Time to go Stage II!

[Alky V6]

When they figure in lash and deflection, did they have a range from coil bind that they recommend? I've been told .040-.080.

I believe .060" minimum is the general recommendation, which would be in the middle of what you've already been told.
A minimum clearance to maintain between working coils is .008". Aim for .010-.012". Some spring manufacturers may recommend even less and some more. Pay attention to their recommendations.

 

[Alky V6]

The time is getting close to figure out the ring package. I'll be moving away from the Total Seal rings with this engine. I'm looking hard at the Hellfire ring. I just need to find out how well they work with a 9000+ rpm application. A few local performance engine builders seem to really like them.

 

[turbobitt]

With a naturally aspirated Stage II Buick V6, Jim Ruggles suggests using a seat pressure of 220 lbs. for a 9200 rpm redline using titanium valves. How much more seat pressure would be needed in a blown application? I get the impression that you need to run 1 additional psi seat pressure to 1 additional psi of boost pressure.
It looks like Jim used straight 3/8" dia pushrods. I'm going with the 3/8 to 7/16 single taper pushrods again. I'm a firm believer in the theory behind tapered pushrods.

Maybe for a blower application but in Turbo applications pressure differentials are near NA applications. Key word being pressure differential.
Allan G.

 

[turbobitt]

I believe .060" minimum is the general recommendation, which would be in the middle of what you've already been told.
A minimum clearance to maintain between working coils is .008". Aim for .010-.012". Some spring manufacturers may recommend even less and some more. Pay attention to their recommendations.

For you intended RPM range I would run them as close to coil bind as possible to keep the springs out of surge. Springs will actually last longer.

Allan G.

 

[Alky V6]

Ring package brainstorming.

The second ring will be a typical 1/16 cast iron. Most likely an inverted torsional taper faced ring.
The gap for the second ring will be set up with .003" more than the top ring.
The piston will have a pressure balance groove between the top and second ring.
The oil ring package will be a 3/16" low tension set.
Piston to wall clearance will be .006-.0065" (JE piston).

The top ring will be either a plasma moly ductile iron ring, or the Hellfire. The thickness will be either .043" or 1/16". The face style and non-torsional or torsional still to be determined.
I understand that the thinner top ring is less prone to flutter at high rpm, but is it still a good choice when lots of boost is also involved. Is the thin ring strong enough?

 

[Dusty Bradford]

I believe .060" minimum is the general recommendation, which would be in the middle of what you've already been told.
A minimum clearance to maintain between working coils is .008". Aim for .010-.012". Some spring manufacturers may recommend even less and some more. Pay attention to their recommendations.

I set mine up at .040. I had to adjust the ratio of the rockers to get it to work out. This was also figuring in .020 deflection.

 

[Alky V6]

For you intended RPM range I would run them as close to coil bind as possible to keep the springs out of surge. Springs will actually last longer.

Allan G.

I've never heard of this technique. Is this something that cam and/or spring manufacturers actually endorse?

 

[Alky V6]

Maybe for a blower application but in Turbo applications pressure differentials are near NA applications. Key word being pressure differential.
Allan G.

There was something that was brought up in the article that I linked to about spring pressures and blown applications that I thought was very interesting. That is the VE of the engine and because of it the difference in pressure between the intake runner and the cylinder when the intake valve is closing.
In a turbo application, exhaust back pressure vs. cylinder pressure when the exhaust valve is closing has to be taken into consideration. Especially in a typical turbo setup where you are running up to 2 times the exhaust back pressure to intake boost pressure. Not even taking into consideration that the cylinder pressure will be less than intake side pressure due to VE limitations.

 

[turbobitt]

I've never heard of this technique. Is this something that cam and/or spring manufacturers actually endorse?

Don,
This is nothing based on my experience but I do have an engine builder that has played in this RPM range with a SB2 engine. He is actually listed in National Dragster as the currrent record holder in his class along with another guy he built an engine for in another class. They are pushing over 900+ HP running a single spec 750 carb (I think, or maybe 850). I have a lot of respect for him and know he tries a lot of stuff to be on top of the game.

Well anyway, when picking his brain about some things, he was telling me about the spring life and his correspondance with the spring company. The Spring company recomended closing up the installed height to keep them out of surge. He reported to me that they actually live a lot longer since he did this. I would ask around and see if others find this to be true.

Allan G.

 

[turbobitt]

I understand that the thinner top ring is less prone to flutter at high rpm, but is it still a good choice when lots of boost is also involved. Is the thin ring strong enough?

Why would it not be strong enough ? Those rings are huge and bulky.

Allan G.

