85_305

I think I know the answer, but am not positive.
Ok my dad owned the car before me. He said that as long as he can remember it needed 91 octane. It is a 305 w/ 200k miles on it. Well, this past winter i tore it down and rebuilded it. I noticed that the Distributor was BEYOND shot, and that there was about 1" of slack on BOTH sides of the timing chain. (There was MANY more little things like this, but these seem to stikc out in my head for the question being asked).
Do you think that because of the distributor being shot, and having so much slack in the timing chain, was the reason why I was getting HORRIBLE economy, and why the car would ping if anything under 91 octane was used?
Thanx all,
Matt

Black305RS

the timing chain might have something to do with it but the distributer woul have a lot more to do with it. the pinging you heard was most likely pre-ignition because the distributer was set badly. higher octane gas is less volatile than lower so it takes longer to burn. the lower octane gas was mosti likely igniting during the compression stroke do to excessive heat build up in the chambers causing the ping.

85_305

Well when I took the dist. apart, underneath the cap where the rotor is was all white and stuff.. my hot-rodder friend Jim said that it was BEYOND junk, so I am taking his word for it..
But you dont think that because the timing chain was mangled, that the cam timing was advanced/retarded causing the engine to run differently?

Black305RS

it could cause that but timing chains usually dont slip even with a lot of play in them so id rule that out if that was the case your engine would probably trya nd hop out of the cradle lol.

85_305

^Oh ok.. I didn't know that there still wouldn't be any timing changes w/ play in the chain

BTW.. very nice Camaro Just keep playing with it and modding it.

Black305RS

thansk and i will but i didnt mean to say that there "wouldnt be" i meant that it most likely wouldnt be it can still happen but you generally cant jump time with a chain or so my teacher says.

85_305

Rob the car *was* stock, my dad got it w/ 32k miles on it in '90 or so. It had 200k miles when it was rebuilt. My dad said the ONLY gas taht WONT make it ping is 91 or higher. Do you think that because the dist. being shot it was requiring higher octane, or are you saying that is not possible?
Black305RS how old are you? BOCES, college or what?

Black305RS

lol im 21 i go to elgin community college for automotive ****,

85_305

^Oh thats neato; you like it?

Black305RS

yeah its fun i have access to machining tools which ill be using to port and polish my new 350's heads as well as a nify 3 angle valve job. i just wish their dyno worked but it costs too much to fix it. what sucks is i might have to bore the block i dont really want to siince that means ill have to get new pistons but if i have to ill do it.

85_305

^How much hp/tq you expect to gain from porting/3-angling your heads?

For a LONG time I wanted to be a mechanic, but soon after relized that computers was the way for me

Black305RS

somewhere around 20 at the most but thats streaching it but i dont really expect it to be near that maybe around 5 to 10 realisticaly.
its all about the little things though. it all adds up in the end.

hoswever i do know a little trick for certain piston types that will give about a 10 percent increase in torque

85_305

Only 5-10 hp?? Why is taht all? How would you expect from the heads on LG4's as they are supposed to port and flow REAL nicely ?
What might that little piston trick be ?

Black305RS

in general thats all i expect form ported heads it may be more but i really cant say. ive decided to give up on unreasonable expectation to avoid being disapointed in the long run.

it only applys to pistons with offset pins.
if you install them backwards you get more torque but the trade off is excessive wear good for drag cars though.

85_305

Why would putting them in backwards result in more torque?