FE Timing

[Michael C Henry]

Piston stop bolt goes in place of #1 spark plug with the timing marks some where close to but not actually on Top Dead Center. Turn the crank by hand in one direction untill stop bolt is contacted and stops #1 piston, mark the place the timing pointer indicates on balancer. Then rotate crank shaft by hand in the other direction untill #1 piston contacts stop bolt. Mark the point the pointer indicates on the harmonic balancer. TDC is in the middle of those two marks. the closer the piston gets to TDC before it contacts the stop bolt the smaller the distance between the two marks. Do not adjust the stop bolt between going the two different directions as that would change things and the center would be off.

[Michael C Henry]

With mine the more spark timing advance I ran the less carb idle screw I needed to maintain idle rpm. Or if I turned up the distributor spark timing advance up the engine idled faster so I'd have to back the idle screw out to bring idle down to a reasonable idle RPM.
Back in the day when points were the way , I could connect a test spark plug to #1 spark plug wire and ground it so the spark jumping could be seen. I could turn the crank and set the timing marks on about 14° BTDC while #1 was on compression stroke with both valves closed and then rotate the distributor untill the test plug in #1 wire sparked and then snug up the distributor clamp and it would end up being about 8° BTDC. IT DIDN'T WORK with modern pointless ignition. I was way too late After TDC.

[jlb169]

Mike That sounds like what this is doing. The more I advance the higher the idle gets and the crisper the engine runs. Only problem is its hard to turn over when its at running temp. I'm going to try the pointer tomorrow night and see where I get.

[Michael C Henry]

The Mallory HyFire 6 has a lot of features that I'm not using but tht two different programable RPM limiters and the the programable spark retard operates under 500 RPM as in starting, are the features that I'm using. The programable spark retard let me start the engine without all the advnace fighting the starter and then increase the spark advance back to the initial set point once it started. I had a wild idea that I could switch to the lower RPM limiter if I had to let someone else drive the car as in my grand daughter. She'd find the switch anyway.

[undy]

I'm still not convinced it's not a fueling issue, lean mixture=high exhaust temps. At this point in time I'd recommend a AFR monitored chassis dyno session. I'd be very curious to know what the AFR was when your mis occured. Worst case scenario, you lose 75 bucks worth of dyno time. If nothing else it'll help you dial in the carb and tell you how much of the real deal you're putting to the ground.

[Michael C Henry]

What do the spark plugs look like? My piston stop bolt is manufactured and packaged by Comp Cams. It's all brass. 18mm x 1 theads, about 1/2 inch of threads, #4792 When my ignition was cutting out the plugs were all souty carbon fouled. I cleaned them in spark plug cleaner ( small sand blaster). I'm still using the same spark plugs today.

[Excaliber]

Well it SHOULD run poorly as you approach 'TDC and it's not surprising it doesn't even want to run at all at TDC. BIG cams, and there is NO DOUBT you got one, like a lot of advance. 22 BTDC isn't unreasonable for the best idle, power, etc. Yup, it's hell on the starter though.

Rule of thumb: Set the base timing as high as possible, 22 if that's what it takes, then back it down "just enough" to get the starter to spin OK. Finally, adjust the mechanical advance limit to give you a total of 32-35 and your timing is "done", move on to something else. That is NOT the problem.

Myself, I use my vacuum advance to direct manifold vacuum signal which gives me a "fast idle" speed when I hook it up. No problem, just adjust the carb throttle screw for a lower idle speed with the vac hooked up. Added benefit of this method is it helps or stops "run on" when you shut the hot engine off. It stops the run on because the carb throttle butterflies are pretty well closed up already. This in turn prevents the engine from drawing additional air/fuel into intake and the hot combustion chamber thus igniting the mixture. That's why some call run on, "dieseling".

I really like the vacuum advance unit for cruise rpm conditions. It add's another 10-15 degrees to your mechanical plus base timing for maximum mpg. Or in my case, for maximum CRUISE RANGE with a small gas tank! 32 total, plus 10-15 with vacuum advance and your looking at 45 to 50 total. Which is OK, maybe, how much you can get away with is dependant on the combustion chamber design, quench and other factors. MOST engine builders will NOT recommend a vacuum advance because it adds another level of potential for a "mistake" and a warranty problem.

