Thread: HEI tuning

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Me and my dad just got the HEI working good, put the plug wires on just havn't gotten the plugs gapped yet. We were doing some power timing and it ended up 8* BTDC was probably the best run but now that it's in, it won't smoke the tires like it used to, so that's how we know it has lost a lot of the low end it had. what should we do to get this to run like it used to? is messing with the mechanicle weights what we should be working with? thanks in advance.

You ha got to gap thos plugs. Look for .045 with HEI. You are not using all of the spark that you have available. Once you regap (preferrably with new plugs), you will find that you can move the distributor for more power.

What did you find the problem to be before?

the modual was burnt up. got a new 1 from the local carquest.

I was thinking it was all in the gapping myself, but my dad didn't think it would make much diffrence so he hasn't bothered yet.

Most early HEI systems gapped at 0.045 inches. If a person adjusts the iqnition timing "looking" for the sweet spot, he is not taking advantage of all of the power available. The spark is "hotter" when is is allowed to jump the larger gap. The hotter spark will affect the flame front in the combustion chamber.

Denny,

I, too, can quote and recite basic theory.

However, the only point that I wished to convey was that he was not taking full advantage of the power at hand. The information that you posted will, though, remain beneficial to all future readers.

A prescribed amount of air/fuel mixture is delivered to the combustion chamber due to a series of mechanical events that cause a lesser relative pressure in said chamber. Assume that said amount is completely independent of the ignition system. A "hotter" spark will lead the combustion process to burn more completely (as it takes advantage of more of the ignition coil's potential). Lets call this increased thermodynamic efficiency. Due to this increase and the fact that we have the same amount of fuel/air moving through the system, the system must produce more power (with a properly timed ignition source, and assuming several other constants).

Interesting.

As you must know the Rudolf engine operateson an entirely different theory.

Yes, yes;Pre-ignition (again we are assuming some things here)

Relative pressure always exists.

Denny,

I think that we must be of the "overqualified" group mentioned on the "i give up" thread.

OK overqualified guys!!!....lets be real. Gapping at .045 will have no noticeable effect on his engine power. The theory is right, but it's not something one can feel in the seat of the pants. At least, I never have been able to tell anyhow. Matt, you lost power because you retarded your timing. The higher initial timing you had before is where you picked up power. Im assuming your 8* btdc is without the vacuum advance? Im certainly more into big blocks than small, but we usually run 16 or 18 initial timing. Im not sure you can get away with that much, but if you can, it will run really strong. Maybe more small block guys will chime in. I would think you could run at least 12* without problems. Running the best fuel you can? Yes, messing with your mech. advance is your next project. You want your total timing all in by about 3K rpms. If your mech. advance picks up quicker, it will help with your power problems too. I would re-gap the plugs too, but in my opinion, that's the least of your problems. John

My dad runs 87 which, I have told him to run at least 89. it is an 8.5:1 engine and hasn't ever pinged since he's owned it so I guess it's ok.. I found an article on the net that says to buy cranes advance kit, and use 1 silver and 1 blue spring, and that will cause the advance to start at 800 Rpm and be all in at 2,800 RPM, and get the crane ajustable vac advance can with 9 turns on the dial and use the lock out cam to lock out all but 12* of vac advance. which would be 32* of advance b/c a HEI has 20* of mech built in. an I on the right track? we will be gapping new plugs to .045 when we get a chance.

Quote:
Originally Posted by 1JohnnyO
OK overqualified guys!!!....lets be real. Gapping at .045 will have no noticeable effect on his engine power. The theory is right, but it's not something one can feel in the seat of the pants. At least, I never have been able to tell anyhow. Matt, you lost power because you retarded your timing. The higher initial timing you had before is where you picked up power. Im assuming your 8* btdc is without the vacuum advance? Im certainly more into big blocks than small, but we usually run 16 or 18 initial timing. Im not sure you can get away with that much, but if you can, it will run really strong. Maybe more small block guys will chime in. I would think you could run at least 12* without problems. Running the best fuel you can? Yes, messing with your mech. advance is your next project. You want your total timing all in by about 3K rpms. If your mech. advance picks up quicker, it will help with your power problems too. I would re-gap the plugs too, but in my opinion, that's the least of your problems. John

All I can say is, you will notice it in the seat of your pants when it does it's mis-firing thing

You know I was just bustin on you, right? I am well aware that you know your stuff. By the way, I have a good Ford joke. When the time is right. And what do you mean by 'mis-firing'?

I'm up for more discussion!

The "internal" distributor operations (describing the axial rotation of the reluctor ring past the pickup/trigger that will send the signal to the ignition module to discharge the ignition coil), are part of my assumptions. Although, GOOD LUCK finding a distributor from parts store "X" that includes:

1. True axial rotation about the shaft's center
2. Unworn, perfectly constructed reluctor
3. Pickup/trigger in plane with above mentioned reluctor
4. Mount surface on rotor button in plane with mount surface of dist cap
5. Available dist cap with mount surface in plane to cap contacts (or uniform contacts for that matter)

If he has a "remotely" precise dist, properly timed, and using a quality coil, there will be no misfires due to running a 0.045 inch plug gap. That said, we are still holding some assumptions and he must be using properly gapped, new spark plugs of sufficient quality.

Once a sparkplug has been fouled, it is not ever the same.
Since he has had at least two distributor failures, has run with the "improper" plug gap,and likely also has some air/fuel mixture issues- Yes, those plugs are going to misfire. Now, it will not be a "dead" miss as if a cylinder dropped out, and many would not say that the engine is mis-firing-However, an O-scope would show you that you have some ignition issues.

I would "feel" the difference.

NIght and day difference in plug gaps,especialy on emissions motors.I try to run the largest gap possible ,with no misses.My 460 bbF likes .070 to .080 plug gap

Ok guys. were going to get new plugs and gap at .045 and get new HEI wires cause the HEI wires we bought are for a '86 Chevy truck 350 and because they are the under manifold wire, there is 1 wire that is just too short ( there pre crimped ), we got it to kinda fit but the manifold heat shield digs into it. we just got back from a cruise in and it's obviouse the ignition still needs work, when it's hammered for passing/ whatever it backfires through the carb, it used to do this only when cold now it's most of the time. what should we do beyond new plugs/ .045 gap? Thanks

Oh, My Falcon likes to foul the #5 & #6 plugs and I have went through 2 sets of Champions and finally bought a set of Autolites and I just recently had the # 5 plug foul out on me, instead of getting another plug I cleaned it off with a rag swaped it with the #3 plug and it runs great now, just have to remember this trick when it foul's again.