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Will I be able to open up the gap on my plugs any?

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93fordguy
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Will I be able to open up the gap on my plugs any?

Post #1 by 93fordguy » Mon Jul 11, 2011 7:23 pm

I ust ordered this accel coil and taylor 8.2mm wires. Will I be able to open up my spark plug gap any, if so how much. Here's the specs.

Coil Wire Attachment Male/HEI
Coil Style E-core
Primary Resistance 0.200 ohms
Coil Internal Construction Epoxy
Coil Color Black/Yellow
Maximum Voltage 48,000 V
Turns Ratio 132:1
Secondary Resistance 8.8K ohms
Mounting Bracket Included No
Coil Wire Included No
Ballast Resistor Included No
Coil Shape Square
Quantity Sold individually.

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Re: Will I be able to open up the gap on my plugs any?

Post #2 by CZLN6 » Mon Jul 11, 2011 8:07 pm

Howdy:

What are the plugs currently gapped at?

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Re: Will I be able to open up the gap on my plugs any?

Post #3 by 93fordguy » Mon Jul 11, 2011 8:30 pm

Regular autolites gapped at .45. Thats with a disc gapper not a feeler gauge though.

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Re: Will I be able to open up the gap on my plugs any?

Post #4 by THE FRENCHTOWN FLYER » Mon Jul 11, 2011 11:10 pm

There are several reasons you might want to upgrade ignition systems:

increased compression requires more voltage to fire the plugs
lean or stratified mixtures require more voltage to ignite the charge
the presence of excessive EGR requires a larger gap /more voltage to fire to ignite the charge

By spreading the plug gap you can increase your chances of igniting the charge in the cylinder at the proper time to insure a good burn rate and minimize the chances of a misfire / slow burn.

You didn't mention what state of build-up the engine is. Increasing the plug gap results in a larger flame kernal, the initial fireball that ignites the remaining charge. I you have any of the above conditions it may help. On the other hand advancing the timing a couple of degrees to give the flame kernal a little more time to develop into a larger flame front, assuming it ignites in the first place, does quintessentially the same thing as increasing the plug gap. And it costs a lot less to advance the timing than to install new ignition system components. So if the engine suffered from the above maladies or increased compression then ignition system component upgrades make sense. But an engine that runs well with no mixture distribution issues will not see any benefit to upgrading the stock ignition system. Most Fords with EGR specify about a .055 gap.
Last edited by THE FRENCHTOWN FLYER on Mon Jul 11, 2011 11:20 pm, edited 1 time in total.
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Re: Will I be able to open up the gap on my plugs any?

Post #5 by 93fordguy » Mon Jul 11, 2011 11:19 pm

Timing is set at 16*, high flow intake and before the thing is ran again it will have a Walker Y pipe, performance cat and a turbo muffler from cherry bomb or dynomax. It's going to be 2.5 inches all the way to the bumper. Oh yeah, the hot coil and wires too. :D
With the timing aready set at 16 degrees should I widen the gap? Can someone explain the benifits of copper core plugs and side gapping too. Thanks for your insight FTF, I'm learning more and more here. Does anyone make a performance TFI module or is it even worth it or safe?

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Re: Will I be able to open up the gap on my plugs any?

Post #6 by tom954x4 » Tue Jul 12, 2011 10:02 am

93FordGuy - There are some threads on this forum on side gapped plugs and ignition upgrades from a year or two ago, do some searching. I have noticed with side gapped plugs, hotter coil and wires, MSD ignition that the gap increases during use more quickly than without side gapping. I am currently running about 0.060 - 0.065 side gapped, stock Autolite plugs. I did not advance the timing.
1995 F-150 XL, 300-6, 4x4, ex-cab, sb, 3.08 5-speed, 2 1/2 in. exhaust w/flowmaster 50, MSDignition failed with no warning, now out, canopy, 179,000 + miles. Gone but not forgotten 1965 F-100 240 3spd lwb "the green hornet"; 1960 F-250 4x4, 223 six, 4sp with wrap-around rear window, two-tone paint, overhead camper.
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Re: Will I be able to open up the gap on my plugs any?

