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1957 Chevy Bel Air Convertible; ZZ4 w HEI ign; 700r4; 9" rear w/3:50 gears; pwr disc fr w drum rear
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Discussion Starter · #1 ·
I am going to update my ignition system with a electronic distributor (Pertronix III with separate 45K coil)

I have been searching forums about plugs and plug wires.....lots of confusing information. I'm trying to decide what type of PLUGS and WIRES to buy.

RESISTANCE is the question....should I use "no resistance" plugs and low resistance wires for the hottest spark?

I have a stock 327 (PO said it was out of a 63 Corvette)

Better quality wires seem to have 500 ohms per foot resistance, but....
I've been looking at Taylor wires - they have the SpiroPro wires with lower resistance (350 ohms per foot) but also have some very low resistance wires (thunder volt) at 50 ohms per foot.:confused0006:

side note: Pertronix install notes say to avoid solid core plug wires
 

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Non resistor plugs and wires will/can make listening to the radio???
 

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1957 Chevy Bel Air Convertible; ZZ4 w HEI ign; 700r4; 9" rear w/3:50 gears; pwr disc fr w drum rear
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Discussion Starter · #3 ·
Thanks OB, I figured that would be one of the main issues....

Taylor's low resistance (50 ohm) wires say they provide Optimum RFI and EMI suppression. And I read on sparkplugs.com that resistance type plugs do not affect performance (in most cases) would anyone disagree?

Maybe a good combination would be resistor type plugs and low resistance wires.

For my engine, Sparkplugs.com called out for Autolite AP85- Copper Core, Platinum Tip, Heat Range 5 ......and I'm guessing I could regap a little bigger than .035 (OE gap)
I thought I would try .045 since I would be producing a better spark with the electronic ignition?

appreciate all the info I can get...
 

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Plug heat range is basically just to get the coolest plug operating temp that still gets to self cleaning temp for the compression ratio and available fuel with out being so hot as to preignite the charge. Too cold of a plug will ping easy, too hot of a plug will oil foul easy as it actually pulls the cylinder wall oil film towards it (heat range definition is opposite what combustion temp is - cold plug transfers less heat to the head and cooling system therefore the electrode insulator stays hotter).

Gap is mainly to get the flame kernal going at the right speed for a flame front that allows enough time to completly burn the fuel (quite similar to the need for advance ign spark). the resistance in an r plug is a parrallel resistor therefore neither the kernal or the heat range is effected!

Use r plugs if you do not use supressor wires and have any on board computers, or radios including digital guages etc. If you use supressor wires the plug type really doesn't matter - most "noise" comes from the length of wire - not the short core of the spark plug. I personally like the Moroso Blue Supressors - they are pretty blue, numbered on both ends, fit well and hold up to heat, oil, fuel and handling damages with very little maint work. But yea they are pricey. Loom em protect em and they will return the investment. Then I can grab any plug they got with the same heat range - plugs should be changed a heck of a lot more often than wires! So the wires become the standard and the plug the accessory!

Gap is not really an issue - more of a fine tuning issue - but rule of thumb is as compression ratio goes up, total fuel available for combustion goes up or RPM goes up so should gap (and heat range should go down). 9:1 at 5800 with a mild to moderate RV cam, .045 gap is just fine! Porting also plays a part here as a well ported engine delivers more of the atomized mixture with less "fall out" in the charge. With a REAL hot coil you can actually get a good flame front with .095 gap - but a stock to hot (high voltage in cap type) the kernal starts scattering at around .075. Lower RPM does not like wide gap - higher RPM does not like narrow gap.

