Vega 140 ARP head stud torque

[kgroombr]

I am installing a Vega 140 head using the ARP head stud kit 131-4002. What scares me is that the instructions say to torque to 80 ft lbs:

http://arpinstructions.com/instructions/131-4002.pdf

Where the shop manual calls for 65 ft lbs.

I think 80 is a bit much. Any suggestion on what torque I should use?

Thanks,
Ken

[cjbiagi]

You should go by the stud manufacturer recommendation. They know what spec is needed to get the correct stretch on their studs. It is not unusual for ARP to recommend a different torque value. GM torque recommendations are for GM studs.

[hammerdown7]

I would be concerned with that much torque. Remember your pulling the torque on aluminum. I have ARP studs on my Cosworth and have never had a problem with factory settings. The head has been off and back on a minimum of four times since I have had it and before that it was in the race car and I have no idea how frequently it was apart.

Dick

[kgroombr]

I called them and they said 80 ft lbs is what to torque it at, but something in my head just says "NO". Googling didn't find anything about the Vega 140, but I did read about some stripping out the threads in the block by following their instructions. I think I am going to follow factory specs.

Thanks,
Ken

[res0o7eb]

80 lb-ft doesn't seem overly high to me. I would go with what ARP says - they are the experts.

Probably need to get some of their Ultra-Torque lubricant:

Following the manufacturers recommended torque sequence tighten the nuts in three equal steps to 80 ft lbs with ARP ULTRA-TORQUE FASTENER ASSEMBLY LUBRICANT.

[hammerdown7]

I checked the torque rating specified for small blocks and they give the same ratings of 80lbs, longer studs are 85lbs. Again, on a Vega it's aluminum. I would still use the factory settings. I doubt ARP checked and tested these studs on a Vega engine.

Dick

[cjbiagi]

Why not just split the difference and go maybe 70-75 lbs? A stud or bolt needs to be stretched to apply the proper clamping load and remain tight. Some studs are "stretchier" than others, that's why the difference in torque values. Are these head bolts or studs? I believe studs are easier on the block thread than a bolt is.

[Kenova]

When a bolt is torqued it creates a lot of strain on the threads in the block. It is twisting and pulling at the same time. When torquing a stud there is no twisting force on the block's threads, just a pulling force. With the twisting force removed the threads can handle more torque on the stud.

At least that is the way it was explained to me.

Ken

[hammerdown7]

I checked with another Cosworth owner that has used the studs on a number of engines and he followed ARP's 80lbs. I'll just repeat I didn't and haven't had any problems including a 12.7:1 engine.

Guess I didn't help much!

Dick

[kgroombr]

In addition to calling them, I also inquired via email. I received a more detailed response:

Eighty ft/lbs is the standard torque. If you feel you need to lower the torque then you can lower it to 70 ft/lbs with the ARP Ultra torque Lube, absolute lowest at 65 ft/lbs. You definitely don't want to pull them out of the block. If you drop the torque 10% then you lower the clamping load by the same percentage. You have the block in front of you so you will have to use your judgment for the final torque.

I read quite a bit some posts via google. Here are some of the mistakes others have made with using these:

Before installing, the threads need to be chased. Several folks were using tap and die sets. This will remove more metal from the existing threads thus weakening them. I used a thread chaser, but there were two on the front right of the block that didn't go as deep as the others. I was afraid to try to go deeper as I know people that have cracked blocks by cranking on bolts. I am not sure why they don't go as deep as the others and was thinking about using a tap and die to go deeper, but stopped not knowing what I may have broken or cut through.

When I installed the studs, I used anti-seize on the threads that go in the block as a precaution.

I followed the instructions and torqued to 70 ft lbs. Process went very well, and whatever their ultra-torque lube is, it makes those nuts spin on like there was nothing there. Anybody having to install a head, this makes the head line up square immediately.

If anybody has a reason why the two front right holes don't go as deep as the others, please let me know. All the others lined up nicely.

Thanks,
Ken

[hammerdown7]

Ken,
I don't have a bare block to check but one possibility is that because the oil pump mounts there, they needed more room for oil passages and therefore the holes are shallower. Just a guess.
Dick

[kre25]

I race a Vega on a 3/8 mile oval.
Won a Championship in 2009 and 17 races along the way.

Lots of Compression Ratio.
We never torque the head more than 55 lbs with the screw in studs.

Use Fel Pro Head Gaskets!

Did you know that the Fel Pro Head Gaskets come in different thicknesses?

Have never had any problem with the Heads leaking or any other problem.

Do not like installing heli coils in the block is why we dropped the torque, as per my engine builders instructions.

[hammerdown7]

kre25,

Where do you race? You must have one of the rarest cars running.

Dick

[Monza Harry]

Well Ken I don't know if this will help or hinder but her are a few links from ARP webpage to highlight some of the design criteria and I am Sorry! http://www.arp-bolts.com/pages/technical_design.shtml and a little more "LIGHT" reading http://www.arp-bolts.com/pages/technica ... urgy.shtml and this one from "Unbrako" a major industrial fastener supplier, I didn't read this, this time and it appears to have been updated since I did, but the older paper version has a large amount of relevant info, a good read if you go this way! http://www.unbrako.com/dnloadengg.htm (you have to download the files) Harry

[kgroombr]

Thanks for the info.

I contacted ARP and they were insistent that the 140 block could handle that torque using these studs, but they said I could go a little light if I was paranoid. I torqued it just like they said, and they are holding great after 3000 miles.

For anybody that is still using the 140 engine, I highly recommend using these studs. It makes mating the head to the block a breeze.

Ken