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any reason to not use cast iron cylinders

I'm thinking of boring my 2.2 cylinders and stroking to 2,4 w/ JE pistons. any reason to be leary of this?
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Old 05-03-2005, 11:28 PM
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It will probably be more cost-effective to just get a 2.4-2.7 crank and rods and stroke it, rather than spend the money to do a custom bore job. Shop around and you can usually find a good set of rods with a crank for around $500.
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Old 05-04-2005, 07:24 AM
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I should clarify... Is there any reason to be concerned about usnig cast iron cylinders vs. other cylinders. I am going to build a 2,4 and am going to stroke it. I would like to use my current cast iron cylinders unless there is a real reason not to. I was planning to get JE pistons for these cylinders too.
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Old 05-04-2005, 12:26 PM
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So what is your final displacement target? The stroker crank gets you to 2.4 - are you then going to bore the 84mm pistons to get to 2.5, 2.7, 2.8...? If it was me I'd be worried about heat dissipation for anything over 200hp. I've got a modified 2.4 running iron cylinders, and heat management is an issue - especially as I am currently without an external cooler (it's going on soon). If I were considering using some 84mm to bore them out, I'd find Birals. I don't think you can bore them out very far (do a search for exact limits), so if you're looking at a 2.7 or greater, then you need to find some 90mm Nikasil cylinders.
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Old 05-04-2005, 04:57 PM
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Depending on your budget you might check out Charles line of cylinders at LNengineering

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Old 05-04-2005, 05:35 PM
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those cylinders are sweet... but I would rather save the $2500. That's why I'm interested in using the cast iron cylinders.
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Old 05-04-2005, 05:51 PM
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Bore the cylinders one over, or two over, and have 85, or 86 mm pistons made, no need to stroke things, you will end up with a 2.3 something engine.

I think my first rebuild 20 or so years ago I morphed a 2.2T inrto a 2.3-4 displacement engine using Arias pistons. That engine ran for years and pulled like a freight train for a teeny lil motor..

Bore the sleeves.. get some JEs made.. and total seal rings.. all should be good
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Old 05-04-2005, 08:27 PM
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Boring the iron cylinders and reusing is no problem. 85mm bore will give you a true 2.4L (stock 2.4 motors are really only 2.34L) To get to 2.5 you'd have to bore close to 87mm and I don't think these cylinders can handle that because of the CE ring. I think they can handle being cut to 86mm though. Maybe someone can chime in who's done it.

I think boring the iron cylinders is a good compromise considering your starting with a 2.2 motor. If you want go beyond 2.5 I would think finding another motor for your starting point would be a better option.

As Dave pointed out, the iron doesn't disipate the heat as well but I think that just translates into a shorter life for the cylinders. So boring them will atleast give you the same basic life span that they originally had, which wasn't that bad.
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Old 05-04-2005, 10:15 PM
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Bobby makes great points. To really home in on the best solution though, we need more information about your desired end product. Tell us more about your HP and CR targets, intended use for the engine, budget...
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Old 05-05-2005, 07:30 AM
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If you end up using the cast iron cylinders, I would stick to a 1mm overbore to 85mm and use some total seal rings like Tim recommended. What kind of mileage are you planning of putting on the engine and what usage will it see (track/street)? I would sincerely recommend finding some birals at the very least and bore then out to 85mm if you're using the 2.4 crank, since you're asking a lot of the cast iron cylinders if you exceed 20-ish horsepower per cylinder and still expect to be as reliable as it was in stock form. With 200 horses, I would expect an overall reliablity of maybe 50,000mi between overhauls, maybe less, depending on how hard you drive it.

BTW, I would recommend cryo'ing the cast iron barrels, it helps them stay round longer and burn less oil.

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Old 05-05-2005, 08:03 AM
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The car will be a weekend driver. I mostly just want some more pep than I have out of my T. I have to rebuild so I figured the 2.4 stroke was the best way to go, don't really want an S motor. I do have a carrera oil cooler I'll be installing so that should help the heat equation.
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Old 05-05-2005, 10:04 AM
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Then you should be fine depending on your climate and how you drive. You'll want to keep the rpms up and fight the temptation to use 5th unless you're cruising over 3000 rpm at the bare minimum. I'm more concerned with head temp rather than oil temp, although the carrera oil cooler won't hurt.

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Old 05-05-2005, 11:47 AM
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That's more or less what I thought... That's how I'm going to go -- unless some kind soul wants to give me a steep discount on some nickies . Probably get pistons in a 9:1 CR and stroke to 2.4 w/ E cam.
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Old 05-05-2005, 12:12 PM
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Check out just retarding the T cams by about 10 degrees (and check the piston to valve clearence) you may get most of the E for nothing. Also make sure the cylinders are finsished with a grape or bottle brush type hone, this will greatly increase the power and lesson the break in period.
Old 05-05-2005, 10:42 PM
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Quote:
since you're asking a lot of the cast iron cylinders if you exceed 20-ish horsepower per cylinder and still expect to be as reliable as it was in stock form. With 200 horses, I would expect an overall reliablity of maybe 50,000mi between overhauls, maybe less, depending on how hard you drive it.
I guess I'm awfully confused about this statement.

1) Where did the 200 HP limit come from? What's the 20-ish per cylinder??? That just doesn't add up! Iron liners have been standard issue for F1 engines up to maybe 4 or 5 years ago. So they were putting out something like 150-200 HP per cylinder.

2) Iron bores are standard on many engines (SBV8 for example) with very reasonable service lives. Maybe not quite up to the silicon impregnated aluminum as was perfected with the Nikasil cylinders, but I wouldn't expect it to be bad.

