Well I got the LT4 ED timing chain in this weekend, put everything back together and started her up......and she sounds pretty rough inside. Alot of clattering and it needs alot of gas to even stay running. I guess my valves hit again the piston tops because the springs/rockers/pushrods seem fine. So what would you guys do? GM said $2000 for a valve job, but I'm pretty handy and have all the tools as well as a garage. I was thinking of pulling the heads and having Lloyd Elliot port them and getting a CC306 with all the goodies (Manley Valves, 1.6RR, springs, hardened pushrods, etc.) Is this the direction for the most power but keeping the car reliable?

 

$2000

$1500 buys you combination motorsports' stage 2 heads that flow like a beast and they are complete with vavles...

 

I'm not sure what you did when you installed the chain, I'm guessing it either wasn't at TDC when you installed it or the valves were adjusted wrong, either way sorry to hear about the misshap. $2000 for a valve job though??? At worst you could just buy a complete set of stock heads with valves in the FS section for anywhere from $200-300 and install them yourself. Hopefully you didn't do any piston damage at the same time though, that could get more complicated. Good luck.

 

When I installed the chain and gears the dots were at 6 and 12 o'clock right next to each other. I even had a mechanic help me do it. Something is loose inside......

So whats the next step?

 

My memory is a little fuzzy but if I recall, you could have the opti off a little, changning the timming.

Do a good thurough search for timming chain installs and opti installs. You should find a few blunders in there that might help lead you to the problem.

Your next option is to pull the plugs, get a mirror, check the tops of all the pistons for dents/dings (can you do this? What angles are the plugs at, lol???). if your spring/rockers push rods seem fine and there are no dents or impressions in the pistons (assuming you can see all of them) you just have the timming whacked. Whacked timming does the exact thing you decribe too.

 

I would really like to fix this problem without taking the motor apart. Have you tried the mirror idea? Would a leak down test give me info about the valves being damaged?

 

A compression test of each cylinder would tell you if you have bent a valve or a pushrod, I believe thats just another name for a leakdown test. It would be much easier than pulling the heads to check the valves, I would try that first.

 

Hey man, I am sure you would!! I have a $40 part that will cause me to have to remove my whole tranny to replace it so I know what you are going through.

No, I have not tried the mirror thing yet, thank god no need, BUT, you have a serious problem you just cant ignore. I would try the cheapest easiest solutions first and move on up, hence the mirror bit and what not. Sure, if you cant do the mirror check, a compression check will help. I would go for a leakdown test too. Unless you are exactly sure were your timming is/at, your gonna have to pull the valve covers off to make sure the int/ex lifters are all the way closed, or, unscrew the rocker nuts to be sure, when doing a leakdown test. So, I guess go for the "search" like I said first, then mirror, compression..........etc. Add it all up and see if you need to progress further.

 

yeah, if you broke it while ideling chances are the valves are fine.

 

A bent valve, yes. A bent pushrod, maybe not. If an exaust pushrod is bent, you will have plenty of compression, hence fooling the compression test.

Also, a compression test can only work to a limiting factor of a leakdown test. A leak down test is specificly used to, well, see how air tight the cylinder is and how much it "leaks" over time. You cant hide a bent valve from that and unless your very canny with engines and know exactly what to look for, a leakdown test would be my top choice to go with.

On the down side, you need a compressor and time but other than that, its much better than pulling heads!!!!!!!!!!! Then again, if you are going to get the heads redone, who cares??

 

True, thanks for the correction.

 

No correction needed, just a slight insertion . I can buid the world but I too dont catch everything all the time. Your welcome

 

The chain snapped at about 3500 rpm in second gear @ about 50 mph.....

I didn't do any adjusting of the valves and have put about 6 opti's on so I know that's right. So either the timing is off (can that be possible when the dots are lined up correctly on the cam and crank gears?) or something internal is damaged. This really sux

 

Well, sounds like you are familiar with the optis but I have read a few post way back, about 1.5 years, where optis go on fine but still get the timming off, somehow, I just forget the specifics. I think it had to do something with the cam/opti dowel alignment.

I would go for the leakdown test next if you think the opti is fine. Since you have to take the valve covers off to loosen the rocker nuts (to make sure the valves are closed), your that much closer to taking the heads off if the leakdown test fails.

Oh, and come to think of it, make sure the plug wires are on correctly in the opti. Sounds simple but an easy thing to over look. Again, a simple thing to check before tearing things apart.

 

I don't see how the timing can be off if you put the dots together on the crank and camshaft sprockets during installation. The crank sprocket is keyed, so it can't go on wrong and the camshaft is essentially keyed also with the prong on the camshaft going through it. To me, it also seems hard to put the opti on wrong, especially on a 95+. Firing order would be the only thing that can be messed up. If something is loose in there, it would have to be from the camshaft up (lifters/pushrods/rockers/etc...)

Sam