The higher the gap the sooner you are replacing the plug - just like backing up the stick when welding makes a larger puddle zone - increasing the gap makes more of the center electrode wear from the arc. If you have an endless budget for spark plugs you can gap em as high as they will fire and stay unfouled. New electrodes are very squared at the edges - like a nice clean band saw cut on a piece of round stock - as they wear it's like chamfering the round stock with a bench grinder - when you can see the rounding without a scope - they are well done! Race engines use the higher gaps as they operate at higher RPMs and spend more time a WOT than at partial or idle, and change plugs more often. The red lights on the highway have ya using off idle and transitioning circuits in the carb more than WOT - so it's best to run as close a gap as will still work at 5800 than to go the other way and have em carbon fouling when you are cruising.

the most important aspect here is available voltage - just go with a hot coil and don't worry about the small stuff! Unless you are racing a street car - in which case only trial and error will tell you where your balance in the gain/loss of performance needs is. Obviously a gain in racing power is gonna be a loss in longevity/street driveability.
 

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1957 Chevy Bel Air Convertible; ZZ4 w HEI ign; 700r4; 9" rear w/3:50 gears; pwr disc fr w drum rear
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Discussion Starter · #5 ·
very helpful info thanks!
 

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JWMBISHOP I have to ask. did you write the encyclopedia for automotive excellence. That was the most amazing explanation I have ever read. THANK YOU for that.
 

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The Pertronix unit does not have enough firepower to run a big gap. Stick with .030"-.035".

With a street driven engine, I would not run a gap of more than .035" with anything but an MSD-6 or -7. Even then I don't think it's a good idea because the gap will grow too rapidly.

An HEI will fire a bigger gap when the plug is new but won't consistently get it done very well over time.

You can run a big gap with a race engine because you inspect and replace the plugs more often.

On the wires, the low resistance suppression wires (around 50 ohms/ft) will work but I wouldn't bother with them. They are really race items, they cost more, and they are unnecessary. Stick with a premium moderate resistance spiral core suppression wire that's 350-500 ohms/ft. There are several good brands.

Engines are not real sensitive to plugs and plug wires as long as they are in good shape, plugs are not gapped too wide, and the heat range is reasonably close to correct.

If you want to step up, ditch the Pertronix and get an MSD or similar unit. That will make a far bigger difference than your choice of plugs or wires.
 

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JWMBISHOP I have to ask. did you write the encyclopedia for automotive excellence. That was the most amazing explanation I have ever read. THANK YOU for that.
No i did not write it - but have read it. Engines have been my love all my life. Built my first with my Dad when I was 11 and paid attention - my first solo when I was 13 - a 350 - and no car to put it in so lovingly ran it on a "rack" and by the time I did have a car had "rebuilt" (basically upgraded) it about three times. It has seen service in 5 cars so far with over 400,000 total miles on three maint rebuilds (different crank, rods pistons and of course the hard seats we had to do in "82 to accomodate unleaded) that one is now in my best friends 72 Malibu - she pampers it and has done so for 180k of those miles over the past 15 years) its mild so never got abused (my Godfather taught me the value of keeping the daily and hotrod separate so I have never owned less than two cars - currently own 7) so I never had to repair build it (running til it breaks is much more expensive) - tear down and soft parts every 100 at the most - that helps.
By 15 I was doing most of the maint on our cars clubs member rides on weekends. When all my friends started jobs (fast food etc) I was aready making three times as much side jobbing from my garage. I was an NAISE certified master at 23 - converted those to some of the course pre-reqs when I finaly decided to pursue a degree. I do have some sae papers attributed (from when in college in '88) - but never really interested in publishing. I ain't smart - but my love for engines is why I have aced every test I have ever taken in the field - including the Navy engineman schools on Gas, diesel and Gas Turbines.
In another thread here someone mentioned about the kid that got picked on. that was me - so I buried myself in engines and cars as they repaid me for being "different" (at 13 I was 6' tall at 85lbs) - so if you read much of the threads you might understand as I mentioned in another why blowing my back out was so devastating to me. The desk part of the automotive industry was NOT an option - it mocked me. If I am to ride a desk - I figgured it should be one that pays well as I often shorted myself on wage just for the love of the work.
So now I just putter with em and enjoy sharing what I have learned along the way - I was never smart enough to figgure most of it out on my own - but I have had the blessing of excellent teachers on the way. Glad I can repay some of that.
 

