Hey fellas, quick history. 2003 car was running consistent 11.8s at 118 mph. Last year switched to hooker long tubes and it dropped to 11.94 best @ 114 mph. Car was dying past 5500 and I short shifted to get some ET out of it. Anyhow, I have been trying to figure out why it got so much slower!

Only problem I found: worn distributor gear(1991 stocker) Questions:

Could this be the problem??

The gear wore on one side. In the middle of the teeth, but like there is runout on the shaft. Could this be the cams fault?? The distributor bearings feel fine. Could this be a heat treatment issue? Is there a typical wear pattern? I do have a hardened gear pressed on the cam from comp cams.

Is an MSD distributor worth it? Should I just swap a new gear on the stocker?

 

Had the same thing happen after a hard nos backfire. The dist shaft bent and I didn't pick up on it. It chewed a gear as you described. I robbed a shaft out of a junk unit and checked runout with a dial indicator to confirm it was tru. Never an issue since. As a result of this I also use a new dist gear anytime I install a new cam. The become a matched (worn in together) set.

Edit: the shaft was only bent .005 to cause the mess I had. Could not feel it but could barley see it. Dial indicator confirmed.

 

Wow, .005 and that caused all that mess?? Did the motor run poorly?

 

Nope, ran well. Lost 1 tenth of a sec every week. When 1/2 sec was gone I decided to do some troubleshooting. I was quite suprised and now check every dist, every time it is on the bench. Only takes a minute.

 

yep, My friends nova done the same thing. He lost about 5 tenths. The car kept getting slower. The gear was chewed up also.

He went to a Pro billet dist and it went back to normal. Car runs 6.30 flat in the 1/8 with a 408.

 

to what extent chewed up? like missing teeth? or just worn teeth? Thanks so much for the replies!

 

My gear had wear that was so severe , it made the gear teeth razor sharp. It also did in the cam gear.

 

wow, lets hope the cam gear isn't worn!!!

 

Sounds like a high volume pump, and excessively thick oil... like straight 40 or something. Another good reason not to run a HV pump and to use the right oil.

 

I agree, however, in my case it was a standard volume pump, using 5w-30 oil. Nitrous backfires do bad things.

 

RB,

WHy do you think mine did it? It has been in there for two years. I do have a HV pump but I run dino 10-30 always in this motor. My teeth are pretty sharp too, I will snap some pics and post them soon....


I guess maybe the stock 120 plus mile distributor could play a role?? SHould I do an upgraded distributor?

 

When I changed over from TPI to carb, I bought a used dist. The gear was worn and were about razor sharp also. I did have trouble with the timing jumping around a bit.

I went to my local machine shop and found a new stock dist gear. A guy had it removed and replaced with a bronze gear. The machine shop just give it to me. No marks on it, it hadnt even been installed in a motor. Can you guys say "freebie"

I hadnt ran the old dist much, but enough to give me problems with the timing. I didnt pull the cam, but I dont think it caused much damage considering the short time it was installed.

Whats the possibility you guys might could use a shim under the dist? Maybe the cam and dist gear is meshing together with out enough clearance? You know kinda like getting a good pattern with a ring and pinion gear.

 

Some cams (especially the hard metal roller cam ones) can wear out the distributor gear in a very short time. When I converted my 1984 LG4 to a 1990 L98 I had the L98 gear pressed onto the LG4 distributor to keep it correct. I will pull my distributor in the spring to see how it looks, jic.

 

side note: should I just buy an msd distributor? thoughts?? thanks!

 

The stock GM units can be upgraded to handle quite a bit.

The MSD Pro Billits are nice dist. Id say if you can swing the $, then yes buy a new aftermarket one. You can sell the other one here at thirdgen.

I gave $100 for my used GM unit. It did have a accel supercoil and accel plugwires with it. I ended up replacing the cap, rotor, gear, springs and a few other parts. Oh yeah, the wires were toast also. I would have rather went with the MSD one, but $ didnt allow it at the time.

 

Food for thought, before I stepped into the MSD set-up I had a GM HEI reworked and tricked out, total bill $225 and that was spun balanced to 9K.

New MSD billet here in town cost me $210.

I had similar deal, first got car out last season after drivetrain swap and only mustering 12.0? passes. Sick to my stomach with what I had spent. After some time we had a guy over installing/degreeing cam in buddies BBC and told him what was going on. He had me pull my MSD billet and looked it over real well for a few minutes, then found out I was missing a slide and bushing in the counter wieghts. Bought a new MSD that night, reinstalled with timing curve that guy installed, when to track first pass out was 11.4?, did some jets, next pass 11.20. Did some timing changes and jets got down to consistent 11.0? So yes, distributor plays big time into how these things run. I just got lucky motor did not blow from timing jumping all over the place, funny thing was, even when it was running poorly and slow, that things was very consistent!!! Won 2 races in that condition

 

mine is injected, so that changes it some. i just dont want to buy a new distributor and have it chew the gear all the same!

 

check it out guys, comments much much much appreciated! (I am trying to paste a picture, If I make a mistake I'll try again) Zoom in to really see the 7 megapix detail.

 

Yeah, My gear was worse than that!!! The guys was using a bronze gear and bought a new dist. He swapped the bronze gear out for the old wore one. Guess who got the wore gear!!

But yeah, mine was worse. I should have known better than try to use it in the first place.

 

Oh yeah, with a ridge worn in it like that it's toast. There should be a smooth, shiny wear pattern witnessing contact with the distributor gear, but definitely not a ridge of any kind.