woodmaster9

I just finished an engine overhaul. I have a new(reman) head and new pistons. I also have a new water pump, timing chain, alternator, starter, oil pump, and carburetor.

The truck is running pretty well. The problem I'm having is with setting the timing. The spec is 8-deg BTDC but I can only get about 4 before there is no more adjustment from the distributor. The range I can adjust to is a few degrees after TDC -to- 4 degrees before tdc.

I tried removing the distrib and engaging one tooth over but then my range is way off the scale on the btc side -to- about 10 degrees before tdc. In other words, I cannot get the correct setting.

I'm considering enlarging the adjustment slot on the distrib hold-down to allow just a little more adjustment range. I don't think it would take much- maybe just 1/16" or so.

This truck did not have this issue prior to the engine work. Has anyone else seen this? Is this because the head was machined? I did notice that my chain does is now a bit longer--- but wouldn't the gears still be in the same relative position?

I'm just trying to understand so that I can make an intelligent decision about how to repair or compensate.

Any ideas or opinions sure would be appreciated!

(First time engine rebuilder)

Thanks

Yopar

iTrader: (2)

That's what I would have done, jump a tooth over, but I don't know, hopefully someone can chime in. I'd say clearance the adjustment slot, but I'd like to hear why the range is off. How much did they take off the head and/or block?

woodmaster9

I don't know how much they shaved. I bought is as a "remanufactured" head.

After sleeping on it, I do think that the head work is the problem. If the crankshaft and camshaft are closer together, the tight-side of the chain will cause the two shafts to be slightly out of time. I saw this upon re-inspection. With the crank at 0 the mark, the mark on the cam is not straight up and down but is slightly advanced. This, in turn, is causing the distributor to be slightly off. If there were a way to tension both sides of the chain then this wouldn't be a problem. Another fix would be to install a head shim. I wish I had known. Had I been aware of this potential problem I would have used one but I really don't want to tear it down again right now.

I think for now I'm going to carefully enlarge the adjustment slot on the distributor. If I ever have a reason to remove the head again, I'll use a shim.

woodmaster9

Well I found the perfect solution. This will correct not only the distributor timing, but slight camshaft discrepancy as well. Even though the camshaft is only off a little and the truck runs good, it can't be "optimum" if the timing is not near perfect.

Dumb me, I didn't know these existed. Obviously I'm not the only one that has experienced this problem.

http://www.toyotacatalog.net/M1WebGe...5-B8C4EF49BB1D

xxxtreme22r

that's not gonna solve your timing issue. I have had my block shaved 10 thous almost the max you can go, I have no cam gear and I can still get full range out of the distributor. You distributor is 1 tooth off I am 95% certain.

suncomb1

You should set your timing at 30-32 degrees TOTAL timing with it all in at around 2000 RPM. You must use a timing light with the TOTAL TIMING feature (Sears). I never worry about my intial timing because it usually falls in about 10-12 degrees by using the total timing method.

woodmaster9

Well I guess that sounds good... I don't know. I've never heard of "total timing". I've been tuning cars since the 60s. I guess it must be something new. I'm old, like this truck.

I'm simply going by the Toyota Factory Service manual that says to set 8 degrees at 850rpm.... mind you this is the point at which the plug should fire on #1 cylinder..... 8 degrees before the piston hits dead top (0 degrees) and no, my distributor is not off one tooth. I tried moving it one tooth in both directions. One direction and the engine won't start. (too far retarded). The other, correct, direction moves it too far advanced.

35 degrees at 2000 rpm, huh? Well I don't know. That's not in the FSM. It seems to me that without a factory spec I wouldn't know where to start because of the centrifugal advance of the distributor has to be taken into account. You get the thing firing too soon and you can cause problems. I'll just have to set mine the way Mr. Toyota intended.

I'm quite sure that the problem is that the camshaft is slightly out of time to the crankshaft because the distance between them has been reduced by the machining. It is obvious. The CS timing mark is not 90 degrees straight up like it was on my original head, like it is supposed to be. Since the distributor gear is driven by the camshaft gear, it throws that off as well. Unfortunately it's not off enough to simply jump one tooth.

Now that I have discovered the problem, I'm also a little concerned about the cams being at a less-than-optimum setting. Not building a race truck; I just want her dependable and running like new.

Thanks!

Yopar

iTrader: (2)

If you set your timing to around 8 btdc, and then look at the timing mark when you rev it up, you will see it climb to over 30, where it will finally settle in and not move any more. This is your total timing, which Suncomb1 is saying instead of using the factory method, use the "final" timing setting of 30-32 by 2000rpm. Then the initial timing (factory spec) will just fall where it wants to at idle. It might be 8, or 9, or 12, it doesn't matter. Total timing is what matters. I like to use a light to check things, but I also like to use the "advance it till it pings and then back it off" method, driving the car and seeing how the engine feels and sounds. Factory specs get thrown out after machining anyway. Sounds like you could use that adjustable cam gear, you'll get the most out of the powerband.

Yopar

iTrader: (2)

Sometimes cams can fall into a great position, sometimes not. Degree it up and see where it's at, you can do that before you get the adjustable gear, but you will need a degree wheel, and a dial indicator w/ a magnetic base, and you will have to read how to do it several times. It's not hard, but you have to take your time to follow the math.