I have no idea of the quality, but Speedway Motors has dedicated 305 head gaskets with the correct bore size. .038" thickness.
Speedway Small Block Chevy 305 Head Gasket, 3.736 Inch Bore | eBay

 

Too bad nobody makes the correct 0.021" for them. Those would work for a zero deck build, but less than ideal for a stock bottom end. Even back in 2003 the stock head gaskets had been discontinued.

 

Yes, but it's better than using a gasket for the 350 bore size.

 

If you want a .015 steel shim head gasket for on a 305. use the felpro 1094 350 head gasket.
Nothing bad is going to happen.
The big DROP in compression ratio of using a .038-.041" replacement head gasket on a factory non-decked block. (typical .025" deck clearance @TDC will have a BIG negative effect on your 305 engine performance.

The original OEM 305 steel shim head gasket was pn#462690 The only difference is the gasket bore size.. 3.87" VS 4.10".
That Felpro 1094 gasket will work fine on either engine.
Install clean and dry on clean dry surfaces.

 

.021"? As in piston to head clearance?

 

As in compressed thickness. My 83 had stock flat tops with 6cc dish from 4 eyebrows and were 0.022" down the bore, it had the ~3.80 bore 0.021" shim and 53cc 601 heads.

 

When I read:
I was seeing that as zero deck with .021" gasket.
I'm looking at .036" for the current engine being assembled (.008"-.009" deck and Clevite's/ Victor Reinz .026" gasket) and I think THAT'S tight.
​​​​​​​When I saw .021", I'm thinking maybe you knew something I didn't. (Which you do!).

 

Race engine can get as tight at 0.035 or so. Wouldn't do it on the street because of carbon buildup at low speed operation around town.

I was merely stating your 0.038 compressed find would work great on a zero decked build.

 

I'm lost.

Is this a good thing, these Speedway gaskets? There are (or were last time I looked) a ton of "thick" gaskets like this one. What you can't find are gaskets with a much lower compressed thickness.

Or at least that what I found that last time I looked.

 

Gonna post this one more time:
If you want a thin .015" shim style head gasket for your 305 build. use the 350 felpro #1094 .015" head gasket on your 305. its 4.10" x .015" compressed.
It works fine on 305 engines.
Not that hard.

 

From my post...Think instead of Thick....typos abound.

Yes, I've seen that, and appreciate the input. I bookmarked it / made a note of it. But if a thin, proper 305 bore gasket option comes along, I'd prefer that.

 

If you are using any sbc head intended for the 4.00" bore you want to use a 350 head gasket. EG: the L31 062-906 350 vortec heads.
The 305 shim head gasket is only good if using a 305 sbc head on a 305.
Measure across the chamber to see why.

The difference in crevis volume of the two shim gaskets (3.87 vs 4.10 )is so tiny it is insignificant. Combustion will not enter that tiny .015" space. The small difference in bore size is insignificant.
Don't sweat the small stuff.