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 Page 1 of 2 12
Username Post: colder spark plug vs. hotter plug        (Topic#256362)
octanejunkie 
Contributor
Posts: 466
octanejunkie
Loc: Los Angeles area
Reg: 11-12-09
01-23-11 07:32 AM - Post#2035864    

I went 2 steps colder in spark plug to see if I can keep my truck from pinging when coming out of cruise on the hwy, but now it feels weak out of the hole. I had been running 1 step colder plugs for about a year already.

I have read that folks use 2 sets of plugs, one set for the street and a hotter set for the track - but what performance trade off am I looking at with colder plugs all the time? I don't want to swap plugs too often.

This is a street driven vehicle only, but I like to launch it occasionally... gotta have some fun in life.

Plugs in question are:
1 step colder - Autolite 5144, RS12YC equivalent
2 step colder - Autolite 103, RS9YC equivalent
'59 Chevy 3100 Stepside
0.040-over 350, mild (214/224 @ .050) 112 LC cam,
vortec heads, air-gap, 600cfm carter, 2-1/2" rams horns,
built 700R4 w 2200rpm stall, 3.42 posi rear on top of 31.5" BFGs


 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 16197
grumpyvette
Age: 66
Loc: FLORIDA USA
Reg: 03-16-01
01-23-11 08:15 AM - Post#2035880    
    In response to octanejunkie

if you noticed a change in power look at the plugs carefully,and make sure the gaps set at .043-.045 if they are fouled that could cause it, if not you may need to do some ignition mods to increase the spark as there should not be a noticeable drop in power just changing to a colder plug
" " IF YOU CAN'T SMOKE THE TIRES FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK !"


Edited by grumpyvette on 01-23-11 08:16 AM. Reason for edit: No reason given.

 
IgnitionMan 
Valued Contributor
Posts: 2713

Reg: 04-15-05
01-23-11 05:23 PM - Post#2036174    
    In response to grumpyvette

If the engine is pinging and the plug heat range is correct for the static and dunamic compression ratios, then, I'd want to hear how the vacuum advance on the distributor is set up, and which port it is sourced from.

Usually, it is the other way around for heat ranges, colder for racing, because the engine is usually running in the power band, and warmer for street use, because the engine lugs more.

 
Rick_L 
Honored Member
Posts: 25770

Loc: Katy, Tx, USA
Reg: 07-06-00
01-23-11 06:28 PM - Post#2036210    
    In response to IgnitionMan

Colder spark plugs won't keep your engine from pinging. That is dealt with by timing, compression ratio, or fuel changes.

On the other hand you want your plugs to match your needs. It's just that they don't work miracles.

 
octanejunkie 
Contributor
Posts: 466
octanejunkie
Loc: Los Angeles area
Reg: 11-12-09
01-23-11 07:15 PM - Post#2036244    
    In response to IgnitionMan

Static compression is around 9.3:1, dynamic compression is around 7.8:1

Vacuum adv on full manifold vacuum and is adding 14 degrees for a total of 32 degrees of total timing, 12 degrees initial with 375 center and 41 weights and a fairly progressive curve.

She seems to ping around 1800 rpm when mildly gassing it while cruising in overdrive.
'59 Chevy 3100 Stepside
0.040-over 350, mild (214/224 @ .050) 112 LC cam,
vortec heads, air-gap, 600cfm carter, 2-1/2" rams horns,
built 700R4 w 2200rpm stall, 3.42 posi rear on top of 31.5" BFGs


 
octanejunkie 
Contributor
Posts: 466
octanejunkie
Loc: Los Angeles area
Reg: 11-12-09
01-23-11 07:21 PM - Post#2036252    
    In response to Rick_L

I have read many posts and threads about the "correct" plug for vortec head applications, most seem to be in the ball park of RS12YC to RS14YC.

From my understanding, I can avoid the plug's contribution to pre-ignition by using a colder plug that retains less heat.

