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main cap bolts

3K views 8 replies 5 participants last post by  B1-16V 
#1 ·
Alright, this is something that's been kinda bothering me for the last few days because I can't seem to find a solid answer.

Are the main cap bolts on a 16 valve engines reusable if they are the original bolts from the factory?

I ask because per the Bentley manual, they should be torqued to 48 ft. lbs. and nothing more; to me says they are not stretch bolts. However, if you buy new main cap bolts from lets say techtonics tuning or something, they specify 48 ft. lbs. + 90*. So I'm just curious for my own knowledge in the future what's the right thing to do as I've reused them in the past and never had any issues, but my most recent engine build is quite far from stock and I really don't want any issues down low spinning it to 8000+ RPM.

Any input is appreciated!
 
#4 ·
If the bolts do not have threads the full length under the bolt head, they are not stretch bolts. My 9A had them as well as many others that I have built in the past. But, for $20, it is good to replace them or spend a bit more for better ARP if you intend to push the rpms up.
I know, ARP was the way I should have went, but at the time the guy doing the machine work (Lou at LRB Performance in Northern NJ) and myself figured it would have been okay to use them because as per the Bentley manual and his various books with torque specs for nearly everything we decided it was okay to reuse them. I especially trusted his input since he builds winning race engines for various applications so if he didn't think it was okay he would have said so, and in this case he was right. The bolts I have are not fully threaded therefore, not stretch bolts.

I would switch to ARP now, but the main problem I have is that the engine has already been line bored for stock hardware and is together and running. My main reason for posting this was that someone mentioned to me that the main cap bolts were stretch bolts and I immediately thought oh F**K I didn't replace mine. My 16v sees 8,200 RPM every once in a while and may see some auto-x or an open track day here or there, but it's not as if I'm pushing it to the max all the time by any means.

Regardless I picked up some new bolts yesterday and plan to replace them this weekend just for piece of mind.
 
#3 ·
If the bolts do not have threads the full length under the bolt head, they are not stretch bolts. My 9A had them as well as many others that I have built in the past. But, for $20, it is good to replace them or spend a bit more for better ARP if you intend to push the rpms up.
 
#5 ·
The good things is that changing the bolts will not affect your align bore and you can do it in the car using a thin wall socket for the #1&#5 journals.
 
#6 ·
Yeah exactly. I was worried about that but then I remembered using the new stretch bolts will not effect the align bore. If I could change to ARP now I would but it's not an option, but the new OEM bolts will do the job just fine in the end.

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#7 ·
Alright so I changed the main cap bolts and torqued them to spec. 48 ft. lbs. + 90* and all seems good.

But yesterday I decided to change my oil pan gasket and windage tray because it was leaking a little bit. I was getting ready to install the oil pan and I looked down and there were 3 metal flakes/shavings :banghead: but nothing else. Nothing in the oil pump pickup, nothing mixed with the oil, no small glitter like pieces nothing, just 3 pieces of metal which felt like aluminum and looked like aluminum.

I don't have any pictures of them, but the car runs great and the oil pressure at idle is about 65 PSI while cold and 33 PSI while warm. This is a brand new engine with less that 1000 miles on it and the crank was turned down .25mm and proper bearings were fitted for a 100% true fit that is as good as it can possibly be. I plan to inspect the main and rod bearings today or tomorrow in hopes that it's not a bearing.

What do you guys think?

Here's a picture of what they looked like, this was from another thread on here with a 1.8l 16v.

 
#8 ·
It may just be some metal that was loosen during the rebuild and ended up in the oil pan.
Most likely from the head as that IS aluminum!
I wouldn't worry about it but it you can remove the oil filter and cut it open to expose the filter media I would.

If it looks "normal" then just re-install the oil pan and drive it!
 
#9 ·
Alright, this is something that's been kinda bothering me for the last few days because I can't seem to find a solid answer.

Are the main cap bolts on a 16 valve engines reusable if they are the original bolts from the factory?

I ask because per the Bentley manual, they should be torqued to 48 ft. lbs. and nothing more; to me says they are not stretch bolts. However, if you buy new main cap bolts from lets say techtonics tuning or something, they specify 48 ft. lbs. + 90*. So I'm just curious for my own knowledge in the future what's the right thing to do as I've reused them in the past and never had any issues, but my most recent engine build is quite far from stock and I really don't want any issues down low spinning it to 8000+ RPM.

Any input is appreciated!
I know, super old thread. Just to benefit someone coming along in the future doing a search like I've been doing, here's an update.
I just got off the phone with Techtonics, and as it would seem, VW did supersede the bolts with stretch bolts. The old ones can, technically be reused, but the new ones aren't that much. The new ones, and NOT the old ones, should have the extra 1/4 turn.
I'll be taking my pan off and giving them the extra bit they need. Glad I didn't fire it up yet.
I discovered this because I recently was looking at my pack slip from my Techtonics order, and saw the 1/4 turn note.
Non stretch = partial thread (like an ARP)
Stretch = full thread.
Hope that helps.
 
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