Engine and Transmission Tech

Didn't have a lot of time this weekend to work on the car, but did do a little...

Pulled the plugs (#8 was a pain -- had to shift the steering u-joint to get a socket on it), cleaned, regapped (.028 for now per Fred). They looked good to me except #5 but I'm interested in your opinion of the color & especially likely reasons for #5 being so fouled compared to the rest. I guess I need to watch the valve/spring on that cylinder and check compression? What else to check?

A couple of additional updates...
*Carb is an Edelbrock 1405 (600 CFM)
*Plugs were gapped way too much. They were around .044; I didn't check them all, but #5 was a bit more - about .050
I'm hoping that's why it was fouled so much more. What do you think?
*I'm going to change the oil -- didn't smell a strong fuel smel in it but did smell some.

Hey Rob,
Your engine is probably just fine.
What happens is, when your fuel mix goes way rich the plugs soot up like # 5 and the engine starts to misfire and stutter.
The misfire happens because the soot is a conductor and shorts the plug out.
Back in the old days this didn't happen as much.
Mostly because the ignition systems couldn't tolerate today's wide plug gaps. And partly due to today's very high additive load.
With the shorter gap the plug will still fire even when fouled.
Once the engine starts to warm up and the plug starts to fire the soot burns off leaving the grey contamination that you see on the other plugs.
That's why you short gap the plugs while you are dialing in your fuel mix.
It makes the ignition less of a variable while tuning.
Once you get the mix closer you can open the gaps back up so that the engine will tolerate a leaner idle and cruise setting.
What does your ign. consist of? It just might be happier with the smaller gap anyway.
Cheers
Fred

Ignition is MSD6AL; MSD 8579 distributor; plug wires are Taylor 8MM (one of which has the silicone melted from coming in contact w/header, but it's not #5. I have new plug wires to replace them) and, plugs are AGSP32C.

Note, there is something wrong with the MSD box I think -- the tach output on the side is suspect (either that or I have two bad tachs). I will be testing the tach output tomorrow or Wed evening after work but am pretty sure it's broken or has come loose.. the 1/4" spade connector feels loose in the box and neither my dash mounted tach (autometer) nor a SunTech one I've used under the hood when timing in the past show any RPM's. According to the MSD tech, if that output is bad, it shouldn't be affecting the rest of the ignition - including the info just in case you guys have had different experience.

Did some adjustment today...

1. Unrelated, but because I needed a tach, I checked the tach output on the MSD box & it was working... So next checked the voltage at the other end of the wire... Or at least went to do that... That's when I realized I'd connected my Speedo sender to the tach & vice versa. Tach now works & assuming Speedo will too but didn't go for a drive.

2. Checked the advance. Remember, mechanical advance only, no vacuum advance on the distributor. Result:
- 10° @ idle (600 rpm)
- 10° @ 1000 rpm
- 10° @ 1500
- 17° @ 2000
- 20° @ 2500
- erratic, bouncing between 30 & 10 very rapidly @ 3000

3. Idle reasonably smooth @ 500; have it set to 600 rpm; 1/4 turn in of an idle air screw drops rpm by 50-75 rpm

4. Manifold vacuum @ idle was generally moving between 8 & 9.5. Every few seconds it'd drop down to 7 for about a second and then return to about 8.

5. There's a noticeable popping in the exhaust on deceleration if I quickly rev it to about 2000 rpm and immediately drop it back to idle, but it did rev better and transition from idle was smoother (no real load, just opening the throttle by hand in the driveway)

6. My son was playing with a non-contact thermometer @ noticed the header primaries were all running 250-310° except #5. It was about 190. Not sure if the ceramic coating might be thicker there but since #5 was the plug that was way more fouled, thought I'd mention it. Engine has only been run for about 20 minutes since cleaning the plugs (blast cabinet) & gapped them at .028; I didn't pull the plug to look at it again.

I haven't changed the step-up spring, rods or jets from the way the carb came (orange spring, .100 mains, .070x.047 rods.)

So, what do you recommend as the next step?

I would turn in both idle mix screws 1/4 turn re adjust the idle speed and take it out for a drive.
That should help out with the backfiring and make the idle more stable.
The erratic timing at 3000 is a concern but it might just be your timing light.
If it's really moving around, you will feel it on the drive.
You might need some more initial timing but lets get the carb set up first.
I'm surprised that your carb has orange springs. These are probably a little too weak. Sadly pink is your colour Rob.
The orange springs will probably cause a flat spot on moderate acceleration. They won't affect full throttle power though.
cheers
Fred

Adjusted air/fuel screws in 1/4 turn each & replaced orange step up springs with pink. Hard to describe how it's running now. Idle is about the same. More lope than I remember other B cam 302's but the idle is consistent. Feels like it doesn't have the power it should, almost like it's missing a little until about 2500 rpm. Accelerating moderately hard to 5k it felt strong.

What to check next?

