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1969 Camaro Restomod
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Question probably gets asked a lot, but trying to find a definitive answer is sometimes difficult because we're not talking stock engines and factory specs for plugs from 1969. So I've got a mid-70's 454 (.030" over), forged pistons, steel crank, CompCam Xtreme XS274S with solid lifters, Holley 4150, Edelbrock Performer intake, 781 Oval port heads, long tubes, Chevy Distributor with Pertronix Ignitor Kit and Pertronix Flame Thrower coil.

Plugs that were in the car are AC Delco R43TS and they are sorta sooty and black so I was going to move up to a 45, but AZ didn't have 8 LOL. So I opted for Autolite 26 plugs which are the comparable heat range to the Delco 45's. Here's the old plugs.



So you can see how black and sooty the plugs are. And plugs are cheap enough to try an alternative. Thinking I should gap these at around .041" (?) but wondered if anyone has a somewhat similar setup. Pertronix only says to gap plugs .005" greater than normal, but I've heard that some guys will gap these at .045" so I'm curious.
 

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1969 Camaro Restomod
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Discussion Starter #3
Just my noob opinion but I think you need to find out why it is so rich and fix that first.
Thats going to be next on my list LOL. But in the meantime, it'll be interesting to see what the new one range hotter plugs look like after driving a bit.
 

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I would gap .030-.035 but like Mike said I would fix the issue. As bad as they look I don't think a range or two hotter will fix that. Maybe more initial timing, mixture, etc.
 

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With HEI you open the plug gap from points ignition gap of 0.032" to 0.045"

Increasing the heat range could move you closer to detonation, and the heat range has no effect upon the air fuel ratio.

As has been pointed out you are running pig rich. You didn't mention the cfm rating for your 450 series Holley carb, but the factory used a 780 cfm on the 427 and the 454. If you are reving the snot out of your BBC then you go bigger on cfm. (as an aside I have had much better results with a 4500 series Holley as the engine seems to like it better than a 4150; even when both are the same size, which over laps in the 750 cfm size).

I am of the opinion that your carb (regardless of size needs tuning due to your choice of cam).

COMP Cams Xtreme Energy Camshafts
Comp Cams Grind Number: 12-677-4
Basic Operating RPM Range: 2,000-6,400
Cam Style: Mechanical flat tappet
Intake Valve Lash: 0.016" in.
Exhaust Valve Lash: 0.016" in.
Duration at 0.050" inch Lift: 236° int./242° exh.
Advertised Duration: 274° int./280° exh.
Valve Lift with Factory Rocker Arm Ratio: 0.501 int./0.510 exh.
Lobe Separation (degrees): 110°

This is a very mild cam for a solid cam grind (not crazy about the lift numbers), but it has more than enough duration to create reversion in the intake manifold which causes the carb to run rich in response. Carburation relies upon vacuum, not pressure pulses from a piston pushing air back into the intake manifold through an open intake vavle.

Big Dave
 

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Take this information as it is given, from someone that designed, and builds his own HEI ignition conversions, many, many of them, I do this for a living,

PerTronix Ignitor, all of them, and no matter the input volts, nor the coil used, IS NOT AN HEI, it is a simple point replacement system (TCBI), and does not have the driver circuits to push a coil to make more volts to the plugs over what a stock point system makes, PERIOD

That said, .035 is MAXIMUM, no matter the setup with one.

And, although some sources say a real HEI can take .060 to .080 plug gaps, as suggested in some older Oldsmobile specs, that is not the case, for all MSD, and HEI, .045 is maximum. What GM found out with the larger gaps over .045, they caused both coil and module failures within the warrrantee periods, way too many of them. So, GM revised the plug gaps DOWN to the .045 spec, and the failures stopped. So, don't believe what some over hype ads say about aftermarket coil in cap HEI coils, they, too require the .045 gaps, NO LARGER.

Although a lot of ignition systems will bridge extremely large gaps when they are not firing a spark plug in upwards of 2K PSI pressure, a good quality HEI will bridge up to an inch, they will not fair well when compression resistance to the spark plug takes over in a running engine.

Just info to consider.
 

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I am not familiar with PerTronix Ignitor; I thought it converted points to HEI just based upon the size of the module and the introduction of a reluctor wheel. My apologies for misinforming.

