273 commando Build

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stroker402 said:
just measured the sb arp bolts and the stock head bolts .. approx 3/8" difference. arp bolt # 144 - 3602. so it appears stock bolts have more thread length and gripping forces.
Also , what did you mean by this Quote " I think I'd run stock 273 head bolts at 85 ft lb anymore, maybe with hardened washers. " ?

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Makes me want to use stock hardware even more.
 
What I used back in the '70's on my 273 Bracket Racer was a steel shim head gasket (most likely specifically for the 273 bore size) along with a copper wire I epoxied into a grove in the gasket that surrounded the cylinder bore. You may consider this a poor man's version of machining an o-ring groove into the block or cylinder head. It was overlapped very slightly where the two ends of the copper wire met one another. When I disassembled the motor, it was obvious the copper wire was flat and had done its job in helping to seal the head gasket (also used copper spray on the gasket). This was not my original idea, must have read this technique in a magazine or some other written publication. Was decades ago, so I don't have any photos of this to share.

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toolmanmike said:
Makes me want to use stock hardware even more.
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yes .... sure does... I called arp they are investigating this issue why there bolts are shorter....so I can honestly say there bolts were not bottoming out.. but there bolts being at least 3/8" shorter might be a problem.
 
I also noticed that problem with the ARP bolts and was very disappointed they were too short. Hard to believe (maybe not) this error could continue for so long a time.
 
dibbons said:
What I used back in the '70's on my 273 Bracket Racer was a steel shim head gasket (most likely specifically for the 273 bore size) along with a copper wire I epoxied into a grove in the gasket that surrounded the cylinder bore. You may consider this a poor man's version of machining an o-ring groove into the block or cylinder head. It was overlapped very slightly where the two ends of the copper wire met one another. When I disassembled the motor, it was obvious the copper wire was flat and had done its job in helping to seal the head gasket (also used copper spray on the gasket). This was not my original idea, must have read this technique in a magazine or some other written publication. Was decades ago, so I don't have any photos of this to share.

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I was thinking about laying a copper wire in that void of those huge fire ring bore composite gaskets like you did .then it will have 2 fire rings. double protection . or better yet ask cometic to make a copper fire ring for the small bore 273 since they don't want to start a production on the proper shims. gasket.
 
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stroker402 said:
and yes these new Arp bolts were loosening up some bollts as much as a 1/4 turn on the torque wrench before I disassembled the 273. still have NOT found the smoking gun yet.
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Are you using a clicker torque wrench? Having always used stock bolts and never had your problem using standard Felpro gaskets and info from "Perfacar", I'm thinking stock bolts are just fine. Your experience is very hard to get a handle on. Seems like you are doing everything right...
 
66fs said:
Are you using a clicker torque wrench? Having always used stock bolts and never had your problem using standard Felpro gaskets and info from "Perfacar", I'm thinking stock bolts are just fine. Your experience is very hard to get a handle on. Seems like you are doing everything right...
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yes used a clicker and I used a friends clicker to double check.
I'll have to say this .... these arp bolts really did not hold the torque spec at all. too many bolts had loosened up. just sayin !
 
stroker402 said:
yes used a clicker and I used a friends clicker to double check.
I'll have to say this .... these arp bolts really did not hold the torque spec at all. too many bolts had loosened up. just sayin !
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I have only used a beam torque wrench. I have seen good brand name clickers go out of calibration. I worked in a calibration lab, before getting my degree.
 
thanks 66fs ! Another scenario i was thinking is this blown head gasket issue always happened only when I stabbed the pedal to the floor in first gear 4 speed low first gear.... the rpms would respond to 5800 arms in a sec blowing the tires away..REV LIMITER SET AT 5900 could it be .... the fast revving to 5800 could be an issue ? it revs so fast the pressure builds up in the cyl and finds its weakest point when it blows. I have free flowing long tube hooker super comp headers 1 5/8' 2.25 head pipes into 2.25 dynomax ultra 2.25' inand out dumped before the axle. SO THERE IS NO RESTRICTION.
 
stroker402 said:
and yes these new Arp bolts were loosening up some bollts as much as a 1/4 turn on the torque wrench before I disassembled the 273. still have NOT found the smoking gun yet.
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Contrary to popular belief, the heads need to be retorqued.