Oh, and I did check our local gas station & the pumps do say "Contains Ethanol. This product may contain up to 10% ethanol by volume."



Edited 1 time(s). Last edit at 01/16/2012 07:22PM by rficalora.

Rob, I'm no mechanic-but, is it possible your getting some "cam phasing" due to timing chain wear/stretch ? If so, this will contribute to timing wander. I suspect #5 exhaust is cooler because of misfire. I know it's a partial band aid, but have you considered platinum or irridium plugs ? Good Luck, roverman.

I won't rule timing out... In fact, I'm wondering if the next step should be to adjust timing either using the vacuum method or just increasing a degree or two at a time & testing... My thinking is without vacuum advance, I'm not getting enough advance off Idle till I get into the 3k range. But, my only experience is with stock MG's, Triumphs, and a few Jags while helping out at a small British repair shop when I was in school (and that was over 25yrs ago) so, I hoping to hear from others before doing that.

As for wear/stretch, I don't think so. The motor was bought 2nd hand, but, it was a new Ford Racing Parts crate motor that had never been installed. (was bought for a customer's 57 T-bird resto-mod. He ended up in a divorce and the wife got the money. Shop was selling off all the parts they'd bought. I got a copy of the receipt from when they bought the motor.). My odometer isn't working, but I doubt I have more than 30 miles on it at this point.

Rob, Try 12-14 initial,back off if pinging. I'd check the connections on both ends of #5 plug wire.

Rob, take your car for a run in 2nd or third gear and accelerate @ 3/4 or more throttle from 1500 to 5000 rpm.
Does it pull smoothly all the way through?
If it does. then drive it at a steady 2000 rpm in the highest gear that you can. How is it now?
Just trying to narrow down the variables and avoid the shotgun approach to tuning.
Cheers
Fred

I didn't have the note above with me so went off memory and messed up the detail... but what I did will probably give some good info...
third gear, held it at 1500 rpm for a few seconds, then floored it to about 4000. Spits & pops out of the exhaust till it gets around 2000 or a bit more, then spitting goes away and accelerates more smoothly.

third gear, held it at 2000 for a few seconds, then floored to about 4000 - no spitting or popping.

Will redo the test tomorrow all te way to 5k & also do the steady 2k test.

Ran Fred's tests...

* 1500 rpm to 5000... Initially bogs down, low power, then a bit more power (but not full power) & bucks & pops out of the exhaust up till around 2300 or so (one run did it thru about 3000), pulls strong from then to 5000. Pops every second or two out of the exhaust as it decellerates (I took my foot completely off the gas after each run).

* 2000 steady in 3rd or 4th isn't as smooth as when it is accelerating but doesn't buck or pop.

I'm assuming that means it's rich under load (power mode?) but not in cruise mode, right?

Edit: Forgot to mention, I checked the plug wire connections & they were good. Also checked compression on a few cylinders to see if #5 was different and it isn't. #1, #2, and #5 all showed 110.



Edited 1 time(s). Last edit at 01/21/2012 07:00PM by rficalora.

Hey, where'd everyone go? Did I bore you with this?

I got a PM that got me thinking about the basics & suggested I check a few things so I did.

* retested header primary tube temps since plugs are short gapped - should be firing but #5 is still significantly cooler than the rest.
* swapped #5 & #6 plug wires (@ both distributor ends & plug ends) to see if low temp moved from #5 to #6. It didn't; #5 is still cooler.
* pulled #5 and it is already starting to foul.
* pulled the left side valve cover & ran the engine for a few seconds. Can't tell for sure of cours, but valves on #5 appear to be moving as much as the other cylinders.
* also checked distributor cap - still looks pretty much brand new. No signs of arching, moisture, cracks, wear, etc. Same with the rotor.
* while swapping plug wires, I noticed my header bolts had loosened up - most of them were loose, not just the ones near #5. I'll clearly need different header bolts (they're currently Allen head & even with an allen that I cut shorter it's still really hard to tighten a few of the bolts due to the tube locations)
* while I was at it, I checked for exhaust leaks at my band clamps. I knew it was leaking some because I could hear it but it didn't sound bad. Turns out oval pipe and band clamps don't seem to mix well - they are all leaking enough I can feel the exhaust where the band clamps come together on all 4 (before & after each muffler). Will have to come up with a better answer for that too.

So, at this point I'm thinking I need to sort out the exhaust & figure out why #5 isn't firing right before I go back to trying to tune the carb.

Since compression on #5 is the same as #1 & 2, I'm assuming it is not a head gasket problem. Make sense?
Similarly, I think the compression test suggests the rings have seated on #5 too. Right?
And since it is just #5 it's not likely to be the ignition box or coil (my thought is those would tend to be more random than clearly/consistently #5)
And, since distributor cap/rotor look good and swapping 5/6 plug wires had no effect, seems like the only ignition cause would be the plug, right?

