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Author Topic: Blown Head Gasket On My Trailblazer  (Read 1708 times)

High On Octane

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Blown Head Gasket On My Trailblazer
« on: May 20, 2013, 05:31:12 AM »
So after hearing my head gasket blow while out on a ride this morning I decided to not waste time and to tear the heads off tonight.  Sure enough, the right cylinder had completely blown out about a 1/4" section of gasket towards the inner side of the cylinder.  Upon examination, I also found that that gasket was leaking slightly on the left cylinder but the gasket was in tact.

I also inspected the piston tops, some carbon build up but no sign of damage, pre-ignition or lean conditions.  The cylinders themselves looked absolutely amazing.  I'm not sure if the pistons were replaced or not, but they were at least definitely re-ringed and cylinders professionally honed.  No scoring what so ever, in fact, you can still see all the the brush marks on the cylinder walls from when it was machined.

So, it looks like I got off lucky and just need to replace the head gaskets and other associated gaskets.  I'll be placing an order with Hitchcock's tomorrow morning and hopefully have the parts by the end of the week.

Does anyone know the torque specs for the head bolts?

Scottie


Blown Gasket


Left Head


Right Head


Piston Tops


Cylinder Walls
Bulldog Kustoms - Denver, CO
Specializing In Kustom Paint

The Blackhawk
1958 Enfield/Indian 711cc Twin

Building the 1st EVER Supercharged RE Twin
FULL RACE motor with ACE Performance

ace.cafe

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Re: Blown Head Gasket On My Trailblazer
« Reply #1 on: May 20, 2013, 10:20:07 AM »
I'd recommend checking the cylinder and head mating surfaces in that area for flatness. Or for any other reason that the gasket blew right there.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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ERC

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Re: Blown Head Gasket On My Trailblazer
« Reply #2 on: May 20, 2013, 12:32:58 PM »
The heads look like it was redone with very few miles on them. Ace is right about checking flatness. Also get the composite gaskets. I've been torqueing mine to 20ft.lbs if I remember correctly.  ERC
2-57 Apaches, 2-57 Trailblazers, 60 Chief, 65 Interceptor, 2004 Bullet, 612 Bullet chopped.

High On Octane

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Re: Blown Head Gasket On My Trailblazer
« Reply #3 on: May 20, 2013, 12:55:01 PM »
Should I use l like the edge of a metal ruler to check for flatness?  Also I planned on getting the composite gaskets, they aren't that much more.  And I agree, I think someone has already been through this motor at some point.  Possibly the motor was rebuilt and the msg failed very shortly afterwards.  Also as far as that right gasket blowing out. It very well may have been that the head wasn't torqued properly.  The head nut by the spark plug was incorrect and also the head on 1 of the long head nuts on that cylinder has been "shaved down" to the next smaller hex size. I ordered replacements for those as well.  And the head bolts on the right cylinder weren't nearly as tight as the head bolts on the left cylinder.  This may have been a case of the bolts loosening up just enough for it to cause a problem.

Scottie
Bulldog Kustoms - Denver, CO
Specializing In Kustom Paint

The Blackhawk
1958 Enfield/Indian 711cc Twin

Building the 1st EVER Supercharged RE Twin
FULL RACE motor with ACE Performance

ERC

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Re: Blown Head Gasket On My Trailblazer
« Reply #4 on: May 20, 2013, 01:09:28 PM »
It could be the bolts were never re torqued after it was done. Your best bet to check flatness on the heads is to get a sheet of 1/4" plate glass and tape a piece of 220 grit paper to it to see where it touches the head when swirled around on the sand paper. Other than that take it to a machine shop.  ERC
2-57 Apaches, 2-57 Trailblazers, 60 Chief, 65 Interceptor, 2004 Bullet, 612 Bullet chopped.

High On Octane

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Re: Blown Head Gasket On My Trailblazer
« Reply #5 on: May 20, 2013, 06:16:11 PM »
Good news.  I just got off the phone with my local head pro and he's going to jet blast my heads for $10.  Score!!!  I'll have him take a quick peek at the mating surface and make sure it's flat and true.