Next coil voltage in the secondary circuit (the plug out put) is determined not by the number of windings in the secondary compared to the primary the way it is determines the voltage in an AC transformer; but by the resistance in the secondary circuit.

The less resistance, the lower the voltage in the secondary circuit, as the power levels can not continue to rise to a Marketed valve, if the current has already overcome the resistance in the circuit and is flowing to ground. So yes if you were using an Accel Super Coil with an advertised 70,000 volt value it will only out put 40,000 volts if that is as much resistance as you have in your secondary side to ground.

Things that determine resistance is the plug wire conductor (metal conducts better than carbon impregnated fiberglass strands), the spark gap, and the resistance in the plug (the R in the designation of an AC-delco plug denotes an internal air gap to prevent power from bleeding off too soon). And the condition of your plug wire insulators that break down if roasted by a header tube or a steel wire loom cuts through the silicone rubber insulator. You can add the type and quality of the terminals as well as brass conducts better than steel and how they are attached makes a difference as well.

Big Dave
 

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No problem, Dave, so many people are duped into believing the over hype sales ads that a simple TCBI system somehow becomes an HEI, simply by a sales department "fudging" on the truth. LOTS of people.

I battle this EVERY DAY in my services, people blindly insist I am wrong, don't know what I am saying, but, every scope test, and other measures I do, proves it, over and over again. I was one of the GM Skunk Works engineers that helped develop the original Unitized, and coil in cap HEI's. MANY years experience with them.

As far as coils go, to attain the possible giant voltages to the plugs some lesser systems claim, they would need circuits inside them such as an HEI has, those that extend the storage currents into the coil between firing intervals, and, they simply do not have them. So, no matter what the coil, nor the system input volts, the system will simply be an electronic set of points, with the only benefits being that they do not change timing from point erosion/gap changes, nor do they degrade the actual output from point face pitting.

Proven for a century or more, many engines will run just fine with points, or, their simple point electronic replacements, but, there are better ways to get to a much better result.

BTW, on pints they should never be filed, as they are tungsten coated to help retard pitting. filing them, simply removes that tungsten, and pitting is then enhanced, faster, which adversely affects point current levels, less spark energy delivered.
 

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Rufas just to know that most of what you and Dave are discussing is over my understanding. I do have a problem with a question about spark plug gap.
I have a 540 with Comp cam, MSD 6-AL box and MSD 8207 coil. The cam is a CBXR280R-10. The cranking history has been very good in past.
After dyno and engine put in car several years have past with this project. Several system failures and finish body and paint have just taken a long time.
The cranking has always remained good.
Now after setting for months the engine will not start. (Corrosion in distributor bad fuel who knows).
Now going back thru the timing I want to use the best spark plug gap. My distributor is a Summit Racing HEI.
Please suggest your decision for a gap setting.
Thanks
Clint
 

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OK, simple to understand, ALL Ignitor drop in ihnition systems are simple point replaceme4nts, NOT HEI, NOT MSD, only a set of electronic points, no greater. they do not have the electronic drivers to increase spark one volt over a brand new set of points on their very first spark.

This includes idiosity like running one without the ballast resistor b4ecause some over hype info says a system on full voltage will make more spark, and, using a coil that has 40 billion volts (available). Key wpord there is (available), right there on the box the coil comes in. Yes, it will make 40K volts, when run on a capacitor discharge system like an MSD< BUT NOT ON A SIMPLE PERTRONIX ELECTRONIC POINT SET THAT NEEDS A RESISTOR TO RUN RIGHT AND LIVE LONG.

And, yes, I have heard all the self proclaimed know it all's tell everyone to take the resistor out, and seen the page on their website telling people to take that resistor oout. I have 7 55 gallon barrels of broken Ignitors, that were run with no resistor, fried, done, busted, burned up.

Plug gaps with Ignitor should be NO LARGER than with a set of points, .032/.035 maximum, stock GM point cil, run with the resistor is just fine for any Ignitor. .
 

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Changing carb jets does not change the afr during idle and cruise, that would be idle air bleeds and hsab's. Mine ran pig rich I did not touch the jets because wot was fine but idle and cruise were horrible, I opened up the idle air bleeds and it worked for me.
 

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Cleaned plugs, set with .034 feeler gauge, set QFT 1050 cfm carb idle at 1.25 open and engine is well
again. WOT is strong.
Thank you all.
 
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