Blew a head gasket, what's the cause?

[Moespeeds]

So riding out of DC at the top of 4th gear I blew the head gasket on the rear cylinder. I took the heads off and was going to change my head and base gaskets, but a knowledgable friend told me last night that there is probably some reason that it blew, and it's not likely to just be wear and tear. I am hard on my bike, I've got about 17k on this motor. Never had the heads off before, no motor work. Oil temps coming out of DC were around 200-240. We were in traffic for a bit, but I think we were on the highway long enough to cool it down. Anyone know how I can check the torque on the studs in the case? Maybe one pulled out a little? Also, while I have the top end off, is there anything I should do or check? I'm going to check the clearances on the rockers. What else?

 

[Moespeeds]

 

[TheDeadOne]

Hey Moe,
Sorry to hear about the problems.
Block studs are sometimes installed with a thread locker, don't know if BDM or S&S recommends. But if none of them loosened up or pulled out during head removal, I'd doubt it's stripped out, maybe just loosened.To remove or install studs, "double nut" top of stud and tighten nuts together to lock. Then you can loosen or tighten stud. I'd have to look up torque specs. don't remember off the top of my head. But I check for a loose one first, easily try and remove, if you're thinking you pulled one out. If one is pulled out, I'd recommend that you or someone that's experienced in the installation procedures, install a "Helicore" into the block. But as far as what else to do, I go ahead and re-work the Top end while it's down that far. Hone the cylinders, re-ring, deck the cylinders and head for a least trueness (flat), re-lap the valves, check or replace springs.
But, that just me. I look at it, if it's down, you might as well take care of anything that needs to be checked or repaired then! I don't want to do it twice!:2thumbs: :2thumbs: :2thumbs: :2thumbs:

 

[Little-Boo]

The torque on the stud is 10 ft pound, with blue thread locker. One thing you need to check is to make sure you head or heads are not warped. This would be a good time to deck the head. As you know heat is deadly on head gaskets. That could be a combination of several reasons one being detonation which will eat up a gasket and eventually blow at the weakest point.

Double nut your stud to remove them and see if they come out easy or see if they crack when you first turn them, if you hear a crack, that means they were torqued. Clean out the thread with a thread chaser to remove all the thread locker and re-install with blue thread locker torque to 5 lbs first time around and 10 the on the final round.

I used Comatic head and base gaskets both of which were under stock spec to increase my compression a little. I used 0.030 head and 0.010 base. I have the part numbers if you want to go that way. If you are going with the stock gaskets I can send you set for free that I had left over from my engine build up.

As mentioned above hone the cylinders and use new rings and you should be good to go.

Carlos

 

[Moespeeds]

Carlos that is a very generous offer. I will send you a prepaid UPS label you can print and slap on the gasket package. Just let me know the approx dimensions if it's a box, or the size if it's an envelope. I would rather not mess with the compression. I ride alot, mostly short trips around Philadelphia and I spend lots of time idleing, and lots of hole shots on a hot motor. I don't want to do anything that may increase the heat or stress on the motor. I'm way more show than go, I could care less how much horsepower I'm making. I'm going to check the trueness of the heads, and maybe hone the cylinders. I'll order rings. What is decking the heads? My head bolts all cracked when I pulled them, but one of the rear head bolts had a white pwder on it, looked like some type of corrosion. The rear gasket is the one that blew. I'll check those studs tonight. Thanks for all the advice!

 

[Thumper]

I would rather not mess with the compression. I ride alot, mostly short trips around Philadelphia and I spend lots of time idleing, and lots of hole shots on a hot motor. I don't want to do anything that may increase the heat or stress on the motor. I'm way more show than go, I could care less how much horsepower I'm making.

A mild cut would be simple now, with a bump to 10:5. Jmo, not going to hurt and you will notice a huge difference in power. I'm assuming you already have a 600 cam?

 

[TheDeadOne]

Moe,
I think Boo is off presently. Decking the heads is "truing" or checking for "flatness". With what I can see, I'd strongly recommend it. If you're going to re-ring, I'd definitely hone the cylinders otherwise, what's the use of re-ringing if they're not broke? The new rings will seat better to a "truer" (honed) cylinder. As far as the white powder? That's the dried thread locker comming out when you loosen.

 

[Raywood]

The torque on the stud is 10 ft pound, with blue thread locker. One thing you need to check is to make sure you head or heads are not warped. This would be a good time to deck the head. As you know heat is deadly on head gaskets. That could be a combination of several reasons one being detonation which will eat up a gasket and eventually blow at the weakest point.