 

[Alky V6]

Don,
This is nothing based on my experience but I do have an engine builder that has played in this RPM range with a SB2 engine. He is actually listed in National Dragster as the currrent record holder in his class along with another guy he built an engine for in another class. They are pushing over 900+ HP running a single spec 750 carb (I think, or maybe 850). I have a lot of respect for him and know he tries a lot of stuff to be on top of the game.

Well anyway, when picking his brain about some things, he was telling me about the spring life and his correspondance with the spring company. The Spring company recomended closing up the installed height to keep them out of surge. He reported to me that they actually live a lot longer since he did this. I would ask around and see if others find this to be true.

Allan G.

It sounds like an interesting idea. The spring that is used would have to be picked so that you could run it at close to coil bind for the lift you plan on using without coming up with a seat pressure that is way more than what is needed.

 

[Alky V6]

Why would it not be strong enough ? Those rings are huge and bulky.

Allan G.

Oh my. Are you running something thinner than .043"?

 

[Alky V6]

It sounds like an interesting idea. The spring that is used would have to be picked so that you could run it at close to coil bind for the lift you plan on using without coming up with a seat pressure that is way more than what is needed.

For instance, using the spring that was recommended for me by Crower, for me to run .040" to coil bind, and still maintain my target .700" lift, I would have to use an installed height of 1.93". The seat pressure at that height would be between 361-388 lbs. The open pressure at .700 lift would be as high as 759. The open pressure doesn't alarm me, but that seems to be way more seat pressure than what is needed. That can only increase valvetrain wear beyond what is necessary.

 

[norbs]

Why have the 2nd ring gap bigger than the top? The 2nd ring will never get as hot as the top ring? I was reading to make them the same, bigger will just create more blowby???

 

[turbobitt]

It sounds like an interesting idea. The spring that is used would have to be picked so that you could run it at close to coil bind for the lift you plan on using without coming up with a seat pressure that is way more than what is needed.

I don't know for sure but I think this was per PAC's recomendation. Not trying to tell you how to proceed with your build but I would urge you to check into it.

This subject came about when I broke my spring on the dyno. We were thinking that it could have been spring surge since I was know where near the max recomended lift or coil bind. I guess this is not the best way to run the springs.

Allan G.

 

[turbobitt]

Oh my. Are you running something thinner than .043"?

Yes and no,

Top is 1.2mm, middle 1.5mm, oil 3 mm.

Allan G.

 

[turbobitt]

Why have the 2nd ring gap bigger than the top? The 2nd ring will never get as hot as the top ring? I was reading to make them the same, bigger will just create more blowby???

Oh boy, another debate. This is the "Old School" thinking. Suposedly stops ring flutter by exhausting trapped pressure. I say if that was the case then may as well eliminate the second ring.

Allan G.

 

[Alky V6]

Why have the 2nd ring gap bigger than the top? The 2nd ring will never get as hot as the top ring? I was reading to make them the same, bigger will just create more blowby???

To keep the top ring from lifting and losing seal due to a pressure build up between the first and second ring.
I suppose if you knew exactly what the gaps were under actual high load operating temperatures, you could figure out what the cold gap could be to make sure you didn't end up with the chance of a pressure build up between the rings, but I don't know of any way to do that accurately.
The better you can control the pressure between the top and second ring, the better the top ring will seal.
When the top ring does lift and lose seal, and maybe begin to flutter, two things happen. Blow-by is increased, and the piston begins to build up more heat, since it can't pass that heat to the cylinder wall through a fluttering ring. More than a normal amount of heat also builds in the area between the rings. The second ring is then tasked with having to transfer a higher load of heat from the piston to the cylinder walls, which would tend to close the gap on the second ring even further.
Ring flutter and lifting is more of a problem to be concerned about when pushing rpm limits.

 

[Alky V6]

Oh boy, another debate. This is the "Old School" thinking. Suposedly stops ring flutter by exhausting trapped pressure. I say if that was the case then may as well eliminate the second ring.

Allan G.

The second ring is also important for oil control. That is why the second ring is typically set up with a tapered face that resembles a scraper.

 

[Alky V6]

Yes and no,

Top is 1.2mm, middle 1.5mm, oil 3 mm.

Allan G.

If you convert that to inches, you're very close to the same top and second as a .043, 1/16 package. Your oil ring package is thinner than standard which really cuts down on drag, but are you sacrificing oil control?
My Stage I engine ran a 1.2, 1.2, 3mm ring package. It was amazing how much it cut down on drag. This time around, I'm going with the standard 3/16" oil package, but low tension. I want to put some distance between the oil scraper rails for better oil control. The more distance between the oil control rails allows larger drainback holes in the groove behind the rails.