loud snap after motor swap

[evil tsi]

i just swapped a 2.0 out for the 2.3l i was having issues with. the engine is a stock longlblock with hks 264/272s. it still has balance shafts and all.

the engine ran for about 5 seconds, made a very loud snap( like shooting a .22) and died instantly. the only thing i could see that was out of place was that the timing belt was VERY tight. i attempted to crank it over again, the weird thing is the power steering belt and alt belt were the only belts that would spin. absolutely no movement from the timing belt. I pulled the timing belt and valve cover, then pulled the cams and rotated the crank. it spun freely, so i think it was valves snapping.

i took the head off my other motor and took it to the machine shop to be decked and pressure tested.

I am really stumped as to what would have caused it? the timing marks were dead on and I spun the motor and they all lined back up? Any ideas

 

[BogusSVO]

Check the woodruff key in the crank snout, it indexes the crank gear for the timing belt

 

[stuckwithgsx]

You said you took the timing belt off. What does it look like?

Did you pull the spark plugs and check for any chunks of anything on the piston tops?

Was it a metal snap sound or a backfire type sound?

Was one or both of your cams 180 off?

 

[evil tsi]

i cant get the gear off... even with a 800ft/lb impact... i didnt build the motor, it was one i had just picked up. i did verify that it was at true tdc. If im able to get the crank gear off, what would i be looking for? a snapped or missing woodruff key?

 

[bryanwheat]

So does the engine turn over without the head on it? Did the cams turn fine?

 

[evil tsi]

You said you took the timing belt off. What does it look like?

Did you pull the spark plugs and check for any chunks of anything on the piston tops?

Was it a metal snap sound or a backfire type sound?

Was one or both of your cams 180 off?

it was a brand new oem belt

i pulled all 4 plugs and nothing wrong with the plugs, i didnt look down the cylinders though

it was a metal snap and both cam dowels were straight up and ALL of my marks lined up, thats why im at a loss

I also reinstalled the cams and the exhaust cam when i attempted to rotate it(as if putting the timing belt on) and the cam didnt rebound like it normally would, it just stuck where ever i left it

So does the engine turn over without the head on it? Did the cams turn fine?

with the cams out, the bottom end turns fine

 

[stuckwithgsx]

Do you have any way to perform a leak down test?

There's an unsafe way to get the crank bolt out. That is using a breaker bar and then bumping the starter. If you're not sure of how that would work, or if that doesn't sound like something you want to try then please don't!!

I had an old engine that someone had literally welded the timing gear to the snout of the crank. Using the pulley mark was useless and I am glad I checked tdc before everything.

So did you time your engine with cyl #1 at tdc or did you use the harmonic balancer and the mark on the timing cover?

If ALL of the marks lined up then you would also be including the one on the oil pump. If you can't get the harmonic balancer off then I presume you're not including that mark right?

Do you know how long this longblock sat before you turned it over? If it sat for a while then it may have been the balance shaft belt snapping off?

I'm also guessing that there is no lower timing cover on at all? Since you did get the timing belt off without getting the crank bolt out correct?

 

[evil tsi]

Do you have any way to perform a leak down test?

There's an unsafe way to get the crank bolt out. That is using a breaker bar and then bumping the starter. If you're not sure of how that would work, or if that doesn't sound like something you want to try then please don't!!

I had an old engine that someone had literally welded the timing gear to the snout of the crank. Using the pulley mark was useless and I am glad I checked tdc before everything.

So did you time your engine with cyl #1 at tdc or did you use the harmonic balancer and the mark on the timing cover?

If ALL of the marks lined up then you would also be including the one on the oil pump. If you can't get the harmonic balancer off then I presume you're not including that mark right?

Do you know how long this longblock sat before you turned it over? If it sat for a while then it may have been the balance shaft belt snapping off?

I'm also guessing that there is no lower timing cover on at all? Since you did get the timing belt off without getting the crank bolt out correct?

When I picked the motor up it was still in the car and got to hear it run and all that. The guy pulled the motor in front of me also.

I verified true tdc by using a screwdriver down number 1 cylinder after being off at the crank on my last motor.

And I pulled the lower timing cover and the balance shaft belt is good...

Im starting to think more and more its the woodruff key so ill try the starter method, as long as it doesn't trash the starter or take teeth off the flywheel

 

[XiKeiyaZI]

The starter method is unsafe but works, from personal experience. The key is the only thing that really stands out as being the true culprit here. What troubles me is you say there's not resistance in the cams? Like, they don't want to rotate a specific direction when you manually turn them?

 

[bryanwheat]

How is the starter method unsafe? I've done it 100+ times on many different cars and have yet to damage anything.

 

[greengoblin]

How is the starter method unsafe? I've done it 100+ times on many different cars and have yet to damage anything.

It can be unsafe to the person if they don't know what the hell they are doing.