I'm hoping you folks can help me with a problem. I just purchased a '78 Pace Car with the L48 engine. The car seemed to run fine but I felt like it was missing power but I'm comparing it to our C5. It has 97K miles on it. Engine compression appears OK (135-140PSI) and no vacuum leaks. When I hook up a timing light, I can't see the mark on the balancer. I started doing some checking and it appears that the distributor is off a tooth or two. I can get the timing to near zero degrees by rotating the distributor as far counterclockwise as possible before it interferes with other things. The problems is that when I get the timing near zero, it starts to miss.

Any ideas? It's been awhile since I've done this so hopefully it's just a mental problem and not an engine problem. I did remove the vacuum line to the distributor before checking timing.

Thanks in advance for your help,

Al

 

Al, it's very likely that you have a slipped balancer hub. Below is a picture of the old and newer replacement from my 1974 LS-4 454. The old one is slipped about 20 degrees, as you can see by the marks I made. Both hubs are sitting with TDC of the engine facing directly toward you. There are several threads in here on how to check for a slipped hub, but it mainly involves getting the engine to TDC by threading something into the #1 spark plug hole and gently rotating the engine. I believe that Lars has a paper on it, but I haven't found it yet.

If the outer part of the hub has rotated, there is probably no way for you to get the marks lined up, and if you do, the engine certainly won't run properly.

Steve

 

While Steve is probably right, your problem might be in your expectations. It would take a fair bit of modification to bring your L48 up to C5 numbers.

 

I doubt the 8" balancer slipped, it may have but it's properly your timing chain stretched. You have a plastic gear and should replaced anyway. I just did mine last weekend with a Cloyes True Double Roller...

 

Your timing mark is not supposed to point to zero, it should point to whatever the stock advance is, been so long but I thnk it's 6 deg BTDC.

If you disconnected the vacuum advance and plugged the line going to the carb yo should be able to see the mark aobut 6 degrees off the 0 degree mark with a non adjustable timing light.

If you can't see the mark check the weights in distributor aren't rusted frozen or something like that.

 

lets keep this in perspective I took my 77 L-48,th350,129 k to the dyno on monday. it runs well and burns a little oil, it pulled 142.7 hp and 235 ft lbs of torque. this is probably less then 1/2 of the c5.... these mid 70 cars are beautiful but not powerful....

 

Thanks for all the suggestions. I realize the L48 is less than 1/2 the HP and torque of the LS1 engine but that's what got me started down this path. Now I am concerned that the timing, or something else, is messed up. Since the car runs good with no missing or hesitation, my first guess would be Steve's suggestion of the slipped balancer. That would explain the situation the easiest. Of course, it's never the easy solution!! I'll look for Lar's TDC procedure and try it out. The timing chain is a possibility as well.

I appreciate all the help. This is a great forum, very informative.

Al

 

Al -
Any engine will miss and run like a New York garbage truck if you run the timing down to 0 - that is normal. Set your timing to 36 degrees total and disregard the initial - take whatever you get with 36 total. This will most likely give you an initial timing setting of about 16-18 degrees. The car should run very well at this setting.

 

Lars,
Thanks for the advice. Please help out a rookie! When you say total timing, what are you refering to? Does that include connecting the vaccum advance to the distributor? A what RPM do you adjust the timing? I'm at the same altitude as you (Ft. Lupton, CO). Does altitude have an impact? I remember back in the '70s I use to advance timing 4-6 degrees beyond factory recommendations for altitude. Basicaly, I was taught to advance the timing till it knocked then back of a couple of degrees.

Thanks for you help!!

Al

 

There are four types of advance: initial, vacuum, centrifugal and total.
-Initial is the timing at idle with the vacuum can on the dist plugged off.
-Total is the timing at maximum centrifugal advance with the vacuum can blocked off.
-Centrifugal advance is the amount of advance added by the weights inside the distributor at different RPMs. As the RPMs rise, so does cetrifugal advance...to a point (that point is total advance). By varying the weights and stops and springs, you can adjust the "curve" or character of the centrifugal advance.
-Vacuum advance is used only under partial throttle and is controlled by the metal can on the side of the distributor. The can is connected the carburetor. On most distributors this is not adjustable.

Generally timing measurments are done with the vacuum port plugged at the carb. To measure total timing, you'll need either an advance timing light or a damper ticked off for at least 36 degrees. Run the engine up until the timing marks stop moving (or redline, whichever is first). Note the timing at that RPM. That is your total timing. It should be about 36 degrees. According to Lars, centrifugal advance should be all in by about 2500. I have no reason to doubt that number.

 

Al -
I didn't even notice your location when I last posted...

Just bring the car over and I'll set it up for you and show you how to do it. There will be at least 6 Vettes over to the house this Saturday, so stop on over. I'll show you the total timing method and what it all means.

Drop me an e-mail for phone number and directions. I'm 15 minutes from Ft. Lupton in Lafayette.

V8FastCars@msn.com

 

Do NOT pass up this offer.

 

Guys,
Thanks for all the help on this problem.

Lars,
I will definitely take you up on your offer ... but it will have to wait. I got under the car tonight, with the help of my Kwiklift , and found my distributor timing problem. I can rotate the outside of the harmonic balancer by hand. In fact, it has slid back of the internal pulley by 3/8". Another 1/4" or so and it would start hitting the front of the oil pan.

So the next question is, what's the best harmonic balancer to buy?

And by the way, how do you get the fan shroud off without pulling the radiator? I'd just as soon leave as much intact as I can.

Thanks again for the help,
Al

 

Al, just got back home from some minor surgery and saw this. Glad to see you found the solution. Try to stay away from units made in China, beyond that, someone else will have to offer a suggestion. My LS-4 replacement came from a forum member who took it off his 502 crate motor during a buildup. Also, as everyone says, you got an offer from Lars that you can't pass up. Fix the balancer, buy some beer, and give him a call.

Steve

 

Al -
Stop over to the house on Saturday anyway and meet the CCC (Colorado Corvette CraZies - the Ultimate Corvette Tuning and Beer Drinking Fraternity). We can give you some input on balancers and installation. Drop me an e-mail here at my office today (Thursday) and I'll send you phone number and directons.

 

Al -
Stop over to the house on Saturday anyway and meet the CCC (Colorado Corvette CraZies - the Ultimate Corvette Tuning and Beer Drinking Fraternity). We can give you some input on balancers and installation. Drop me an e-mail here at my office today (Thursday) and I'll send you phone number and directons:

lars.grimsrud@lmco.com

 

Fluidamper or Rattler. Expensive, but good.

 

good pic to show

 

Hey Steve, I thought I recognized that balancer in the picture. Hope it works for you. Bill.