[Midnight Goat]

Ive got a 67 goat with a 74' 400, 670 heads, holley 770 cfm street avenger and other than that as far as i know stock. I bought the car about a year ago and after much trouble finally got it running. Ive been getting random pinging even at idle but now only above 2000 rpms (after regapping the plugs, adjusting the carb, and fiddling with the timing). After i was running the engine for about a half hour or maybe a little less coolant started spraying out of the overflow hose attached to the radiator cap. Does this mean my engine is overheating or what? It sprayed out a crap load of coolant and im a little worried now. Any advice on what could be causing this or even how to fix that damn pinging above 2000 rpms?

[Jack Gifford]

Coolant out the relief hose could mean many things, but commonly is because the system wasn't fully purged of air before running the engine up to temperature. Cross your fingers that it's nothing more than that!

[bobbyj1]

670 Heads have small combustion chambers unless there has been some porting or the pistons have been dished you will need to run some high octane, 110, gas to avoid the pinging. A stock 400 with 670 heads has around 10.75:1 compression. Need to be closer to 9.5:1 for pupmp premium. I have a 67 GTO with stock heads and pistons and I have to go 50/50 on the 110 and 93 octane to avoid pinging

[Midnight Goat]

Originally Posted by bobbyj1

670 Heads have small combustion chambers unless there has been some porting or the pistons have been dished you will need to run some high octane, 110, gas to avoid the pinging. A stock 400 with 670 heads has around 10.75:1 compression. Need to be closer to 9.5:1 for pupmp premium. I have a 67 GTO with stock heads and pistons and I have to go 50/50 on the 110 and 93 octane to avoid pinging

i added some 104 octane booster to a tank of 93 and didnt really help the pinging does it have to be 110? i dont even know where i would be able to get 110 around my area.

[speedshopmike]

let's redress thsi a bit from a more basic point of view.
midnight, runa compression test on a cylinder or 2.
this will establish, w/in reason, where you stand on cylinder pressure and show what is causing problems.
reducing timing/reconfigging the advance curve can help, fattening up the carb a bit, dropping water temps, colder spark plugs, etc are all means to help reduce detonation.
water injection, too.

[Tripower455]

MG,

Great to see you over here on PY! We'll get your issues straightened out!

BTW, if I understood correctly on your post on LS1GTO, you were getting a popping sound from the exhaust on acceleration? Pinging is a different (yet equally if not more important) issue! Pinging comes from detonation, and sounds like you have a bag of ball bearings rolling around your engine when you get on it....

BTW, your car looks awesome!

You might try posting your troubles in the Pontiac Street section, as it will likely get more views......

[Midnight Goat]

hey tripower! good to see you over here too. as an update to the coolant problem it seems to have gone away after topping off the coolant so ill keep my fingers crossed and hope its not a major issue. I think ill try posting my other engine problems in the street section. thanks for your help tripower on both forums! lol

[Geoff]

Never heard of an engine pinging at idle. Is that an accurate description of the noise? Or maybe you meant popping, as someone else suggested.
Because of the unknown history, it would be worthwhile checking your TDC timing mark to make sure it is accurate; maybe wrong parts [ timing cover, dampener ] have been substituted. You can make a TDC checking tool with an old spark plug. The cam companies, such as Comp Cams, Erson, etc describe the whole procedure on their websites.

[MrPushrod]

remember .....audible detonation is the worst.....if you can hear it you got a major problem..........on a scale of 1-10......pinging is a 11 !!!
octane boosters dont work.....dont waste your $$$...
are your spark plugs bright white.....maybe your just really lean.
check your plugs and re tune the carb.