Misaligned crankshaft with camshafts


#1

94 Mazda 626 either ES or LX, with the 2.5L KL-DE v6 side-mounted engine. From what everyone tells me it is not an interference type. Timing belt was locked into place due to jumping off alignment and chewing into plastic timing belt cover. As a result the crankshaft has been rotated independently of the camshafts. I am now attempting to realign them before installing the new belt, with no belt on mind you. My questions are these.

If the crankshaft is on the wrong stroke, exhaust I believe?, then will that cause extra pressure when attempting to rotate the camshafts?

Should the built pressure in rotating the camshafts be so great that I require more than a ratchet to rotate it? They are currently spinning back into position when released and I am told that is the valve spring pressure. I have a couple solutions for keeping the cams locked once aligned but currently they do not want to rotate more than a quarter-to-half turn before the pressure makes me think I need a breaker bar or may bend a valve.

Valve cover removed so I can manually turn the camshafts by the square built into the camshaft about 1/3 in, told this would avoid snapping anything as I force past the pressure, as opposed to using the camshaft pulley bolt.

Either I fix this car myself or it goes to the scrap yard so it is definitely a DIY.


#2

Do you have a service manual for the car? It will explain the procedure in detail…

You set the crankshaft to TDC, there is no “wrong stroke”.

Yes, overcoming valve spring pressure may require more than a ratchet.

Good advise about NOT using the pulley bolt…

Check timing mark alignment twice before buttoning it up…


#3

I have a hayne’s repair manual which as I’m sure you know can be a little lacking in explanation or details. However, it does state there is more than one TDC stroke. “…Each piston reaches TDC on the compression stroke and again on the exhaust stroke, but TDC generally refers to piston position on the compression stroke.”

It also instructs to rotate the crankshaft 360 degrees to change the stroke from exhaust to compression for TDC #1. Not that I know whether or not it’s on the proper stroke since the rotor position that would tell me is unlinked.

I really appreciate the advice and quick response but it seems like you might not know the specifics that I need.

My main problem is getting front and rear camshafts to rotate properly. If I force it I’m concerned I will bend a valve. Will changing stroke on the crankshaft, or moving it incrementally, allow me to rotate the camshafts further? I.e. go through each stroke for each piston until the camshaft timing markings align. Remember belt is already removed. If that isn’t the case it seems I must simply force the camshafts to move past the spring resistance.


#4

As Caddyman said, there is not ‘wrong stroke’. The crankshaft turns two times for every one turn of the camshafts. However, both camshafts need to be lined up with the timing marks as well as the crankshaft turned to TDC before you install the belt to keep everything lined up correctly. My belt guide also shows this not to be an interference engine, so the cam shafts and crankshafts can be turned independently without causing damage. No need to worry about valves crashing into pistons. Just get them lined up is the most important thing.

I’d highly recommend replacing the tensioner pulley and any idler pulleys associated with the timing belt since the timing belt jumped off. Weak tension can cause the belt to get sloppy, wander around and jump time. Since you’re doing this much work, it would be a shame if bad pulleys are the root cause and you re-use them.

Once you have the new belt on, rotate the crankshaft twice by hand (with a wrench, of course) and re-check that the timing marks on the camshafts line up properly when the crankshaft is back to TDC. (Remember, twice around).

If the tension is still good, go ahead and button it up.


#5

Turning the crankshaft 360 degrees only makes a difference when there is a timing belt properly installed…It is the camshaft position that determines whether it’s on the exhaust stroke or compression stroke…In a non-interference engine, the valves will not hit the pistons by simply turning the cams to line up the timing marks…The Gates timing belt online guide identifies interference engines with an Astrix (*) if you have doubts…

In an interference engine, you must loosen the cams so they can be rotated without hitting the pistons against the valves…


#6

When the belt is off, there is no defined stroke. A stroke is defined by the direction of movement of the crankshaft in relation to the position of the valves. Since the valves are not being actuated because the belt has been removed, the stroke is not defined.

You can remove the spark plugs, that will make rotating the crankshaft pretty easy. Alight the timing mark to TDC. Now when you align the camshafts according to the manual, that will then define the TDC of #1 cylinder as the TDC of the compression stroke.


#7

Wow, three posts all composed at the same time, saying the same thing.


#8

My apologies to Caddyman then, is the wrong stroke the manual talks about at the camshaft end then? (yes it is, thank you keith) I have looked over multiple sets of instructions and feel confident the timing markings will do the trick. So, if my engine is not interference type, and the crankshaft is at TDC, then do I simply force the camshaft to rotate to the proper alignment and then clamp it down so it doesn’t spin back? I have to tell you that spring tension is pretty intense. I can only turn it halfway to where I need it before it feels unmovable, though that was when using the crankshaft pulley bolt with a ratchet, and I backed off that pressure. I had the spark plugs removed already, and thank you three for the tips.


#9

Hopefully, when the cams are in the correct position, there will be no spring pressure on the cams…If the cams want to turn, you will have to hold them in position (a helper) while you slip the belt on…


#10

The pressure confuses me a little, but then I really don’t know how the whole engine works. I would think that valve would start to close and the next one open as it moves through the rotation but at no point did that pressure weaken so it hardly seems like a cycle. Will be using two open wrenches and a clamp to hold the cams in place I think, though I’ve heard a bolt or drill bit in a specific area will also lock the cams.


