What are the chances that I bent my valves?

[kane66]

I was doing a engine swap this weekend and bent the tension pulley on the timing belt. I replaced the pulley, and thought that I was being careful not to change the timing. Well I wasn't being careful enough and sure enough when I turned over the engine I heard the unmistakable sound of pistons hitting valves.  :oops:. I then spent the 15 minutes or so timing the engine, like I should have to begin with and turned the engine to look for binding then fired her up.

It runs rough, will drive a little but dies intermittently. and overheats very fast (this was a good running engine before I started). I wasn't able to check pump timing perfectly as I left the tool at home. But I'm wondering if this sounds like bent valve issues. Or may be I was tired when I timed it and the timings way off. Anyway any help would be appreciated, I'll be going back to work on it next weekend and need some feedback on what might be wrong.

[Vincent Waldon]

If you're not sure you got the timing correct it's worth having another pass at just in case, but in general if you heard the clunk, and the starter was driving the engine at the time, then you pretty much need to pull the head and find out how many valves you're buying. :cry:

[arb]

Vince said it well. If you're lucky, you only bent one valve. After you recheck the timing, put a wrench on the crank bolt and turn it over by hand. Mark TDC at this end of the engine and notice if all 4 compression strokes are the same. If one more does not have the same force, your valve is bent and not sealing. You could also be more scientific and do a real compression test, but I think the manual process will tell you enough.

[jtanguay]

i heard of guys busting timing belts while at low speed, and just putting a new belt on with everything lined up and it ran good.  they must be lucky or something...

i guess the problem with the starter is that it gives some good torque   damn those electric motors and their full torque at >0 rpm!

moral of the story is to always turn over the engine by hand before going at it with the starter.

[kane66]

I know I should have turned it over first, I've done it every other time, but I guess it just takes once, lesson learned. Would a bent valve be whats causing it to overheat.I figured a bent valve would just cause a dead cell. Like I said I have a week to come up with every reason for why it wont run before I will have a chance to work on it again.

[jtanguay]

I know I should have turned it over first, I've done it every other time, but I guess it just takes once, lesson learned. Would a bent valve be whats causing it to overheat.I figured a bent valve would just cause a dead cell. Like I said I have a week to come up with every reason for why it wont run before I will have a chance to work on it again.

you're right.  the compression should be significantly lower on the bad cylinder if you've bent the valve enough.  like i said though some people are just lucky.  say for example the piston is right at the bottom, and has enough momentum from the starter to slam upwards then the chances of a bent valve are greater.  but if the piston is already halfway or more up there, then the chances are lower (but there can be even slightly bent valves which still work alright... i guess they just wear out the valve guides a bit quicker?)

do you know any of the history of the engine you swapped in? did you check/replace the t-stat and inspect the water pump? its best to check the obvious first though.  clean the grounds/contacts for the temp gauge wiring, and then confirm the rad is kicking on (i like my princess auto infrared thermometer to check the temps ), and then once all that is done, the dreaded t-stat change while hopefully not getting coolant in the face   don't forget that you need to 'burp' the cooling system if you haven't already done so.  i just let mine run up to temp without the rad cap on while revving it a bit.  a few minutes while up to temp should be enough to get the air out.  you need to rev it too to get it flowing to push the air through.  

i personally recommend coolant flushing as well.  others may disagree, but IMO the heat transfer between bare metal to rusted/mineralized metal is much greater  :wink:.  i used prestone heavy duty flush.  i had very good results when i did it to my car.  the stuff that came out was this rusty brown colour!  down right nasty!!!  :lol:

[kane66]

The engine was good. I drove it up to Portland (100 miles) before I did the swap. So I know it was running fine. I didn't "burp" it though. I'll have to give that a try when I get back up there. And I'll keep my fingers crossed about the valves. Who knows  I might have gotten lucky. And if not I have another head (on the engine I pulled) that I can swap if I need to.

Another quick question how do I tell the dif. between an hydro head an a mech. I know the engine I pulled is hydro but the engine I put in is of indeterminate year. I'm hoping that, worst case scenario I will be able to just do a quick swap and have it running.

[burn_your_money]

Look behind the pump for a bulge in the head/block. If it's there it's hydro. You can compare it to the old engine.