Scottie
Bulldog Kustoms - Denver, CO
Specializing In Kustom Paint

The Blackhawk
1958 Enfield/Indian 711cc Twin

Building the 1st EVER Supercharged RE Twin
FULL RACE motor with ACE Performance

ace.cafe

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Re: Blown Head Gasket On My Trailblazer
« Reply #6 on: May 20, 2013, 07:12:56 PM »
Good news.  I just got off the phone with my local head pro and he's going to jet blast my heads for $10.  Score!!!  I'll have him take a quick peek at the mating surface and make sure it's flat and true.

Scottie

Be careful that he doesn't knock off any fins with that high pressure blast. The fins break off pretty easy on these things.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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Bullet Whisperer

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Re: Blown Head Gasket On My Trailblazer
« Reply #7 on: May 21, 2013, 01:03:48 PM »
I recently rebuilt an early 700 Meteor [1953]. About 800 miles after the rebuild, the left head gasket blew at the innermost part, facing the other cylinder. The other head gasket was also going downhill, due to the heat / flame that was escaping past the blown one. Dark areas on the cylinder heads' gasket faces bore witness to a slight distortion of the gasket faces at this area of the heads - a hot spot where each head is right next to its' neighbour.
 I placed some fine emery on a known flat surface and refaced the gasket areas of the heads.
 Next came a bonus - I asked, assuming they were available, for solid copper head gaskets - the blown ones had been the copper 'sandwhich' type and they can blow quite easily at times. Solid copper gaskets came, but would not fit. It turned out there were no solid gaskets for the 700 twins, only the 500 Meteor Minor and this is what I had been sent. I had to enlarge the cylinder holes in them, to make them pass over the cylinder spigots [the M.M. 500 has no spigots] and file out the pushrod holes a little and then they fitted. Job done and I doubt it will have any problems with head gaskets again.
 That central area, where the two heads meet is a weak and 'hot spot' area, needing special attention. As for torque figures for the head nuts, just tighten them equally and don't overdo it, two of them are only accessible with a spanner anyway.
 B.W.
« Last Edit: May 21, 2013, 05:21:36 PM by Bullet Whisperer »

ERC

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Re: Blown Head Gasket On My Trailblazer
« Reply #8 on: May 21, 2013, 04:54:53 PM »
I'm suprised you couldn't get the solid copper. Won't the later solid copper ones fit? I know they're a different #. Haven't had one that old apart to know.  ERC
2-57 Apaches, 2-57 Trailblazers, 60 Chief, 65 Interceptor, 2004 Bullet, 612 Bullet chopped.

High On Octane

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Re: Blown Head Gasket On My Trailblazer
« Reply #9 on: May 21, 2013, 09:28:08 PM »
Well, I have great news!  I picked up my heads this morning from Heads By Drew after having them degreased and we took a look at the decks together.  On both of the heads there was a little bit of warpage in the area where the 2 heads meet.  You know, where it has known problems.  Drew didn't have a jig to mount the heads to a mill machine, but he did have a bad ass industrial belt sander.  He asked if I wanted him to give the heads a try on the belt sander.  Given his excellent reputation in the Denver Metro, I figured why not, there's obviously a problem there.  After great finessing on the belt sander, he was able to remove about .001 off of each head and get them true again.  And he only charged me $30 to clean and true them!

Left Cylinder After


Right Cylinder After


After that I stopped and picked up some new wire brush wheels to clean the piston tops and combustion chambers.  After cleaning the piston tops I made an interesting discovery.  Brand new pistons stamped +040!  So the top end has definitely been apart on this bike, and most importantly, that means I have a 750!  Also, when I do the full build this winter, I won't have to bore the cylinders for the high compression pistons.  After cleaning the pistons, I decided to clean up the cylinder decks.  I pulled all the head studs dropped the pistons and filled the cylinders with rags, and took my really nice sanding block and some 220 paper and carefully sanded the cylinders decks.  They appeared to be in good shape and didn't require a lot of attention, but I finished them off with my flat sharpening stone.  I decided I'm going to replace the 4 heads studs on the inner portion of the head/cylinder.  Can't hurt, right?!  Now all I need is parts.    :D

Scottie



Bulldog Kustoms - Denver, CO
Specializing In Kustom Paint

The Blackhawk
1958 Enfield/Indian 711cc Twin

Building the 1st EVER Supercharged RE Twin
FULL RACE motor with ACE Performance

Bullet Whisperer

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Re: Blown Head Gasket On My Trailblazer
« Reply #10 on: May 21, 2013, 10:14:40 PM »
Looking nice and clean there, Scottie. BTW, you probably have approx. 715 cc there, the [736cc] 750's ran a 93 mm stroke as well as a 71 mm bore.
 B.W.