Truthfully, with the RS9YC equivalent Autolite 103 plug, it's tendancy to ping was greatly reduced, but so was off the line performance, so far...

I am putting the truck on the dyno in the next week or two to get more info and I will pull the heads at some point to check things out, changing to colder plugs is just a step to try and boost my knowledge/experience, but what I don't know is exactly which plug/heat range of plug should I be using?

Suggestions? Is there a formula to follow?
'59 Chevy 3100 Stepside
0.040-over 350, mild (214/224 @ .050) 112 LC cam,
vortec heads, air-gap, 600cfm carter, 2-1/2" rams horns,
built 700R4 w 2200rpm stall, 3.42 posi rear on top of 31.5" BFGs


 
Mr.Axlesauce 
Forum Newbie
Posts: 33
Mr.Axlesauce
Reg: 01-17-11
01-23-11 09:39 PM - Post#2036323    
    In response to octanejunkie

Have you tried reducing the amount of timing the vacuum advance is allowing? I would try limiting the vac advance to 6 or 8 degrees and see what happens.

 
octanejunkie 
Contributor
Posts: 466
octanejunkie
Loc: Los Angeles area
Reg: 11-12-09
01-24-11 06:01 AM - Post#2036405    
    In response to Mr.Axlesauce

I need to take a watch my vacuum gauge when she pings and note how much vacuum the engine is pulling. I know a spot where I can get it to ping consistently, I will do that today.

I can of course limit the vac adv, which is relatively easy to do, which will also limit my total timing - but everyone keeps telling me I can/should be running MORE timing.

If I limit my vac can to 10 degrees I will have a total of 28 degrees of timing, and the consensus out there seems to say I could/should have 32-34 degrees of total timing...
'59 Chevy 3100 Stepside
0.040-over 350, mild (214/224 @ .050) 112 LC cam,
vortec heads, air-gap, 600cfm carter, 2-1/2" rams horns,
built 700R4 w 2200rpm stall, 3.42 posi rear on top of 31.5" BFGs


 
greg_moreira 
Very Senior Member
Posts: 3264

Reg: 10-06-03
01-24-11 07:28 AM - Post#2036428    
    In response to octanejunkie

limiting vacuum advance wont limit total timing.

When we speak of total timing, were talking about the performance aspect and what you see under full throttle.

At full throttle...the engine/manifold/carb should not be seeing more than 2 inches of vacuum. 1-1.5 inches preferred. Thats not enough vacuum to operate a vac advance, so vac advance wont even exist under full throttle. Your engine only sees 32 degrees.

For full throttle, under power, yes you definitely need more than 32 degrees.

Id add more total, limit vacuum advance, and if you have to...try a little heavier spring than you currently have just to slow down the timing curve a hair. might give you a few degrees less mechanical at 1800rpm where you say it pings(I wouldnt want total coming in later than 3k for a performance app though so keep mindful of that).

Might need to get involved in carb work here too, but start with ignition first and we'l see where were at




 
octanejunkie 
Contributor
Posts: 466
octanejunkie
Loc: Los Angeles area
Reg: 11-12-09
01-24-11 07:42 AM - Post#2036436    
    In response to greg_moreira

This is what my current mechanical curve looks like without the vac adv can connected

idle 12*
900 12*
1000 14*
1250 18*
1500 22*
1750 26*
2000 28*
2250 29*
2500 30*
2750 31* - stopped advancing
3000 31*
'59 Chevy 3100 Stepside
0.040-over 350, mild (214/224 @ .050) 112 LC cam,
vortec heads, air-gap, 600cfm carter, 2-1/2" rams horns,
built 700R4 w 2200rpm stall, 3.42 posi rear on top of 31.5" BFGs


 
C10 Sleeper 
Valued Contributor
Posts: 3426
C10 Sleeper
Loc: Redding Ca
Reg: 03-17-09
01-24-11 04:00 PM - Post#2036648    
    In response to octanejunkie

Im with greg on that note. Your total timing will not be affected by vacuum advance. The vacuum advance only works with high engine vacuum like while at cruising speed where it sounds like you are having your problems. I would probably start by cutting your vac advance down to 6* and see if that solves your problem. Then if it doesnt ping try bumping it up another 2*.

