hi, im about done with the comet. this is so frustrating.. I finally purchased a timing light and set my initial timing at 12deg. and reset my ezefi. now it run like complete crap. keeps backfiring. for 5.0 explorer bottom end. trickflow 170cc heads 1.6 rocker arms trickflow stage1 cam msd distributer for msd box, msd6a, msd wires. (no vac advance) only mechanical ive been reading where people with bigger cams are running as much as 20deg initial timing. I noticed that it runs better when I advance it. any ideas?
Sounds like your balancer or timing pointer may be mismatched, so it's not set at 12*... I used same TF cam, heads & rockers on my 5.0 T-Bird with factory EFI, was more than happy with 12* advance... Of course the computer then added another 24-26* so totaled 36-38*, the total timing is what it's all about...
I concur. Ford has three different timing position keys, typically referred to as A, B & C. Remove the #1 spark plug and bring the #1 piston up to TDC on the compression stroke (putting your finger over the plug hole will allow you to feel the pressure building). See where the pointer is relative to the index marks on the balancer. Some aftermarket balancers have all three index keys while some only have one. This issue has messed a lot of people up when timing these things, so its worth the effort to positively identifying TDC and marking the balancer or changing the pointer location appropriately. While you are at it, make sure your firing order is appropriate for the cam you are using.
I am using the same pointer, balancer, the whole shortblock is original from the 97 explorer downer vehicle. I checked my firing order several times. I am thinking of getting a new balancer to verify.
It doesn't sound like an initial timing problem. When were the heads, cam, etc. installed? Did you do the modifications or someone else? Has this engine with modifications as you described ever run properly? It could be the valve lash is not set correctly or the cam timing causing the backfire.
i built the engine myself, never ran properly. cam timing is correct (timing marks) checked the valve lash twice, 1/2 turn past zero. i did a compression test, and all the cylinders were 150 psi, within 3 psi. oil pressure is 50psi cold, 45psi hot. 10w30 oil ive built many chevy engines before. first ford. ive rebult small engines and diesel's as well.
BUT are you using orig timing cover?? Passenger side pointer mount location can vary from approx 10 to 11 o'clock... As a FYI read through this thread... http://mmb.maverick.to/threads/timing-marks.105577/#post-1071267
same timing cover, pointer, accessory drive, , basicly an explorer engine, different heads, intake, efi
So tell us about the EFI you're using, I'm dumb on anything other than factory stuff... But before we go there, something to think about... A unloaded engine should rev freely with 12* initial and no other advance at all... No it won't be happy under load, likely start popping back once revs are up a bit...
I agree completely. Would be even truer statement with 22° of initial spark lead. Something is way off to act up like this. To help push through tough times, I used to just tell myself.. "self.. it ain't worth crap if it ain't running so I gotta fix it either way". Worked every single time.. I'm too tight to lose that much money all at once. lol IOW.. you're on the home stretch here and in the grand scheme of things?. tuning is the easier gravy part even though it can be more frustrating and time consuming than the actual buildup was. At least you're down to the really small handtools now. Here is how I would approach it. Electronics aside for now and start with the motor first. As mentioned above be DAMNED sure that the timing pointer is it true TDC. Eliminate the cam timing right away and check it off the list early on. Next is to double check that the rotor is lined up with #1 cap terminal @TDC of compression stroke. Being 180° out has screwed up about every engine builder I have ever known, professional or otherwise, at one point or another. One of the reasons I made a "compression stroke whistler" out of an old spark plug long ago because I got sick of the OCD like quadruple rechecks just to be overly sure I "don't screw that up again like that last time". It still happens to the best on occasion too. Always confirm the baseline before moving forward up the troubleshooting chart. The FAST EFI unit you have is self learning/auto calibrating, correct? If so, and I assume that it is with the "EZ" designation and that most higher end units are nowadays.. then why don't you give it the higher initial advance numbers it likes and prefers while the EFI controller compensates over on its end? Maybe you don't know how to rebuild the advance curve?.. or simply because the MSD bushings won't let you take enough mechanical advance out to effectively lower the total advance number back down after adding heavier initial? MSD sucks that way and they make bushings in the aftermarket to limit the mechanical timing sweep more than MSD's bushings will allow. And the bigger the cam.. the more likely you'll need some beyond what MSD makes. Not taking into account the increased NOX emissions being added as a result of very high idle/off-idle spark advance.. there is absolutely NO downside whatsoever to having more intake manifold vacuum because it specifically denotes an engines efficiency based off BMEP(Brake Mean Effective Pressure).. or in layman's terms.. effective cylinder pressure(which BTW is what we want more of so long as the engine doesn't detonate on it's intended fuel quality). Can you go into better detail on the way the engine is running, greater cam details will help too, and how it reacts to the throttle? Popping back up through the throttle body at all? EDIT: forgot to say that spark intensity should be physically eyeballed and confirmed to be hot enough with an extra plug grounded out someplace visible. Otherwise.. the little things can get you.
I talked to trickflow, they told me to run 14deg initial, and 32deg total. so I am going to try that. that means I need to set the timing, and change the advance stop. should be easy, going to do that tomorrow. my compression should be 9:1 with my setup. flat top pistons with 61cc heads.
Like Tom said above. Those are safe numbers to get you going in the right direction.. but my turrets just kicked in and I have to say that guy you talked to should probably just stick to selling cylinder heads. Don't mean to be so harsh but trust me here bud, I seriously wouldn't spend the effort to help you back in the right direction if the major gains weren't there to be had. The fact-o-the-matter is that regardless how good the cylinder heads chamber is, lower compression motors inherently have weaker mixture motion rates on the compression stroke and slower flame front propagation. Both of which traits require MORE timing advance.. not less.. or "average numbers". Plain and simple, the vacuum gauge tells you what the motor wants. Also keep in mind that a vac advance pot is not a bad thing to have on a street car. Otherwise you will be leaving much on the table for light throttle snappiness and overall efficiency if that motor only makes 20° or less between idle and say 1,600-1,800 rpm. Newer cars can go over 50° advanced with low throttle angles and lighter loads. Even my 11.6:1 383 Blazer took 54° between 900 - 1,700 rpm. Got me up to 16" of manifold vacuum compared to around 12" when I bought it. And that's from a moderately sized cam too. Now the car couldn't do bunny hops to save it's own life. Jab the gas lightly and the tires just instantly spin. Didn't even come close to that same performance with 30° less initial timing. Much softer feeling and not nearly as responsive as it is now. All in all, I'm just trying to get across that spark timing can make a big difference to the way an engine feels and reacts under your right foot and shouldn't be underestimated in the least. It's free power that you already payed for with all those good parts. A little light reading to help you along. https://www.fordmuscle.com/archives/2000/03/timing/
I just quick peeked at the EZ EFI setups. Too bad you don't have the newest 2.0 version since it would give you full ignition control capability so you could simply lock the dizzy out and make quick tool-less timing changes on the laptop. Otherwise, unless you can somehow update(doubtful) or upgrade to their newest control box this is the one(except I ran the 7 series version) on my truck and have another sitting on the shelf for my Comet. MUCH better control than any mechanical setup and it's MAP based tuning gives you built in vac advance capabilities. http://www.msdignition.com/Products/Ignitions/6530_-_MSD_Digital_Programmable_6AL-2.aspx