I ran out of time to see if it is firing, but will do that next. If it's not that, what would you check next.. After I closed it up for tonight, I thought about rockers. They're stud mount. Seems like if the nut was loose or there was too much preload, that would show up in the compression... Or would it?



Edited 1 time(s). Last edit at 01/23/2012 11:04PM by rficalora.

Rob,I suspect you would lose "a lot" of valve lift to measurably affect compression reading,(low cranking speed). Just for giggles, swap on another carb ? "Color Tune" spark plugs may still be available,(ising glass). Cheaper than (8) wide band O2 sensors.#5 definately sounds fat, perhaps part of the backfire problem. Had the distributor on a dyno ? Good Luck, roverman.

Sorry Rob,
Been out shoveling snow and fixing my shop roof for the last week.
I would be inclined to replace your plugs at this point. # 5 is probably dead.
Also try another timing light and see if your timing is still erratic @3000 rpm.
Set your total timing to around 34' for now and let the base timing fall where it may.
listen carefully for any signs of detonation and back off accordingly.
With all your exhaust leaks it's going to backfire on decel for sure.
Compression tests are not very accurate and will only show major faults.
A better test is a leak down test but I don't think you need one just yet.
Cheers
Fred

I've got a feeling something simple is wrong and you'll smack your forehead pretty hard when you find it. Happens to all of us from time to time... Possibly two things are wrong at the same time; and that can really confuse diagnosis (sometimes especially if one is ignition and the other is fuel system related.) Without reviewing what other people have already suggested, I can tell you three of the things I would have done a long time ago:

(a) Put a brand new spark plug in the number five hole. It will be nice to scratch "defective/damaged spark plug" off the list of possible problems.
(b) Clamp your timing light on the number five spark plug lead just to make sure you're getting a good steady spark there, just like on number one.
(c) Back at the beginning of the process, I would have removed the MSD box and the fancy coil you're probably using with it... because even though they're almost certainly NOT causing your symptoms, they may well be masking other symptoms. Maybe it's still a worthwhile idea. (MSD boxes cause lots of problems too, but mostly at high load / rpm. You've got it well grounded, don't you?)

My personal experience is that OEM quality control beats aftermarket quality control hands down. Based on what I've heard in your last post, I wouldn't rule out the possibility of a manufacturing defect in the distributor or distributor cap. If you have one laying around, now would be a great time to plug-in a Motorcraft distributor. If not, I'd think about changing caps. One day you'll need a change of spark plugs, a new cap, and a new rotor... you might as well invest in them now. Swapping parts isn't the most elegant way of diagnosing engine problems but sometimes it's the the most pragmatic. For that matter, swapping a "known good" spark plug wires from your pick-up truck or commuter-car for that number five lead might not be a bad idea. It only takes a second.

Just another off-the-cuff thought, but on a late Ford HO engine, cylinders 6 & 5 fire sequentially - you're not getting cross firing going on between HT leads are you?
I'd also check resistance of #5 HT plug wire to see if it jives with the others - maybe a bad end connector or something?.



Edited 1 time(s). Last edit at 01/24/2012 06:28PM by ex-tyke.

If a new plug works for a while then goes south again it might be a marginal piston oil ring or a margin valve guide or seal.

This site might be some help.

[www.autotap.com]

Ok, you guys have redeemed yourselves -- no one gets fired today ;)

I've got locking header bolts on the way. They're a double hex style so should be able to get them all properly tightened & with luck they'll be there when I get home from work Friday.

Haven't figured out what I'm going to do on the exhaust. If I weld it at the mufflers, it'll be solid from the headers all the way to the tail pipes. Not even sure I could get it back on like that. I guess it'd be too easy to have something that could wrap around the pipe under the band clamps. Probably have to get some flanges & put them in before the oval starts & again where I transition back to round to go through the rear suspension. Any other way to effectively seal the joints? The oval pipe slips into oval inlet/outlets on the mufflers.

Plugs are easy; probably should have swapped #5 out earlier - at least to see if it fires. I also like Curtis' idea about putting the timing light on #5 -- that'd tell me the plug is getting voltage consistently -- not necessarily that the plug is firing, right?

Don't think I'm getting cross firing -- at least no signs of it. And, since I swapped #5 & #6 leads and #5 stayed cold, I think that rules out a bad plug wire.

Don't have a stock points distributor, but will probably keep an eye out for one next time I'm at the pick-a-part. Wonder if parts stores even stock points any more? Don't want to go on a tangent, but what would it take to convert a stock distributor to work with the MSD ignition -- is there a magnetic pick-up module that'd work? Thinking out loud here - don't recall why I got a mechanical only distributor.

Rob, You still may have an issue with #5 distributor cap terminal. You can test if the cold exhaust moves by moving your wires one terminal and retiming. Late 70's Duraspark II(magnetic breaker type) will work fine with MSD and has vaccuum advance. You can lose the adapter and use the old style small cap and rotor if you like. I have an article on setting up the advance curve for one if you go that route.