Locked up DOHC 3.4

[BumpRacerX.com]

Spinning the dohc backwards is a bad idea because it allows the timing belt tensioner to take tension off the belt and could throw the cam timing off....but that sounds like the least of your issues.

Did I just read that your motor locked solid at 6500 rpm?! It went from 6500 rpm to 0 in the blink of an eye? I'm going to guess broken rod.

Since the DOHC doesn't have rocker arms or pushrods there isn't too much in the top end to make noise. It is pretty much limited to collapsed lifters (which make tap like sounds not knocks) or bent valves. If its knocking, running on 5 and locked solid at high rpm I think the bottom end is trashed.

Yes sir, you read correctly.

I've never had the DOHC apart, so I'm not 100% familiar with the top end layout. If I'm understanding you correctly, it's pretty unlikely that something broke in the top end and dropped down into the cylinders.

Let's run with the bottom end being trashed for a minute. I'll have to dig out the books, but is it possible to swap out the crank assembly complete w/pistons and rods without removing the engine? I've got two parts engines in the yard that I can steal/build an assembly from.

I'll try to get a video tonight so that you guys can hear what the knock sounds like.

[jmgtp]

I wouldn't attempt to swap out the bottom end without pulling the engine. You can't even get the oil pan off in a W car because the subframe is in the way (well maybe you can but its not worth the trouble to do it that way). Plus, if the bottom end suffered that catostrophic of a failure I wouldnt trust that the block came out unscathed. Pulling the engine out isnt that hard if you have the right tools for the job. I had mine out with trans attached relatively quickly, a load leveler on your hoist is very beneficial.

If it is determined that the bottom end is no good and you have spare engine lying around I would take the easy way out and install one of the spare motors rather than try to swap internals from one to another.

But, before you go ripping the bottom end out. Pull off the timing belt covers and get a good look at the belt. I had a belt fail at around 3500 rpm because the tensioner broke (normal driving) and from the point of failure to the engine completely not running was maybe 3 seconds. During that time the engine made some funky clunks and sounds and then died. I was lucky and none of the valves kissed the pistons, new timing parts and I was good to go. Unfortuneately, I dont think this is your problem considering your engine didnt "spin down," rather it just siezed up but it is worth a look before going any further. You can remove the plastic covers to see the belt, pullies and tensioner. You can even start it up as such and watch everything in motion. Like I said, I don't think this is your problem but it isn't much time investment to inspect.

edit: and wow! Not to be un-sympathetic to your situation, but a lockup at 6500, man I wish I was there for that! Is your car a 5spd by chance? I could see that being big trouble locking the front wheels up instantly!

[BumpRacerX.com]

I was a pretty sudden stop, even on the slick surface I was on. I bruised pretty good where my 5 point cut into my shoulders, but ultimately it kept me out of the steering wheel, so it's all good.

Didn't get to play with it at all today. Pretty sure I'm just gonna drop another long block in and then put this one on the stand and tear it down.

I'm working on getting ahold of some video. Normally my wife tapes everything, but didn't go to the races with me on this trip due to the cold.

[pocket-rocket]

I wouldn't attempt to swap out the bottom end without pulling the engine. You can't even get the oil pan off in a W car because the subframe is in the way (well maybe you can but its not worth the trouble to do it that way). Plus, if the bottom end suffered that catostrophic of a failure I wouldnt trust that the block came out unscathed. Pulling the engine out isnt that hard if you have the right tools for the job. I had mine out with trans attached relatively quickly, a load leveler on your hoist is very beneficial.

I would completely agree with all of this. I wouldn't think anything in the top end would be strong enough to bring the entire rotating assembly to a complete stop, especially with the weight of the car turning into twisting force on the crank. This sounds like a piston or rod let go and the bottom end jammed. If it is a 5 speed, I just hope your tranny made it out without any problems since they are so hard to find, and expensive when you do find one.

[BumpRacerX.com]

Just bought this as an insurance policy. Trans is an auto.

I need to pull the plugs tomorrow and see if any of them are smashed now that it's ran a little. Also shine a light in the cylinders and see what I can see.

[pocket-rocket]

Wow, $300! I wouldn't bother even tinkering with the old engine since you have a brand spanking new 0 mile one on the way. I would just start stripping the old one out and get the car ready to drop the new one in and be done with it.

[BumpRacerX.com]

Wow, $300! I wouldn't bother even tinkering with the old engine since you have a brand spanking new 0 mile one on the way. I would just start stripping the old one out and get the car ready to drop the new one in and be done with it.

That was what I was thinking. I'm still waiting for the "too good to be true" moment to happen on this deal.

[pocket-rocket]

Well, as long as you paid by paypal, there will be no "too good to be true" moment

[BumpRacerX.com]

Well, as long as you paid by paypal, there will be no "too good to be true" moment

Yep. I think it's gonna turn out great. The guys got a ton of positive feedback on these engines on there. I talked to him personally (his number is listed in the ebay listing), sounds like he either owns or run the chevrolet dealership. They bought 50ish LQ1's and are down to their last 10 or so. I'm seriously thinking about buying 2 or 3 more if this deal goes good.

[pocket-rocket]

I would hop on one myself, but I've got the 91, the 92, a 20k mile crate engine on a stand, a good DOHC block, and there is a whole other complete engine at Ben's parents he said is mine as well, so I think I'm set for a while, lol. Although if I decided to have some crazy fun and shove a 200hp shot of n2o down the tb of one, but that would be wasting money and good parts.

[BumpRacerX.com]

Finally got the crate engine in and running. Need to Dx a check engine light, but other than that she's a BEAST. What a pain in the nuts to do this swap. Only a couple little issues with the crate engine, the biggest being that that I couldn't use the stock A/c bracket due to where the oil pressure sending unit has to go. I was able to fab up something to work.

[pocket-rocket]

Awesome news

Have you decided to pull the old engine apart to find what went wrong?

[BumpRacerX.com]

Awesome news

Have you decided to pull the old engine apart to find what went wrong?

Yeah, I'm gonna rip it apart, just not sure when I'll get to it. I left it at my buddies shop, he said if I don't get to it in the next couple weeks, he'll put it on a pallet and shrink wrap it for me. I've got a couple other parts engines sitting over there already, so we are going to try to build one junkyard good engine out of the 3.