[penguinjohn]

I have a 68 396 Camaro that serves as my daily driver. The previous owner installed 454 heads (how many cc's are these?) but left everything else pretty much stock. I imagine that I am running pretty crappy compression with this stock piston/454 head setup and had some questions that no one around here can seem to answer:

1. What compression ratio do you imagine I'm running with this set up?

2. What is the least expensive/most reliable way I can boost compression ?

and most importantly. . .

3. What compression ratio can I safely and reliably run every day on 93 octane?

I am interested to see your replys, especially on the last one, as I have heard anywhere between 9:1 and 11.5:1 and am now totally confused. Thank you in advance for your replys.

John

[mike brown]

my pretty much stock ss 396/350hp l34 (has hotter comp 280 h cam and slight head work) came with stock 10:25 c/r and seems to run fine on ammoco 93. i thought ahout trying the mid grade just to see how well it would work, but hadn't yet.
p.s. if you have any "big lots" stores in your area, they carry the slick 50 octane booster for $3 supposely good for 5000 miles?. don't see how it could last this long, but i've seen the same product at wal mart for $12.

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To see a pic of my car, click here... pages.prodigy.net/mtbmtb/rf396ss.jpg

[gheatly]

You need to take one of your valve covers off and get the head casting number. Post it here and I'm sure someone can answer your question about combustion chamber size. Simply knowing that the heads came off of a 454 isn't enough information. That's why you have gotten such a wide range of estimates of your compression ratio.

[JimM]

Remember, comp ratio alone isn't the killer, it's peak cylinder pressure. Modern heads, such as vortecs and performers will live with a higher max pressure because the flame front is managed better, and lots of things, like timing, cam centerline, and overlap have a big effect on max pressure. Also, carb engines often go a little lean or rich here and there, which don't help. That's why an LS1 runs 11:1 on 87 octane pump gas!