Dunc

Background:
So this is kind of a weird problem. The exhaust manifold studs are sheering off and the OEM (brand new) locking nuts are backing out and falling off under normal driving. Normal driving for me is cruising down the highway to and from work/school at 70mph for about an hour each way...and also regular city driving. It's not like I'm beating the hell out of it every time I hit the gas.

What I've done:
- I used OEM studs and locking nuts. The entire top row of studs sheered off. Amazingly I didn't have an exhaust leak haha
- I replaced those with "Automotive Studs" from ACE Hardware which are supposedly very strong. I bought new OEM locking nuts and tried again. Result: one stud has sheered already and two nuts are gone within like 4 hours of driving.
- I made sure that the manifold holes were big enough to get around the studs without touching them. So it's not like I am forcing the manifold on the studs.
- I am tightening the nuts with a normal 12mm wrench starting from the bottom middle and working my way out. I'm also not tighting the crap out of them either...just a normal snug/"plenty tight" type thing.
- I tried a normal nut with a locking washer on one OEM stud before I switched them, and that just sheered off as well after a bit.


Question:
Has anyone ever had this problem before? It's really weird to me that these studs are sheering the way they are. Any suggestions? I'm about to buy some ARP studs and see if they hold up...I would assume the ARP's would be the strongest stud I could find, but then again I've never heard of anyone having this happen before. It's not rocket science to put a stud in a hole and put a nut on the thing haha.....clearly it must be close to quantum physics though for me

Jared

seen it twice, in both cases the manifold flange was warped.

non-VTEC

do you have a flex section in your downpipe?

if not then there is to much stress/flex in the exhaust causing stress on those studs....

thelate1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by non-VTEC &raquo;</TD></TR><TR><TD CLASS="quote">do you have a flex section in your downpipe?

if not then there is to much stress/flex in the exhaust causing stress on those studs....</TD></TR></TABLE>

thats what i was gonna say. correct me if i'm wrong, but a single 6" flex should provide enough compensation for engine flex. if this is incorrect, someone, please correct me.

Dunc

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jared &raquo;</TD></TR><TR><TD CLASS="quote">seen it twice, in both cases the manifold flange was warped.</TD></TR></TABLE>
Good point...I didn't think about that. That's going to be really annoying if that's the case.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by non-VTEC &raquo;</TD></TR><TR><TD CLASS="quote">do you have a flex section in your downpipe?

if not then there is to much stress/flex in the exhaust causing stress on those studs....</TD></TR></TABLE>

Yea I have a flex in both the downpipe and the dumptube. Although I don't need it in the dumptube anymore since it's no longer routed back into the downpipe.

siblues

iTrader: (1)

These are very nice but pricey?

http://www.stage8.com/

Jared

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by siblues &raquo;</TD></TR><TR><TD CLASS="quote">These are very nice but pricey?

http://www.stage8.com/</TD></TR></TABLE>

the stockers are just fine, i think he has other issues.

mahatma

any way to brace the turbo/mani against the block? maybe use an a/c bolt hole and fab a brace....?

rmcdaniels

I'm with Jared, check your manifold flange. I used studs for years (whatever ones that I had laying around in my big box of Honda bolts) with Ace stainless nuts tightened with a 12mm wrench, never had any problems with it, and I was using a giant LoveFab SST that weighed a ton.

Dunc

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rmcdaniels &raquo;</TD></TR><TR><TD CLASS="quote">I'm with Jared, check your manifold flange. I used studs for years (whatever ones that I had laying around in my big box of Honda bolts) with Ace stainless nuts tightened with a 12mm wrench, never had any problems with it, and I was using a giant LoveFab SST that weighed a ton.</TD></TR></TABLE>

I agree with you guys. The stock ones should be plenty fine. They have been until just recently. I'll check the flange when I get a chance and take it from there. I figure if I haven't needed to brace the thing in the past then there is no reason to do it now.

agrn93ls

I do have kind of a similar issue i keep losing the factory lock nuts at the ends of the manifold. not shearing any studs though.

i had the manifold on a LS/VTEC set up, spun a bearing, went with a built GSR bottom and put same head manifold and everything back on. now im loosing nuts and never did before makes no sense to me since the only thing that changed was the block?

except had a runner crack welded but not near the flange so wouldnt think that would affect it. suppose it could but the person that welded it has been weldin these manifolds and is a high end tuner/fabricator so i know its not related to his work just maybe the flange wasnt checked.

b18bEKcoupe

Stainless hardware will cause more problems than high quality steel. During thermal cycling the stainless hardware will start to loose clamp load and eventually they WILL back out. Stainless hardware is frequently used in the marine industry to inhibit corrosion but in areas that see high thermal cycling such as an exhaust system they can not be used. This may not have anything to do with your problem but it might be good for other to know.

HiProfile

You also get free, natural 'locktite' with non-stainless nuts - RUST! Seriously though, with high-grade steel, it won't be more than surface rust, unless you run 40k miles/month through winter in Wisconsin where they DUMP salt on the roads.

If the flange was warped, you'd get the nuts lifting more on one side, and that puts all the load on one side of the studs/threads, and sheers them off from the excessive stress. BTW did you put them on with a torque wrench to the right specs, or did you just 'get em snug'?