Fixing misfires/flaming exhaust Reply #15 – September 01, 2016, 08:28:52 PM I've got 60cc Edelbrock Performer heads on my car and it has a 9.4:1 compression ratio. Your combo has to be higher than 9.8:1 with 54cc chambers. Quote Selected
Fixing misfires/flaming exhaust Reply #16 – September 03, 2016, 03:57:02 AM Quote from: thunderjet302;457015I've got 60cc Edelbrock Performer heads on my car and it has a 9.4:1 compression ratio. Your combo has to be higher than 9.8:1 with 54cc chambers.What pistons and gaskets are you using? Dome, flat, or smaller dish pistons with 54cc heads would be higher compression. Back in the day, I chose these to keep around a stock 9:1 with gt40 heads from a '93 Cobra (later gt40p and tw 170cc). Quote Selected
Fixing misfires/flaming exhaust Reply #17 – September 03, 2016, 10:56:27 AM Piston choice has just as much to do with compression ratio as head choice. Using the summitracing.com compression ratio calculator, he's right, his CR is 9.8:1. Quote Selected
Fixing misfires/flaming exhaust Reply #18 – September 03, 2016, 11:15:44 AM I've got a 4.030" bore, 3" stroke, 60cc head volume, Sealed Power flat top piston with 4 valve reliefs (forgot the number) with a 5cc dish, .00 deck clearance, and a gasket with a .039 compressed thickness (Fel-Pro 1011-2). According to the summit calculator it's at 9.57:1 compression (I used a different calculator before that spit out 9.41:1). 16* base timing and Shell 93 octane results in no pinging.What is the dish on the pistons you are running? If I milled the heads I have down to 54cc the engine would have 10.32:1 compression.... Quote Selected
Fixing misfires/flaming exhaust Reply #19 – September 03, 2016, 12:38:05 PM Quote from: thunderjet302;457031I've got a 4.030" bore, 3" stroke, 60cc head volume, Sealed Power flat top piston with 4 valve reliefs (forgot the number) with a 5cc dish, .00 deck clearance, and a gasket with a .039 compressed thickness (Fel-Pro 1011-2). According to the summit calculator it's at 9.57:1 compression (I used a different calculator before that spit out 9.41:1). 16* base timing and Shell 93 octane results in no pinging.What is the dish on the pistons you are running? If I milled the heads I have down to 54cc the engine would have 10.32:1 compression....More dish, and thicker gasket.http://www.foxtbirdcougarforums.com/showthread.php?39788-Fixing-misfires-flaming-exhaust&p=456947#post456947 Quote Selected
Fixing misfires/flaming exhaust Reply #20 – September 03, 2016, 01:45:11 PM I don't see how compression has any meaningful effect on problem, engines are run from 8 to 11:1 and higher and don't have issues with flame out the back... In the 5.0 I ran Trick Flows cut .010 with flat top pistons(no valve reliefs) .003 out of hole... Dunno exact compression, ran great and had 170-175 PSI cranking...I'd think it is over fueling from injector or MAF issues, excess pressure or defective regulator diaphragm... Quote Selected
Fixing misfires/flaming exhaust Reply #21 – September 03, 2016, 08:49:31 PM I think that having the wrong cc chamber and resulting higher compression is over fueling. So it goes exactly along with your own theory of over fueling. Is it possible to have too much fuel delivered by the injectors for the chamber size? I thought cams, injectors and heads had to be matched up with the same purpose in mind. Cams have rpm ranges they work best at. If you have a high rpm cam (high top speed) they you want a certain flow carb. If you have a low rpm cam (fast starts) then you want a lower flow carb. Two much fuel is counterproductive. Chamber size probably needs to be matched properly too. As do injectors. There are different injectors. Ones that squirt, ones that spray, ones that mist. Just like carbs have 2 barrel, four barrel and different size tubes and bowls.Don't match things up right and more fuel results in less horsepower or less performance, detonation problems and possible flames out the back. Quote Selected
Fixing misfires/flaming exhaust Reply #22 – September 03, 2016, 11:42:16 PM It's the AIR/FUEL ratio that determines whether the mixture is lean or rich... Not compression ratio... Quote Selected
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