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I’ve got a 2 bolt 454, standard bore, standard deck height 2 w/ 781 heads, mild porting an oversized 2.19 intake/1.88 exhaust. Currently I’ve got 30cc domed LS6 pistons in it which I plan on replacing with some speed pro hypers. My “engine buddy” seems to think I should drop to 22cc to have a more manageable daily street motor, as the compression drop would make it closer to 9:1 an less temperamental. He says I may be sacrificing as little as 10-15hp but the benefits of the lower compression would far outweigh it.

I‘m new to big block power and wanna build this right the first time, so my question is, based on my set up.....will I be noticeably sacrificing much by dropping to a 22cc? Dropping it in a 69 camaro, an I don’t plan to run a crazy intake as I plan to use the stock SS hood. I also will be making an entirely new cam selection though I do intend on staying hydraulic flat tappet. What’s your personal opinions....more or less compression....? And any cam recommendations?
 

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We have a 69 SS396 with a flat top 454 with 101 cc chamber ovals,compression is about 8.9:1 and has a [email protected] 114 LSA old school flat tappet hydraulic cam in it.
With 3.42 gears it runs 12.4-12.5 @107-108 MPH on street tires burning 87 octane. Drive it anywhere,anytime. Its a beast on the street,it will blast the tires nicely whenever you ask it to.
693938
 

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Discussion Starter #4
We have a 69 SS396 with a flat top 454 with 101 cc chamber ovals,compression is about 8.9:1 and has a [email protected] 114 LSA old school flat tappet hydraulic cam in it.
With 3.42 gears it runs 12.4-12.5 @107-108 MPH on street tires burning 87 octane. Drive it anywhere,anytime. Its a beast on the street,it will blast the tires nicely whenever you ask it to. View attachment 693938
Man, that’s just the kind of Real world experience I was wanting to hear. I figure the torque outta that 454 is gonna be plenty for that unibody. I don’t want a world beater, I def want big power, but I also wanna drive it in the Texas heat w/ a vintage air unit running w/o boiling over. Appreciate the input.
 

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I have a 78 454 with stock 781 heads, its around 9:1.. I love the low compression! I'm running the initial at 22 with 14 mechanical all in by 2800, no vacuum advance, its a beast!! I have a turbo 400 with 2:73 gears. All that torque gets multiplied at the converter with those gears to dig in to, it goes like hell and on 87!!! I tried premium and it runs best on Marathon or Sam's Club 87.. What I like is how easy it is to start with the lower compression and it runs cooler..
Listen to your buddy and run 9 to 1... All those cubes don't need a lot of squeeze for the street.. For years I ran high compression in big motors mostly Pontiacs and it was a royal pain in the a$$, Sticky, cranky hot starting, sensitive timing, pinging on hot days. My 454 does none of this and runs every bit as fast maybe even faster since I can crank the timing up..
Keep the cam streetable. Something that will give you 18-20" of vacuum at idle with a wide lobe seperation and short duration. No need to rev this beast like a 302, keep the power band down low where you need it on the street.
 

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General rule of thumb when you raise compression by 1 point you gain in power around 7% of the displacement. So with 454 CID, going from 9 to 1 to 10 to 1 will gain you around 31.78HP.
 

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Compression makes power. The more compression makes more power. If you are not running a computer that can change the fuel ratio and make the mixture richer to avoid pinging or knocking or have a knock sensor or other means to detect a problem and pull timing you will have a problem if you can't. Hey come on please. Every high performance car from yesteryear including cars today made big power with compression and all require high octane even today. Now cleaning up slag in castings or better yet CNC aluminum heads or block that helps because it can dissipate heat fast or remove hot spots. Compression creates heat ie power.
 

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Those 781 cast iron heads will probably be ok with 10-1 compression as long as the cam is large enough.
The ZZ502 cam should be big enough and it's only 224/234 with ~.540 lift.
It would give about 13-14 in of vacuum and a slightly choppy idle, but it is a hydraulic roller.
 