Quote:
If it was me I'd be worried about heat dissipation for anything over 200hp. I've got a modified 2.4 running iron cylinders, and heat management is an issue - especially as I am currently without an external cooler (it's going on soon).
Cast Iron has a conductivity of 58 W/mK at 27 degrees C, and aluminum is more then 3x that at 202W/mk. Great. But that may not be such a big deal when you consider that while the combustion area may have a temperature of 2000 - 2400 degrees C, and the head has a temperature in the range of 200 to 250 C, the tops of the cylinder walls (near the head) will generally have a temperature of about 160 - 220 C, and near the crank case a temperature of 100 to 150 C. The point is that the cylinders have a lot less to do with conducting heat away then the heads. BTW, this is why the fins on a cylinder are longer near the top and smaller near the bottom of the barral. If it was just a question of the ability of the iron cylinders to conduct heat, you would expect that they could have just put more fins on the barrels. But this would have added weight which appears to be a path that the 911 engineers generally avoided at all costs.

A good feature of the iron cylinders is that they expand less then the aluminum cylinders -- actually by a similar amount to the steel studs -- so I'd expect that you'll rarely find an issue with snapped or pulled studs with iron cylinders. Also since they don't expand as much, they'll hold the bore dimension better which means that the pistons will fit better in a wider range of situations.

I guess as I understand it the benefits of the two choices are...

Aluminum (Nikosil): Lighter, longer wearing, conducts heat better (but this may not be critical in the case of the cylinder walls).

Cast Iron: More dimensionally stable under a wide range of temperatures, stronger

Did I miss something?
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Old 05-06-2005, 12:53 PM
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John, you didn't miss anything. I have friends who are both racers and engine builders in the SBC/BBC world, and they would have to agree that cast iron blocks wear better and remain more dimensionally stable than their aluminum block'ed siblings. But when they race, they go aluminum regarless, since it's both lighter and runs cooler. Where the comparison isn't a fair one to our application (aircooled), is that those blocks are water cooled and remain at a very controlled and almost constant temperature. That's why the 959 had water cooled heads.

The figures I'm quoting are from direct dyno observations. If you look closely, only the 911T had cast iron cylinders (please do correct me if I am wrong), and they didn't make much more than 20 HP per cylinder. After that, Porsche went to a biral cylinder to improve the cooling capacity of the engine. We've made this same observation of four cylinder engines - 20 hp per cylinder. The 200 (some quote 210-220) figure is a fairly regularly quoted one for reliable service from a mag cased 2.7/2.8 and also comparatively speaking, we've seen normal life expectancy on four cylinders putting it at around 60,000 mi when pumping out 36-37 HP per cylinder. Past that you have to take measures to improve the cooling or efficiency (create less heat). The more heat the cylinders can pull away from the heads, the cooler they run. Not only does this make more power (increasing volumetric efficiency), but it reduces valve guide, seat, and valve wear, not to mention reduces the frequency of valve adjustments. These are all observations we were able to make when we introduced aluminum cylinders to applications where none previously existed, i.e. Porsche 914. For those who use my product in that application, everyone knows what I am talking about.

I can't argue with the expansion issue, especially with mag cases. It's almost always imperative to put case savers or timeserts into the block to reduce the chance of pulling a stud with the expansion and contraction of the aluminum cylinders stressing the case. And if you don't thermal overload a cast iron cylinder, yes, it will remain dimensionally stable significantly longer and yield excellent street life, as evidenced by the numerous 40 horse vw type 1 engines that have seen 300,000 mi with religious maintainance. Not enough power to do any damage.

The flipside is that when everything is aluminum, it all expands at a similar rate, reducing both seepage at the case and head leaks. The head leaks themselves are directly proportional to how hot the heads (and cylinders) get. Then you're back at the reason why Porsche moved from cast iron to biral then to aluminum (nikasil and alusil). Even before the 911, Porsche knew that if they made more than 20 hp her cylinder, they needed more cooling, like with the birals on the 912 and the chromal and ferral cylinders of previous engines, like the 4-cam.

Of note, the alloy used in Porsche nikasil cylinders including the 3.2 and 3.3's is 120 W/mk. The alloy used in the Nickies is 240 W/mk. That's one huge difference between the cylinders, other than price :-) Also, the higher the thermal conductivity, the more head can be wicked away from the heads (also observed on the dyno with side by side comparisons of cast vs biral vs aluminum).

Hopefully I didn't get too long-winded, but as you can see, I live and breath this stuff and done lots of research and testing on the subject.

Charles Navarro
LN Engineering
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Old 05-06-2005, 03:03 PM
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Old 05-06-2005, 03:08 PM
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Oh. I get it now. You gave some good answers without over simplifying.
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Old 05-06-2005, 03:42 PM
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uhhh... so should I use my cast iron cylinders????
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Old 05-06-2005, 04:46 PM
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Absolutely yes! Even if you manage to get 180HP or 30 hp per cylinder (not likely) you should be ok. I run cast iron cylinders in my 912 race car at about 45 to 50 HP per cylinder with reasonable wear for the application so half that should be very safe and long lasting.

Notice that they only cool the heads with water, not the cylinders. Porsche engineers stopped at about 50 HP per cylinder for an air cooled street car. Higher powers are known to have severly shortened life. Any street engine should make 100K miles without a rebuild.

Last edited by snowman; 05-06-2005 at 05:40 PM..
Old 05-06-2005, 05:37 PM
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