Ignition - 3Y vs. 4Y

[Flounder]

Hello all,
From all of the technical documentation I can find, the 3Y engine was equipped with vacuum timing advance and the 4Y with mechanical/electronic. Does anyone know if they're interchangeable?
The reason I ask is, one of the people with whom I work has an '86 4wd cargo that he wants to sell - but it's not starting. From the symptoms, it sounds like a problem with the ignition coil. He says the original owner replaced a 4Y engine with a 3Y. The engine does look like a 3Y. Tonight I examined his distributor; it looks like the ones on the 4Y engines in all of my vans (no vacuum advancer assembly on the front of the distributor). I'd like to order the right parts for his ignition and get her running.

[timsrv]

The 3y & 4y engines are interchangeable. When you swap one out I suppose you could use the ignition components from the donor vehicle, but this would create a bunch of extra work. In the case of putting a 4y into an earlier van I could see some advantage, but not when going the other way. IMO, the best way (and easiest) is to strip the donor engine down to a long block, then build back up using ignition components, sensors, etc that belong with the van you're fixing (to use the components from the donor engine would require swapping and/or modifying harnesses and ECU's). In the case of swapping engines from 84-87 into 88 - 89 (or visa versa), I would also swap intake manifolds (along with injectors).

That being said, the engine block could very well be a 3y, but all other "bolt-on" components are almost certainly from the original 4y. Not seeing the vacuum advance diaphragm there pretty much confirms this.

BTW, 4wd vans weren't introduced until the 1987 model year. If the door tag shows manufacture date of 7/86 - 6/87, then it's an 87. Tim

PS: If the body is in good condition, and you decide to pass, please pm me his information as I may want a shot at this.

[Flounder]

Thanks very much for the top-notch info, Tim! There are quite a few unused connections in the engine wiring harness. This makes me think that whoever swapped engines just transplanted almost everything off the 4Y and onto the 3Y. I'll order the 4Y ignition components. I have to stay at work tonight, so can't check the door tag for manufacture date. There must be a label plate somewhere on the engine proper, but durned if I can find it.

I'm going through much the same thing with my '88 2wd. She would crank just fine, and *almost but not quite* fire up. Just swapped out the coil, but discovered a lot of wear on the cap and rotor plus a crack on the rotor's side. She fired right up, but runs rough. (Don't think I disturbed a vacuum line, but will recheck.) Getting new cap and rotor from Heartland Toyota tomorrow afternoon (Friday).

Will let you know if I decide to pass on it. (The van is in Bremerton.) It has a few other small problems, but nothing insurmountable. Gwen is probably lurking - but I know she doesn't like cargos w/o side windows all that much, she wants more visibility...:silvervan: (Hi Gwen! Hope to see you and Jim when I'm down there!)

[timsrv]

There is a flat spot on the block close to the oil filter area.

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/Engine/IMG_2327_zpsa1f30927.jpg

The 1st 2 digits are the engine designation (for us it will say either 3Y or 4Y).

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/Engine/IMG_1798_zps98c2699e.jpg

The head has large characters cast right into it:

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/Engine/IMG_1982_zpsc7074586.jpg

[robgagnon]

I have read here and else where in these threads that Tim said that he would swap the intake manifold with all the injectors. I recently swapped a lot of 1987 components onto a 1989 engine for a 1987 van installation and I just swapped the injector rail (with new injector o-rings etc). Is there something about the manifold and/or intake plenum that is different that I failed to notice? Should I have swapped the intake manifold as well? The intake plenum and throttle body was loose in a box an there were several of them. I did not see a difference in those either.

Thanks - Rob

[timsrv]

Plenums on 84 - 85 vans have round ports (ports are square from 86-89). 88 - 89 injectors are different than the other years (although the plenums are the same as 86 - 87. You may or may not want to swap the later year plenums based on several things. Often I will opt to swap the entire plenum so as to not disturb the injectors. When injectors are removed the o-rings and insulators should be replaced. If you're purchasing these parts from Toyota that will usually take a couple of days & ~$75 to get. If you swap out the plenums as an assembly then there's no need to disturb the injectors (saves time & money). Of course there's the intake/exhaust manifold gasket when you swap plenums, but since it's common for the exhaust manifold to crack, this usually needs to be removed anyhow.

If you're pulling the injectors for cleaning, and the exhaust manifold is okay, then there's no need to swap plenums (just swap injectors). Tim

PS: Intakes from 84 - 85 can also be swapped out with the Intakes from 86 - 89, but I would try to avoid that as the ports will mismatch a bit. Not such a big deal using the intake from a 4y on a 3y head, but I would avoid going the other way (3y ports don't flow as well). I have never tried to swap halves of intake manifolds between 3y's and 4y's, but would also try to avoid that for the same reasons. Tim

[tassie2]

Hello have a 3y in an 85 hiace lwb australia. Last owner stripped head for gasket change. Parts in box. Parts include 4 thin valve spring top washers and 4 thick. The washers are ones about 1 inch diameter. Q) my repair manual doesn't comment on differences. Q) thick go on exhaust valves ? Can't find info anywhere on www.

[timsrv]

If you're talking about the washers between the springs and the head, they are shims used to adjust spring tension. When the head is assembled the pressure required to open each valve is tested. If/when a spring tension is too low a shim is added to increase tension. There are several thicknesses available so each spring can be dialed in. If the shims have been removed and not kept in order, then tension will need to be tested to be sure all valve springs are within their specified range. On the 3Y/4Y, all springs (intake and exhaust) should allow the valve to open with a range of 63.5 - 78.7 lbs of force. Tim

[tassie2]

Thanks for information. Couldn't find it anywhere in manual or www. We assembled head using logic that all 4 exhaust valves would need more tension. Van seems to be running OK. Q) you would test static with head off? Or instead on motor? With a weight gauge ? The washer sets were 4 of one type 4 of other. They sit at top of springs . Differerence is slot maybe 3mm between the 2 sets.May have random valve settings it seems. . Nick Oz.

[timsrv]

They have special tools for this: https://www.youtube.com/watch?v=Jms_3aJfaLU, but I have always improvised in other ways. I documented it in my blogs the last time I did it: https://www.toyotavantech.com/forum/entry.php?38-4yec-Engine-Rebuild-part-2. If you scroll about 3/4 of the way down the page you'll find the spot where I talk about this.

It's been a while since I did this, but I don't think there should be any washers or shims between the top of the springs and the spring retainers. If we're talking about the same thing, the shims should sit between the aluminum head and the bottom of the spring. Tim