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The Pertronix unit does not have enough firepower to run a big gap. Stick with .030"-.035".

With a street driven engine, I would not run a gap of more than .035" with anything but an MSD-6 or -7. Even then I don't think it's a good idea because the gap will grow too rapidly.

An HEI will fire a bigger gap when the plug is new but won't consistently get it done very well over time.

You can run a big gap with a race engine because you inspect and replace the plugs more often.

On the wires, the low resistance suppression wires (around 50 ohms/ft) will work but I wouldn't bother with them. They are really race items, they cost more, and they are unnecessary. Stick with a premium moderate resistance spiral core suppression wire that's 350-500 ohms/ft. There are several good brands.

Engines are not real sensitive to plugs and plug wires as long as they are in good shape, plugs are not gapped too wide, and the heat range is reasonably close to correct.

If you want to step up, ditch the Pertronix and get an MSD or similar unit. That will make a far bigger difference than your choice of plugs or wires.
I think you hit it right on the head Rick - too often folks, believing the race stuff is "better", mis apply it and go the wrong way in the overall cost, life, performance and maint trade offs aspect of the design. But it is fun to play with all them pretty parts ain't it? And using the principals and theories and applying them - right or wrong (learning the hard way) is a huge chunk of why we rodders do what we do.
 

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1957 Chevy Bel Air Convertible; ZZ4 w HEI ign; 700r4; 9" rear w/3:50 gears; pwr disc fr w drum rear
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Discussion Starter · #10 · (Edited)
Thanks jwmbishop and Rick......this is exactly the type of information I was looking for. I am definitely not pursuing "race" level, high maintenance performance..(at least in this application. It's a convertible...a car for fun.) I just want good average daily performance, a little response when I put my foot in it, and no maintenance hassles. Reliability is critical, and checking/changing plugs frequently doesn't interest me.

Input from experienced mechanics/members really helps us "shade tree mechanics" sift through information (and mis-information) and avoid a lot of brain damage!

Rick, now that we know I'm not looking for racing products, and really want good "average" performance and daily reliability, do you think I'm smarter with the simplicity of a matched Pertronix dist & coil........ OR hotter spark MSD unit (which I assume you mean distributor + multi-spark box set up.)
 

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1957 Chevy Bel Air Convertible; ZZ4 w HEI ign; 700r4; 9" rear w/3:50 gears; pwr disc fr w drum rear
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Discussion Starter · #11 ·
Thanks for the info as I waded through all the products out there. I ended up buying an MSD HEI kit (Small diameter Ready to Run Distributor and Blaster SS E-Coil). I can add the 6A box later if I feel the need to enhance. I also picked up a set of the MSD super-conductor wires. I'm going to organize the wires under the manifolds with some Moroso looms, and run a new starter/ignition HEI Harness (American Auto Wire). I'm also going to add some spark plug heat shields, and a starter solenoid heat shield to attempt to keep all these expensive new wires in good shape.

I'm sure I made Summit and Danchuk very happy yesterday as I ordered all the parts!

Ace
 

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Thanks for the info as I waded through all the products out there. I ended up buying an MSD HEI kit (Small diameter Ready to Run Distributor and Blaster SS E-Coil). I can add the 6A box later if I feel the need to enhance. I also picked up a set of the MSD super-conductor wires. I'm going to organize the wires under the manifolds with some Moroso looms, and run a new starter/ignition HEI Harness (American Auto Wire). I'm also going to add some spark plug heat shields, and a starter solenoid heat shield to attempt to keep all these expensive new wires in good shape.

I'm sure I made Summit and Danchuk very happy yesterday as I ordered all the parts!

Ace
The only issue I have ever had with the MSD sets is that if you are rushing they pull off the plug end a little too easy. never had a problem if careful - but when time is off essence and the folks doing the pulling are being rushed by the clock it seems they end up getting yanked off a lot. But they do perform well and stand up otherwise.
 
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