was in the center of its travel. I verified that the wires were in the right order: 1-3-4-2. The engine still would not start. So we repeated that entire process. When it became apparent that the engine almost wanted to start at the limit of the distributor's travel, we decided to try advancing the distributor a tooth. It almost ran. At this point, out of curiosity, we advanced the distributor tooth-by-tooth until we found a position where the engine would actually start. We checked with the timing light to see where we actually were: 45 degrees BTDC. Obviously, this is very wrong. We considered the following possibilities:

1.) Something happened while the car was sitting over the winter that caused the plugs, coil, or igniter to go bad, resulting in a weak spark

2.) The camshaft timing was somehow still off

3.) Stale gasoline

Once again, not wanting to burn either of us out, I called it a day. The next day, we pulled the distributor again, made sure that the timing belt was correct, that there was no play in the system, that the engine was indeed at top dead center on the compression stroke, and then replaced the distributor. I removed the coil, igniter, and plugs from my other car, which ran fine as of a month ago when I moved it into the garage (despite the fuel in its tank being about two years old, which is why I eliminated stale gasoline as a possibility for a total failure to start), and installed those components in this car. Still, it would not start with the default 5 BTDC ignition timing.

At this point, this left, to my mind, three possibilities:

1.) Some kind of mixture or other fuel delivery problem

2.) Incompatible carburettor (I don't know how different the 3AC and 4AC carbs are internally)

3.) JIS supremely gorked something in this engine when they rebuilt it

The next thing I am going to do is verify that the notch on the balancer is in the right location with a screwdriver in the #1 spark plug hole. I have considered the possibility that this is a repeat of the time the crankshaft key broke on another engine, and if the #1 piston is not at top dead center when the mark says it is, then this will be cause to pull the balancer and investigate further. I'm otherwise out of ideas and running out of time.

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Re: Issues with 4AC swap in a 1981 DLX

Post by Petros » Wed Jul 17, 2019 11:30 pm

sounds like you have been having a frustrating experiance with it. several things come to mind:

sometimes the bond of the elastormeric layer in the harmonic balancer will break lose from oil or gasoline soak, and the outer ring (that has the timing mark) can wander off the "zero" mark. verifying the zero is indeed at TDC should verify if the balancer is good.

another issue, one forum member found the gear on the end of the distributor shaft had seared the pin and the rotor was off by about 30 degress. if it held in the same position, it should not matter, but if the gear is free to slip back and fourth it would not result in good running.

Also, if your mechanical advance is frozen/rusted, the car will run badly above an idle. make sure the mechanical advance is free to rotate through its full range, and return back to zero advance by the internal springs.

something struck me as odd in your detailed description, you said the distributor went "straight in". the gear has a helix angle, so as you push the distributor down, the rotor will rotate about 15 degrees, it can not go straight in. This has been the cause of me getting the rotor installed off a tooth. Interestingly, when that happened it would only run about about 45 deg advance (and it ran very weakly). I pulled out the distributor and rotated it back further than I thought necessary, and push it back in, and it ran well and timed properly after that.

Personally I have found if you attempt to follow the installation procedure in the service manual you may not get it installed properly. I mark on the side of the distributor housing the location of the number one spark plug terminal on the cap, than install the dist assembly so the timing clamp is in the center of its travel, and the rotor pointing at the #1 terminal location that I had marked no the side of the housing. it will always start from that position. than I set the timing at 10 deg BTDC (I do not recommend the emissions compliant 5 deg, you can damage the engine long term) using a timing line (vac lines removed and capped of course).

a weak spark may cause similar behavior, but you had tried swapping out the components, and I doubt both sets of components would be bad. but it might be worth a second check, and all the contacts, if you find nothing else wrong.

good luck.
'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)

ErickC
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Re: Issues with 4AC swap in a 1981 DLX

Post by ErickC » Thu Jul 18, 2019 4:52 am

It's been very frustrating, yes. I've spent a lot of time dealing with 3A and 4A engines, and they've generally been very forgiving of all manner of maladies. The only time I had issues like this was when the Corolla's original engine had the previously-mentioned sprocket problem (which is one of the reasons why my mind keeps drifting back to that episode). When I say the shaft didn't move, I mean we were sure it stayed where we put it as we guided it through. I was really concerned about the shaft rotating out of position from finagling the distributor while trying to get it to mesh, figuring it wouldn't take much for it to end up off a tooth. We found out that if we set it to the marks, lined up the shaft, kept the #1 and #4 terminals in a straight vertical line, the whole assembly would slide right in and easily mesh with the gear, at which point, whatever it does is inconsequential.

