bent valves

[zneubauer]

what do you think?

s13 sr20det redtop, stock boost, fresh rebuild.

I was idling and my car shut off, not to start again, so I went to go change my front timing cover like I was going to anyways, I pull the valve cover and low and behold, the keyway to my intake cam is broken.
the cam sprocket was spinning freely.

so I replace the timing cover, oil pan, etc.
I turn it with the ratchet wrench and it turns smoothly.

I haven't pulled the spark plugs yet because I haven't been back to where my car is because of the holiday yesterday.

would it spin regularly if I would have bent my valves? would it be harder to turn it? would it make noise?

[Walperstyle]

Its is likely you have bent valves. I would pull the plugs and see if you can see the top of the cylinders, its the best way to see besides feeling inside the intake and exhaust ports.

You sound like you kinda know what you are doing.

[KiLLeR2001]

I'd pull the head off and inspect, the SR is an interference motor so the likeliness of bent valves is high.

[ka4life87]

Compression test is way to go, u can also try using vacuum gauge if engine starts, needle will fluctuate up and down as the bent valves cause vacuum loss

[jr_ss]

Borescope is your friend. I think an easy test would be to pull the cams, youll have to remove the one with busted index anyway and fill cylinders with air. If you hear air coming from exhaust or intake, you've found your problem.

[zneubauer]

well I replaced the cam, bolted everything back up to torque spec and put new oil in it. after charging the battery it started up and I held the throttle all the way up to 2500 then let it drop, going through a cycle of small revs. nothing abnormal other than my idle issue which existed before (dies after a few seconds of idling). I'm going back today to run the compression test and I'll be back here with the results but as far as I'm concerned I got really lucky because I didn't hear any clanking or clinging. when I looked down the spark plug hole I didn't see anything abnormal either.

[zneubauer]

oh and for people rebuilding their SRs, torque spec is the way to go, if they give you a range pick the upper end. cam sprockets are whatever-116 ft-lbs. loctite is your friend if you know what you're doing and if you dont plan on pulling the motor apart anytime soon.

[zneubauer]

sorry to add such a late bump but I have another mystery on my hands.

never really had time to get that compression test because a few days and a few improvements later my timing chain snapped. I was backing out of a parking space when I heard a loud pop and my car shut off. we towed it home and I opened the hood to remove the valve cover to find my chain had snapped. also more interesting is the top timing guide (the one next to the cams) was just sitting there, no bolt to be found. the tensioner still has oil pressure and my other guides are still in place.

I am making efforts now to remove the engine and find out if the head is screwed or not.

I know timing chains don't snap for no good reason. I should have replaced it when I rebuild the motor, but I didn't think too much of it because it was still in good shape.

updates are soon to follow and I have a few theories on why the chain snapped:

one, over wear. didn't look worn when I put it on and I never went above 3k because its my break-in period. so, maybe.

two, the top guide bolt could have came loose and got lodged somewhere and when I cranked the motor it snapped the chain.

three, the tensioner (idk if this could happen or not) didn't hold correct pressure, thus letting the chain off by a tooth and maybe it got crooked.

or four, I don't remember how the lower timing sprocket/collar goes but I'm pretty sure it goes in one way, and if not, I could have put it in the wrong way, creating more tension on the chain, snapping it.