3ac engine: valve interference or not?

[Petros]

I recently came across something on a parts web site that called the 3ac engine an interference engine, but doing a search on this site shows most have found it is not. What is the risk of valve contact if the belt breaks? Is the 3a indeed a clearance engine?

Also, one of the repair guides on this site noted the front pulley bolt was 17mm, all of mine have been 19mm. Do some of the later engines have 17mm pulley bolts?

I might be buying an '85 with a broken timing belt soon.

Thanks

[splatterdog]

I really don't think so. Haven't snapped/stripped a belt yet though. Don't tell the seller....

Interference info out there is not always good. Or I've had more than a couple very lucky motorists. Better to play it safe on most cars though.

Maybe a blanket "intereference" statement is to cover ones backside?

Can't remember on the crank bolt. Did you lose your 17mm socket? haha

Sounds like you may have a good deal brewing.

[teranfirbt]

As a general rule Toyota engines with timing chains *are* interference, Toyota engines with Belts are Non-interference. There are of course exceptions.
All of my Toyota engines have had 19mm crank pulley bolts (22R-E, 3A-C, 2RZ-FE).

[Petros]

The car is in another state, and it is dirt cheap. My plan is to pick it up on my trip to drive my daughter to TX from WA in her car, fix it there and drive it back. I want to minimize the tools I bring, and I can do everything with my lightweight 3/8 drive sockets, except remove that pulley bolt, I just packed one 19mm 1/2" drive socket and the breaker bar. Doing research on this site I found member logbear listed his pulley bolt as 17mm, which is smaller than mine, and seems rather small. Could be an error, but I will throw in the 17mm 1/2" drive socket just in case there are some out there. I hope I do not need a puller, I have never needed one before.

I am going to replace the belt and the crank, and cam seal while I am at it (it is a high milage car, about 300k miles). Any other inexpensive and simple suggestions on what else to do while I have it apart? I am bringing a water pump and belt tensioner, but do not plan on replacing them unless the bearings feel bad.

Thanks

[takza]

The belt on my wagon stripped some teeth at low speed and the engine quit...new belt...no problems. With my first belt job (in cold windy weather) I actually used screwdrivers and a chisel to force the pulley off...not advisable, but the oil pump is pretty strong. Of course I was up against a heavy rib on the casting. Just treat that radiator like it's made of real thin metal...cause it is? Maybe a new top rad hose and GOOD clamps?

[Highlander]

The 3A-C is NON-Interference. I've blown 2 timing belts, one at high RPMs in the middle of passing a slow van, at night, on a two lane mountain road . No contact between the valves and the pistons- just realign it put on new belt and tensioner and away you go.

[keith]

With the stock cam, its a non interference engine. Somewhere here I posted some pictures of clay molds I made with the pistons at top dead center and the cam rotated 360 degrees. I can't find them now so I will post them again.



Photobucket is getting harder to use.

The two on the left are with the timing belt hooked up, so that is the dynamic impression. The two on teh right are with the piston TDC, no timing belt and the cam rotated 360, worse case.

[Petros]

yes, thanks. I saw that thread with those pictures when I did a search on the topic. Good research BTW, it was nice to share it with us. When changing deck height, pistons, or cam profile this is what is done with a new build-up. Too bad there is such bogus information out there for the stock engine.

[kevbriga]

Thanks for the info on the 3AC motor not being an interference motor. I am pretty new to working on cars and am currently tearing into my newly acquired 87 tercel wagon. I need to change my timing belt (worn but not broken) and noticed oil leaking around the cam and crank shafts (crankshaft seal leak is bad.) I ordered cam and crank seals. Last night I followed the FSM to get the timing belt off. I put the engine in TDC (crankshaft mark lined up with 0 mark on lower timing belt cover, and camshaft pulley hole lined up with TDC mark on camshaft bearing/seal cover). Pulled the timing belt off. To take the camshaft pulley off the FSM shows that you need to use a crescent wrench to hold the camshaft in place while spinning the camshaft pulley bolt off. On the camshaft there is a flat spot (metal point facing down in FSM picture) where the the crescent wrench holds onto. The only problem I have is that when I set my engine to TDC (while the timing belt was on) the cam is not spun in the correct orientation to allow a crescent wrench to hold the flat spots of the camshaft. To take the camshaft pulley off, keep in mind the timing belt is now off, I had to spin the camshaft about a quarter turn Clockwise to be able to put the crescent wrench on the camshaft as shown in the FSM. The FSM didn't say anything about turning the camshaft after the TDC was set originally, but it needed to be done to hold onto the cam. I figured the FSM was made for professional mechanics who don't need every step Itemized. I simply don't want to destroy my engine by doing something wrong.
Now that I successfully pulled the camshaft and replaced my seals I was wondering how to get the camshaft back to it's TDC mark. Since this engine is non-interference and I have also not moved the crankshaft, I should be able to freely spin the camshaft clockwise until the pulley matches the TDC mark on the camshaft bearing/seal cover. With the cam and crank now back at their respective TDC marks, I can put the timing belt back on a get on with life. Thanks for your posts. Couldn't of done this without them.

[Petros]

since my original posts I have actually turned the cam shaft full revolution without the belt, with the crank at TDC. No contact at all. I have worked writing service procedures before, and there is a certain amount of information that is assumed. Also, since many times the service manual is written by engineers, often recent hires, many of which have never handled tools before, the information can be just out right incorrect (I have even seen some really stupid ideas in them too, like the Tercel FSM instructing to use two screw drivers and a hammer to remove a circlip! NO!!! use circlip pliers). Do not treat them as holy writ, but only as a guide.

I know of a number of companies that intentionally write their manual or user guilds vague so they owners will bring the it back for service, or as with the case with specialized software, to you buy support and send your employees to take user classes. Crooks.

[marlinh]

I've seen both sizes of crankshaft pulley bolt head as well.

[kevbriga]

My '87 for sure has a 17mm crankshaft pulley bolt. Did my timing belt/water pump recently and 17mm it was.

[keith]

I want to add to the test that I did with the clay, I did it without a head gasket to represent the clearance if you need to shave the head a little. If you go to a high performance cam, then it can become an interference engine.