judgetread 757 Posted January 15, 2016 Well heres the problem, I though Id throw it out there and see if anyone has any ideas or experienced the same thing before. Car hooked up to a dyno. Timing is locked and set to 34 ... no mechanical or other advance As the engine is revved, timing is dropping/retarding itself so at the end of a run its back 5 degrees and 29, some where and somehow something is forcing it to retard so before I throw a bunch of money at it has anyone see this happen before of a sbf? I know on chev's the cam can walk a bit causing this but dont think its possible with fords and the thrust plate (being checked atm anyways just incase). Have pulled the dizzy out and checked for any play anywhere, put new pins to hold the gear and bearing in it and checked the pickup as well.. So Im starting to suspect the hyfire 685 box? Either cant keep up or faulty somehow, maybe for some stupid reason it thinks theres a map sensor on it or ... coil (did replace it with brand new of same type) fucks me ,... Share this post Link to post Share on other sites
slydog 7,873 Posted January 15, 2016 Well on a xflow you set timing @ 3000 cos @ RPM the timing is known to retard a fair bit. So in my case I set mine @ 29 degree's and it is usually closer to 27ish. So is yours @ 34 @ idle after a pull or doe's it go back to 29? Share this post Link to post Share on other sites
judgetread 757 Posted January 15, 2016 yeh 34 at idle, 29 at 6k, then back to 34 at idle you can watch it retard over 3000 just keeps dropping the harder you rev it... Wierd bit is if the timing is rock solid, it doesnt waver if you hold steady rpm sp if you hold sa 4k it would have dropped from the idle but itll say steady but go to 5 and another degree will drop out Share this post Link to post Share on other sites
judgetread 757 Posted January 15, 2016 surely it cant be cam flexing its a solid billet cam Its coming home today till I get it sorted, I guess its till to borrow some parts and eliminate them as I go Share this post Link to post Share on other sites
slydog 7,873 Posted January 15, 2016 Chain stretch homey...no never heard of it on a SBF but xflows are bad for it. So set base timimng higher than normal and check where its at when rpm is @ 3000rpm. 1 Crazy2287 reacted to this Share this post Link to post Share on other sites
judgetread 757 Posted January 15, 2016 Chain stretch homey...no never heard of it on a SBF but xflows are bad for it. So set base timimng higher than normal and check where its at when rpm is @ 3000rpm. Yeh possibly brand new 200 km ago tho but you never know i guess Maybe time for a quite set of gears :S or a belt set if I can find one Share this post Link to post Share on other sites
Crazy2287 1,886 Posted January 15, 2016 Hmmm, If you HAVE to eliminate this then IMO the best (and cheapest) option would be computer advance? Add a degree of timing every 700rpm above 3krpm. Share this post Link to post Share on other sites
judgetread 757 Posted January 15, 2016 Hmmm, If you HAVE to eliminate this then IMO the best (and cheapest) option would be computer advance? Add a degree of timing every 700rpm above 3krpm. Yeh thats a possibility, rather find the cause tho Its estimated to be possibly losing 20-30 hp from this issue pita but that cars for you Share this post Link to post Share on other sites
slydog 7,873 Posted January 15, 2016 I'll ask Smithy if he has any small weezors that suffer from chain stretch. Don't panic about or think it's buggared cos it is very common in xflows ay. 1 judgetread reacted to this Share this post Link to post Share on other sites
judgetread 757 Posted January 15, 2016 yeh they dont believe its anything to do with cam/chain more likely pickup or iginition box. They've let me a msd box to try and they are going to get a dizzy to me try ... Share this post Link to post Share on other sites
judgetread 757 Posted January 15, 2016 got a pic of the HP output but cant seem to get it off me phone Considering the issues and hasnt been jetted yet its not to bad ... Share this post Link to post Share on other sites
Outback Jack 6,352 Posted January 15, 2016 I reakon be that ignition,is only logical answer. On an msd it should work fine... ignition box is only thing that can cause that sort of drop off without sonething being busted. Jack. Sent from my GT-S7583T using Tapatalk 1 gerg reacted to this Share this post Link to post Share on other sites
