[Richelieu]

Ok, I've been reading my "how to rebuild small block ford engines" book, and found a chart on page 38. It is a Compression Ratio/Cylinder Head Interchange chart.

Could someone please tell me how to read this? The horizontal axis has all the different engine years and sizes... (starting with 221, hitting the 289, 302, 351, Boss 302, etc)... The vertical axis has Combustion Chamber Volumes. starting at 45 cc and going up to 69 cc. Numbers in bold face on the chart are for originally installed cylinder heads... now lets use my '78 302 as an example.

45cc = 11.2, 54.5cc = 9.8, 49.2cc = 10.5 and so forth.. the bold value for my heads is 69cc = 8.4

Ok... Now I want to get, say... 1970 351W heads (wow, where does this stuff come from? *grin*) I look at the chart, and it has different values... the original installed number is 60.4cc = 9.5

Ok, so if I put those 351 heads on, as stock, am I going to go from 8.4:1 compression to 9.5:1 compression? am I reading this right? Someone, please explain this. I keep hearing by adding 351W heads to a 302, I'll lose .5 in compression... where does that come from? I don't see it anywhere on this chart?

Rich
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'66, 302-4bbl, Granada disk brakes, etc, etc...

 

[Teebone]

the chambers are bigger on 351 heads..yes you will lose approx. half a point on a 302..check out this site..it has lots of head info..year by year:
http://www.mustangii.net/head.htm

'59 T-Bird..'70 Mustang Convert...'72 Mach One
www.geocities.com/theadgroup/T-Bone.html

 

[Richelieu]

The problem is, according to the chart, the chamber on my 1978 302-2V is 69cc. The chamber on the 1970 351W head is 60.4 cc.

That says the 351W head chamber is smaller. See where I'm getting confused? Now, if I were to use the same chamber value (69cc) with the 351W head, the chart gives me 8.7:1 compression... so my compression would go up .3...

I'm just majorly confused. Is this chart just full of crap?

Rich
----
'66, 302-4bbl, Granada disk brakes, etc, etc...

 

[Teebone]

I was thinking of the older 302 blocks..sounds like a nice way to pick up some compression

'59 T-Bird..'70 Mustang Convert...'72 Mach One
www.geocities.com/theadgroup/T-Bone.html

 

[Richelieu]

Sorry for the double, but I just checked the site, and it gave me the same exact information that my book did... the 1978 302 heads were 69cc, the 1970 351W heads were 60.4 cc...

which would mean I would be going up in compression ratio, yes? if this data is indeed correct?

Rich
----
'66, 302-4bbl, Granada disk brakes, etc, etc...

 

[Richelieu]

So, if I kept the heads stock, going from the 302, to the 351W heads could make me go from 8.4:1 to 9.5:1 compression... if that chart holds...

holy cow... forgot those new pistons... problem solved.

Rich
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'66, 302-4bbl, Granada disk brakes, etc, etc...