Rep Power: 666

What is the difference in the 643, 374, and 561 lt1 head castings?

I was planning on doing either an AI 190 or LE2 heads and cam package, but AI wants the 643 or 374 castings for that set up (LE does not specify on his site). I have an lt1 out of a 97Z with the 561's. What years had what heads and what is the best performance that I can get out of the 97 head?

 
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except for a select few (forcefedz) and a couple others, it seems like most people on this site are more concerned with looks than performance, so i dont know if your going to get much info on here about this kind of stuff.

 
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I thought forcefed would chime in. I don't know much on casting numbers especially for the newer engines

 
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i was about to say the exact same. not any different either. im not even joking. lol i have been saying chime a lot lately

 
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So far, I have found out that the 561 is the best flowing head in stock form, but does not have as much extra meterial for extensive porting. The the 643 and 374 castings have more room for porting and come on 93-95 cars. The 96s may have either the 643 or the 561 (probably early:643, late:561). All 97s have the 561. So now I need to contact Lloyd and AI and see how much power they can make with these heads. Worst case, we eat the core charge and get the heads we want.

 
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how about an aftermarket set? I would think they would outflow any of the stock ones (that's what is typical anyway)

 
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Bang for the buck if you are building a stroker motor meant for some kind of power adder, Trick Flow heads might be a nice set to look at. With the bigger combustion chamber and the added flow on the runners, those will be your best bet.

But as far as getting heads to make squeeze and strictly power N/A probably a set of AFR's- but you are lookin at quite a stack of benjamins to get into a set of those.

I honestly don't know that much about casting numbers- I have two extra sets of LT1 heads out in the shop, let me go look at them and see what they are..perhaps they are exactly what you might be looking for-

 
Rep Power: 666

I have been doing some extensive research on the head topic lately. I have decided that I will definately be going with Advanced Induction. I have seen or heard nothing but great reviews of thier product. I can not say the same about the LE packages. The AI stuff is more expensive, but is still in our price range. I talked to ron at AI today. They have raised the bar a bit, the base port is now a 185cc (up from 180) and they will be phasing out the 190 cc for the 200. I can do the 185 port with the 97 heads, but have to get the 93-95s to do the 200. So far it looks like we will be doing the 185 unless we can find a usable core at a smokin price.
Here is a link to thier lt1 heads:http://www.advancedinduction.com/AiProductsLT1.html
Also take a look at the lt1 results, the times and hp claims that are "advertised" there have been backed up and proven in real world combos.
The 185 kit with all of the supporting mods and a good tune will have Stephs car performing with, if not out performing most cammed ls1s ($hit, I had better be on my toes in my car!). Now she just needs a little more seat time in a car with a stick. I will be taking off the big and littles on the Cobra and hooking up the swaybar this week. After that she can start driving it again. I did not feel comfortable letting her drive it on the skinnies, talk about ill handling! With a 12 bolt and some slicks, I hope to get her car to run around an 11.40 @ 117 N/A, and give it a lil shot into the 10s. We'll see........

As for the aftermarket ones flowing better, It looks like the AI stuff is right there with the out of the box AFR heads http://www.airflowresearch.com/195sbc_lt4.php. With a little clean up the AFR's are hard to beat, and the TFS head are nassty with a full port. But like Forcefedz stated earlier, you are starting to get into the big bucks then.

 
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Here is a link with some pretty good info about the lt1 heads: http://web.camaross.com/forums/showthread.php?t=427346

 
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all i really know about LT1 heads is that cast iron and aluminum debate. iron heads are better for porting, they offer more flow, yet the basic characteristics of aluminum heads make them far superior. contact lloyd elliot directly and he will help you and make whatever you have work. ive heard a lotta good things about him.