O-ring + stock HG = high boost and no issues of any sort.

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Fred
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O-ring + stock HG = high boost and no issues of any sort.

Post by Fred »

http://www.e30tech.com/forum/showthread.php?t=22030

I'd heard of o-rings before, but not doing it with MIG wire on a stock soft head gasket. A nice idea for sure :-)

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Re: O-ring + stock HG = high boost and no issues of any sort.

Post by SleepyKeys »

Pretty slick for sure. My findings are this, typically a good after market gasket will provide enough seal for most apps. O-rings provide such a good seal it puts rods at risk of breaking/bending when you push your combination too hard(500hp worth of nitrous :) ). Rather replace a head gasket than a set of rods. Just my 2cents for what its worth.

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Re: O-ring + stock HG = high boost and no issues of any sort.

Post by Fred »

Would you really??

To me, replacing a HG means :

fully disassemble head
skim head (cant do that too often)
fully reassemble head

Pistons will always succumb to detonation before rods, and if you are just making too much power for the rods rather than pinging, then you just needed better rods! :-)

If you have a good tune and good bottom end setup and high boost, this is a goer. So many people have so many problems with copper gaskets etc...

OEM gaskets will hold quite a lot though, as you say. More than enough for most people.

Here is one that a guy I know blew with a bad tune on the same engine as mine :

Image

I don't think it protected his pistons though. I think it smashed both at once. Then again, you'd have to pull the head to get the pistons out anyway.

I guess it just means you can leave the motor together longer when stuff does start dying. And also of course that if your tune is good that it doesn't fail when it doesn't need to.

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Re: O-ring + stock HG = high boost and no issues of any sort.

Post by SleepyKeys »

ah, I was being narrow minded. 90% of what I work on are push-rod engines, a lot easier to do a HG on than more modern designs. True about the rods and the headache that CP HGs can be, but I have seen the best rods money can buy break with copper HGs.
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Re: O-ring + stock HG = high boost and no issues of any sort.

Post by Fred »

seank wrote:ah, I was being narrow minded. 90% of what I work on are push-rod engines
I often have the exact opposite problem ;-) Though I actively try to remember those pushrod donks, it's not easy :-)
but I have seen the best rods money can buy break with copper HGs.
Really? ouch. They must have had huge cylinder pressures.

Was that by chance also on an older engine, if so I have a theory as to why. Modern cylinder designs promote fast flame travel and therefore low advance levels for correct PCP. Older stuff was sometimes fine back as far as 50* advanced. If you got some knock at 50* I can see it breaking a rod, but at 20* I can't see that easily happening. Still, I guess if cylinder pressures were silly high AND it went bang instead of burn, then sure, but you'd just about expect to see the head through the bonnet at that point :-)
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Re: O-ring + stock HG = high boost and no issues of any sort.

Post by SleepyKeys »

I wouldn't doubt it one bit that poor head design and excessive advance contributed to rod failure. These engines have after market heads and typically see 30* advance. From what I have read nitrous as a power adder increases the cyl pressure more than any other at a given power output. Like you said, when you bang a motor the pistons are usually the first to go.

I thought I might add to your theory. Also with more advance comes more BTDC rod angle under fire, it may see a lot more "side" stress. Maybe a case of too high an octane fuel along with excessive advance?
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Re: O-ring + stock HG = high boost and no issues of any sort.

Post by GartnerProspect »

I've been a big fan of the concept of O-ringing but haven't built an engine yet to try it out.
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