'79 or '68 Heads?

[wrifraff]

I have a '79 302 that I'm planning to swap in. Digging around in my garage the other day, I found a pair of '68 302 heads that my dad had. Is there any difference between the two? Would I be able to run 87 octane with higher compression? What would be better to run?

 

[red85]

The 68 heads have smaller combustion chambers. They measure out to 58 cc which will give you a higher compression and some more power over the 79 heads. The only thing you may have to deal with is the valve seats. Leaded gas was the norm in 68 and the valve seats will likely need hardened inserts to contend with modern fuel. If compression goes over 10:1 you should run higher octane fuel to take care of pinging.

 

[gotmudd]

The 68 heads have smaller combustion chambers. They measure out to 58 cc which will give you a higher compression and some more power over the 79 heads. The only thing you may have to deal with is the valve seats. Leaded gas was the norm in 68 and the valve seats will likely need hardened inserts to contend with modern fuel. If compression goes over 10:1 you should run higher octane fuel to take care of pinging.

+1. lucky score

 

[red85]

+1. lucky score

I talked to a guy about a week ago that had a set of D0OE's that he was putting on a 351W He showed them to me and we compared them with an E6SE head in my shop. There's just no comparison between the 2. As with all stock SBF heads, the exhaust ports were small and restrictive, but the combustion chambers are much better shaped in the earlier heads. If you want more performance out of stock heads, it's only a carbide burr on your die grinder away LOL.

 

[Totalled]

The D9 heads make nice door stops..

 

[red85]

The D9 heads make nice door stops..

...or nice anchors for your boat LOL

 

[wrifraff]

My only dilemma is what octane I can run. I don't know how to figure out my compression ratio, so I can't figure out if it would be over 10:1. I can't afford to run 93 octane. I have a stock short block, so what would my compression ratio be?

 

[1990 sc]

i've done the 68 head swap. the compression ratio on a dished piston is around 9.1 . an on a flat top 10.1.. yes the 68's will work better . but dont use them till you put hardend valve seats in them .. the combo i used was in a 79 capri using e 303 cam from racer walsh the d0oE head an a performer rpm intake it ran pretty good i ran 85 pump in mine also with the timing at 8 degrees btdc then i hoged out a set of e6's an milled them 20 an holy chit man what a differance they run alot better in the mid range to top end i ran a full 12 btdc an a 303 b cam alot of differance between the 2

 

[baddad457]

Octane requirements will also depend on the cam grind. You can run midgrade with a 10 to 1 ratio. But don't bet on a 10 to 1 ratio with 58 cc heads. It could be more or less, that will depend on the pistons pin height as well as the top configuration. Zero deck flat tops with a 58 cc head will give you 10 to 1. 64 cc heads will lower it to 9.5. As will a piston with a 1.585 pin height (this measurement varies among 302 flat tops from 1.585 to 1.610, the later gives you a zero deck) Do your homework first. Choosing flat tops in a 302 isn't as simple a job as most people think.

 

[baddad457]

i hoged out a set of e6's an milled them 20 an holy chit man what a differance they run alot better in the mid range to top end i ran a full 12 btdc an a 303 b cam alot of differance between the 2

And after you "hogged out" those E6 heads, you ended up with a chamber bigger than the D8OE's. The E6 chamber "as is" has a volume of 68 ccs. I'll bet you ended up with a volume of 80 ccs after you were done.

 

[1990 sc]

i was using the car for drag racing so i was looking for huge air flow the chamber stayed the same . umm hoged out means porting milled means taking off material . on the surface of the deck on the head..when i was done after cc'ing the head it was 60 cc's lol an holy shit thi head worked good but not after spending a ton of money on them

 

[baddad457]

I took hogging out to mean, you unshrouded the valves, that would take mucho material out of the chamber. That shrouding is what makes these heads flow so badly.

 

[Hjcraver]

Compression Calculator

To calculate your static compression is fairly easy. The things you need to know are :
Cylinder Head Volume (58cc)
Piston Head Volume ( notch cc)
Gasket Thickness (.037")
Gasket Bore (4.060")
Cylinder Bore Diameter (4.000" ? )
Deck Clearance ( in.)
Stroke ( 3.00 in.)
Try Kieth Blacks website and it is easy.......www.kb-silvolite.com/calc.

If you want less compression you can use a .060" copper gasket, but they cost around $140.00/Set. Good Luck

 

[baddad457]

To simplify that, piston head and bore (area around the bore, between it and the piston) is usually 4-5 ccs,(4 ccs for a 4 relief flat top piston, 1 cc for the rest) gasket volume for a small block is 9 ccs (.042" gasket) All you then need to figure is bore, stroke,deck clearance volume, and chamber volume. Add everything together, then divide by the chamber+piston top+gasket+ deck clearance volume.

 

[Dan B.]

Fuel and compression.......I'm running WP 2.02/1.60 heads on a well built 351W. The CR is a tad under 10.7:1 and it runs very well on 87 octane fuel.