High On Octane

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Re: Blown Head Gasket On My Trailblazer
« Reply #11 on: May 22, 2013, 12:57:13 AM »
Looking nice and clean there, Scottie. BTW, you probably have approx. 715 cc there, the [736cc] 750's ran a 93 mm stroke as well as a 71 mm bore.
 B.W.

I didn't realize the Interceptors had a longer stroke.  As if it wasn't long enough.    ;D  Either way, it's refreshing to see the cylinders/pistons in brand new excellent shape.  I'm also excited that the heads came out so good with minimal effort.

Just placed my order through Hitchcocks, so hopefully I can get the top end thrown back together early next week.

Scottie
Bulldog Kustoms - Denver, CO
Specializing In Kustom Paint

The Blackhawk
1958 Enfield/Indian 711cc Twin

Building the 1st EVER Supercharged RE Twin
FULL RACE motor with ACE Performance

ace.cafe

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Re: Blown Head Gasket On My Trailblazer
« Reply #12 on: May 22, 2013, 01:07:31 AM »
Looks like you saved some money on the build!

Always a nice surprise!
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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rotorwrench

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Re: Blown Head Gasket On My Trailblazer
« Reply #13 on: May 22, 2013, 06:51:23 PM »
The 692cc (700) had 5/16 studs to hold the heads & barrels down. George Helms and several other racers used to replace the 5/16" studs with the 736cc (750) studs that were 3/8" diameter. He also used the Interceptor tube nuts to hold everything together but the 700 tube nuts can also be modified to fit 3/8" if necessary. Blown head gaskets have always been a problem on the RE big twins. It would have been less a problem if they had made castings in one piece for the twin cylinders instead of separate castings. The parts started out 500cc then ended up 692cc with high compression pistons and cams to boot so the original design was pushed to the limits of power output. The 736cc Interceptor stuff was the strongest of all the RE big twins. For folks that just put around town, it's usually not a problem but racing is a different story alltogether.

When I surface my heads, I put sheets of silicon carbide paper on a surface plate with a bit of oil and lap the heads till the warpage is just gone. I don't trust too many machines on those little castings plus I only remove just what is needed to get the job done and no more.
« Last Edit: May 22, 2013, 06:55:42 PM by rotorwrench »

High On Octane

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Re: Blown Head Gasket On My Trailblazer
« Reply #14 on: May 22, 2013, 07:02:08 PM »
The 692cc (700) had 5/16 studs to hold the heads & barrels down. George Helms and several other racers used to replace the 5/16" studs with the 736cc (750) studs that were 3/8" diameter. He also used the Interceptor tube nuts to hold everything together but the 700 tube nuts can also be modified to fit 3/8" if necessary. Blown head gaskets have always been a problem on the RE big twins. It would have been less a problem if they had made castings in one piece for the twin cylinders instead of separate castings. The parts started out 500cc then ended up 692cc with high compression pistons and cams to boot so the original design was pushed to the limits of power output. The 736cc Interceptor stuff was the strongest of all the RE big twins. For folks that just put around town, it's usually not a problem but racing is a different story alltogether.

When I surface my heads, I put sheets of silicon carbide paper on a surface plate with a bit of oil and lap the heads till the warpage is just gone. I don't trust too many machines on those little castings plus I only remove just what is needed to get the job done and no more.

Thanks for that information rotorwrench.  I do in fact plan on doing a performance build over the winter and installing the 8:1 compression pistons and lightened connecting rods and Constellation cams, so I will definitely make sure to modify the block to accept the 3/8" head studs.  Now where the hell do I get a tap for the British threads?  Also, is there any modifications that need to be done to the head to accept the bigger studs?  I'm assuming I'll need to drill out the mounting flange.

And my order shipped from Hitchcocks today so, YAY!

Scottie
Bulldog Kustoms - Denver, CO
Specializing In Kustom Paint

The Blackhawk
1958 Enfield/Indian 711cc Twin

Building the 1st EVER Supercharged RE Twin
FULL RACE motor with ACE Performance