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To Aluminum or Not To Aluminum?

639 Views 10 Replies 6 Participants Last post by  xMLMx
I have a '66 with 383 and I'm about ready to put in a better trans and motor. I'd probably buy one of the motor/tran "Connect and Cruise" kits that's supposed to have everything (yeah, HA!) for around $19k. I'll use the aluminum block motor to save front end weight, unless there are good reasons to use iron.

Another option is to keep my motor and fit an 8L90E (8 speed) tranny.

I want the setup to be as quiet as possible.

So, are there reasons to prefer iron?

Thanx, guys!
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So, are there reasons to prefer iron?

Thanx, guys!
Only if you're turbo charging it.....
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You and I are in a similar circumstance. About ten years ago I had a 380 SBC built for my 67 with a 700R4 to keep the revs down. It is a great engine, however even with Holley Fuel injection it had horrible gas mileage. What's worse at the time I couldn't find a 3.75 crank for a one piece seal block. I was told a simple adapter would allow me to run a two piece crank in a one piece block. Well it works fine for racing but for the street it leaks like a sieve. I bought another crank designed for the one piece block and do plan to have it swapped out but I didn't want t wait so I had an aluminum 5.3 built with mild cam, CNC ported heads and total seal rings. Because I'm sure I know more than the next guy, I had the best local builder put it all together and bolted to my TKX 5 speed. I think I would have saved $$$$ buying a crate package.😒
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Out with the old and in with the new! I shouldn't be complaining. I have never been able to buy crate motors cause I'm so picky with what I want. And that costs $$$ 😁 I knew if I were ever to add some boost:unsure:I would want total seal rings. I also wanted just a slight overbore so I could say I have a 327. 😁
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I’d say the big reasons to go aluminum over iron are:
you could shave a couple 10ths off of your 1/4 time.
Second reason would he weight transference. The third would be because you just want it to look trick and the last would be because you’ve got several thousand dollars extra you really want to splurge on an aluminum block.

If i had an unlimited budget, I’d probably go aluminum myself. For most folks I think that the few thousand dollars you can save on an iron block would be better spent into other upgrades.
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Just buy the 480 horse LS3 connect and cruise with the 4l70 transmission and be done with it. That's what I'm planning on doing one day.
If i had an unlimited budget, I’d probably go aluminum myself. For most folks I think that the few thousand dollars you can save on an iron block would be better spent into other upgrades.
I bought my 5.3 aluminum block for $400.00 Then I bought an iron block engine and switched everything over. I wanted the lightest front clip I could produce. My next engine will be a V6 from a 2017 Camaro. 320HP and the lightest of all. Then I add my GT45 turbo and call it done. 😁
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@Pragmatist forgive me, when he said aluminum I most certainly thought “aftermarket SBC” or bbc, not ls and fwiw if there was a choice between iron or aluminum at the same price I would take aluminum
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I was thinking the same thing @unstable. These kids and their LS motors... ;)
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@xxdabroxx they are awfully cool…And despite working in Information Technology for more than 20
years now and dealing with computers and data…I really struggle with relying on computers to run a motor.
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If money is no object, aluminum blocks are a nice way to save some weight. Most of the aluminum blocks are also more "high performance" than their iron block, garden variety cousins.

Case in point: an aluminum L33 out of some Silverado has flat top pistons, floating wrist pins with a larger bore, a slightly warmer cam with more duration, shorter head bolts (since the block structure was improved), and 799 heads (which are basically "Z06" heads). BUT, they are largely more expensive by 2x compared to an LM7 (which has dished pistons, 706 heads, etc).

I picked up an LM7 with 140k on it and everything still attached for $600; basically a take-out of a running motor. The nearest L33 I could find was $1,200 and had no accessories, no starter, and more miles. I used that saved cash to buy the cam, lifters, head gaskets, and head bolts.

Eventually, it will be force-fed, and likely rebuilt with larger bore pistons and other junk in the future, so the iron block is actually a desirable trait for me. But, if I was going to go with a sub-600hp, NA build... I would have spent the extra bucks for an aluminum block starting point.
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