Get it right and it's sweet! I'm getting 14 mpg with DUAL CARBS on my side oiler and thats without an overdrive! Just a top loader and 3:31 rear gears, cruise mpg about 70. NOTE: My forged pistons ARE custom designed specifically to add quench to the combustion chamber and my C.R. is 9.6 to 1 with iron heads.

[jlb169]

Mike: Plugs look good, light brown. Weathers clearing here on the east coast so I hope to try the changes soon.
The post by Excaliper also makes a lot of sense. The motor is camed. "supposed" to produce 500 HP when it's right. Gas mpg was not high on my list when I had the motor built and it shows Very quickly. I'm also going to try running on the mech. advance only and see what I get. I may also need to change to a high torque starter for hot starts. Any other suggestions will be appreciated. Jack

[Excaliber]

MPG was not a consideration when I rebuilt my motor from "race ready" to street use. I simply wanted a more reasonable power band than the solid roller lifter monster cam and massive jet dual carbs with 12.5 to 1 compression had to give. Heck it wouldn't even make decent power below 3,000 rpm! Got 6 mpg.

Solid lifter flat tappet with a nice "lumpy idle", vacuum secondary smaller carbs with reasonable jets and the right power valve combined with lower compression and more quench achieved that goal. Before it was 660 some h.p., flywheel. It is estimated I gave up 150 h.p. with the rebuild. 1/4 mile E.T. went from 11.90 to 11.99. So close you can't "feel" the difference, but street manners have improved tremendously. Essentially, I didn't give up anything, I gained a bunch! Mpg and thus the RANGE on a tank of gas is more than double. A pleasant surprise.

You CAN have good power AND good mpg, with a carb (or two in my case). Look at the new cars with terrific horse power and great cruising mpg. It's because the engines are more efficient. Efficient means more horses and more mpg at the same time! You can have your cake and eat it to. Timing and carb settings are the key components. Typically Cobras run much richer than they need to be, that's #1. Typically they don't utilize enough advance in cruise conditions. Like I said, when you get it right (timing and carb) it is sweet. Throw in some combustion chamber tricks, like adding quench, and the pay back can be significant in terms of drivability, mpg AND horse power!

I went for a geared starter as well, $250 or so, still broke the drive gear on the starter in time. Eventually I just backed off the base timing until a STOCK starter would crank it and then added enough mechanical advance to come in a little quicker and that solved the problem. Still, I WOULD like more base timing than the 17-18 or so I'm running now to eliminate a slight stumble when conditions are just right. I'd have to buy an electronic MSD control to retard the timing for a hot start, which I'm not crazy about buying. But I would prefer that over a geared starter. The other problem is the dang MSD cannot be limited enough with how much mechanical advance it provides. Leaving me with TO much mechanical and base timing before the vacuum even kicks in. To limit the mech advance MORE than MSD allows I went with a custom bushing to further reduce the max allowed mechanical advance. Got it from some shop in Cottage Grove, Oregon, via the internet, can't recall the fellows name now...

[jlb169]

Ok Guys got to take the car out today. With timing set at 12 deg. and mech. advance only. The car ran like crap from idle on up. most of time it stubbled and wouldn't run past idle . I took it back and adjusted it by ear to maybe to 18deg. It ran much better up to about 4000 rpm and then starts to backfire through the exhaust. After I took it back to the garage i shut it off and tryed to restart it, and that was not going to happen. So it sounds like I need to change to a geared starter and keep advancing the timing. Any thoughts?

[blykins]

Wouldn't hurt to check that TDC is true TDC. Do you have a way to verify that? You can use a piston stop that screws into the spark plug hole.

[undy]

Originally Posted by blykins

Wouldn't hurt to check that TDC is true TDC. Do you have a way to verify that? You can use a piston stop that screws into the spark plug hole.

What's a little elastomeric slippage between friends?

