Ohc journals

saturn
vue

#1

There are no locating pins or tabs on my cam journals. You remove the caps and take off cam. Than reverse process. Why does the cap have to be put back in exact location with north/south orientation? The bolts are only “alignment” to speak off. And the journals clearance holes have a lot of wiggle room. There are no bearings. I think my snowblower has the same setup.


#2

It’s common sense.

Anytime you disassemble an engine, and plan to reassemble an engine, you keep things in order so those components that were removed are put back in their exact place.

Tester


#3

The final machining is done with the caps bolted in place. If you reverse the cap, the bearing surfaces will not line up as machined and the cam will probably not turn once the bolts are torqued.

It appears that on the left side of the cap where the bolt is showing through, there is a line. There should be a line in the head that it matches up to to help keep things in order. The caps used to have a number cast into them, one on the cap and one on the casting so not only did you line up the numbers, but you kept them in the proper order.


#4

i do have the cams and journal caps arranged in order. Manual says remove all 4 cams before removing heads. The exhaust cams have to come out because the head bolts are under them. But the head bolts can be removed without taking off the intake cams.


#5

So your question is why there are no locating pins/whatever, right? I think that’s because the cam itself aligns the journal as you put it on.


#6

I’m surprised there are no bearing shells used in that design, but I guess that’s just they way they do it. Another possibility for the need to keep the orientation the same, it might well have been at the time the engine was initially assembled, the orientation didn’t matter. But now that the engine has been run for many, many hours, a wear pattern may have developed, and it has to be matched upon re-assembly or problems will ensue.


#7

This. Plus connecting rod caps and crankshaft caps also have this rule, at least on the Honda engines I’ve had apart.


#8

Many (most?) OHC and DOHC designs with alloy heads don’t have separate bearings, I think. Also true for most motorcycles, I believe.


#9

after 150k miles i would assume the journals have “slight” wear so putting the caps back on north/south may not have an effect on the cap squish. seems to me it is always clearance since you want oil to flow around the journal.


#10

Are you sure there is nothing to keep you from reversing the journal? The bolt spacing, maybe?


#11

Why would you not want to replace parts back in exact placement? Never upset a mechanical wear pattern.


#12

If the journals are not replaced in the exact location and position they were removed from it is likely that the camshaft will be seized. In fact it is unlikely that the journals would ever mate to the head. Of course if anyone wishes to give it a try please post your results.


#13

The first time I took a head off and sent it to the machine shop to be cleaned, magnafloxed and surfaced, I didn’t know enough to remove the,valves, springs rocker shaft etc and got all my (dirty parts back in a box and a suggestion the lap the valves. It was an early polyhead mopar.

No disaster resulted.

The reason I had pulled the heads was because of coolant getting in the oil and when I pulled the heads there was no obvious breach in the gaskets but the steel sandwich gaskets used by the factory had a reputation for seeping if they were over revved. That must have been the problem because more conventional gaskets worked and no more coolant in the oil.