Twins without o-rings??
02-11-2007, 06:21 PM
#34
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Back on topic, here.
O-rings are NOT necessary with twins. Period. But they probably are a very good idea.
The concept of "necessary" means different things to people, hence the disagreements. I mean, is air conditioning necessary in a daily driver? I suspect residents of Alabama might differ in their answer from those in Alberta, eh?
So the "necessity" of O-ringing has to do with the power levels, timing levels, and turbo selections you've decided to run.
The most important factor in HG longevity is timing, because timing affects cylinder pressure in a dramatic fashion.
But there are other factors to cylinder pressure. PEAK cylinder pressure is what pops gaskets. AVERAGE cylinder pressure is what makes torque. So, you simply want the most of one you can get without pushing the other too high.
In English, this means timing retard as boost comes up. But not just boost-- air mass in the cylinder is really what you're concerned with.
Mixture density also affects optimum cylinder timing. The more overfueled you are, the more excessive timing you can get away with because the burn happens so much slower.
You'll notice that my two points above seem to run contrary to each other. While both are true, the reality is that you have to strike a balance between them. Richer mixtures need/want more timing, but they also tend to bring boost up, and higher boost levels want LESS timing.
In the end, they almost cancel each other out, unless you are talking about the fringes of the operating ranges.
If you have to err on either side of the timing issue, too little is better. You can make it up with a little more boost. All you lose is a little MPG perhaps. If you run too much timing, then you've got bigger problems.
I personally wouldn't feel it necessary to O-ring if I had ARPs unless I was shooting for 550+horsepower.
JMO
O-rings are NOT necessary with twins. Period. But they probably are a very good idea.
The concept of "necessary" means different things to people, hence the disagreements. I mean, is air conditioning necessary in a daily driver? I suspect residents of Alabama might differ in their answer from those in Alberta, eh?
So the "necessity" of O-ringing has to do with the power levels, timing levels, and turbo selections you've decided to run.
The most important factor in HG longevity is timing, because timing affects cylinder pressure in a dramatic fashion.
But there are other factors to cylinder pressure. PEAK cylinder pressure is what pops gaskets. AVERAGE cylinder pressure is what makes torque. So, you simply want the most of one you can get without pushing the other too high.
In English, this means timing retard as boost comes up. But not just boost-- air mass in the cylinder is really what you're concerned with.
Mixture density also affects optimum cylinder timing. The more overfueled you are, the more excessive timing you can get away with because the burn happens so much slower.
You'll notice that my two points above seem to run contrary to each other. While both are true, the reality is that you have to strike a balance between them. Richer mixtures need/want more timing, but they also tend to bring boost up, and higher boost levels want LESS timing.
In the end, they almost cancel each other out, unless you are talking about the fringes of the operating ranges.
If you have to err on either side of the timing issue, too little is better. You can make it up with a little more boost. All you lose is a little MPG perhaps. If you run too much timing, then you've got bigger problems.
I personally wouldn't feel it necessary to O-ring if I had ARPs unless I was shooting for 550+horsepower.
JMO
02-12-2007, 07:24 PM
#37
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Thanks for checking on this, I called them to late to get ahold of a technician today. He is suppose to call me back tomorrow.
Just guessing but it ought to hold as good as the cr gasket or better with studs holding it down. I am still going this way to avoid the hassles of oringing and getting the head to seat properly. I had a bad experience on my 12 valve with oring and it's to far in to fight it.
I'm thinking with twins the back pressure won't be as bad as a single and be a little easier on the gasket. I've been running up to 65 psi on the twelve valve with 19.5 degrees of timing without any problems yet. I think HOHN is on the money with peak pressure spikes but good head seal comes with good machine work and torqueing procedures.
Just guessing but it ought to hold as good as the cr gasket or better with studs holding it down. I am still going this way to avoid the hassles of oringing and getting the head to seat properly. I had a bad experience on my 12 valve with oring and it's to far in to fight it.
I'm thinking with twins the back pressure won't be as bad as a single and be a little easier on the gasket. I've been running up to 65 psi on the twelve valve with 19.5 degrees of timing without any problems yet. I think HOHN is on the money with peak pressure spikes but good head seal comes with good machine work and torqueing procedures.
03-23-2007, 12:59 AM
#38
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guys im running a custom set of twins on my truck and im building over 60 lbs of boost. not sure how much but im burying a 60 lb gauge in third gear. my head gasket blew yesterday, and i got arp studs and a stock head gasket on the way. what else do i need to hold this much boost. im saving money for a external wastegate so i can turn the boost down a bit. do i need fire rings or anything like that?
03-23-2007, 09:55 AM
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guys im running a custom set of twins on my truck and im building over 60 lbs of boost. not sure how much but im burying a 60 lb gauge in third gear. my head gasket blew yesterday, and i got arp studs and a stock head gasket on the way. what else do i need to hold this much boost. im saving money for a external wastegate so i can turn the boost down a bit. do i need fire rings or anything like that?
You better O ring it ! You can fire ring instead,i preffer the o ring for a street truck,but both will work,the fire ring can hold more ultimately as long as it is installed perfectly.It is very easy to make a mistake with both of them,the cut depth and location is critical,go with a trusted vendor here,or someone who comes recommended and has done many that hold up.
03-23-2007, 06:08 PM
#41
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i ran my truck for 20,000 miles with twins but mine has a wastegate on the bottom charger. but i saw 50+ boost many times before seeing some steam come out from under the hood on my way to dodge to get a new cup holder bracket and there went my head gasket.
Thinking about going to a 66 though..