Ok Guys.
I have a 79 with the L82, eddlebrok carb.
I changed the timing gears and chain. got everything back together, hasd the rortor off by 180*. got that fixed. the car runs but is very rough, heavy knock on cold idle. I replaced all the plugs. timing is set to 12* BTDC as per this forums rec. the car has no low end power. Once I get going it sounds better. there is no smoke in the exhaust, no oil leaks. to my untrained ear, when it idles and runs it almost sounds like 1 piston isn't firing. thier seems to be a sound like it is compressing, but not exploding. Does that make sense? I am thinking to change the plug wires next, but figured I check with the experts.

Thanks

 

you said that you changed the timing set.
it almost sounds like you are a tooth off when you put the chain on.

 

You know the old addedge measure twice, cut once. I was pretty methodical in making sure those where lined up. I evan had a second set of eyes check it out So I am hoping it couldn'e have changed.

 

Have you double checked your distributor alignment? As in #1 cylinder at TDC on compression stroke, and rotor pointed at #1 plug on cap? Trust me, this can be very easy to get wrong, and will cause the problems you are describing.

 

Since you've verified the timing, I have to think that the timing chain is installed incorrectly - likely retarded. Many crank sprockets have three crank keyways for installing 'straight up', 4 degrees advanced, 4 degrees retarded.

Why did you change the timing set?

 

Did you set the timing with the vacuum advance plugged? Just checking, as it sounds like your timing is retarded...

 

I had to change the timing because the gear sheared. It was the original with the nylon coating, and it just wore out.
This is what is frustrating. I know the spokets are aligned. Also, the rotor shaft is slotted on the end, so it can only go in correctly or 180* off( already did that and corrected it). the only things I can think of at this point is a bad plug wire, or the timing is 1-2* off. I will have to recheck. Or perhaps the vacume advance is off, but I didn't change anything there.

 

Yea did remember that. If the timing is off by 1-2* will that make it that bad?

 

The timing being a couple of degrees off might cause a bit of sluggishness, but it wont make the car run rough.

 

If the timing actually jumped before you replaced the chain set, you need
to run a compression test now. You may have had a piston hit a valve.

 

more inspection is likely required. I don't think it's just a timing issue, although it could be a bad wire, etc.

 

Too.

 

I just did my timing chain too. Did you align for #1 or #6 top dead center? Where were the dots on the gears? 12 and 12 or 12 and 6 o'clock? Did you bring the rotor in the distributor to the number 1 plug spot? 12/12 should be at #1 and 6/12 should be at #6. To be 180 degrees off you whould have had to align the marks wrong.

Did you pull the distributor out to fix the 180 degree problem? Chances are you dropped it in off a tooth.

If you hand crank and get the mark on the balancer to "0" on the timing plate where does the distributor point? 1? 6? or somewhere else? Once you have the crank aligned then pull the distibutor. Depending on your intial alignment you should be at 1 or 6 or there about. There about meaning you are off by a tooth on the distributor install.

I brought mine to "0" before removing the chain. So I had the crank lined up but found the cam sprocket was off by a good inch probably jumped a link. So the rotor did not point to number 1. Once the crank was at "0" on The timing mark and the dot on the gear was at 12 I aligned the cam sprocket too so the mark was at 12 and noted the postion of the rotor in the distributor was pointing to #1. My cam mark was off about an inch with the old chain on. You can't really screw this up If you aligned the marks and were point to the right places it should be fine. Only thing I can think off is you were at 1 when you should have been at 6 of visa versa. Once done my timing was at 4 after top dead center not 6 before top dead center. the reason for that was me trying for years now to set the timing with the old chain and since it was off at least a tooth I was never able to get it right.

Jim

 

Thanks jim. I may have realised a problem. My Harmonic balancer may be wrong. I just rotated my distributor cover, got it to run smooth. But now the timing is at about 18* BTDC
I am thinking I may have a L48 instead of the L82.
I have the numbers off the engine casing.3970c10 where can I check that.

 

I can't find any reference to that number. Go here and look up under identification. http://www.corvetteactioncenter.com/...979/index.html

Your balancer should be two parts. The inner is separated from the outer by a rubber ring. The two parts may have slipped. You may need a new balancer...which is cheap.

Here is a suggestion for you. Bump the engine until you get the timing mark to zero.You may have to remove the fan belt pulleys on the crank. But find out where the grove is on the crank that the balancer goes on....if you take the pulleys off you can feel for it. You can do one of two things buy a balancer and compare where it slides on with were the marks are or post your findings her and ask. I supect yu would be better off spending the $40 for a balancer. Anyway you can hold the new one down there and roughly align where it would go on and do a visual on where the timing mark is. If its not exactly the same your balancer has slipped on the ring.

Jim

 

with your year the 5th digit of your vin tells you what engine GM installed in your car. If it is an 8 you have the L48 and if it is a 4 you have the L82. Doesn't help you with power but it does help with parts purchase.

 

Jim, would it work if you find TDC on cyl 1, moving the engine by hand (probably easyer without sparkplugs) and then the balancer line should be on 0 degrees?
So if the balancer outer ring sliped, when he feels tdc on cyl 1 ... the line should be somewhere else?

 

Yup you are right same thing. I took off the distributor cap and bumped the engine until it was pointing to number 1 and then looked at the timing mark which should be at '0". But since he has had the distributor out you will not know if its out or the balancer has slipped. There is only one thing for sure the balancer can only mount one way. Since he has it running he can tell if its the balancer or the distributor by trying what I suggested.

The only thing that should be for sure is a new balancer will line up exactly to factory spec. So if there is any variance from it to what he has you know its the balancer slipping.

Jim

 

In most of the engines i played with, to find tdc, u would put a screwdriver in cyl one and look at it move till is all the way up and u knew it was in tdc right before it started going down. I`m guessing hte same can be done on the vette engine even if the spark hole is more horizontal than vertical ?