judgetread 757 Posted January 15, 2016 I'll ask Smithy if he has any small weezors that suffer from chain stretch. Don't panic about or think it's buggared cos it is very common in xflows ay. Yeh thanks mate Not stressed, its pretty safe retarding like that, if it was advancing id be worried Share this post Link to post Share on other sites
NZXD 2,328 Posted January 15, 2016 Hey dude, what's it like with locked timing? So you have it set at 34 degrees from start up?<br /><br /> Share this post Link to post Share on other sites
judgetread 757 Posted January 15, 2016 Hey dude, what's it like with locked timing? So you have it set at 34 degrees from start up?<br /><br /> yeh its ok Ignition box has a 10 degree retard on start so it start pretty good. Share this post Link to post Share on other sites
NZXD 2,328 Posted January 15, 2016 Oh ok, yeah I don't have an ignition box, just mechanical advance, think it's 16 on idle and all in at 34 by 3000. 1 judgetread reacted to this Share this post Link to post Share on other sites
slydog 7,873 Posted January 15, 2016 So here's Smithy's explanation of it.Windsor's issues is end float but more up and down due to pump load unlike a xflow which suffers more from the chain stretch. "Ok so very common in Ford engines........ My race engines have done it, here's what it is,The timing retards due to oil pump load, which forces the distributor up the gear on the camshaft. I usually check distributor end float which is the climbing the camshaft gear and retarding. Tighten the end float or raise the idle timing to say 40 to get 35 @ 6000. Make sense ??" Now this guy use to build race engines for HRT for a living and has some of the fastest touring car masters cars getting around. Just saying... So in the end as expected just bush the dizzy as tight as safe and give it more base timing then check timing @ 3000rpm,No biggy cuzzy 4 judgetread, Crazy2287, NZXD and 1 other reacted to this Share this post Link to post Share on other sites
judgetread 757 Posted January 15, 2016 thx sly much appreciate it!!! ill check it out tomorrow 1 slydog reacted to this Share this post Link to post Share on other sites
PRO250 1,506 Posted January 15, 2016 all my clevos do it, never looked why I just set it the timing so its safe and forget about itone runs a acell dissy other a msd billet one the other a factory bosch onewait till the chain flogs a little the brown v8 corty has a old engine, man timing walk on that HAHA its like a merry go round just hope for more then 20 LOL 2 judgetread and dougie77 reacted to this Share this post Link to post Share on other sites
judgetread 757 Posted January 16, 2016 ok so end play is 30 tho so its a little large but not overly big. 1 Outback Jack reacted to this Share this post Link to post Share on other sites
judgetread 757 Posted January 16, 2016 scrap that, it 18 tho end play Share this post Link to post Share on other sites
judgetread 757 Posted January 16, 2016 checked end play and reinstalled definitely still retarding although its all happens quicker than I expected. From idle to 2.5k is back 5 degrees. I thought it was happening later in the rpms but its not. Will swap over the cdi next and see else might have to rip cover off and check chain/thrustplate Share this post Link to post Share on other sites
slydog 7,873 Posted January 16, 2016 Nah just bush the dizzy and adjust base timing and it will be fine.Be surprised at how much you gain/loose??? by taking end float out of the dizzy. Share this post Link to post Share on other sites
judgetread 757 Posted January 16, 2016 Nah just bush the dizzy and adjust base timing and it will be fine.Be surprised at how much you gain/loose??? by taking end float out of the dizzy. It needs play to expand when warm but yeh? Well msd 6al didnt help it 1 slydog reacted to this Share this post Link to post Share on other sites
judgetread 757 Posted January 16, 2016 well fucks me ..... what about as suggested add programmable and do some weird timing maps lol or set it at 34 whenever it stop retarding and using the nos retard feature hooked up to starter to give it some more start restart Share this post Link to post Share on other sites
