Ok I did a search on timing chains. Joe and I figured this would be the cause of the balancer marks movement.

So for the background story:

Car ran like crap. We tackled the obvious. Took care of all codes and vacuum and exhaust leaks. Blocked off the egr. New plugs, wires, msd coil. But still it was running 20s in the 1/4 & backfiring.

Then back in July, we rebuilt my dist and set the timing to 14 degrees in my 1987 2.8L v-6. Now I noticed a serious power difference. It was like the car had its power back. We were concerned that the car accepted the 14 degree timing. It was running with no ping on 87 octane. We thought it was possible that the balancer was walking. The backfiring disappeared also.

Later I got the car dynoed. I have flowmaster muffler & 2.5 high capacity cat. I mildly ported and polished the pleunumm, runners, and exhaust manifolds. The car has ram air, but this does nothing on the dyno. Well I got numbers dead in line with a new stock 2.8L.

We were happy with the fact that now it should run 17s like any other stock 2.8. But we were also concerned that i should have seen some gains from the porting, freer intake, and exhaust.

So based on the above, Can I assume I have lost power due to a 50,000 to 60,000 mile old chain?

Also we noticed the timing that was once set to 14 is now back to jumping b/w 11.5 and 12. Is this also caused by chain slop. Will this actually move the timing?

 

I can only assume that the chain is bad after 60K. The symptons you describe [bouncing mark, relatively weak performance (given the mods)] tell me the chain has had it. If you are not going to a v-8 yet (i.e. a couple of months), I would recommend the Cloyes double roller chain and gears as it probably is more durable. Check the recent post called "result of timing chain swap". The guy who did it said his car performed alot better and some intervals on when to change it are given there.

 

It could also be that you didn't tighten the distributor hold-down bolt enough, and that it loosened up, and messed up your timing. Although, usually, you'll wind up with over-advanced timing, not retarded timing. Did any other mechanic work on the car?

 

That was my first thought, Tom, but the distributor hold down was tight, both this time and the last time (the last time was with a different timing light, and I attributed the difference to it, incorrectly apparently). Shannon had said the timing chain was fairly fresh, but its actually got maybe as much as 60k on it, and who knows what quality it was to begin with. No other mechanic touches the car anymore, just us. As soon as we get my SS back together, we'll change out the chain and hopefully regain some of the lost power. We're replacing the injectors with some cleaned and flowed ones at the same time.

 

Nope. It was Joe and I and we checked the dist hold down to see if it loosened up on us and its tight. So its not that... It was our first guess too. Joe tried to twist the dist and it would not budge, so we can't blame the dist on this one!

 

The plan it to go with the double roller chain. We still have to build teh v-8, so who knows when it will be ready go in. So might as well have a bit of fun with the 6 right!?!

 

 

So how much HP do you think the car is down with a sloppy chain?

 

This is a rebuilt motor, isn't it? Did you two put the new chain on yourselves, or did the rebuilder?? I wonder if someone put a new chain on with old sprockets- which is a no-no. Chains take a "set" to the sprockets, and everything shares the same wear pattern. Put a new chain on old sprockets and you've got the sprockets attacking the chain, and the new chain attacking the sprockets. So this could've caused a big timing chain death.

Only thing I'm worried about is that the timing really shouldn't change itself unless your chain skipped a tooth. If your chain skipped a tooth, that means your valve timing is also off! (And if this happened, good thing a piston hasn't hit a badly-timed runaway valve!)

Is the balancer in good shape, i.e., the rubber inertia ring isn't separating from the center hub, and trying to "escape" past the outer ring with the timing mark etched onto it?

 

The motor was rebuilt...if you can call it that...before we even knew each other, so I have no idea what was done for sure yet. Of the three people who have worked on it, only one is someone I would trust...and hes not the one who did the work. It wouldn't surprise me if he left the crank gear on, rather than get a puller to get it off...that would explain a lot, since I figured even a low quality timing set would last longer than that.

I tend to agree with you on the skipping a tooth...don't know what else could change that. I reset the timing last night, so we'll see if its in the same place tonight.

The balancer appears to be in good shape...but the fact that the car can take 14 degrees of timing on 87 octane makes me wonder if the mark is in the right place, maybe slightly off from the factory? The car runs like crap at 10 degrees.

