What kind of compression are you 351c owners running on pump gas?

[nuck]

About 1000 years ago I had a built 429cj that I ran 11:1 compression on. That was premiuim leaded fuel and I had to cut it with avgas to run any kind of timing. What are you guys getting away with now, and how?

 

[Hack]

The closed chamber heads from 1970 (or the Aussie 2V) can run higher compression without detonation. Depending on exactly what you are building, a cam with a lot of duration will help. The dynamic (effective) compression ratio will be lower than the mechanical geometry suggests. Obviously, the cam duration also affects whether you will want to drive it on the street.

With the open chamber heads and a mild build I believe you want 9 or 9.5 to 1. I am planning on putting a 351C in my car, so I've done some research - - however IMO you should go to this forum.

http://www.network54.com/Forum/119419

There's a link to a build forum near the top. People post their builds, this should help a lot. There are way too many variables to reduce this to a short answer.

 

[nosaj122081]

My 2V open-chambered 393 will be 10.4:1, IIRC. Thats static though, and would knock like mad with a mild cam. But I'm using a solid lift Comp Cams 248 i/e @.050" 108 LSA, so theres gobs of overlap to bleed off static compression. My dynamic was down in the low 9's IIRC.

 

[nuck]

The car I'm looking at is a 72 351 4v so it has low compression already. If I go higher compression I will probaly look at water/alky injection rather than downgrading the heads. It seems to work pretty well on the turbo applications I have seen and is pretty inexpensive.

 

[7DMACH1]

I'm running a 408c, with 11-1 comp. 1970 Closed chamber 4v heads. Cam is a solid roller, 248 @.50 and .623 lift. Runs fine on 94 Sunoco and no pinging.

 

[nosaj122081]

The car I'm looking at is a 72 351 4v so it has low compression already. If I go higher compression I will probaly look at water/alky injection rather than downgrading the heads. It seems to work pretty well on the turbo applications I have seen and is pretty inexpensive.

You'll have to upgrade heads rather than downgrade to get any more compression; 72 4V's had open chamber heads, to get the best compression increase you'd need closed chamber heads with a zero decked block. The only thing that will save me with open chamber heads is my big cam.