Im still learning about the more tech side of performance engine builds. Can someone explain what exactly a good compression is, and what happens in compression, how it's achieved. Basically, what the heck happens.

Is a .60 over 454 w/ steel crank making high 13-1 sound good?

Thanks in advance as usual smile.gif

Hi Phil, Compression is a double edged sword. it is possible to have too much compression. The level of compression should be a ratio that is arrived to based upon the camshaft, power band, and engine use. I type too slow to go into great detail, But I will offer this advice. Get a few How to books on BBs from summit or where ever. It will be the best money you ever spent on your car!!!!! Good luck

Milan

Yeah I figure it's not something to pickup in a few minutes smile.gif I'll find a good book on BBC's definately having the project starting within the next 2 weeks.

You will love those books. I read mine from cover to cover a few times but I am whacked out like that. Have fun

Milan

The most compression you will honestly ever need is about 10.5 to 1 IMHO

That can be achieved by either having a large piston dome (.270) and large combustion chamber(122 cc's) or by having a small dome(.095) and a small combustion chamber(101 cc's) in addition to piston to deck height.

So the compression created widely depends on the type of heads and pistons used? What is deck hieght? Another block im looking at is 13-1 the guy says. Can JUST a block have a compression without anything on it? Maybe thats what he WAS running it?

Also stroke and bore. Larger stroke or bore = higher compression, all other things remaining equal. That's why it's often to your advantage to run as big a stroke as you can fit in the block, and in turn run a lighter flat top piston.

Phil Static Compression is the ratio of total cylinder volume (Engine assembled all components included)when the piston is all the way down BDC. and the volume when the piston is all the way up TDC. that ratio is the static compresson ratio. it gives us information on how tightly the cylinder contents is packed in there. That info should be incorporated with the camshaft lift and duration(how long the valve stays open) to provide a suitable DYNAMIC Compression ratio. That is the ratio that is really important and determines the characteristics an engine will have.
read, read, read, you will really get into it.
Milan

Originally posted by TJC:
Also stroke and bore. Larger stroke or bore = higher compression, all other things remaining equal. That's why it's often to your advantage to run as big a stroke as you can fit in the block, and in turn run a lighter flat top piston. I would have to disagree with that. Larger strokes allow for greater compression and so would a larger bore but it isnt an advantage as often as youd think. Its easier to make big power with big cubes but longer strokes make for a less efficient engine and one can make less power. truthfully a race engine seeking maximum power Would benefit from a larger bore more than a longer stroke i.e. a 302 or 327 that winds to the moon but for daily's and mild cars torque is best and cubes make torque down low.

No-one ever said its a race engine!

Why would this guy have had this .60 over block with 13 to 1 compression? Im not building for the track smile.gif Just one beafy A$$ every-other-day driver.

Phil if I were in your situation I would not assume that it is in fact 13;1 ratio. I think you need to verify that first 100% and go from there.
I suggest you get a piston number or get some modeling clay and press it to the top of the piston to determine the size of the dome. Then go on to calculate chamber size and the other pertinant specs and then calc. the comp ratio for your self.
Milan

Jeeeeeeeze, blocks can get so expensive. I found a 454 .60 over heat tanked, new freeze plugs, looks like a brand new engine. This guy wants $900! If I buy a nice 454 block, one thats already been tanked and just needs the bore and freeze plugs, I wonder what that would set me back. Im starting to think about the MPG on a 489-496. Anything under 8 is a little frightening for me. It isnt about MPG though, but it's still good to think about.

Doubt you'll get that bad of gas mileage unless you up and run it once it at least starts up well; I know that the 496 is going to take in more volume than a 454 or smaller, but I think if you set it up correctly, drove it well,, good carb tuning, good timing etc, you could still get mid-teens, which is very good. I think I've heard of people with 454s and Holley 750 DPs getting 22ish MPG, due to tuning and stuff..

:eek: Thats extremely refreshing to hear. Im probably getting like 11-13 right now. I havent done a good calculation in quite a few months, she isnt running as good as she could though. Just changed the oil yesterday so it may get better.

But $900 for the block! errrrr. Which may not be that bad, but more than I was hoping to NOT spend smile.gif