 

Yeah, weird, my 240,000 mile 2.8 runs great at 10 degrees advanced...

 

We might as well pick up another balancer while we're at it. It has to come off anyway...

 

I found this on the Fiero Forum:
http://www.fiero.nl/forum/Forum2/HTML/027311.html

 

Link is not working Joe.

Nevermind it woks. There must have been a connection issue with the t1 line

 

Try it again...it worked for me.

 

The new timing set and flowed/cleaned injectors go in next week. Just for fun, we took the car to a local 1/8th mile track and ran it last night...we only got to make two runs, both in the 11s, which approximated a mid 17 second quarter using the standard conversion. So, at least the mods we have made have offset the problem, and its running like a stock 2.8. Our next trip to the dragstrip will be Oct 13, the GAFBA F-body Shootout at Silver Dollar Raceway, so hopefully our numbers will be better then. Its still a drastic improvement over what the car ran its last time at the track!

 

What that guy said on the fiero bored sounds like my 2.8l in my s10. I need to try that spin the crank and look at the dist. However, I set timing at 0, and runs like ***. (s10 is to be set at 0, not 10) I need to find me 50 bux and get new chain set.

 

there should normally be some advance, maybe not 10 degrees, but definately some. If it's set at 0* advance, by the time the ignition fires to the plug, the piston will be sitting 1/3 of the way down the cylinder when the burn accurs, this won't give you the type of power you're looking for at all.

 

When I rebuilt my brother's 4.3 liter V6 in his 1991 GMC sierra, the timing was set to 0 degrees by the factory. The decal said that it needed to be set at 0 with the computer advance disabled. I set it to 4 degrees advance, and it runs much better, still on 87 octane gas. If you advance it much more, you start to get detonation. I wonder what the difference is that causes the 60 degree to run so much more initial advance?

 

Yeah, that is weird. Are v8's set up like this? If so, it'd make sense, because we know the 3.8/4.3 is basically a 305/350 block that's had two cylinders cut off. My car won't even run at 0 degrees base timing... found that out after doing the distributor rebuild. I re-did the rotor location, found TDC of #1, and dropped the distributor so the rotor pointed to the #1 terminal of the distributor cap. The car didn't start. (I thought I was screwed, never rebuilt the distributor before.) Turned out that by spinning the cap so the #1 cylinder was at TDC, but the rotor was between the #1 and #2 cap terminals (spun counter clockwise), the car started right up.

Same thing happened with that 2.8/2.8 swap I did for my friend, except I forgot about putting the rotor between #1 and #2. So when I realized it, I was turning the distributor cap as he cranked the motor... ouch: https://www.thirdgen.org/techbb2/sho...tributor+shock

 

If you doing the timing light test be sure to STILL keep your computer connector unpluged. I USE to belive that test, but then I unpluged my computer during a time check and the MARK was on the money at 90,000. IF the computer was pluged in it would jump around because the computer was playing. Also watch out, if your engine misses it can make it act a little jumpy and not mean a thing.

 

My 1995 TBI 350 V8 in my truck is the same as the 4.3 in my brother's truck. The decal says to set the timing on 0 with the computer disconnected. Apparently they have more advance done by the computer than the 6 cylinder cars do. Weird that they wouldn't make them the same, though.

 

Ok, here's something else thats VERY strange. The car ddin't make good power at 12, so I bumped it to 14. Still ran like crap. To test a theory, I bumped it to 16. Got a little better, no pinging. Its now sitting on 19-20, no pinging!!! Something isn't right here. Either the timing tab is wrong, or the mark on the balancer is wrong (slipped, or maybe wrong balancer?) .WTF??? I'm confused now, because I KNOW the thing can't possibly run that much timing, esp not on 87 octane!

 

It would be best to start a new thread about it. The others may not get that the topic has morphed

 

LT1guy I would say you have timing light problems, borrow somebody elses working timing light and see if they say the same, are you sure your pulling the brown wire connector apart??

 

Timing light is new. The 2nd new one actually! So its functioning correctly. I wish i could blame it. We are getting a new balancer to be on the safe side. $43.00 NAPA

 

Yes, its being pulled apart, and the timing light is new. I think the problem may be spark scatter, caused by too much endplay in the distributor. I'm going to pull it out, put in some extra shims (Moroso), and see if that makes any difference.