checking for bent valves?

[madbim]

I took a chance on a motor, pulled it apart tonight and found a broken timing belt and 2 broken rockers the #2 and #6 intake. Pulled the head, no visible damage to the pistons or the head\valves. What is the best way to check for bent valves?

[TobyB]

flip it over and pour water into the chambers. Your leakers are prolly bent.

Quick, dirty, and about 95% accurate.

t

[madbim]

flip it over and pour water into the chambers. Your leakers are prolly bent.

Quick, dirty, and about 95% accurate.

t

I would have to turn the cam to TDC for each cylinder correct? Or can I loosen the rockers enough so I can test then all at once?

[TobyB]

Yeah, you're right, you'll have to turn the cam. Otherwise, you'll find 10 bent valves, at least! heh...

t

[Slicktop_serg]

just went thru this and the only way to tell if they are bent is to take them to a machine shop and get them inspected. Luckily the machine shop i go to was kind enough to inspect for free

[ahlem]

If you have the valves out, you can put a turn of duct tape or a chunk of nylon hose over the stem and chuck them into a drill press without severely torqueing them down and spin them. You can also roll them on a good hard surface and watch for wobble.

[madbim]

Thanks guys, should have time to tear the head down this week.

Sent from my XT1060 using Tapatalk

[TobyB]

...or mark the valve with blue dye (or a black sharpie) and spin it in the seat, as if you were lapping it.

If it's bent enough to matter, it will only shine up on one spot, but if it seals, it'll shine up all the way around.

t

[madbim]

Got the head on my bench, its obvious all 6 exhaust valves are bent. Oddly the intake valves appear ok to the naked eye, which is surprising because I had 2 broken rocker arms on the intake side. Is it typical the intake valves survive a broken timing belt?

[Cabriolet]

found a broken timing belt and 2 broken rockers the #2 and #6 intake. What is the best way to check for bent valves?

the valves are bent! period. you will need to have them replaced and the guides as well.

don't waste time checking it's a given with an m20.

[ahlem]

I've seen a number of timing belt failures and all of them had broken castings on the cylinder head. You may want that checked out before you start doing other things.

[ForcedFirebird]

I've seen a number of timing belt failures and all of them had broken castings on the cylinder head. You may want that checked out before you start doing other things.

Yup, the rocker arm bosses break off at the top.

I have never seen all the valves survive a timing belt failure.

One head I opened had all 12 valves bent, 6 broken rockers, bent rocker shaft and the valves bent so bad they knocked out the guides!

[TobyB]

Yup, the rocker arm bosses break off at the top.

Rocker SHAFT bosses, right? I took one apart that had done that- and the rockers
were intact. Shafts unbent (????)
Go figure.

t

[madbim]

Rocker SHAFT bosses, right? I took one apart that had done that- and the rockers
were intact. Shafts unbent (????)
Go figure.

t

This is the part of the casting the rocker shaft slides though? Will it be obvious or does the shaft have to be removed to find this out?

[ForcedFirebird]

Rocker SHAFT bosses, right? I took one apart that had done that- and the rockers
were intact. Shafts unbent (????)
Go figure.

t

Correct, the shaft bosses :/

No matter how you slice it, failed timing belt means lots of replacement parts.