I think what Blykins is eluding to is as harmonic balancers get old the 1/8" to 3/8" thick elastomeric band tends to get hard, crack and shrink. In addition, if the old engine's spewing oil out the timing cover seal it tends to prematurely degrade that rubber ring too. That band separates the outer ring (where the timing marks are) from the inner hub (that bolts to the crankshaft). As it's age progresses it's more and more prone to slippage, meaning the outer ring is not in sync with the inner hub .. i.e. incorrect ignition timing if the marks are used for timing adjustments.

Then there's the cheap Chinese/Korean/Malaysian etc. balancers that a lot of our local auto chain stores sell... In performance applications they can slip right out of the box.


I've used a wooden pencil through a plug hole on numerous occasions with complete success, eraser end down. You can feel the rise and fall of the pencil. Depending on whose accomplishing, it can be pretty accurate on finding top TDC. Plug hole accessibility and a few other variables come into play also.

[jlb169]

Undy, This is a brand new rebuild by a professional engine builder. I would shutter at the site of an oil leak with the amount of money spent on the motor. I am going to try an piston bolt this weekend. The further I get away from TDC the better it runs but won't turn over to start it once it hot or warmed up to operating temps.

[blykins]

Don't take offense to this, but I've seen it happen by accident...

Do you have the timing light on the correct plug wire? Some people are used to working with GM junk and forget that #1 cylinder on a Ford is on the passenger side.

[patrickt]

Originally Posted by jlb169

Undy, This is a brand new rebuild by a professional engine builder. I would shutter at the site of an oil leak with the amount of money spent on the motor. I am going to try an piston bolt this weekend. The further I get away from TDC the better it runs but won't turn over to start it once it hot or warmed up to operating temps.

Considering it's a brand, spanking-new engine, I say it's time to take it back to the builder; there is obviously something wrong. As a general rule, if you have the gun on the proper wire, and the balancer hasn't slipped, you should be able to plug the vac. advance and set the initial timing on 12 degrees and the car should run pretty good (not necessarily great, mind you, but pretty decent) and then start right back up when it's hot. We all enjoy armchair engine diagnosis, but it's time to take it back to the guy that built it and tell him to fix it.

[undy]

The lack of cranking capability could be a separate issue, not tied to the ignition timing. ...not saying it is either, but i could be inadequate wire size, defective/inadequate starter/relay or a poor ground to mention a few.

I've seen used balancers reused by engine builders before, jus' covering all the bases. I wasn't saying YOUR engine could have a leak, just the engine that the balancer "could" have been on in a previous life. I was just descibing things that typically kill a balancer.

As said before it's "normal" for it to run better (to a limit) the further you go BTDC.

As Pat said, you're probably at a point you need to return it to the builder.

[jlb169]

I think you Guys are right it's time to take it back to the builder before something important happens. For my own satisfaction I will check it with a piston stop this weekend. One private post has suggested the springs are wrong in the dist. I didn't know the Unilite's had springs. Can anyone enlighten me. Thanks for all your help!

[blykins]

Yes they have springs, they're just a pain in the butt to change compared to an MSD. You basically have to disassemble the whole distributor if I remember correctly.

Easiest thing to do would be to verify TDC....then get a timing light, check base timing, then just grab the carb and open it up slowly until the time quits advancing...then have someone peek in the car and look at the tach. You can tell if it's a quick curve or not.

[Wbulk]

When you are doing the piston stop thing to find TDC, remember to pull all the plugs. A couple of years ago I was finding TDC on an LT1 Camaro and didn't want to pull all the plugs because they are really, really, hard to get to. In the end it was very hard to feel the piston stop because of the compression. The stop I was using had a "really soft bolt" and I ended up bending the bolt. I was lucky to get it out.

[Excaliber]

It aint the dist springs, I'd bet money on it. That only controls how fast and possibly how much mechanical advance is coming in. Which is easy to check with a timing light anyway.

Point is: You DO have enough advance at 18 and even a little bit of mechanical advance would add more to that. There is, in my opinion, "enough" advance for the motor to run pretty darn good at 4,000 rpm and higher. Therefore, I must conclude, "timing" is NOT the issue here. Running lean maybe, a BAD distributor in general maybe, possible valve float (but that would be a major screw up on the builders part). Timing? Thats a red herring, ignore it and move on.

This assumes of course TDC really is TDC, and likely it really is, something else going on I tell ya...