Double nut your stud to remove them and see if they come out easy or see if they crack when you first turn them, if you hear a crack, that means they were torqued. Clean out the thread with a thread chaser to remove all the thread locker and re-install with blue thread locker torque to 5 lbs first time around and 10 the on the final round.

I used Comatic head and base gaskets both of which were under stock spec to increase my compression a little. I used 0.030 head and 0.010 base. I have the part numbers if you want to go that way. If you are going with the stock gaskets I can send you set for free that I had left over from my engine build up.

As mentioned above hone the cylinders and use new rings and you should be good to go.

Carlos

Hey Moe,
Sorry to hear about the problems.
Block studs are sometimes installed with a thread locker, don't know if BDM or S&S recommends. But if none of them loosened up or pulled out during head removal, I'd doubt it's stripped out, maybe just loosened.To remove or install studs, "double nut" top of stud and tighten nuts together to lock. Then you can loosen or tighten stud. I'd have to look up torque specs. don't remember off the top of my head. But I check for a loose one first, easily try and remove, if you're thinking you pulled one out. If one is pulled out, I'd recommend that you or someone that's experienced in the installation procedures, install a "Helicore" into the block. But as far as what else to do, I go ahead and re-work the Top end while it's down that far. Hone the cylinders, re-ring, deck the cylinders and head for a least trueness (flat), re-lap the valves, check or replace springs.
But, that just me. I look at it, if it's down, you might as well take care of anything that needs to be checked or repaired then! I don't want to do it twice!:2thumbs: :2thumbs: :2thumbs: :2thumbs:

I'm putting all this good info away for a rainy day. Never know when you might need it!

 

[05chop]

Moe Where did the other piece of the blown gasket go? Can you take a close up of the head gasket with the missing gasket?

 

[Chopper Dave]

I'm putting all this good info away for a rainy day. Never know when you might need it!

yep...me too Ray! :2thumbs:

 

[Dakotabos]

If you need any torque values or part # for gasket kit let me know
I have all that info we have the say make and year bikes

The top end gasket kit would be DRAG PN 90-9503. the rocker covers are
? Do you have S&S Rockers covers? Chromed with round circles in the
middle six 1/4" cap screws holding top cover on? The DRAG PN 90-4091.

O.K. the 5/16 bolts torque to 15ft lbs, use red loctite. The 1/4" like
5ft lbs. use red loctite. The bolts holding down the cover, snug them
using red loctite. 1ft lbs.

 

[Moespeeds]

The blown chunk of gasket is out on 95 somewhere I guess. Got a bud honing the cylinders for me this week. Going to do the valve gaskets and rings, and check all clearances. The white powder was on the outside of the head bolt, not the threads. Looks like dissimilar metal corrosion but its just on the one bolt.

 

[TheDeadOne]

ok, probably caused by condensation or oxidation. Everything sounds Good! Good Luck! :2thumbs:

 

[john sachs]

Moe,
You need to be ABSOLUTLY sure a stud is not pulling out.I find this on S&S cases.(Kinda like Evos).If 1 is,DO NOT use a Heli-coil.Use a Timesert.You can try S&S for warranty.They may or may not !
I use S&S head and base gaskets,because of this problem.I don't want to be blammed if other studs pull.
The only deviation I use is: torque the heads to 10 ft.lbs...then 20 ft.lbs....then 90 degrees.Usually equals 38 ft. lbs.IMO a little low,but oh well.Put oil under the washer and on the bolt threads.
You must be sure that you don't hammer the bike till it has thoroughly warmed up.:up:
John

 

[TheDeadOne]

Thanks Mr. Sachs, I'd forgotten that "solid inserts" needed to be used in this application. Thanks Again! DUH!

 

[Moespeeds]

I called S&S and they told me not to disturb the studs unless I'm sure they are pulling out. I can look at the shoulders and measure them to determine if a stud moved.

 

[TCALZ06]

So What causes this?

I think this is the first blown head gasket on this board in about 2 years I've been around

 

[mobsta]

i blew both head gaskets on my 04 107.put 2 knew gaskets blew in 20 miles.pulled it down again and found studs in the v pulling out.could tell the first time.i used helicoils.now after about 1300 miles since repair getting a dull pop when cold.this was the same noise before they blew.time certs may work better.those pictures of your gasket look like mine.mosbsta