The service manuals... they're interesting. There must have been a huge leap in quality in Toyota's writing staff sometime between 1982 and 1987, because the Tercel's manual leaves out a lot of important things (such as: disconnect air conditioner compressor from hoses if removing engine) and is very unclear in several places. The photos are also overexposed rubbish. The procedure for the distributor in the Tercel's FSM has you line up the protrusion with the #1 terminal instead of the dimple on the stator, which is the procedure that is outlined in the 1987 Corolla's FSM. We did it the first way the first time, but followed the later procedure each subsequent time we removed and re-installed the distributor.

What irks me is that my original impulse was to drop in the '82s 3AC since it would be a more direct swap (though we'd still need to change the exhaust manifold as the 81s is different and that rusty pipe ain't going anywhere without breaking). I fell into the "this engine is practically still new" argument, which, for any other engine, would be perfectly logical, but this 4AC never really ran right when it was on the Corolla, either. This is the main reason why I have been so obsessed over the camshaft timing throughout the whole experience. With that said, when it was in the Corolla, it fired up at the factory timing. I should have checked the valves while I had the engine on the stand. I shouldn't have trusted anything, really. Verifying the position of the lower sprocket and balancer would have been much easier when the engine was on the stand. I have a bad feeling that something is very wrong internally, but I need to verify the accuracy of the balancer before going any further. Hopefully, it'll be cool enough to do that today.

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Re: Issues with 4AC swap in a 1981 DLX

Post by NWMO » Thu Jul 18, 2019 11:32 am

EricK,
When I say the shaft didn't move, I mean we were sure it stayed where we put it as we guided it through. I was really concerned about the shaft rotating out of position from finagling the distributor while trying to get it to mesh, figuring it wouldn't take much for it to end up off a tooth. We found out that if we set it to the marks, lined up the shaft, kept the #1 and #4 terminals in a straight vertical line, the whole assembly would slide right in and easily mesh with the gear, at which point, whatever it does is inconsequential.
When I read
kept the #1 and #4 terminals in a straight vertical line
, it sounds like you had the distributor cap on when installing the distributor? Installing the distributor without the cap (so you can see the rotor and have it pointed to the #1 firing point on the bottom of the dist cap, which is removed)is how it should be done.

And I assume when you say it went "straight" in, you mean it went easily. When the drive gear meshes with the cam gear, the rotor will rotate 1/16th of a turn or so.

Chris
Psalm 37:4 "Delight yourself in the Lord and he will give you the desires of your heart"

In remembrance of my friend ARCHINSTL:

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Petros
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Re: Issues with 4AC swap in a 1981 DLX

Post by Petros » Thu Jul 18, 2019 9:16 pm

what??? you can not install the distributor with the cap in place, you have to position the rotor as you push the distributor down. when you do that the rotor will turn about 15 deg because of the gear helix. I still do not know what installing it "straight" means. if push it straight in, the rotor will turn (you will only see that if the cap is off).

Are you trying to install the distributor assembly with the distributor cap in place?!?!!? that will never work, unless you get very lucky.
'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)

ErickC
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Re: Issues with 4AC swap in a 1981 DLX

Post by ErickC » Fri Aug 16, 2019 2:01 pm

Installing the distributor with the cap in place is the exact procedure outlined in the FSM, and I can guarantee that it's how it was done at the factory. I've done it that way several times, and it always lands very close to 5. At any rate, it's one hundred percent irrelevant, because I have a timing light and can, indeed, verify where the spark is while the engine is cranking. It's right around 5, where it's supposed to be, and the engine won't fire with the ignition timing less than 40 to 45 degrees advanced (again, this isn't a guess, when 5 did not work, we advanced the timing tooth-for-tooth until the engine fired, and then used the timing light to measure).

