Cast Iron Vs Aluminium Alloy Engine Block

[Venom XR6]

  BionicXR6T said:

Just so we're comparing "apples with apples"..........

Does anyone know the exact weight variance between them?

Its a bit hard when no alloy block Barra I6's exist.

I've heard Ford cast a few alloy blocks years ago to test but they couldn't be machined properly on the current block line due to the incompatible tooling. Something like the softer alloy clogging up the cutting tools or something?

[NB4C]

  Venom XR6 said:

How much do you think a bare I6 block weighs. I've seen people pick them up with bare hands, big guys but I've seen it. I'd say 50-60 kgs maybe?. Even if alloy was half that it would only be 25-30 less, but once you add the cast iron sleeves and main caps etc it would come down to maybe 20kgs? Plus an alloy block would need a bit more material thickness in it to retain strength.

I'm assuming the main caps in all alloy engines need to be steel or cast iron?

I would have initially guessed 200 kg for a 4L engine, now I'm guessing 100kg. It's really hard to tell unless you weigh the block. Did those guys strain much ? A big adult weighing 100 kg could probably lift 70 kg from an uncomfortable position and 200 kg all out in an ideal position at a gym.

Edited 31/03/09 11:51 AM by NB4C

[RegSpec]

  Venom XR6 said:

Its a bit hard when no alloy block Barra I6's exist.

Doh....for some reason, I was thinking V8......sorry guys

As an aside though, Ive got a mate who bought an alloy block for his XR8.....

Weighing the car before and after......its now 50kgs lighter on the front end and, (weight wise), comes in just a tad lighter than an iron block XR6 turbo....

With both blocks on the factory floor....the alloy one could be lifted with one hand......while the iron version took two men and a chiropractors appointment......

[Venom XR6]

  NB4C said:

I would have initially guessed 200 kg for a 4L engine, now I'm guessing 100kg. It's really hard to tell unless you weigh the block. Did those guys strain much ? A big adult weighing 100 kg could probably lift 70 kg from an uncomfortable position and 200 kg all out in an ideal position at a gym.

There was one guy who worked on the block line, about 6'5 and 100+ kg. He was a big man and could bend down into crates and lift them out. He was older than 50 too.

[RegSpec]

Now theres an OH&S nightmare.......

[PAH]

Hi Guys,

I just sold my VY Gen III prior to buying the FG XR6T. My Gen III never copped a hard time, but it was always a tad rattly at cold start-up. That's apparently a characteristic of the engine. Even the blue printed torque plate honed rebuilds are a bit rattly on start-up (so I've been told by a reputable engine builder).

So I've now got an iron block XR6T that starts without rattles. Pity about the clunky 6 speed manual. What's the common denominator? Anything made in the USA??

I doubt that the cast iron liners in the Gen III add much in the way of weight. Here's a quote:

The engine uses centrifugally-cast, gray-iron liners. The liners to be quite thin, but very strong due to centrifugal force increasing the density of the iron during casting. The sleeves are, then, cast into the aluminum block at the foundry. When asked in June of ’96 about these sleeves' tolerance of overbore during rebuilds, Juriga said that a thickness figure was unavailable and that, to date, GMPT had not addressed the service overbore issue. In a second interview, in March of 1997, John Juriga told me that the LS1 engines for MY97 and 98 will tolerate only about a .005-in. overbore which really amounts to just a clean-up hone. In 1999, the sleeves will be revised such that service overbore of .015-.020 is possible without compromising durability.

http://www.idavette.net/hib/ls1c.html

It doesn't sound like Gen III liners have much metal in them.

PAH

Edited 06/05/09 10:50 AM by PAH

[straughsberry]

  Venom XR6 said:

How much do you think a bare I6 block weighs. I've seen people pick them up with bare hands, big guys but I've seen it. I'd say 50-60 kgs maybe?. Even if alloy was half that it would only be 25-30 less, but once you add the cast iron sleeves and main caps etc it would come down to maybe 20kgs? Plus an alloy block would need a bit more material thickness in it to retain strength.

I'm assuming the main caps in all alloy engines need to be steel or cast iron?

Yeah they're not that heavy. I picked up a bare block to put it on an engine stand and I'd say about 50-60 is correct. I also put my 4 speed into and out of the boot when I took in for a reco. That weighed 57kg because I weighed it Felt similar to me. 20 odd kg is not heaps on it's own, but as far as percentages go it's immense.

Edited 06/05/09 11:14 AM by straughsberry

[7MA61]

  PHANTMXR6 said:

Not to mention aluminium blocks transfer more noise.

Might want to tell that to Lexus. My 4L V8 is the quietest engine you will ever hear (well you probably won't hear it lol) until I put on an exhaust on it. At idle the only engine bay noises are really the squeaky pulleys as they are now 17 years old.

Can balance a 50c coin on its end on the inlet manifold & rev the thing out to 5000rpm before it finally starts moving & eventually falls. Strength people have put 25psi in with stock 10:1 compression & it didn't go boom.