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Keep the compression at 9.5-10:1, use a Mahle piston as the metric ring pack is worth a fair amount of power. Then choose a nice hyd roller cam, and it will make a lot more. Generally accepted ratio for 87 octane is 8.5-9:1 with iron heads. But the cam specs play a big part in that.
 

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Two years ago I had a .030 454 that had flat top pistons, 236 peanut port heads with a small solid cam and a couple of different intakes on it. Car ran best of 11.70'[email protected] with 8:1 compression. It could run on 87 octane if I wanted it to.
 

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this is really a trade off questions... lower compression to have a potentially cooler running engine in the hot days as well run less than 91 octane. If your truly cruising around the country you will find crappy gas, just a mater of time. as scott noted you can make the same power with a different cam. or keep the compression high, keeps engine efficiency high and less cam. side effect are more heat

as everyone will tell you, what is your power goals, this really determines your build criteria
 

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Being one that's pushed the limit of street fuel with dynamic compression ( what it takes for a 427 to beat 502s) I'd not want the drama and would keep it at no more than 9.5:1. You're not looking to squeeze every pony out of it. Gas quality wont get better.
 

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My 433" is a solid 10.4 : 1 Ratio, Hyd Roller cam, Timing set at 36 degrees all in. Runs on 92 Octane all day long, never gets over 180 degrees coolant temp, no detonation. And I drive it about 1000 miles a year.
 
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My 496 with 781 heads had right at 10:1. It was never a problem with 93 unleaded. Raced it hundreds of passes and a fair amount of street driving - never heard it ping even one time. Ran mid-11's at 114-115. Cam was the Isky 228/238 hydraulic roller that Mark Jones often uses in his builds.
 
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Compression ratio with the 22cc pistons calcs at 9.2 to 9.8 depending on overbore, deck height and chamber cc’s. It’s about .7 higher with the 30cc pistons. Where maximum output isn’t the priority I prefer to not push the limits with compression.
 

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General rule of thumb when you raise compression by 1 point you gain in power around 7% of the displacement. So with 454 CID, going from 9 to 1 to 10 to 1 will gain you around 31.78HP.
Another swag "rule" of thumb. Compression = octane. 87 octane will tolerate an 8.7 compression ratio. 95 oct will go to 9.5 to 1. Aluminum heads will go 1 more compression point.
 

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we just broke in my 489 that's 10.77:1 comp with alum heads on the dyno with 91 non eth and dynoed it with that and 93 non eth to 589.5 at 5700 and 600.6 tq at 4200 with no pinging or knock, its in the car with 6 mon. old 90 non eth and no problems, if this helps anything ?
 

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But what about somebody (like me) who wants to build a vintage 396 (or more likely a 402 - .030 overbore 396 L78 block) and wants it to be as correct in the way of original parts or close to original L78 with 11:1 compression?

Could I get away with everything as it would have left the factory in 1967 except for slightly flatter pistons? The 402 bore will lower the compression a bit in itself. I’d have to have solid lifters too! Gotta have that “sound”!

I know most owners of original L78’s seem to manage alright these days.
 

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But what about somebody (like me) who wants to build a vintage 396 (or more likely a 402 - .030 overbore 396 L78 block) and wants it to be as correct in the way of original parts or close to original L78 with 11:1 compression?

Could I get away with everything as it would have left the factory in 1967 except for slightly flatter pistons? The 402 bore will lower the compression a bit in itself. I’d have to have solid lifters too! Gotta have that “sound”!

I know most owners of original L78’s seem to manage alright these days.
The key to this is cam timing. Longer duration bleeds off cylinder pressure. Less dome will equal less compression as well. Good tuning will make worlds of difference. I was looking for either a 396 or 427 this last time around, actually preferring to find a 396 for fuel economy reasons. It worked out that I did a 427, that came in at 10.0:1 even and I think that's about the limit for iron heads on pump gas for the milder kind of cam I wanted. PAW used to list recommended compression ratios alongside their cams, because with a long duration cam and relatively low static compression you can lose enough cylinder pressure to make what should be a good running engine a turd.

Devin
 
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