At any rate, so far I have done the following:

-Verified that the timing mark on the balancer is indeed at TDC by measuring the piston height through the #1 plug hole. It is, which rules out a damaged/missing crankshaft key or damage to the balancer coating throwing the mark off. This allowed me to:
-Verifiy that the timing marks on the camshaft are where they are supposed to be with the #1 cylinder in TDC on the compression stroke. They are.
-Rebuilt the vacuum system with new hose, testing every single component for correct functioning per the FSM. Everything is correct.
-Swapped out ignition components with a car that runs well. No change.
-Swapped in a 4AC carburettor on the off chance that the jetting is significantly different enough to cause a problem. No change. This carb was out of an '86 Corolla that ran exceptionally well, but rusted beyond repair.

Anyway, as I see it, the only remaining possibility is that the camshaft was somehow modified by some modder before JIS rebuilt the engine, and is horrendously out of spec. This engine never ran correctly on the Corolla it was originally installed in, either, and now that I think of it, the mechanics who put the engine in made some comments about it wanting an absurd amount of timing advance.
timing1.JPG
timing2.JPG
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Re: Issues with 4AC swap in a 1981 DLX

Post by ErickC » Thu Aug 22, 2019 4:38 pm

TL;DR: it was the gas.

So today I decided, as a last-ditch effort, that maybe my best friend's comment that, when the engine was on the Corolla, it had no power on the low end but plenty on the high end meant that maybe the camshaft was somehow, with the alignment marks in place, retarded a tooth. So I advanced it and re-positioned the distributor accordingly. No joy. I considered that maybe the fuel was bad after all (Occam's razor applied a month late), and dumped some of the much-fresher gas my brother uses for the lawnmower in the carb. No joy. Well, I finally decided that I'd had enough, put the camshaft in its original position, then started yanking everything that stood in the way of me seeing exactly where everything was:

-I pulled the valve cover to verify the valves were opening and closing at the correct times (they were)

-I pulled the plugs and grabbed a flashlight and looked at the top of the piston to confirm TDC (yep)

Then, to test the off chance that maybe my timing light was incorrect and I somehow really did screw up the spark timing, I decided to set it manually, since it'd need to be reset to its original position anyway - I grabbed a ratchet, set the crankshaft at 5 BTDC, and set the dizzy so the rotor was right on the #1 terminal. The engine started. I thought that maybe I'd been fooled by a difference between the 3AC and 4AC matchmarks combined with a garbage timing light.

Then the engine died.

I tried starting it - we were back to square one. Then a light went off, and a voice screamed:

"HEY, DUMMY, MAYBE IT WAS THE FRESH FUEL YOU PUT IN THE CARB."

So I threw more fresh gas down the throat. It started. I ran it at high RPM for a few minutes, then let it settle down to idle. I drove it around the block. She's still not a happy bunny, but she's a much happier bunny than she was. This does, however, still leave me with the problem of sourcing a functional upper timing cover. For reasons that will become readily apparent, the 3AC one isn't going to work:
covers.JPG
So I need to find out if this is a 4AC/3AC difference, or a 4AC/4ALC difference. There's nowhere for the bolt to screw in.

Also, she really doesn't want to spool down. There's a noticeable delay. I need to determine if this is a TP problem (I kinda doubt it - this is a 4AC carb that was formerly mounted on a 4AC and functioned perfectly) or a return spring issue.
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Petros
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Re: Issues with 4AC swap in a 1981 DLX

Post by Petros » Thu Aug 22, 2019 5:39 pm

you might be able to use the 3ac front cover if you swap out the front oil pump and water pump housing bolted to the front of the engine block. that is what I did on mine and was able to use the 3ac timing belt cover.
'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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