Post #7 by StrangeRanger » Tue Jul 12, 2011 10:05 am

16° BTDC is a bit much. Stock is 10°; most people run 10-12°. Why are you running so much? You may actually be costing yourself power. If the combustion starts that far BTDC, it may actually oppose the upward motion of the piston at the end of the compression stroke. Similarly, if combustion is complete substantially BBDC, the last portion of the power stroke is wasted effort.

Ideally you want the flame kernel to initiate just enough BTDC that it begins to expand rapidly as the piston reaches TDC and not before. You want the combustion process to continue throughout the power stroke and finish just before BDC. At 16° advance, I strongly suspect you are not meeting either of these goals.
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Re: Will I be able to open up the gap on my plugs any?

Post #8 by 76F100guy » Wed Jul 13, 2011 12:58 pm

StrangeRanger wrote:16° BTDC is a bit much. Stock is 10°; most people run 10-12°. Why are you running so much? You may actually be costing yourself power. If the combustion starts that far BTDC, it may actually oppose the upward motion of the piston at the end of the compression stroke. Similarly, if combustion is complete substantially BBDC, the last portion of the power stroke is wasted effort.

Ideally you want the flame kernel to initiate just enough BTDC that it begins to expand rapidly as the piston reaches TDC and not before. You want the combustion process to continue throughout the power stroke and finish just before BDC. At 16° advance, I strongly suspect you are not meeting either of these goals.


I don't want to hijack this thread, but you have my curiosity piqued. I was taught that on a non-computer controlled application, you're most efficient at the edge of detonation. Mine runs best at 18 degrees initial, 42 degrees total (in by 3200, vacuum disconnected). My thought was that the advanced timing would crutch the low compression and (I think mine has this as well) retarded cam timing.

FWIW, I'm also running a 180 t-stat, though I'm thinking about going back to a 195.
'76 F100 Styleside 2WD SB. Low mile, original with 300, 3 speed, and 3.00 rear. No smog, Edelbrock 500 on Offy DP, Ford 4 bbl air cleaner w/ K&N element, recurved distributor, clutch fan, EFI manifolds w/ 2" headpipes into Flowmaster Y, 2 1/2" and turbo muffler. 16 x 8 smoothies with 255/65 Contis. Addco sway bars.

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Re: Will I be able to open up the gap on my plugs any?

Post #9 by StrangeRanger » Wed Jul 13, 2011 2:00 pm

With low compression and low octane (i.e. fast burning) fuel it is easier to initiate combustion and once initiated it proceeds more quickly. If you advance timing to the point where the flame kernel has begun rapid expansion prior to the piston reaching TDC then all the energy which the expanding kernel generates creates downward force on the piston which is still traveling up on the compression stroke. This results in a net loss of power as the engine is working against itself.

Ideally, ignition occurs just far enough before TDC that the flame front begins its rapid expansion right at TDC and continues all the way to just before BDC so no portion of the stroke goes to waste.

In high compression engines, we need higher octane (i.e. slower burning) fuels to prevent detonation but they are harder to ignite and burn more slowly. This requires advanced timing to put the same critical event (rapid expansion of the flame kernel) at the same critical point (TDC). Bumping the timing in a low compression engine running on low octane gas is simply counterproductive.

You cannot determine the point where ignition should begin without instrumentation but Ford had that instrumentation and used it to determine the 10° BTDC initial timing. There were other factors mostly drivability and emissions which went into this determination but given the cost impact of CAFE regulations you can bet the farm that they didn't leave much if any efficiency on the table. I can tell you for an absolute fact that 14° BTDC costs me fuel economy with no appreciable gain in performance compared to 12° BTDC, obviously YMMV
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Re: Will I be able to open up the gap on my plugs any?

