3.4 DOHC timing belt change -short cut method

[freecanadian]

Hi Folks,

 

I have been a member of this forum for about 6 weeks, since I bought a nice 92 Lumina Z34. I had to change the Timing Belt since it was shredded on one side but was still running fine. I had bought all of the parts to do the full job as described in the excellent articles on this site, but as I thought about it, I decided to try a short cut.

 

It didn't make sense to me that I would have to pull both valve covers, the upper plenum, and related stuff just to change the belt, so I took off the serpentine belt and timing covers to see if I could see the timing marks on the 4 cam sprockets and the lower drive cog. I cleaned them up (lots of shredded belt material down there -used a small paint brush) and found the timing marks (paint on the 5 cogs). I slowly rotated the engine clockwise with a breaker bar on the lower crank pulley until the timing marks were lined up (cam timing cogs had the timing marks lined up at their closest point, as shown in the articles on this site; both sets, front cams and rear cams timing marks lined up the same) and the lower drive cog had its timing mark pointing straight down (6 o'clock position). This told me that the belt was in the correct position, so I carefully marked its tooth position on both the front and rear cam cogs and on the belt itself with a white grease pen. Then, I used mini vise grips to clamp the cam cogs together at their cloisest point with the timing marks lined up so that they would not move when I took off the belt. I left the drive gear free to move after I noted its timing mark location. Then I took off the timing belt.

 

I laid out the old belt (which now had two marks that lined up with the marks I had made on the teeth of the front and rear cam cogs) and stacked the new belt on top of it so I could transfer the marks over to the new belt and match these marks on the new belt with the marks on the teeth of the front and rear cam cogs. I installed the 2 new plastic pulleys, tensioner pulley, and its actuator, and then the new belt. I installed new belt tightly between the two sets of cam cogs (making sure my marks on the new belt and the cam cogs lined up on the correct teeth) and the upper plastic pulley, and then used more mini vise grips to gently clamp it there.

 

NOTE, I used GM parts, but I found that the 2 new plastic pulleys had sharp casting lines on them which might damage the belt, so I used a file to smooth them out. I bought the parts in America on a recent vacation, since they were about 1/2 the price of what local suppliers wanted for them.

 

Next, I took out the slack between the front cam cogs and the drive cog (working slowly and carefully, because the drive cog is a very tight fit into the aluminum front cover between the 8 and 6 O'clock positions to feed the belt onto the cog). I had to turn the crank shaft slightly to move the timing mark from the 6 o'clock position towards the 5 o'clock position in order to engage the proper tooth on the drive cog, then turn it back and check its timing position once slack was just taken out between front cam cogs and drive cog. It took 3 times to get this part correct, but then it was on to the final part, which was to feed the belt onto the tensioner pulley, check that the actuator arm was seated in the tensioner slot, and then remove the little clip (paper clip) to activate the tensioner and take up the slack from the last loose part of the belt between the rear cam cogs and the drive cog.

 

After removing all 5 vise grips (3 holding the belt in place, and 2 holding front and rear cam cogs together with their timing marks lined up), I slowly rotated the motor 3 complete rotations, with breaker bar on the crankshaft bolt, and confirmed that the timing marks were still correct. Then, I reconnected the battery and started it to make sure it ran ( I left the power steering lines disconnected and tied out of the way, since the serpentine belt was not yet installed), which it did!!

 

I then reassembled everything and now I am driving it.

 

This allowed me to do the job in half of the time, and I only had to disconnect the battery, remove the radiator overflow reservior, serpentine belt and tensioner, timing covers, power steering lines, and the cam belt and related parts that I replaced. I did not have to drain coolant, remove upper plenum, remove valve covers and spark plugs, nor did I have to mess with clamping cam flats or changing cam timing (which saved me the cost of tools that are used for those parts of the job). I kept all of the gaskets I bought to do the long version of timing belt change, since I can use them when something else calls for these parts (plenum and valve covers) to be removed.

 

I realize that this would only work on a car where the cam timing is OK, but I figured that if it was running good (which mine was), then the cam timing must be fine. I suppose that this procedure probably wouldn't help if your timing belt had broken, or maybe was extremely stretched, since you would probably not be able to rotate two cams at the same time into proper alignment and clamp them there. I had not seen a description of this short cut procedure to change the timing belt, so I thought others might appreciate it. (sorry, but I didn't take pictures)

 

Keith.

(Vancouver, B.C. Canada)

 

[slick]

Obviously, as you pointed out, this will not work for everyone. But, this will work for people that have done there timing belts before and marked the correct location.

 

Now, assuming that your belt had not been changed before, you would have had to pull everything apart to see the cam flats.

[Psych0matt]

mine has the factory timing marks. Ive redone it three times in the past week and a half. I can now do a T-belt in about two hours (less if I can get the stupid actuator quicker )

[Schurkey]

Freecanadian--Bless you for posting the shortcut method.

 

I used it last week; worked great. (My big mistake: Forgot to re-install the stupid rubber plug in the tensioner after I pulled the paper clip out. Now I get to pull the plastic off again...)

 

I did not need to clamp the timing gears together; or clamp the belt to the pulleys--no vice grips used. I used no cam holding tools at all. The retainer clip for the power steering tubes was disconnected from near the alternator for clearance, but the p/s was not disconnected anywhere else.

 

The timing belt kit came from the local NAPA (p/n NBH2521920) and cost $185 with tax. List price is $187 on napaonline.com The kit included three pulleys and a belt.

[1990lumina]

Wow, old thread

[Psych0matt]

Wow, old thread

 

I was gonna post in it, but then I realized I already had

[Heza]

this was a great read because i had considering using a vice grips on my cam cogs for the timing belt change like god knows how many people do on other OHC engines. but, since im doing my timing belt in a month or so...i havent had the opportunity. good to know it works out fine though!

[Psych0matt]

Apparently, though, when I did my engine swap, something is different slightly with the 94 cams on the 96 engine, either that or it got somehow messed up when the tensioner blew up, because IIRC (which i might not) after I put the engine back together and timed it out of the car, and it went it, it seemed right, but that was also after not driving it for 9 months. anyways, the tensioner went, and long story short I timed it ilke 5 times and couldnt get it, so i took it in and paid the 500$. I guess after 7 timing jobs, 500$ isnt so bad