#11

By the way I just wanted to say thank you. Between the three of you I received better information and my questions were addressed directly within what, an hour, on this forum than in days working with others. I really understand all the other steps I have to take, just was deathly afraid when I started rotating the cams and they didn’t want to go. No one would say for certain, ‘yes, force it’, though they claimed the pressure was perfectly normal.


#12

I would suggest at this point in time that you start with the crankshaft at 30° before top dead center and set the cams. At this point, there will be plenty of clearance for valve in every cylinder. When the cams are in position, then rotate the crankshaft to TDC and install the belt.


#13

Ooh, thank you, that is a tip no one else had for me. That even sounds like it may help with the pressure somewhat. Assuming the clearance for the valves or lack there of was increasing the pressure.


#14

If it’s non interference, backing off the crankshaft may “feel good” but will likely have little impact on the cam tension you’re feeling.

I think this is a quad cam motor - two cams per head - so you should use caution not to bang the valves into each other. If I’m mistaken (1 cam per head), ignore this paragraph.

Chase


#15

I do have a quick question, is this engine completely stock? Just want to make sure that no one has put high performance cams in it. The reason I ask is that most of the time, the cams are not that hard to turn unless someone has put in a high performance cam kit with heavy duty valve springs.


#16

This is a quad cam, two camshafts in front and two in back. How might I watch for and avoid the valves colliding? Considering the two camshafts in each block are seated against each other with interlinked teeth wheels then I’m wondering how it would move in a way it ought not to… ? A shame about the crankshaft not being overly helpful, but could always use a little ‘feel good’ in this project. The engine should be completely stock, though it was owned by a federal agency at one point and the back license plate is wired to the alarm. Somehow I doubt they spruced it up.
The camshafts themselves match the pictures in my repair manual as far as I can tell so most likely stock.


#17

Sorry, I didn’t realized they were geared together. They will just turn together so you won’t have to worry about them hitting each other. Just wasted your time and mine. Oh, well…better safe than sorry. I’ve seen both designs.

Telling the stock cams from street cams may be difficult, unless you can get a micrometer in there and measure them, then compare to the manual. You can look closely for a manufacturer’s stamp that identifies them as other than Mazda, but there may not be one. I was thinking with Keith’s post that the springs would be the problem. You really shouldn’t have any trouble turning them over with the right tool.

If you haven’t yet, you might want to pop the front valve cover off and make sure nothing untoward has been visibly damaged.

Unless that government agency was into chasing drug runners, you’re probably right…very little (if any) mods were put into it.

The difficulty moving the cams may be indicative of more damage, and may also be why the belt broke. With a regular 1/2" ratchet (about 10" long or so), you should be able to turn the cams without really all that much pressure (I’m having a hard time describing “how much” is “too much”). They should turn in little sequences as they compress and release each spring, and then they’ll “pop” into the next resting place. One of those places will be TDC, or very close to it.

Chase


#18

It is unlikely that something would happen to both heads at the same time. If the cams on one head are hard to turn, then they should be equally hard to turn on the other head.


#19

Keith’s advise was correct…With the crank set at 30 degrees before or after TDC, NONE of the pistons will be in reach of the valves…The Gates Belt Guide lists it as being non-interference, so they should not have any mechanical issues period…The camshafts will resist turning, but they should turn smoothly using a 12 or 14 " wrench on that square lobe you mentioned…

All this assumes that there is not another issue involved here, like the engine dropped (broke) a valve or something large and hard was sucked into the engine while it was running…Are the cams on both heads equally difficult to turn??


#20

I think we’re going to assume the camshafts and springs are stock, though I will check it over later today for said manufacturer’s stamp just in case. Front valve cover is already off and nothing inside looks damaged or out of place, will preform a better inspection when I check for stamp.

Belt didn’t break, it fell off alignment due to a idler pulley bolt breaking and the idler pulley basically loosening the tension and allowing the belt to chew into the plastic covering. It never snapped and looks in decent shape, except where it dug through the cover. Replacing it regardless. Started the car, backed up a little and it happened.

I have to acquire a 27mm wrench for the camshaft hex portions, as per my repair manual’s tip. Hopefully later today I’ll be going about rotating those camshafts. The difficulty in pressure was when I used a 1/2" ratchet on the camshaft pulley bolt, but didn’t force it further. Am hoping the pressure will be less on the hex portion itself, and a couple folks on other forums insisted this was normal pressure and I just have to ‘deal with it’. Best part is getting 4x27mm wrenches so I can lock those quad cams in TDC #1 position with c-clamps (since they want to spin backwards). Why can’t all camshafts have those nifty holes to drop a drill bit into? Bastards.

The front set dual camshafts and the back set of dual camshafts were equally difficult to rotate via ratchet on their respective pulley bolts. At first they turned a little bit but then built pressure up fast. The way most people explain how to do this step, it seems excessive.

Later today I will try a 27mm on the hex portion of the camshaft and see if I get some satisfactory rotation, but not before I check back here of course. If it works it’ll be off the air-intake and rear valve cover to repeat. Thanks for taking the time fellas.