I have been running the set up that Iman suggests with 8* of vac advance for a couple of years now with great results.
http://photobucket.com/C10Pictures


 
octanejunkie 
Contributor
Posts: 466
octanejunkie
Loc: Los Angeles area
Reg: 11-12-09
01-24-11 04:22 PM - Post#2036660    
    In response to C10 Sleeper

Ping at cruise occurs right around 1800rpm +/-, just about 0" Hg of vacuum, so my curve is the issue

Just for kicks, I retarded the dist 2* and the ping went away - yay! I plan to put the hotter plugs back in and see if the ping returns.

I will revisit the dist springs and try to tame the curve to be a bit more progressive.

At this point, my total mechanical timing is around 29-30 degrees.
'59 Chevy 3100 Stepside
0.040-over 350, mild (214/224 @ .050) 112 LC cam,
vortec heads, air-gap, 600cfm carter, 2-1/2" rams horns,
built 700R4 w 2200rpm stall, 3.42 posi rear on top of 31.5" BFGs


 
IgnitionMan 
Valued Contributor
Posts: 2713

Reg: 04-15-05
01-24-11 07:41 PM - Post#2036773    
    In response to octanejunkie

The amount of complete total differs when the vacuum advance is sourced from the two different vacuum types, full manifold, and ported.

Do you have it on ported vacuum, yes/no?

Just as a rest, disconnect and plug off the vacuum advance feed hose, then, go drive it, see if it still pings.

Edited by IgnitionMan on 01-24-11 07:43 PM. Reason for edit: No reason given.

 
Rick_L 
Honored Member
Posts: 25770

Loc: Katy, Tx, USA
Reg: 07-06-00
01-24-11 08:05 PM - Post#2036788    
    In response to IgnitionMan

IgnitionMan has the real answer here.

Preignition due to a hotter spark plug is not going to affect part throttle operation when the vacuum advance is active.

It's only going to come into play at heavy loads, and there may be a time factor too - i.e, how long do you spend at the heavy load? On the other hand, too cold a plug may load up with carbon deposits that might cause poor idling.

Plug heat range selection is not quite that simple but the above is a start.

 
octanejunkie 
Contributor
Posts: 466
octanejunkie
Loc: Los Angeles area
Reg: 11-12-09
01-25-11 08:00 AM - Post#2036976    
    In response to IgnitionMan

The condition at which it pings is at O" Hg of vacuum - so the vac adv is not involved

My vac adv is connected to full manifold vacuum

I think I need to slow/tune my adv curve with different springs - I have arrived at this conclusion because I took 2 degrees off my initial timing and made the ping in question go away. I am now at 10 degrees initial timing.

Selecting a proper heat range plug is critical, and not necessarily straight forward. The set I pulled look reasonably ok - will post a few sample pics soon, but the flash on my camera keeps over exposing them...
'59 Chevy 3100 Stepside
0.040-over 350, mild (214/224 @ .050) 112 LC cam,
vortec heads, air-gap, 600cfm carter, 2-1/2" rams horns,
built 700R4 w 2200rpm stall, 3.42 posi rear on top of 31.5" BFGs


 
aghaga 
"4th Year" Silver Supporting Member
Posts: 1773

Age: 60
Loc: Altavista, Va.
Reg: 07-05-08
01-25-11 09:44 AM - Post#2037020    
    In response to octanejunkie

I had a simular situation. My engine is a 350 +60 withe flat top pistons and vortec heads. .055 quench and 10:1 static comp ratio ZZ-4 (hot) cam w/1.6 rockers

To get the spark knock out w/93 octane @30 total mechanical advance I had to install a stiffer power needle spring and two steps richer metering rods in the Edelbrock carb.



