It's more about engine load. Gearing, weight etc affect the way the engine is loaded. You can have a car run fine at wot on flat ground, but ping when it goes wot driving up a hill, just because the extra load from gravity.

People that get away with high compression pump gas engines, like 11-12:1, usually are running more gear, in lighter cars, with less timing, more fuel, with bigger cams etc etc etc. Just because one guy ran 11:1 on pump fuel just fine in his car, doesn't necessarily mean that someone else can run 11:1, or even 10:1. There's way to many variables to give a maximum compression for pump gas number.

 

Noone said a definate!

 

Air density is another factor.
Those of us that live at higher altitudes can get away with more compression than the sea level dwellers.

 

Yeah, and humidity as well.

 

I put a 460 crate 10:5.1 comp engine in my 3,900 pound 77 tbird with a 2.70 rearend and the engine pinged because of the weight and highway gear which i knew would happen before i started the project, bought a currie 4.11 center section and lower profile tires and the pinging magically disappeared, magic? nope. The steeper rear gears took the strain and load off the lopey engine with faster revs, were you sleeping in class when you were taught that? msd distributor with 20 degrees initial advance and 18 degrees mechanical and lightest springs, no vacuum advance, nicest car i have owned. Yeah rear gears have everything to do with pinging and load, it's simple basics, duh. I slapped myself in the face a long time ago and woke up, you ought to try it, venomantidote95, it works, lol.

 

Well I have 410 gears that I put in so hopefully the gearing isn't going to be an issue here. The engine will be a 347 with a good h/c/i combo. I just wanted to find out a little about the compression because 87/89 is all we get around here so I have to choose my compression accordingly.

 

Look before you show your ignorance, look at what i am saying!
YOU CANT JUST SAY GET A 4.11 OR YOUR ENGINE WILL BLOWUP! which is the statement that you made!

There are alot more factors in an engine life the a ****ing gear ratio!
(so if i build an engine and use a 4.11 and half *** torque my rotating assembly it will stay together and live regardless?)
thats pretty much the same thing you said? right, use a 4.11 or else!

you now have retracted your previous statement and said it has everything to do with ping and load which is what should have been the originating statement! and still it dosnet have to be a 4.11 to get that issue fixed if you have it! thanks have a nice day!
as i said before thats a dumbass thing to say!

If he used a 4.30 would the engine blow up, what about a 3.90, 3.73? would those gears not suffice in that same situation!

 

I live down here where i get to deal with everything stated above, air desnsity, humidity,


Oh and thats one thing, using a carb is a main portion of your problem. Efi is alot more forgiving than the ol metal pan.thus making most enviromental and atmospheric conditions null and void!