305HO heads on a 400 SBC

I have a chance to get a set of 305 HO, 58cc heads , can i run them on my 400 sbc if i drill out the steam holes? I think there 1984's.
Would it be a big advantage? Can i put a mild cam in without anything hitting? If i use the valves taht are in there can i get away with just doing a valve job?
Also how would i go about drilling the holes?
Thanks
JimV

 

beuller, beuller

 

Use the head gasket to lay out the hole location.
Center punch,and drill by hand.

Check the valve sizes before going too far.

 

May be too much compression for pump gas. Squirrell will know.

 

Unless you have some serious dished pistons, the small 53-58cc heads will crank the compression into race gas territory.

 

Way to much compression. I put a set on a 350 with flat tops and had to take them off. Couldnt run pump gas.

 

I did some quick math. Flat tops with 6 cc valve reliefs, std. bore and stroke, nominal deck height and a conventional gasket thickness puts 58 cc heads in the 13.7:1 area. Way too much!

 

NO NO NOOO, compression jump is astro. valve sizes will KILL performance,Even the bigger "HO" head valves are small compared to 350/400's, Most 305 casting are of the "lightweight" variety - poor perf potential , better off w a shaved /drilled set of stock 350 heads or #461 327's, 305 heads are for 305's ONLY, nothing else is practical.

 

Some tables from Speed Pro. These figures assume standard deck height and compressed gasket thickness. Even with 64cc heads you'll run into problems on pump gas unless your cam has enough overlap to bleed off some low rpm cylinder pressure.


.135 dish

<TABLE style="WIDTH: 260px; HEIGHT: 133px" cellSpacing=2 cellPadding=0 width=260 border=1><TBODY><TR bgColor=#c0c0c0><TD>Part

number
​

</TD><TD>CID

​

</TD><TD>58.0cc

</TD><TD>60.5cc</TD><TD>

64.cc

​

</TD><TD>68.cc

​

</TD><TD>72.cc

​

</TD><TD>76.cc

​

</TD></TR><TR><TD>H601P

​

</TD><TD>400

​

</TD><TD>10.65

</TD><TD>10.38</TD><TD>

10.02

​

</TD><TD>9.64

​

</TD><TD>9.29

​

</TD><TD>8.97

​

</TD></TR><TR><TD>H601P20

​

</TD><TD>405

​

</TD><TD>10.74

</TD><TD>10.46</TD><TD>

10.10

​

</TD><TD>9.72

​

</TD><TD>9.37

​

</TD><TD>9.04

​

</TD></TR><TR><TD>H601P30

​

</TD><TD>407

​

</TD><TD>10.78

</TD><TD>10.51</TD><TD>

10.14

​

</TD><TD>9.76

​

</TD><TD>9.40

​

</TD><TD>9.08

​

</TD></TR><TR><TD>H601P40

​

</TD><TD>409

​

</TD><TD>10.83

</TD><TD>10.55</TD><TD>

10.18

​

</TD><TD>9.80

​

</TD><TD>9.44

​

</TD><TD>9.11

​

</TD></TR><TR><TD>H601P60

​

</TD><TD>413

​

</TD><TD>10.92

</TD><TD>10.63</TD><TD>

10.27

​

</TD><TD>9.88

​

</TD><TD>9.52

​

</TD><TD>9.19

</TD></TR></TBODY></TABLE>​

flat top

<TABLE style="WIDTH: 263px; HEIGHT: 133px" cellSpacing=2 cellPadding=0 width=263 border=1><TBODY><TR bgColor=#c0c0c0><TD>Part

number
​

</TD><TD>CID

​

</TD><TD>58.0cc

​

</TD><TD>64.cc

​

</TD><TD>68.cc

​

</TD><TD>72.cc

​

</TD><TD>76.cc

​

</TD></TR><TR><TD>H616CP

​

</TD><TD>400

​

</TD><TD>11.45

​

</TD><TD>10.71

​

</TD><TD>10.27

​

</TD><TD>9.87

​

</TD><TD>9.50

​

</TD></TR><TR><TD>H616CP20

​

</TD><TD>405

​

</TD><TD>11.55

​

</TD><TD>10.80

​

</TD><TD>10.36

​

</TD><TD>9.95

​

</TD><TD>9.58

​

</TD></TR><TR><TD>H616CP30

​

</TD><TD>407

​

</TD><TD>11.59

​

</TD><TD>10.84

​

</TD><TD>10.40

​

</TD><TD>9.99

​

</TD><TD>9.62

​

</TD></TR><TR><TD>H616CP40

​

</TD><TD>409

​

</TD><TD>11.64

​

</TD><TD>10.89

​

</TD><TD>10.44

​

</TD><TD>10.03

​

</TD><TD>9.66

​

</TD></TR><TR><TD>H616CP60

​

</TD><TD>413

​

</TD><TD>11.74

​

</TD><TD>10.98

​

</TD><TD>10.53

​

</TD><TD>10.13

​

</TD><TD>9.74

</TD></TR></TBODY></TABLE>​

 

I'm a big fan of sportsman IIs. A complete set can be had for $6-700 depending on where you are. Midwest motorsports used to have used ones for sale. I used them on a de-stroked 400, what a screamer!

 

I've got 305 heads on a 400.
erson 270* cam. Runs ok but kills starters. I'm at 1000' elev.

 

I should add that the roundy round guys use em tho.

 

<TABLE id=HB_Mail_Container height="100%" cellSpacing=0 cellPadding=0 width="100%" border=0 UNSELECTABLE="on"><TBODY><TR height="100%" width="100%" UNSELECTABLE="on"><TD id=HB_Focus_Element vAlign=top width="100%" background="" height=250 UNSELECTABLE="off">Because it's a cheap way to bump compression, as stated above. But they don't rely on pump gas.</TD></TR><TR UNSELECTABLE="on" hb_tag="1"><TD style="FONT-SIZE: 1pt" height=1 UNSELECTABLE="on">
</TD></TR></TBODY></TABLE>

 

If it is a stock 400 motor it will have more than -6cc piston dome. A standard "Flat Top Piston" with the 4 valve reliefs is around -6. Stock 350 and 400 Pistons are dished & have valve reliefs. I would guestimate that the 58cc heads would put a stock 400 in the 11:1-11.9:1 range.

I still wouldn't put the 305 heads on a 400 - too much valve shrouding for any performance gains. Also the intake/exh runner volume is about useless. I had a set of small chamber heads (58cc) of a 307 or 283 or 305 or whatever and had them cut for 1.94 intake valves (cheap) the motor was NOT impressive!

 

I"ve got the World Products 58 cc S/R 305 heads (they come with 1.94" intakes and "fuelie" design and size runners) on a tiny 262" V8 and I have to run at least mid range octane to keep from knocking.
But,
If I had them already and a stock dished piston 400 I'd try them just for the hell of it with a big overlap cam to kill some of the compression.

 

Besides all the compression ratio issues, the 305 heads (yes, even the HO versiions) also have too small of ports for real performance on a 400.

If you really want better peformance the aftermarket heads are really a great deal and will match that 400 to run like it should.

 

Yea I agree, to much compression plus they wont flow for what the 400 needs.