 
IgnitionMan 
Valued Contributor
Posts: 2713

Reg: 04-15-05
01-25-11 06:37 PM - Post#2037265    
    In response to aghaga

Another question, which particular port is the vacuum advance connected to?

If you would, take the car for a drive with a vacuum guage connected to THAT port and see if there is any vacuum there at all when it pings, please.

What happens when you drive the car with the vacuum advance disconnected and hose plugged, and HEAVIER mechanical advance springs installed??

 
aghaga 
"4th Year" Silver Supporting Member
Posts: 1773

Age: 60
Loc: Altavista, Va.
Reg: 07-05-08
01-25-11 07:27 PM - Post#2037299    
    In response to IgnitionMan

I made a stop with .086 on the vac advance which is connected to manifold vacuum. I also installed heavier springs....can't remember the color

 
octanejunkie 
Contributor
Posts: 466
octanejunkie
Loc: Los Angeles area
Reg: 11-12-09
01-25-11 09:33 PM - Post#2037361    
    In response to IgnitionMan

The vac adv can is connected to the full manifold vacuum port on the driver's side front corner of the carter afb carb. It is T'd off a T fitting that runs off the same port to a vacuum gauge in my cab.

The ping in question happens when there is an 1" or less vacuum - I have not tried swapping springs in the dizzy yet.

I had driven with the vac adv disconnected for a long time before dialing in my distributor, but I can pull the hose off the can tomorrow and drive with it plugged to operat the gauge only and see it it pings under the same conditions.

I will even put the 2* I took off the initial timing back so I'm back to 12* BTDC initial timing and test.
'59 Chevy 3100 Stepside
0.040-over 350, mild (214/224 @ .050) 112 LC cam,
vortec heads, air-gap, 600cfm carter, 2-1/2" rams horns,
built 700R4 w 2200rpm stall, 3.42 posi rear on top of 31.5" BFGs


 
ss3964spd 
"6th Year" Gold Supporting Member
Posts: 4158
ss3964spd
Loc: Fairfax, Va
Reg: 12-21-00
01-26-11 10:37 AM - Post#2037609    
    In response to octanejunkie

  • octanejunkie Said:
Ping at cruise occurs right around 1800rpm +/-, just about 0" Hg of vacuum, so my curve is the issue....


This is the ping you are trying to cure - at 1800 RPM cruise? Maybe I'm missing something but how do you have almost 0" of vac at an 1800 RPM cruise?

Apologies if I'm not reading something correctly...
Dan

If I recall correctly my memory is excellent. My ability to access it is not.


 
IgnitionMan 
Valued Contributor
Posts: 2713

Reg: 04-15-05
01-26-11 04:36 PM - Post#2037757    
    In response to ss3964spd

On acceleration, moderate acceleration.

 
octanejunkie 
Contributor
Posts: 466
octanejunkie
Loc: Los Angeles area
Reg: 11-12-09
01-26-11 07:40 PM - Post#2037859    
    In response to IgnitionMan

  • IgnitionMan Said:
On acceleration, moderate acceleration.



exactly
'59 Chevy 3100 Stepside
0.040-over 350, mild (214/224 @ .050) 112 LC cam,
vortec heads, air-gap, 600cfm carter, 2-1/2" rams horns,
built 700R4 w 2200rpm stall, 3.42 posi rear on top of 31.5" BFGs


 
ss3964spd 
"6th Year" Gold Supporting Member
Posts: 4158
ss3964spd
Loc: Fairfax, Va
Reg: 12-21-00
01-27-11 12:02 PM - Post#2038069    
    In response to octanejunkie

Ah, thought I was missing something.

Makes sense now, thanks.
Dan

If I recall correctly my memory is excellent. My ability to access it is not.


