ok, i have a 460 with heads from a 69 or 70 lincoln DOVE-C. factory gap is 32 to 36. truck runs ok at fairly high speed but junk when around town or idling.
i have an msd ignition box. i'm reading now the gaps may need to be as wide as 60. any truth to that? i didn't build the engine and the plugs i took ut were fouled and gapped at about 31.

 

oh, the motor is in my 59 f-100. that's why i'm starting here.

 

The rule of thumb is "as wide as you can without misfire" That is to say some will upgrade coil to a hotter coil or change to ei to gain hotter spark.... But spark gap has nothing to do with fouling, fouling is from timing issues (too early / too late) mix ratio (lean/rich) and leaks (oil / water getting into compression area. I advise leave gap as is, re time, check compression and leak down compression - solve your fouling issue first and then worry about gap, but don't touch it till you have everything in order)

 

new plugs aren't fouled. i've been battling the previous owner's de-tuning of this motor for weeks.
the old plugs fouled after a big back fire. the idle screws on the carb were fubar the choke was stuck shut, and there were loose vacuum hoses, etc. just been finding small things over the last few weeks. that all might have been due to the backfire.
the plugs aren't white and they aren't fouled.
i'm thinking i'm going to open the gaps up to about .040 and try it out.
i think the last guy set the gaps to the factory gap, started running rich and then tried to adjust the idle and it all went down hill from there. (maybe that's what i'm hoping happened)

 

You didn't say what coil you're running with the MSD. That, plus the box, is what makes the stronger spark. Electronic ignitions can routinely handle .040-.060 gaps because there's more power to jump the wider electrode gap. The wider gap leads to longer burn times, resulting in lower emmissions and more power obtained from that combustion cycle. But it sounds like you have deeper problems than a wider plug gap will fix. You should probably look at fixing your carb problems before worrying about your ignition.

 

i think i have the carb right. it's an edelbrock 1407. when i started working on it i fixed the choke problem then i went after the idle adjustment.
on the secondary screws the right one was turned all the way in. i synched them and my idle was at 1100 rpm i brought it down to 600 and it started running like junk again. went back to the secondaries and am now idling around 600. just opened the gaps up to .043 and it sounds more like i think it should. it's dark so i just took it around the neighborhood and it seems to have a little more power at take off and doesn't seem to be backing up in the exhaust like it was on decel.
merc i bought this truck, i'm not sure about the coil. it's blue is all i can think of without going out and popping the hood.
another concern is should i be idling this low? it's what the 70 lincoln idled at but i think this may have a mild cam (can't decide it's a cam or just the sound of a big block).

 

It's simple enough to degree the cam to see what kind of cam is in the engine. Google it and get a great discription of the process. That is the place to start if you don't know what you have. I found that the PO had advanced the cam a bit by playing with the timing gear bolts and rebroached a keyway with a new timing mark on the gear. really had me wondering what the heck happened. I wound up replaceing the cam with a diferent grind. That one ran like a top after that.

 

Automatic or manual transmission? 600 rpms is too low for a 460, imho. I'd be looking for closer to 850 in park, dropping to about 700 in drive at normal operating temperature. A Lincoln engine should run perfectly smooth and purr like a kitten. No lumpy bumpy anything. If it's been altered, then all bets are off.

 

ok, that makes me feel better merc. if i tweak the idle up to around 800-900 in park it does idle much smoother.
i've had several people tell me that's too high. but it sounds like it's stalling now and then if it idles lower than that (but, i still think it may have a mild cam)
it's an automatic. i'm pretty sure it's a c-6 but you'd think it was a 2 speed because t doesn't hang around in 2nd gear. it doesn't stay in first very long for that matter.
here's what i know about the engine. msd ignition, dove-c heads, edelbrock performer rpm intake, edelbrock 1407 carb, k&n 14x5 air filter, and headers going into true dual exhaust.
there is a slight exhaust leak at the passenger side collector gasket. it has dual electric fans (in a shroud) instead of a fan on the pulley. on a hot day it does not like to sit and idle. it runs warm.

 

An engine with a hi-perf cam needs a higher idle than a stocker. The numbers I gave are for stock. If it runs better at 900, by all means tune it there. It may even run cooler with the idle and timing set correctly.