Post #10 by 76F100guy » Wed Jul 13, 2011 6:38 pm

Interesting stuff. I'll try backing off the initial and see if I pick up any mpg. This is counter-intuitive to everything I've learned, but I'm never too old to learn, I guess :mrgreen:

On a somewhat related note, I had a couple of 5.0 Mustangs in the late '80s, and one of the first things one did back then was bump the initial from 10 to 14. This was good for about a tenth in the 1/4.

To the OP - my 300 runs best at stock gap. It does NOT like anything wider. Running an original-type DSI, with all new components.
'76 F100 Styleside 2WD SB. Low mile, original with 300, 3 speed, and 3.00 rear. No smog, Edelbrock 500 on Offy DP, Ford 4 bbl air cleaner w/ K&N element, recurved distributor, clutch fan, EFI manifolds w/ 2" headpipes into Flowmaster Y, 2 1/2" and turbo muffler. 16 x 8 smoothies with 255/65 Contis. Addco sway bars.

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Re: Will I be able to open up the gap on my plugs any?

Post #11 by StrangeRanger » Wed Jul 13, 2011 7:59 pm

My Mustang is at 14° BTDC as well.
But it's got about a 10:1 CR, and runs 93 octane fuel
The truck is only 8.8:1 and runs on 87. Not even the same breed of cat.
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Re: Will I be able to open up the gap on my plugs any?

Post #12 by Harte3 » Sun Jul 17, 2011 7:05 pm

Mine is set at 8* BTDC initial. It doesn't like to idle at anything more than that.
'83 F150 300, 0.030 over, Offy DP, Holley 4160/1848-1 465 cfm, Comp Cam 260H. P/P head, EFI exhaust manifolds, Walker Y Pipe, Super Cat, Turbo muffler, Recurved DSII, Mallory HyFire 6a, ACCEL Super Stock Coil, Taylor 8mm Wires, EFI plugs.

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Re: Will I be able to open up the gap on my plugs any?

Post #13 by 76F100guy » Sun Jul 17, 2011 11:14 pm

Harte3 wrote:Mine is set at 8* BTDC initial. It doesn't like to idle at anything more than that.

I'm guessing you're running manifold vacuum? I'm running ported.
'76 F100 Styleside 2WD SB. Low mile, original with 300, 3 speed, and 3.00 rear. No smog, Edelbrock 500 on Offy DP, Ford 4 bbl air cleaner w/ K&N element, recurved distributor, clutch fan, EFI manifolds w/ 2" headpipes into Flowmaster Y, 2 1/2" and turbo muffler. 16 x 8 smoothies with 255/65 Contis. Addco sway bars.

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Re: Will I be able to open up the gap on my plugs any?

Post #14 by Harte3 » Tue Jul 19, 2011 1:48 am

I tried both ways. It ended up being the best on manifold vacuum. It will idle smooth down to 500 rpm MOL. I have it set at 600 rpm.
'83 F150 300, 0.030 over, Offy DP, Holley 4160/1848-1 465 cfm, Comp Cam 260H. P/P head, EFI exhaust manifolds, Walker Y Pipe, Super Cat, Turbo muffler, Recurved DSII, Mallory HyFire 6a, ACCEL Super Stock Coil, Taylor 8mm Wires, EFI plugs.

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Re: Will I be able to open up the gap on my plugs any?

Post #15 by nightwatchman59 » Wed Feb 13, 2013 10:58 pm

Does anyone remember HOT ROD mag. preaching "power tuning" for the street back in the 70's..... oops. Maybe not. Every ride and road is different, as is every right foot... advance timing in small steps until you start getting PING...then back off just enough to make it go away. Carry distributor wrench under the seat.

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Re: Will I be able to open up the gap on my plugs any?

Post #16 by THE FRENCHTOWN FLYER » Thu Feb 14, 2013 11:23 am

nightwatchman59 wrote:Does anyone remember HOT ROD mag. preaching "power tuning" for the street back in the 70's..... oops. Maybe not. Every ride and road is different, as is every right foot... advance timing in small steps until you start getting PING...then back off just enough to make it go away. Carry distributor wrench under the seat.