 
IgnitionMan 
Valued Contributor
Posts: 2713

Reg: 04-15-05
01-27-11 05:23 PM - Post#2038180    
    In response to ss3964spd

I'd think one of two reasons, either too light a spring set, and/or that part of the scroll the weights move, makes for too much timing, too fast. Yes, the curvature on the scroll can make the mechanical advance too fast in certain areas of the curve.

First, try a heavier spring package and let us know what goes, please.

 
octanejunkie 
Contributor
Posts: 466
octanejunkie
Loc: Los Angeles area
Reg: 11-12-09
01-27-11 06:20 PM - Post#2038212    
    In response to IgnitionMan

I wish I could test the springs out side the car to determine what their pull weights were, I have a bunch I harvested from the junkyard while looking for the 41 weights and 375 center I am running now, it would make swapping springs easier than install a set and plot the curve, install a set and plot the curve...

One thing I did try, a bottle of octane boost in the tank, and she didn't ping - darn 91
'59 Chevy 3100 Stepside
0.040-over 350, mild (214/224 @ .050) 112 LC cam,
vortec heads, air-gap, 600cfm carter, 2-1/2" rams horns,
built 700R4 w 2200rpm stall, 3.42 posi rear on top of 31.5" BFGs


 
N8sToolz 
Very Senior Member
Posts: 2315
N8sToolz
Age: 28
Loc: N 42┬░ 53.290' W71┬░ 34.1...
Reg: 10-23-03
01-29-11 11:17 AM - Post#2039015    
    In response to octanejunkie

Arent the vortec heads prone to pinging early because of a fast burn shaped combustion chamber? I am having a similar problem with my truck. I have the distributor turned back for now, I was gonna mess with it again in the warmer weather.
1982 Chevy K20 Converted from C20.
355/700R4
2002 Yamaha XVS1100CL VStar
2002 S10 2WD


 
octanejunkie 
Contributor
Posts: 466
octanejunkie
Loc: Los Angeles area
Reg: 11-12-09
01-30-11 07:04 AM - Post#2039395    
    In response to N8sToolz

Supposedly yes, prone to pinging and can't tolerate too much timing - other than that, they are great...
(sarcastic)

I was all set to start experimenting yesterday when the darn truck wouldn't ping, but it got me thinking: when cruising my vacuum is over 15", if it pings at almost 0" vacuum when mildly accelerating while cruising, it must the the transition going lean, and the position of the needle in the jet is controlling the fuel at that point - what if I went to the next step heavier spring, what would that do to driveability the rest of the time?

Obviously I could go to a different needle too but a heavier spring seems like a logical first step to try...
'59 Chevy 3100 Stepside
0.040-over 350, mild (214/224 @ .050) 112 LC cam,
vortec heads, air-gap, 600cfm carter, 2-1/2" rams horns,
built 700R4 w 2200rpm stall, 3.42 posi rear on top of 31.5" BFGs


 
IgnitionMan 
Valued Contributor
Posts: 2713

Reg: 04-15-05
01-30-11 03:29 PM - Post#2039633    
    In response to octanejunkie

Slow the curve down a touch, Vortec's like less timing.

 
Rick_L 
Honored Member
Posts: 25770

Loc: Katy, Tx, USA
Reg: 07-06-00
01-30-11 06:26 PM - Post#2039722    
    In response to IgnitionMan

"Supposedly yes, prone to pinging and can't tolerate too much timing - other than that, they are great"

Vortecs get better results than other heads with less timing than is required with other heads.

This is a good thing, not a bad thing. But it's certainly something you need to be aware of.

 
IgnitionMan 
Valued Contributor
Posts: 2713

Reg: 04-15-05
01-30-11 07:27 PM - Post#2039764    
    In response to Rick_L

Any idea what the quench distance is on this engine?

Too much/little quench distance, and you won't be able to control the pinging, nor detonation, no matter the head configuration.

 
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