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Stretch (torque to yield) Bolts on 1.6NA
by
Jory
on 30 Mar, 2011 22:00
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I'm building a 1.6NA Diesel out of a 1990 Jetta. In my research, I keep finding conflicting info on whether or not the rod and main bolts are stretch bolts.
How can I determine whether mine are stretch bolts? I vaguely remember reading something about markings on the rod bolt nuts...
thanks
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#1
by
Jory
on 30 Mar, 2011 22:55
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IIRC the mains are not a TTY torque spec and they do not say in the Mk2 Bentley to replace them. I don't see any reason to replace them and so I save my money on that one. I've never had an issue there. The 1.6 rod bolts also do not say to be replaced in the Mk2 Bentley. They do however, have a TTY spec. I have mic'd them over several torques and they do indeed stretch progressively with each proper torque. I also know of several individuals who have reused them and don't know of a single issue aside from Smokey Eddy and that IMO wasn't conclusive. You decide.
This engine had never been apart so the bolts don't have many torquing cycles on them. I also would prefer not to have to machine the rods due to pressing new bolts in.
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#2
by
Mark(The Miser)UK
on 31 Mar, 2011 02:06
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I'm building a 1.6NA Diesel out of a 1990 Jetta. In my research, I keep finding conflicting info on whether or not the rod and main bolts are stretch bolts.
How can I determine whether mine are stretch bolts? I vaguely remember reading something about markings on the rod bolt nuts...
thanks
The non-stretch had 15mm threaded ends, whilst stretch ones had 25mm threaded ends and a circle drawn on the lug end
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#3
by
Jory
on 31 Mar, 2011 21:11
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I'm building a 1.6NA Diesel out of a 1990 Jetta. In my research, I keep finding conflicting info on whether or not the rod and main bolts are stretch bolts.
How can I determine whether mine are stretch bolts? I vaguely remember reading something about markings on the rod bolt nuts...
thanks
The non-stretch had 15mm threaded ends, whilst stretch ones had 25mm threaded ends and a circle drawn on the lug end
Are you referring to the rod or main bolts?
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#4
by
rs899
on 01 Apr, 2011 04:28
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http://www.flickr.com/photos/61264831@N05/?saved=1Re the rod bolts-
I ran into this when I changed the rod bearings on my '91 Jetta. The later pistons used stretch bolts (on the left) . Earlier pistons I had (circa '81) used the non-stretch bolts- so I used them.
So far so good.
This scan is out of the 1980 gasser Bentley. I don't think the early or late diesel Bentley has this illustration- at least I never found it.
As far as I know, all the main bearing bolts are non-stretch- I reused mine ( I pulled a couple of caps off and plasitigauged my mains).
Rick
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#5
by
Jory
on 14 Apr, 2011 23:56
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^thanks for the info. Looks like i've definitely got stretch bolts on the rods.
Guess I need to find some new studs.
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#6
by
Jory
on 25 Apr, 2011 10:01
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Alright, decision time.
I can get the rod bolts through the dealer at wholesale, so it's not completely outrageous. However, it's still $70 that I'd rather not spend.
Who has experience to offer with re-torquing the rod bolts?
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#7
by
Mark(The Miser)UK
on 25 Apr, 2011 16:47
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Alright, decision time.
I can get the rod bolts through the dealer at wholesale, so it's not completely outrageous. However, it's still $70 that I'd rather not spend.
Who has experience to offer with re-torquing the rod bolts?
I have 
My only criteria is to never angle torque unneccessarily! ie when in the plastic range of the bolt, stop. [or for that particular round of torquing for head bolts]
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#8
by
R.O.R-2.0
on 26 Apr, 2011 09:36
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Alright, decision time.
I can get the rod bolts through the dealer at wholesale, so it's not completely outrageous. However, it's still $70 that I'd rather not spend.
Who has experience to offer with re-torquing the rod bolts?
ive re-torqued rod bolts many times, but all the ones ive done, im pretty sure they were NOT stretch bolts..
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#9
by
Jory
on 02 May, 2011 22:05
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I opted to buy new studs from the stealership, just not something I wanna risk it on.
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#10
by
R.O.R-2.0
on 03 May, 2011 12:28
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I opted to buy new studs from the stealership, just not something I wanna risk it on.
thats not necessary unless your old bolts were messed up. 99% of the people on here re-use rod bolts on low and medium performance builds..
only the hot rods really need ARP bolts. plus, when you get new bolts, you SHOULD get the rods re-sized, or atleast checked for out of round. the rods sometimes get out of round when you press in new bolts..
rod bolts ARE re-useable FWIW.. im not the only one doing this practice.
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#11
by
Toby
on 03 May, 2011 15:37
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I have never seen stretch bolts in an IDI NA 1.6, but I have only played with the older stuff. I have however always reused the rod bolts in Audi/VW diesels and never had a failure in more than 40 instances. Maybe the later stuff is different, but TTY bolts look much different than regular bolts and studs. The most striking feature of TTY stuff is that no part of the bolt (except the shoulder to align the rod and cap) is larger than the root diameter of the bolt and they usually lack any kind of shoulder. Compare an 11mm non TTY head bolt to a 12mm TTY example.
It is almost never a requirement to resize the big end just because you change the rod bolts. They go in and out pretty easily. You can't be a ham fisted jerk about it, but is a simple operation.
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#12
by
Jory
on 06 May, 2011 18:51
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I opted to buy new studs from the stealership, just not something I wanna risk it on.
thats not necessary unless your old bolts were messed up. 99% of the people on here re-use rod bolts on low and medium performance builds..
only the hot rods really need ARP bolts. plus, when you get new bolts, you SHOULD get the rods re-sized, or atleast checked for out of round. the rods sometimes get out of round when you press in new bolts..
rod bolts ARE re-useable FWIW.. im not the only one doing this practice.
I realize that people get away with reusing rod bolts, but the ones in my engine are definitely stretch bolts, and saving $60 isn't worth gambling everything else in my engine. I didn't shell out for ARP bolts as I don't plan to be tearing this engine back down.
As for the rod ends, I don't see how there will be any problem. The studs pop right out, and if you support the rod correctly when pressing the new studs in, there is no way to deform them.
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#13
by
R.O.R-2.0
on 07 May, 2011 10:49
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only way you got TTY rod bolts, is if you have an AAZ, or a 90s 1.6L diesel..
IIRC, they started using TTY bolts in 89 or 90 on diesels..
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#14
by
Jory
on 07 May, 2011 12:59
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only way you got TTY rod bolts, is if you have an AAZ, or a 90s 1.6L diesel..
IIRC, they started using TTY bolts in 89 or 90 on diesels..
I'm fairly certain they started around the time vw changed to 12mm head bolts. Regardless, the engine I'm building was made in 1990.