The aluminum heads have a much smaller chamber, and I have flat top pistons with valve reliefs. The CR would be a bit too high for me I think after all was said and done. I want to stay around 10 so I can fuel up at a pump and not an airport.

 

With flat-top pistons, the LT1 iron head chamber might still be too small. What's the chamber size on the heads that don't want to work right?

 

I never found out exactly, but they are 14102193 heads, and have either 65 cc or 74 cc chambers.

 

65cc is pretty close to the LT1 iron heads - I think they're 62cc.

 

Just from asking around I'm told the LT1 irons will work fine on my 405 with the pistons I have. I will still need to find new valve springs though and I have no idea which ones to use.

 

Why not use the LT4-spec springs? What kind of valve lift are you running?

 

I don't recall. It's an LT4 Hot Cam if someone knows how to look that up fast.

 

The following iron small block heads that end in these three numbers all have the larger 76 cc combustion chambers. #993, #487, #441 and #442, if that helps any!

 

Didn't see it mentioned, but would tapping and pipe plugging be preferable to welding the extra passages closed? It's removable and would have little chance of warping the head.

On the LT1 out-put debate, I remember it being stated in a magazine (Hot Rod or Car Craft?) that the internal shortblock specs on a standard LT1 were the same, iron or aluminum head (cam, comp, etc). The major power losses in each model were marketing, insurance, and exhaust dictated. This data was released when the motors were new, and may be incorrect. Also, I have not run any part number on cams or pistons to know if in fact this is true.

The article said, however, that as the iron LT1 heads were a 2nd design, chamber and flow improvements were added that didn't make the initial design (LT1 aluminum heads). So there was more as-cast power potential in an all iron LT1 than in the initial (alum head) engines. LT4 head were something completely different.

Don't know the ultimate truth of this, but I do have a nearly complete late all iron LT1 in the garage that I just need to figure out what I wanna do with it!

Best,
Tom

 

Want to sell the heads cheap?

 

Sorry, DB,

Not yet, this is the one I was looking for the accessories for! But, man, ask me again when I finally bring my POS home, and I might! But by then you won't need it.

Tom

 

Then the LT4 springs will work fine.

The holes in question are fan-shaped.