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Bend valves w/starter?

B

Bricktothefuture

Member
Joined
Aug 11, 2015
Location
Central NH
Ok - as you may have seen I've got the car running. B21F, k-jet, had .040 off the head, rebuilt engine and head, put in an RSI Stage 2 n/a camshaft. One of the last I believe.

Block was tight, apparently during one of my first few attempts to get her going the camshaft jumped 10 or so teeth. Kept trying a few times before I realized it. I know these camshafts can push things towards the interference side - do I need to worry about bent valves, or is that something that only happens when your t-belt fails at high revs? I'll add a video of the idle soon.
 
Right, but I've read on here and elsewhere that some of the more aggressive cams can turn these into interference engines. Not sure if I'm being paranoid...
 
Bricktothefuture said:
Ok - as you may have seen I've got the car running. B21F, k-jet, had .040 off the head, rebuilt engine and head, put in an RSI Stage 2 n/a camshaft. One of the last I believe.

Block was tight, apparently during one of my first few attempts to get her going the camshaft jumped 10 or so teeth. Kept trying a few times before I realized it. I know these camshafts can push things towards the interference side - do I need to worry about bent valves, or is that something that only happens when your t-belt fails at high revs? I'll add a video of the idle soon.
Click to expand...


I'll give you the best tip on cars EVAR!!
Always think simplest thing first..Cheapest thing second.. And you can always escalate as you gather more evidence.

It started and ran?
You didn't bend any valves.
 
What's your piston protrusion and head gasket thickness? If the valves at max lift extend out of the head more than the head gasket thickness minus the piston protrusion, then the engine is interference. [The valves in my cleaned up, but not shaved, 530 head, with a T cam, were about flush with the head surface at max lift -- say within +/- 0.003".]

Beyond this, to bend a valve, you need to have max valve lift at TDC. Normally, the valve is opening or closing at TDC and is not at max lift. If the belt breaks, then the cam is most likely going to settle in a position between lobes so again, not max lift. If the timing belt is way off, then yeah, an interference engine might hit the valves.

If you're worried, try a compression check. (I don't know if you can borrow a tester from your local auto parts store.)

Edit: when you say the block was tight, what do you mean? Could you turn the aux/intermediate shaft by hand? Could you turn the cam with a short ratchet? Could you turn the crank with a normal ratchet?
 
As a quick shade tree compression check (as good as it needs to be for this situation) disable the ignition by pulling a coil wire (or unplug the injectors so they don't squirt, probably a better idea).

Then just crank the motor around and around for a little bit, and listen to how the starter labors over each compression 'lump'. It should sound pretty even if there are no issues. If you have a bent valve, or some other compression leak, it will almost always be in only one or two cylinders. Only very generalized wear will be even across all 4.

So if they all sound even, stop worrying. If you hear some sort of syncopated off kilter pattern like whir-whir-whir-whee-whir-whir-whir-whee then you've got issues that require some more sophisticated diagnostics.
 
Probably incorrectly installed belt or loose belt. I learned a long time ago never to rely on just the spring to tension the belt. I always smack the tensioner with a hammer to make the belt tight, but not too tight.

And I agree that a leak down teat would be more conclusive. It would tell you how well everything is sealing in your rebuilt engine, but don't over analyze the results. If run well, don't trip.
 
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