I now do it as a matter of course. Even the Fel-Pro “perma torque” gaskets need it.
 
here is another thought .. on all the lower head bolts I had to use a 5" socket extension on the torque wrench to clear .. had to get the torque wrench up high enough to turn it. headers were pulled back but still in the way.. so mayby with the extension used it was not get a true spec.
 
stroker402 said:
I was thinking about laying a copper wire in that void of those huge fire ring bore composite gaskets like you did .then it will have 2 fire rings. double protection . or better yet ask cometic to make a copper fire ring for the small bore 273 since they don't want to start a production on the proper shims. gasket.
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You don’t need a cooper wire or anything like that.

If you are going to do that you use stainless wire and you cut a groove in the block and a matching groove in the head.

The wire goes into the head and the groove in the block is the receiver groove.

Plus you need dead soft copper gaskets.

As to bolt length, you need about 1 times the diameter of the bolt of thread engagement.

I doubt bolt length is an issue. If it was you’d be pulling the threads out of the block.
 
stroker402 said:
thanks 66fs ! Another scenario i was thinking is this blown head gasket issue always happened only when I stabbed the pedal to the floor in first gear 4 speed low first gear.... the rpms would respond to 5800 arms in a sec blowing the tires away..REV LIMITER SET AT 5900 could it be .... the fast revving to 5800 could be an issue ? it revs so fast the pressure builds up in the cyl and finds its weakest point when it blows. I have free flowing long tube hooker super comp headers 1 5/8' 2.25 head pipes into 2.25 dynomax ultra 2.25' inand out dumped before the axle. SO THERE IS NO RESTRICTION.
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I've run so many combinations on a 273 from stock 2 barrel, to stock Commando, to 284 duration Offy intake and 600 Holley, to my favorite 273 with the 340 heads and a 71 340 TQ. My 64 was a 4 speed with gears from 2.76 to 4.10 and everything in between. I used to power shift at 6,500 rpm, and I missed a few, scared the heck out of me watching that tach flash without a rev limiter. Never had a problem with head gaskets. My biggest problem was keeping a clutch to hold it.
 
just remind everyone ... I am not going to use this block anymore. I have another commando block I'm building at present .
but I still want to know why the old block kept blowing head gaskets. so it does not happen with this new block .
 
66fs said:
I've run so many combinations on a 273 from stock 2 barrel, to stock Commando, to 284 duration Offy intake and 600 Holley, to my favorite 273 with the 340 heads and a 71 340 TQ. My 64 was a 4 speed with gears from 2.76 to 4.10 and everything in between. I used to power shift at 6,500 rpm, and I missed a few, scared the heck out of me watching that tach flash without a rev limiter. Never had a problem with head gaskets. My biggest problem was keeping a clutch to hold it.
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so would you think a fast revving 273 would act like it had a turbo or pro charger on it to create that fast boost in cyl pressures ?
 
stroker402 said:
just remind everyone ... I am not going to use this block anymore. I have another commando block I'm building at present .
but I still want to know why the old block kept blowing head gaskets. so it does not happen with this new block .
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I'd like to see that block decked .001 at a time to see what is going on.
 
stroker402 said:
so would you think a fast revving 273 would act like it had a turbo or pro charger on it to create that fast boost in cyl pressures ?
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I don't think so, but I don't boost anything. I just know what my car would do. I doubt your engine was as quick as mine with the 340 heads.
 
stroker402 said:
318 composite head gasket were used

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Ok, I’m a bit lost (again lol). That failure looks like detonation. Across from the plug, that’s what it looks like.

Did you post pictures of your plugs? Did you say your compression ratio and cam timing? I apologize if you did.

If you are getting oil in the chambers and you are already on the edge of detonation that will send it right into detonation.
 
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