Thanks again guys! My brother came over this morning and helped me start putting things back together. We go the water pump removed, all surfaces cleaned up, and the new water pump installed. But I haven't been able to find torque specs for the bolts for the pulleys. The factory service manual has all the torques specs at the back of the manual, but I don't see anything for these pulley bolts. At the end of the torque specs listing there is a section called "Unless otherwise specified".



These bolts all have 10mm heads. Those in the water pump pulley are 6T, those in the eccentric shaft pulley are 8T. But when we try to torque the bolts into the front of the water pump to 30 ft-lb it seems like we are trying tighten them too much. Can someone verify what these torque specs should be?

Thanks,
Rich

 

The way I read it, 6T and 8T designate the grade (tensile strength) of the fastener. The heads are marked with a "6" or an "8".

A fasteners torque is in relationship to the diameter of the thread, not the size of the head. So the eccentric shaft pulley bolts may be marked with an "8" but the thread diameter is only 6mm. So the torque according to the chart would be 6-9 ft-lbs (.8-1.2 m-kg). The water pump pulley fasteners are softer at 6T but still 6mm diameter. Their torque would be 5-7 ft-lbs (.7-1.0 m-kg)

 

If I am not mistaken, thread pitch on a bolt will change the torque value as well. More threads, more max torque.

For most bolts that are available to us for our cars, the above explanation is perfect.

To get even deeper in the weeds, I looked up torque specs for bolts and some manufacturers have a separate torque values for nut/bolts that use lubrication and not.

 

Thanks again guys. That's obvious and I should have known that. They aren't going to specify torque based on head size. I'm glad we backed off. We'll hit it again tomorrow.

Just for documentation purposes, I think the water pump pulley bolts are 6T, 6mm, and the eccentric shaft pulley bolts are 8T, 8mm. I'll double-check tomorrow and correct if necessary.

Rich

 

Yes, its called "wet" torque vs. dry torque. Finer pitches (more threads per inch) do provide higher fastening strength of an assembly but the mechanical properties of the fastener material itself remain the same as a coarser pitch fastener of the same grade. They both will yield at the same maximum load.

I believe all the bolts that hold the pulleys and clutch fan are 6 X 1.0mm.

 

Here's the next dilemma. When I restored an '85 a little over 15 years ago it had a burned up 12A in it (I replaced it with a 6 port 13B). At that time I decided to rebuild the OMP in that engine so I ordered a rebuild kit from Lowe's Automotive, as well as a couple of extras for future use. When I looked at that kit and compared it to the one from Atkins in this video I decided the one from Atkins is more complete so I ordered one. It arrived and I started the rebuild but got stopped at one of the first steps. The kit comes with 2 o-rings to replace the seal on the shaft and I can't get those o-rings to seat properly like he does in the video. I tried using WD-40 and motor oil as a lubricant.



The Lowe's kit includes one thicker o-ring for this seal so I decided to give that a try. That filled the channel nicely but it was too thick and I couldn't press it into the housing. Since it was included in the kit for this purpose I figured it must fit so I put it in the bench vice between a couple of pieces of wood and pressed it into place. It did go into place, but not until the housing had been cracked.




So now I figured I have several options.

1) Use the OMP from the 12A I took out of the 12A in the '85. Unfortunately, I haven't been able to find it.
2) Block it off and use strictly premix. Effectively, this is what I've been doing for many years, but would prefer to use an OMP as well as premix.
3) Try to repair the housing with JB Weld. I may do this regardless of the final decision, just to see if I can do it.
4) I was fortunate enough to find one on the auction site for a very reasonable price. It should be here this weekend and I intend to use this one.

So, I think options 4 and 1 are the most viable. But if I go with the one I ordered I will want to rebuild it so will still have the problem with the o-ring(s). Is there anyone out there that has experience with these and can offer advice? Also, do these o-rings need to be some special material (viton, nitrile)? Or will standard rubber o-rings be ok?

Thanks,
Rich

 

The replacement OMP is supposed to arrive today and I plan to work on it tomorrow, so I figured I'd give this a bump. Any advice for replacing the seal on the shaft? Can I use standard rubber o-rings or do they need to be a certain material?

Thanks,
Rich

 

My opinion is that viton is probably the best for the application, if you can find it in the right size. I used viton for my beehive cooler o rings. It has a much higher temperature range compared to nitrile and plain Buna. However I think the sizing is more important than the absolute temperature range in this case given that Buna and nitrile can tolerate the normal engine temperatures.

 

Thanks for the update! My 79 has almost the same issue. It works just fine, but randomly will stop charging the battery. The only downside of having no dedicated volt meter! A few times I have been stranded with a battery too low to crank back up. Intermittent issue, I can drive some days with no issues and battery looks good when I leave the driveway, some days it will strand me. I would say 1 in 8 trips. It is sitting in storage for now...

 

Time for another update...hopefully the last one. Last weekend my brother and I got everything put back together, filled it with antifreeze, and took it for a test drive. Everything looked and sounded good...even got nice heat from the heater. So I put about 40 miles on it over the next couple of days and all is well. Since then the weather has been pretty crappy so I have not been able to put any more miles on it, but will when I get a chance. The oil is pretty fresh so I can't tell if the OMP lines are full of oil or not but I'll be keeping a close eye on the oil level from now on.

So, for now anyway, I'm calling this episode complete! Thanks for all the help.

Rich