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I took my car out today for a joy ride. On a 3rd gear pull well over 6k rpm it popped and shut down. Pretty sure the timing chain broke. I'l tear it down after the holidays. I was running the original chain, so it was kind of expected at some point.
My question. ... are the valves from iron and aluminum heads interchangeable? I'm' thinking worse case is I tear it down and swap out the valves if I bent some. Running a cc306 and 1.6rr. Obviously I'll buy a decent chain to throw back on it. But I'm going to assume that with the high lift cam I have some bent valves.
slightly off topic.... if I pull the motor back our for repair, any cheaper upgrades for a little extra security for the bottom end? Maybe some arp hardware? It's a bone stock bottom end right now. It's a extreme budget car and just trying to make it last.
First thing to do is find out what went wrong - no help to make a plan now then find out it is something totally different.
Is this a stock crank or aftermarket? On an AM crank I would expect a broken crank key or snapped off snout before a broken timing chain.
Not to be a downer, but the worse case isn't just swapping out some valves...worse case is a chunk of the valve face chipping off and getting inbetween the piston ruining the block. Can only bore out roughly .060 on these cylinders so anything more then a shallow scratch basically means new block time.
Hopefully you are correct though! Stretched or popped chain and just an intake or two bent with no other damage would be VERY lucky .
The reason I believe it has bent valves is due to the fast cranking speed. The valve train (rockers) are not moving while cranking which would not be due to a bad opti. Just put a msd cap and rotor on it last week.
I'll probably go ahead and buy a new chain set, then do a compression test and leak down test if needed. Maybe if I'm lucky the valves are ok.
But as mentioned I'll really have to tear her down first. I've been nickel and diming this car since the start. Probably time for me to just pull it all back apart and actually build the engine the right way instead of trying to hotrod 20yr old parts. Lol
The reason I believe it has bent valves is due to the fast cranking speed. The valve train (rockers) are not moving while cranking which would not be due to a bad opti.
Yeah, broken chain. These are interference engines so you will most likely have damage to the valves. It's also possible a piston or two may have taken a bad hit. I'm sure you already know this- If you do change up the valves you will have to reseat them.
Pulled the front end apart tonight. Found the broken chain. Lol. Next I think I'm going to pull the valve covers and probably the rockers. Inspect the push rods and do a leak down test on it. See how bad it is before I rip the heads off. Yes, I do know the valves will have to be seated. Thank you sir. Here's a few pictures of the tear down. I managed to not break the oil pan gasket too. The challenge will be going back on though. Lol. Notice the broken tooth on the crank gear.
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I think I'm going to switch over to an electric waterpump. Any suggestions on a good quality roller chain? Am I correct in thinking that I can run a normal sbc chain with an electric water pump?
I think I'm going to switch over to an electric waterpump. Any suggestions on a good quality roller chain? Am I correct in thinking that I can run a normal sbc chain with an electric water pump?
Correct.
Most people go with the LT4 "Extreme" roller which was crazy expensive last I knew, or the Cloyes 3145 double roller - which some have had issues with cam bolt clearance (but it bolted right on for me with no issues, YMMV). If you have an EWP a standard SBC chain will work.
Update..... pulled the valve covers to start inspecting the valve train. Found multiple bent push rods. I will do a leak down test tomorrow evening to see if any valves are not sealing. Maybe I'll get some dumb luck because I was using the stock push rods. Lol. Wouldn't' that be something. Haha
Make sure you check all the pushrod cups on those rockers if you plan to reuse them.
Those style aluminum rockers are crazy soft - I had a lifter grenade itself and the rocker arm was trashed pretty bad from it both on the valve stem side and the pushrod cup. Like you said though, if you had stock PRs they will be the weak point...
Pulled the heads last night. Looking at them, I have 6 bent exhaust valves. The pistons have some scuff marks but no real damage. Looking good to go back together
Got some new to me rockers last night and fired the car back up. I'm happy the damage that was done wasn't a costly repair. Not bad for two weeks downtown I don't think. lol. New chain, push rods, rockers, and valves.....
12-24-2017, 07:20 PM
Valves interchangeable? 
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Hope you don't have too much damage. 
