Head bolt "situation"...

[Pilgrim]

I was just re-installing the head on my 1983 280ZX Turbo when I ran into two problems:

1) One bolt would not tighten properly. It was one of the last I installed, and when I turned it and got no increase in resistance past about 30 lbs/ft, I decided that I probably had a bad bolt. At least I was smart enough NOT to keep turning it, which would most likely have broken it off. I checked the bolt hole to confirm that there wasn't debris in the bottom blocking the end of the bolt, then re-used one of the original bolts and it torqued down just fine so the head is torqued into position properly. I have a new bolt ordered.

2) Of more concern - I had all the head bolts but the one above installed and realized I had not put the washers from the original bolts under the heads of the new ones. I removed the new bolts one at a time and installed the washers, re-torquing each bolt as I re-installed it.

But - these are supposed to be one-time use bolts. I don't want to blow a head gasket, but I also am not fond of the idea of paying another $100 for a replacement head bolt set. The bolts were torqued and sat for about an hour before I realized the washers were missing.

I have some options...

- Replace the individual bolt, torque it, go on with life.

- Replace the individual bolt, then make one more round of the head bolts adding 3-5 lbs/ft of torque to stretch the bolts slightly.

- Replace the entire head bolt set.

Your thoughts, please?

Edited August 3, 2014 by Pilgrim

[Mark Maras]

I'd go with option 1 and re-torque all of them after a few hot cold cycles & then decide what the next step is based on what I found.

[djwarner]

The design intent of one time use bolts is to stress the bolt to a point beyond its elastic limit. This causes the bolt to deform (read lengthen). This leaves a residual tension near the point of yield. As the engine thermal cycles, some additional creep may occur.

As the bolt yields, the crystalline structures inside the bolt grow. Repeated torqueing to the point of yield causes the crystals to grow more. The weakest part of the steel is the boundary between crystalline and non-crystalline elements. As the grains grow in size, a bolt becomes weaker and more likely to fail catastrophically.

So you may be able to re-torque the bolts up to the specified limit for a second time. They may fail as you torque them down, after a heat cycle or two, or the next time you try to remove them. Point is that it is a shot in the dark. And the question is the expense in time and labor to pull the head and removing broken bolt shanks versus the cost of new bolts now while the head is off. The professional engineers say replace them now.

[LeonV]

I agree with Mark, I'd go with option 1. Just put in the missing bolt and torque it down.

These are not torque-to-yield bolts, I'm curious where you got that bit of info?

[Diseazd]

I'm with Mark and Leon........go with option 1.

[siteunseen]

I used ARP turbo bolts when I rebuilt my '77. After 500 miles I re torqued them as their directions recommend. From the ARP wb site, " Because the head gasket will compress upon initial torquing, make sure studs (or bolts) are re-torqued after the engine has been run."

The Official ARP Web Site | Manufacturing

[Pilgrim]

I went with option #1 - pulled all bolts one at a time, installed the missing washers, and when the replacement bolt arrived, removed it, installed the new bolt with washer.

And...last weekend while I was trying to get the cam sprocket on, I realized the timing chain tensioner had dropped and I'm going to have to pull the front end cover and crank pulley to get the tensioner back in place. That's another thread...

[Pilgrim]

Can't believe that I'm picking this up two years later. I took care of the tensioner, re-assembled everything and kept at it.  Now the car has been together for more than a year, but I still don't have it on the road.  I've gotten it running, but never gotten it to run smoothly - it misses like crazy whether cold or hot.  Over the past eight months, I have checked the following:

- Cam and chain timing are correct.

- Distributor timing is correct.

- Fuel injectors have been removed, bench and flow tested and re-installed.

- New spark plugs, distributor cap and plug wires.

- Fuel pressure and pressure regulator were tested and check correctly.

- Fuel filter was replaced.

- Each fuel injector connector has been tested and all are firing.

- Traced all vacuum lines, replaced hoses and confirmed that all are connected.

- Sprayed air intake path with starting fluid to confirm no vacuum leaks.

About the only thing left that I can think of is bad fuel, although 3/4 of the tank is gas less than 6 months old. However, after sitting for 3 years, the tank may have some debris or varnish. My plan is to bypass the fuel tank, connect a fuel line from the fuel pump intake to a 5-gallon can of fresh fuel, then start it and see if the fresh fuel gets rid of the miss.

 

Comments??

 

[Patcon]

Sounds like a good plan for a next step. Be careful...

[Martzedcars]

Are those injectors firing... AT the right time... when they don't, the engine runs like crap.. put in another ECU.. with same number..

[Zed Head]

22 hours ago, Pilgrim said:

- it misses like crazy whether cold or hot. 

When does it miss?  All the time, even at idle?  Accelerating, cruising...  What is the tachometer needle doing when it's missing?  Try to distinguish between a fuel problem and an ignition problem.  Maybe your power transistor is dying.  Considering the time you're spending, switching to the HEI module might be worth a shot.  $25.

The injectors all fire at the same time, even on the turbo engines.  Sequential injection didn't show up until in the 90's.  Just sayin'...

[Pilgrim]

Good questions. It misses so badly at idle that it won't keep idling unless I keep jiggling the throttle and keep the revs up. It misses at all engine speeds, so it has no power when accelerating.

As noted above, I've replaced cap, wires and plugs, and I've used a timing light on each plug wire to confirm that each plug is getting spark at all engine speeds. Spark plugs appear sooty but are all firing.  The soot may be a clue to bad gas.  You are correct that all injectors fire at once (done research on this) and I've used a NOID light to check that each injector is getting its firing pulse.

I also have a spare ECU and have installed it - no difference.

I appreciate the thought about the HEI module, and would appreciate a reference to info about it in case I end up needing to try that. 

As you can imaging, I'm VERY tired of screwing with this after a 3-year project leading to months of testing one thing after another.

Edited August 25, 2016 by Pilgrim