Posted July 8, 20213 yr comment_624719 To make a long story short, The car runs like crap when the timing is set where it needs to be yet when advanced into the 20's it runs 10 times better, I checked the cam timing and it seems to be on the money. the cam is not factory but somewhere around a 262 grind from the 80's. for reference, the block is a 77 l28 with a e31 is a streched chain a suspect here? Link to comment https://www.classiczcars.com/forums/topic/65576-ignition-timing-question/ Share on other sites More sharing options...
July 8, 20213 yr comment_624720 When you say "run" do you mean idling, or cruising, or getting on it? And, define "crap". Carbs, EFI, engine details will help also. Not much to go on. If cam timing is on the money then stretched chain is not likely. The chain determines cam timing. Link to comment https://www.classiczcars.com/forums/topic/65576-ignition-timing-question/#findComment-624720 Share on other sites More sharing options...
July 8, 20213 yr Author comment_624723 I tried to make a long story short.. The car is a 71, dual webers, header, zx dizzy. "runs" means overall, at stock timing (12-15 ish) poor idle quality, poor drivability, poor acceletation. It runs "normal" at 25 or so. as far as I know the short block is all original, the timing marker and the balancer were not changed or mismatched "cam timing"- At tdc the cam sprocket marks allign with the tower marks. the chain is very tight. Link to comment https://www.classiczcars.com/forums/topic/65576-ignition-timing-question/#findComment-624723 Share on other sites More sharing options...
July 8, 20213 yr comment_624724 I would go through the usual confirming that all of the timing marks are correct. Is piston #1 really at TDC when the other marks are zero'ed, or are you assuming that zero on the damper pulley is correct? If you're at 25 degrees and you add in the typical 18 for full centrifugal advance you'd be at 43 degrees advance under acceleration. You should be getting detonation and knocking. Something's off. Does timing advance when you rev the engine and the light is on it? Link to comment https://www.classiczcars.com/forums/topic/65576-ignition-timing-question/#findComment-624724 Share on other sites More sharing options...
July 8, 20213 yr Author comment_624726 There is no detonation, with this cam it has a turbo like personality, all the power is above 4k, from there it pulls like a fright train. I'll double check everything, I guess its possable for the outer ring of the ballancer to turn on the inner. Link to comment https://www.classiczcars.com/forums/topic/65576-ignition-timing-question/#findComment-624726 Share on other sites More sharing options...
July 8, 20213 yr comment_624729 There is no detonation, with this cam it has a turbo like personality, all the power is above 4k, from there it pulls like a fright train. I'll double check everything, I guess its possable for the outer ring of the ballancer to turn on the inner.And if it’s done that then it’s time for a new one! ;)I’m with Zedhead - my initial thought too was timing marks are off. Link to comment https://www.classiczcars.com/forums/topic/65576-ignition-timing-question/#findComment-624729 Share on other sites More sharing options...
July 8, 20213 yr comment_624730 No detonation at full advance and it runs good? Run it! My 240 is maxed out advance and I even put the chain on #3 hole when I rebuilt the motor. It runs great and loves advance. Link to comment https://www.classiczcars.com/forums/topic/65576-ignition-timing-question/#findComment-624730 Share on other sites More sharing options...
July 9, 20213 yr Author comment_624749 https://photos.google.com/search/_tra_/photo/AF1QipN9IidI9bnZtliZmPggTCwn227HvHlYxZYYblnJ https://photos.google.com/search/_tra_/photo/AF1QipMCB8E7dYOsA1C4j6eH-Zzh4OhpBGHJ9zeDxel3 https://photos.google.com/search/_tra_/photo/AF1QipNy58sgEEN3ERs4pItuXXuQZVYbQVzH_cZeI2Cuhttps://photos.google.com/search/_tra_/photo/AF1QipOYCUelWJeSF9uOY-UeGBIyHIZ6hCBLfjVE2dHuhttps://photos.google.com/search/_tra_/photo/AF1QipOAgvGx4eV2PbxE3OP_YzII_egY65Eq0xIQeJne The lack of detonation is exactly what bothers me, I cannot advance it enugh to cause it to detonate espacially with the garbage fuel we have today., the pics were taken at tdc and the tdc was verified, the piston starts moving down slightly past tdc. the timing marks are right on.. the cam timing marks are confusingbut maybe I'm not reading them correctly., by eye balling the cam it looks to be advanced to me but it could be an optical ilusion as well. I do have another complete long block that is all stock, tommorow I'll pull the valve cover and set it on tdc to compare the cam timing. I was thinking about retarding the cam to make the car more street friendly, right now its a total huligans car. Link to comment https://www.classiczcars.com/forums/topic/65576-ignition-timing-question/#findComment-624749 Share on other sites More sharing options...
July 9, 20213 yr comment_624754 Your links don't work. What else can you say about the engine? Pistons and head combination, for example. I wonder if a low compression engine runs better with more advance. Seems like it might since the pressure isn't there to drive the combustion. Maybe you have dished pistons with a P79 head. Link to comment https://www.classiczcars.com/forums/topic/65576-ignition-timing-question/#findComment-624754 Share on other sites More sharing options...
July 9, 20213 yr Author comment_624762 Stock 77 short block with a E31 head, shaved too, (cam towers spacers included) should have higher then stock compression. The links work for me..any idea of a hosting service? all the old sites I used in the past are gone. Link to comment https://www.classiczcars.com/forums/topic/65576-ignition-timing-question/#findComment-624762 Share on other sites More sharing options...
July 9, 20213 yr comment_624763 Imgur works, but you can also just upload images to this site. Link to comment https://www.classiczcars.com/forums/topic/65576-ignition-timing-question/#findComment-624763 Share on other sites More sharing options...
July 9, 20213 yr Author comment_624764 Tried, the attachment function wants a url unless I'm doing something wrong as usual. Link to comment https://www.classiczcars.com/forums/topic/65576-ignition-timing-question/#findComment-624764 Share on other sites More sharing options...
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