So after days of installing a new short block (that came out of an 02 vette) I got the motor all back together, and tried to fire it up. Well the accessories are spinning, the flywheel is turning, but no compression. I am getting spark, and fuel. So last night I rotated the cam 180, and still nothing....wtf????? Anyone have any idea what is going on with this thing????

Rob

 

Rockers (if adjustable) too tight, holding valves open? Seen that before.....

Or pushrods too long, same difference.

 

checked them 6 times....20ftlbs.....

 

Ditto...but need more info. on the motor. You say "new shortblock" then say it came out of an '02 vette. Is the motor guaranteed from a salvage yard/individual to run? Did you put different heads on it as you only bought the shortblock? What heads?

 

I put Absolute stage II's on it, the ones that came off my old block......and yes, the motor did come out of a running car.....someone sujested to me that it may be the crank position sensors are different from 00 to 02?????

 

Crank position sensor would not cause lack of compression. Not sure what your problem is though. That's pretty weird.

 

So you cranked over the engine twice (1) once with the cam installed correctly, and (2) once with the cam 180 degrees out of phase; right?

I'm pretty certain that you now have bent valves, pistons with large wholes in them or both!

See my reply to your other post, titiled, "Broke bolt in engine block - help"

You need to turn this job over to a professional. At this stage, I don't think it makes economic cents for you to do any more damage.... Your car will thank me for this advice....

 

The correct torque is 22 ft-lb on the rockers. Just because you tighten the bolts down to that torque does not mean the valve train is setup correctly. Sounds to me like you are using pushrods that are too long. That would cause excessive preload and no compression by hanging the valves open a bit. It depends on what lifters you are using. If they are stock then it is 1.5-2 turns from zero lash to 22 ft-lb. If they are comp-r then it is .25-.5 turns. What you can do is rotate the motor till one of the front cylinders is on its compression stroke (both valves closed). Loosen the rocker bolts then tighten to just zero lash. Put the compression guage on that cylinder and rotate the motor. If you get compression then the problem is your pushrod length.

 

The cam can be installed either way. As long as the pistons are at the right spots in the cycle.

 

It my understand that since the crank rotates twice for every one time of the cam that it does not change anything whether the cam is 180 degrees out. All you need to worry about is that you line up the dots correctly. The reason people get p/v contact is that the rollmaster and other chain gear sets had two dots, and only one of them is correct. If it was lined up on the other mark then the advance would be too much and pistons will hit the valves and bend them for sure.

 

Obviously, you should have checked valve clearences using the modeling clay method or a dial indicator.... You also should have checked compression - by hand cranking with a breaker bar and crank bolt socket - after you installed the heads but before you installed the push rods and lifters....

Hand cranking the engine using a breaker bar after the push rods and rockers are installed also is a good idea because it prevents you from bending valves and breaking pistons before you crank the car over with the electric starter.... ...that is, you would probably know if you screwed up the installation of the valve train/cam components by installing the cam 180 degrees out of phase...


...Sometimes you really need to think things out thouroghly, before you make a move and do alot of expensive damage..... it would have also helped if you had a buddy who knows something about Gen 3's to help you work on the car....

At least look at the web page that shows how to install heads and cam in a Gen 3...

...frankly, I think it is too late now, however .... you will probably have to order another engine.... get a stock long block (a short block with stock heads installed - e.g., a complete engine) this time and have a professional mechanic install it....

Hang up you tools, man ...Chalk it up to experience and admit that mechanical hot rodding is NOT your forte'


You might sell the ported heads to someone else who could replace the bent valves and have the new valves re-seated at an engine shop....

We have seen many here on the board who have installed cams out of phase..... if the engine is cranked with the electric starter BIG-TIME damage to the valves and pistons is always the result....

 

Can anyone confirm 777's comment that installing the cam 180 degrees out will not bend valves? ...I assume, at a minimun, the center line of the cam will be "way out of spec" if the phase is 180 out of phase.... right?

I hope I am wrong.... I can't take any more stress reading about the next major problem with this install!!!! HHHHHEEEELLLLLPPPPP!!!!

 

Rob, buddy, i hope you get this figured out!!! I know how much time we spent on this thing and i know all you want to do is get it running.
Nino

 

I don't think he needs to hang up his tools necessarily. This is all a learning experience. I did something along the same lines when I did my first major cam install and I installed it with the timing off. Long story short, broke off a valve and embedded it into the piston. Stock engine was done for it. I can't tell you how many people told me to hang up my tools, that I couldn't do it. But, I learned a hell of a lot from disassembling/reassembling that engine so many times. And what do you know, I taught myself more, and I even swapped a 6.0 into my car without any prior experience/knowledge of doing so. All the things I have done to my car have taught me and gotten me to the point where installs like this are trivial, thanks to what I've learned. If things never messed up, I would have gone on being ignorant of what could have and did happen to my engine. Sure it might end up costing you a lot of money, but you gotta pay to play. I didn't buy this car to take it to a mechanic every time I think something is wrong. I bought it to learn and learn from my mistakes, which is what these experiences do best.

 

Yeah man, lighten up. I still bet the pushrod length is wrong, as I said earlier.

When you pull the valve covers, remove the rockers and see if all the valves come all the way up. If some don't, you're screwed. But if they do, try to turn the motor over with a breaker bar. Bet it gets REALLY hard to turn. Thats compression. Your pushrods are too long.

 

I had 7.40 pushrods in my car last week when we put stock rockers on AFR heads milled .018.

No compression, car would backfire slightly trying to light off. No bent valves.

Measured with adjustable pushrod, determined we needed 7.350. Put them in, car runs great. Morel lifters, preload is one turn. I'd like a 3/4 tunr and may shim the rockers over winter but it works well right now.

 

Yeh, I thought of the push rod issue too and told him earlier in the "busted head bolt" post.

It seems to me that he needs some hands-on help, however. Lets ask him if he has any buddies that are mechanics that could help.


OK - so I agree. Rip of the valve covers and remove the rockers and push rods. Turn the engine over with a breaker bar and socket on the crank bolt.

If your push rods are too long this should identify the issue.

If the engine came from a running car with 5K miles on the clock we can assume the deck has not been resurfaced. The ported heads could be shaved but the vendor should have told him about getting shorter push rods; right?

The rockers and valves are stock so this is probably not the issue. I assume the lifters are also stock length...


How about the cam? Are the dots aligned or 180 degrees out? ...this part makes me nervous... He is using a stock timing chain so I can't see why you would try to install this 180 out....

 

A cam 180* out will not bend valves etc. The compression stroke and the valve stoke would be reversed. But since the LS based motors have a cam position sensor the motor would run.


Rob what are your cam specks again??

 

Polter:
....that is interesting to know..... my cam sensor went bad twice. The last time it was really hard to start but eventiually it would turn over and run...

If the compression stroke and the exhaust stroke are reversed would'nt the spark timing be wrong causing the engine to not run?

So does anyone know if the cam is now 180 out or aligned correctly? Have we confirmed that the heads have been shaved and therefor, the pushrods are too long?

 

i should've asked about the pushrods. I didnt even think about it, he even showed me they were hardened 7.4's Also, when he installed the cam (from what I saw) #1 and #6 were at TDC so I dont know how it would be 180 out...