What are the odds....

In reply to Knurled. :

Sorry.  You're right!  I missed it.

Hmmmm.  I think I may have found a clue.

Pulled the access cover to the flex plate.  At a glance, everything looks fine, but I notice that the flex plate is secured to the torque converter by exactly three screws.  Normal?  There are holes for three more bolts.

A closer look at one of the bolts reveals galling, like the flex plate has been sliding around under the bolt head.   I bumped it around and looked at the next bolt.  Similar.  And where the first bolt was not noticeably loose, this one turns easily by hand.  

So, I think I have a set of flex plate bolts laying around from the Chevy II.  Plan is to torque it up with six bolts and see what happens.

My mood is very much improved this morning! 

It's normal for only three.  The flex plates with six holes are usually dual bolt pattern to handle two different size three-bolt converters, only the real heavy duty applications got six bolts in the converter, and those used a special single-pattern flexplate.

But definitely think you've found your noise!

Well, poop!

Nobody has the required 3/8-16 x 1/2" bolts in stock.  I could use the old ones and some Loctite, but they're boogered up a bit and I'd rather not have to mess with this again anytime soon.

Ordering online.  Wish me luck.  Amazon no longer coming through with next day free shipping.  It's a hard world!

Don't forget the loctite anyway, even on new bolts. At I think least most flexplates call for using red locktite?

In reply to dculberson :

Oh, yes.  The new bolts will be wearing some Loctite.  Found a seller on ebay that has the goods and a solid reputation.  Only downside is that I won't see 'em 'til Tuesday.

Doolies R kool.

I've bought those little short 3/8 bolts for torque converters before at Tractor Supply. Grade 8. Use a washer. Never a problem.

I don't always use Loctite, except on flywheel/flexplate and torque converter bolts.

If those ever work loose, very bad things can happen.  There usually isn't enough room for a torque converter bolt to be able to back itself out and NOT berk up the backside of the engine, for example.

That truck brochure is interesting.  I don’t think I’ve ever seen a step side with a long box . . .

Got my bolts yesterday, but it was cold and rainy.  Today is sunny and nearing 60, and it isn't even noon yet!

Bolts are from Feiock Performance via eBay.  Nice product, grade 8, black oxide finish.  A little longer than stock, but they do not bottom in the holes and the flanged heads eliminate the need for a washer.  Described specifically as GM TH400 torque converter bolts. 

Bolts are wearing red Loctite and are torqued to 35 ft-lbs.  Is there any reason to wait to let the Loctite cure, or can I start it right up?

In reply to 1988RedT2 :

I've never waited.

Apparently the Loctite works not entirely by gluing the metal together, but by taking up the freespace between the threads so it can't be wiggled loose.

Knurled. said:

In reply to 1988RedT2 :

I've never waited.

Apparently the Loctite works not entirely by gluing the metal together, but by taking up the freespace between the threads so it can't be wiggled loose.

Thanks for the reply!  I figured it was a dumb question, so I just let it sit.  It won't matter a bit if the truck sits one more day.  I'll give it the 24 hours the directions ask for.

Ended up spending a good part of the afternoon helping my son with the power seats in his E39.  I was at times wishing I knew how to curse in German.

Update:  Spent some time overthinking the timing before I went back and checked the firing order.  I didn't want to check it, because I knew full well that only a complete idiot could mess up pulling the wires off the old distributor cap and putting them on the new distributor cap.  

Well, news flash.  I am that idiot.  The firing order as GM intended is 1-8-4-3-6-5-7-2.  I had somehow switched the 3 and 6 wires, which sorta idled okay, but didn't like accelerating at all.

So, the truck runs pretty well.  As well as it did before I started this little project.  But my test drive this morning did prove that in the end, the problem I was hoping to solve with the new distributor--an intermittent loss of power or surging that I wrongly attributed to a sketchy pickup coil--is still present.

So, fuel filter is good.  Pump is fairly recent.  It's been 20-plus years since I've been in the Quadrajet carburetor.  So... carburetor?

If its a lean surge, make sure the EGR valve (If your one ton has it) isn't opening fully when its supposed to be only partway open.  There is a pressure balance situation built in to the old ones that can plug and make some odd problems.  Inside the Qjet, make sure the power piston isn't stuck down in the lean position. There is a stop available through a lead plug in the top of the carb that can move the lean position of the jets up a bit.  If none of these solve it, find some jets that are about 10 % bigger.  It was probably jetted pretty lean when it was new, and modern gasoline, even without alcohol, just doesn't seem to have the same amount of fire built into it.  I've fixed a few over the years with the careful use of a jet drill. These are all light or part throttle surge solutions.

If its surging once you have the secondaries open, you probably have a fuel delivery issue.  Bad filter, weak pump, dirty sock in the tank.

This is the only time I will ever find the use of those cheesy glass fuel filters appropriate, because you can see if the fuel pump is pumping solid fuel, or foam.

Was not me but I had someone in the bay next to me get his ass thoroughly kicked by a carbureted Chevy truck that ended up having a rusted through fuel line.  It rusted through at a high spot so it wouldn't leak out, and it was slight enough that the fuel pump still could pull something out of the tank, but it wasn't enough for much more than an idle.

In reply to Knurled. :

A couple years ago, I had an issue where the truck got harder and harder to start.  Replaced the fuel filter  replaced the fuel pump, and still it got worse.  Then I checked the pickup tube at the tank.  It was very rusty, as was the top of the tank.  I put in a new tank and pickup tube and that fixed the problem.  So, pretty much the exact situation you describe. 

In reply to Streetwiseguy :

Yeah, I was considering the EGR.  It does have one, and I've never messed with it, so it's literally old as dirt.  I guess I'll pull it and see what it looks like and whether the diaphragm is doing what it's supposed to be doing.

I need to drive it again and really try to get it to screw up.  The times it has acted up, it's been fully warm, driving a good while, and I've added throttle, to either pull a grade or accelerate onto the highway.  It falls flat, I back out of the throttle, and ease into it and it does okay.  Loafing around, it's 100% fine.

A couple thoughts:

1) Is the ignition advance working? Should be easy to check with a timing light just to see if it changes as the throttle opens and RPMs come up.

2)Does it still have a cat, and could it be clogging or breaking up? When the cat got to a certain point in my S10, it could be eased gradually but any rapid acceleration would lead to it falls flat and dying. 
 

2) Do you still have the heat riser valve on the exhaust? On those trucks it was typically on the passenger side and could restrict exhaust flow depending on how it failed. 
 

3) How's the fuel tank vent? Any chance it's restricted and creating vacuum when the flow increases during acceleration?

In reply to No Time :

1) Yes, advance is fine.  Truck pulls well most of the time.  Problem is intermittent.  Distributor is new.  Did the same thing with the old distributor.

2) Heavy Duty trucks in 1985 came from the factory with no cats.  I was surprised to learn this way back when I bought this truck. No cats.

3)  Pretty sure there is no heat riser valve on the exhaust. 

4) I will look into that.  Possible I suppose.

So is the "rod knock" noise gone with the new converter bolts?

dculberson said:

So is the "rod knock" noise gone with the new converter bolts?

Yes!  Completely!

Sorry, I may have left that out in my rambling narrative where an attempt to fix one problem results in another mostly unrelated problem rearing its ugly head. 

Engine idles with impeccable smoothness.  Low speed operation is entirely satisfactory. 

The original intermittent "loses power during acceleration" issue is still present.

In reply to 1988RedT2 :

Sorry to hear the original problem isn't fixed, but excellent news on the knocking noise.