'84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

[MAtkins]

I'm working on a rebuild on my Merc and I need to prep the connecting rods for new needle bearings.

The guy I bought the rebuild kit from told me that I need to make sure that when the rod/cap are bolted to the crank that there is no 'lip' or groove between the rod & the cap on the inside where the bearing will ride over it.
He says (and it makes sense) that if it's not right the bearings would wear out before long.

He indicated that I need to get the rod & cap aligned perfectly and then tighten down the bolts to spec.
Then try to get my fingernail to catch between the rod & cap.
He said I need to sand those down with emery cloth until my fingernail can't catch anymore.

Any help or ideas on this from you pros would be greatly appreciated.

 

[wired247]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

Yeah, thats not what you do. The rods are formed together and then cracked to separate the cap from rest of the rod. The two pieces really only fit together one way. If you bolt the cap on the rod with nothing in the middle like a crank and bearings its very difficult to get them lined up perfectly sometimes. Put a crank and bearings in there and its much easier. The fingernail thing is what you do on the outside of the rod. You get it all in there and carefully place the cap on and tighten the cap down to 5 ft lbs or less and scrape your fingernail across the parting line. You should feel no parting line. If you do feel the parting line loosen the cap and do it again until its right. Sanding the outside doesnt do squat. Do not ever sand on the inside . Light cleanup with steel wool maybe.

 

[MAtkins]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

Thanks.
I can see that they're made of one piece of metal that was cracked.
It doesn't look to me like it'd be too hard to line them back up.

No sanding the connecting rod! OK - thanks again.

How can I find out the size of the bolt to the connecting rod?
I need a tap to clean out the holes.

 

[Dukedog]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

There two sizes. One is a 24 and one is a 28. Tha 7/8' long is tha 28 and tha 1' long is tha 24. Also "new" rod bolts are a real plus and not that expensive. Its better to torque "empty" and check tha inside with tha finger nail deal with tha "bottom" guided rods as in your case....Oh yeah, 5/16" dia. (.312)

Ya might wanna get a coupla 320 flapper wheels that fit tha top and bottom of tha rods. Give 'em a little touch just ta knock out any kinda flaw. Don't "polish" 'em just a touch ta clean 'em up............jmo

 

[wired247]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

Dont go shopping for bolts by size. Get the right bolts. Mercury or aftermarket. Those tiny high tensile bolts are the only thing holding your motor together.

 

[racerone]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

Well you certainly do not do any " sanding " on the outside when you assemble the rods !!!!

 

[Dukedog]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

Dont go shopping for bolts by size. Get the right bolts. Mercury or aftermarket. Those tiny high tensile bolts are the only thing holding your motor together.

Don't think he is. Just lookin' for something ta chase tha threads with sounds like...........

 

[wired247]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

Don't think he is. Just lookin' for something ta chase tha threads with sounds like...........

Oh , of course. He did say that dint he? In that case either use a notched bolt or an actual thread chasing tap. They sell a set at Sears that has been worth its weight in gold to me over the years. Do not use a standard tap though. They cut oversize and will ruin the tight fit the rod needs.

 

[MAtkins]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

OK, my rod bolts are 7/8" so my TPI is 28.
Thanks DukeDog - looks like you really know this motor!
By '320 flapper wheels' I'm not sure what you're talking about.

Why buy new bolts? The old ones look fine to me.
The rod threads just need cleaned out.
I can't find a 5/16-28 thread chasing tap.
I'm looking at sears.com and can't find the kit.
I'll figure something out.

Thanks much for all your help.
I've gotta get these threads cleaned out . . .

 

[racerone]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

Are you absolutely sure that you should be looking for a 5/16-28 tap.----100% sure ?????----Or perhaps another thread count !

 

[wired247]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

The craftsman thread chaser set # 52105 looks like this ...

Its either going to be the 5/16 x 24 bolt ( more likely ) or the 5/16 X 28 bolt ( never seen one ). The sears kit has the 5/16 X 24 chaser.

 

[Faztbullet]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

Just take a old rod bolt and cut slots longways on threads, this makes a great chaser and NO LOCTITE!!!

 

[Dukedog]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

Are you absolutely sure that you should be looking for a 5/16-28 tap.----100% sure ?????----Or perhaps another thread count !

Think it might have been a early Merc only deal. I've only seen one set since tha V6 came about. Puttin' in new bolts a long time ago grabed some outta tha bin and they wouldn't fit. Did a little pokin' around and sure enough they were listed on tha Micro Fiche. Cleaned up tha old bolts and used tha rods in one of my own motors............Who knows. Its Merc!

 

[wired247]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

X2 on the no loctite. A properly torqued and stretched bolt needs no glue. Personally, I prefer the late model torque to yield bolts. Its a weird feeling torquing those tiny little bolts to what must be 100 ft lbs at 90 degrees after 30 ft lbs but Ive never heard of one failing.

 

[Faztbullet]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

Its a weird feeling torquing those tiny little bolts to what must be 100 ft lbs at 90 degrees after 30 ft lbs but Ive never heard of one failing.

You never torque to spec then twist 90? with torque wrench!!!! You have to use a torque angle gauge! This is more accurate reading as it makes up for torque lost thru thread friction, when done with angle gauge bolts are at about 50ftlbs. MAtkins make sure yo torque rod in (3) steps. !0lbs and check alignments, you can still tap with small hammer /drift pin to align if needed, 20lbs rods 1-6 and check rotation and final torque of 30 lbs as you year doesnt use angle torque, I myself torque to 35lbs on older motors amd make sure you oil the threads!!!

 

[wired247]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

You never torque to spec then twist 90? with torque wrench!!!! You have to use a torque angle gauge! This is more accurate reading as it makes up for torque lost thru thread friction, when done with angle gauge bolts are at about 50ftlbs. MAtkins make sure yo torque rod in (3) steps. !0lbs and check alignments, you can still tap with small hammer /drift pin to align if needed, 20lbs rods 1-6 and check rotation and final torque of 30 lbs as you year doesnt use angle torque, I myself torque to 35lbs on older motors amd make sure you oil the threads!!!

I know that. It just "feels" like its a 100lbs of torque when it is turned to 90 degrees past whatever those torque to yield fasteners get their initial torque setting set at. Its kind of creepy doing it . I know they work well and I understand the metallurgy but it still feels weird doing it.

 

[MAtkins]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

Thanks for all the input.
So, the book says torque it down to 30 and use Loc-Tite.

I'll go with your collective decision - don't use Loc-Tite on the threads.

Should I torque them down more than 30 ft/lbs or not?

 

[Dukedog]

Re: '84 Merc 150 - V6 2.0 - Rebuild - Connecting Rods Prep?

30 lbs and Loc-Tite (just a drop). Just like tha book says. Those aren't torque ta yield. Ya gonna need tha Loc-tite other places anyway.................jmo