 

yeah, i'm going to take it up again in the morning. i'm probably going to run it pretty hard and then open the plug gaps up to around .050 and see how it does. the exhaust smells better (more like it should) with the gaps at .043 if that makes any sense.

 

Stock, Duraspark II electronic igintion calls for .044, so .050 with MSD wouldn't be out of the question.

 

yeah, i've been reading other forums and they are saying anywhere from .044 to .060
i'm just going to have to experiment.
i hate not knowing exactly what i have but i think it's solid. i think the last guy tried to set things for a stock engine and ran into these problems then unloaded it.
the truck has had a lot of stuff done to it and i bought it for 2800.00. the wheels cost half that.
the front shock bushings were gone so it rode rough as hell too. the air shocks on back were bled down completely.
i've steadily been doing small stuff and it is riding better. i'm hoping opening up the gaps and adjusting the idle up will get it running better.
the fuel cell is leaking. i may just pull the carb and re-build it while that's being welded.

 

Eh, I think your plug gapping is compensating for some other problem. you mentioned that you have the D0VE-C heads on it. Those are a quench chamber head, excellent design for combustion in the 460s however, because they are small chambered heads, you could have higher compression. I've got a original-stock '70 Lincoln 460 (with the same heads) in my '76 F100 SWB. I have the plugs gapped at .045 I believe. I have the stock Duraspark ignition and a Holley 600 cfm carb on it. I run about 8* initial because the earlier 460s have higher compression and if I give it anymore advance, it gargles like a diesel. I think the factory spec it 12*. I have it idling at 600 rpm in drive, and it does just fine, never skips a beat. The factory setting for the idle is, in fact, 550 in drive. I thought that was a bit too low, and so does my headlights.

I would take a compression test and see what numbers you're gettin. I have a feeling you may have too high of compression to run regular fuel (i.e. 86/87 octane) You have to be careful which pistons you use with those D0VE heads as you can accidentally build a 10:1 or greater compression engine. Not good for regular fuel. This is assuming that the P.O. went through the engine.

You mentioned popping through the exhaust and the exhaust not sounding right. That brings me back to another engine I worked on. A buddy had a '67 Camaro and he was car stupid and didn't know what he had bought. He had been running it on regular fuel. That thing sounded like **it and only somewhat ran good when you were screaming down the street at 6500 rpms. So i worked on it and worked on it and couldn't for the life of me get it to run worth a damn. Took a compression test on it one day and it was postin 195s and 200s on the gauge. I said WHOA! we got an issure here. Decided to tear it down and found out he had a 283 with .200 dome pistons stuffed into it with camel-hump heads (quench chamber heads) After doing the math it came to be almost a 12:1 engine! No freakin wonder. Long and the short of it, I built him a nice and reliable 350 and we put that in. Ran like a champ.

Another thing you may consider. Take that 750 Edelbrock off and chuck it into the trash. Put a Holley or older Carter AFB on it instead. I've had nothing but troubles with Edelbrocks, getting them to run correctly. the older Carter AFBs and Holleys, never a problem. I don't know what Edelbrock did, but they did something to that design.

 

dano, i only run 93 in it. i've kind of been assuming high compression. i think these engines were at least 9.5 stock and i feel like the p/o was trying to build a race engine.
it doesn't ping or tick. i have thought about buying some racing fuel and adding a gallon to a tank and see what happens.
600 in drive may be ok. but idles at closer to 800 in park to get that.
i think the guy that built this couldn't decide what he was building. he started a custom interior but he went cheap on the bed (plywood with steel over it and the fuel cell exposed in the bed).
then he went broke and the guy i bought it from knew less about getting it to run tight than me. this is my first performance ford engine and i'm reading a lot and asking questions.
so, a lot of what i'm working on is undoing what he tried. the plugs i took out were gapped at .031, the idle screws were in ridiculous positions, and vacuum lines were clamped poorly.
i'm guilty of doing some of the same things. i adjusted the idle and re-adjusted it before i thought to check vacuum lines. i tried closing the gaps before it dawned on me that i should have opened them.
i'm going to run it in a while and see what happens. if it still loads up i'm going to open them more.