I remember reading that stuff back then. Even then, as a younger, stupider me, I remember thinking, "Wow, that is an awful simplistic description of a method that may-or-may-not help the everyday manners of an engine that is seldom at WOT - the only place where that method would be of usefulness."

How often is our right foot at WOT? 1%, 2%, - maybe 4% of total driving time if you're a real agressive driver.

It is far more important to get the part throttle spark map correct for everyday driving pleasure and best fuel economy. A little trial and error tuning with a hex wrench stuck down the vacuum module may also help. A truly correct spark map taking into account the octane qualities of the gasoline as well as the design characteristics of the engine is best done on an engine dynamometer.
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Re: Will I be able to open up the gap on my plugs any?

Post #17 by MechRick » Thu Feb 14, 2013 10:25 pm

Wide gaps are for idle, but go too wide and at WOT you may blow the flame kernel out and have a high speed miss. Over the years I've taken a conservative approach to ignition systems, because I've seen too much aftermarket performance garbage (read MSD, Pertronix, etc...) make a vehicle run worse or stop running altogether, and because, of the big three, Ford stuff was pretty good right out of the box. Except for the TFI scandal (which could be cured by periodic replacement of the dielectric grease, by the way) Blue Oval ignition systems rock.

The stock plug wires have a resistance of 2-4k ohms per foot. It takes voltage to jump a gap. Lower the resistance of the plug wires (or the plugs) and you lower the KV of the entire system. This also raises the current and can play havoc with computers, which is why we have 'suppressor' plugs in the first place.

Efficient combustion chamber designs don't need wide plug gaps to maintain a smooth idle. Extending the center electrode into the chamber and widening the gaps are usually a crutch fix for a poorly designed chamber.

In the past when adjusting timing, the detonation threshold could often be reached before peak efficiency. It's just not the case with modern fast burn chambers. The only way to properly find out where WOT timing should be on these is dyno time or on the racetrack. A good example of this is GT40P Explorer 5.0 heads. They make best power between 30-32 degrees advance at WOT. You have to pull advance out when running these. I think the EFI chambers like about 34-36 degrees total, compared to 38-40 degrees for the carb head.
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Re: Will I be able to open up the gap on my plugs any?

Post #18 by rikard » Fri Feb 15, 2013 12:28 am

Lot of good info in this thread.
I also remember the Hot Rod article and did tune most of my rides by advancing the timing and changing power valves and jets. I also started using a dash vacuum gauge. I have never been a big fan of after market coils for the street and stay with the OEM.
On my 95 300 I run copper Autolites gapped at .050 (stock is .044) and timing set at 12 deg BTDC (stock is 10). It has Taylor low resistance spirial core wires with a good cap and rotor with brass terminals. I did try 14 deg BTDC timing but it was too much for 87 octane. While I haven't picked up any noticable gain in MPG it does have more power accelerating and climbing hills. The only downside to opening the gap is shorter service life. I pull mine once a year. Not a big deal on a 300.
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Re: Will I be able to open up the gap on my plugs any?

Post #19 by BIG 6 farmer » Fri Feb 15, 2013 5:06 am

Back in the day, worked in a Sports Car Shop (1984-94).Used to do a lot of test drives with a Dist. wrench, then ck. it with a timing light. Almost every car would end up advanced 2-5 degrees over spec. Got a book that does a ton of Dyno pulls, testing about everything on a 87-95 H.O. 5.0. V8 One thing was timing on a stock Engine. Best power on most was 3-4 over the Factory 10 degrees setting. Over 5 degrees power dropped off, That was Engines using E7T Cyl. Heads. My guess, on a newer Fast Burn Chamber. ( like the GT 40P 5.0. V8 & EFI 300 six) would like a little less over the Factory setting. That is , with Ford ECCU Timing. Never spent money on Fancy Ign. Dist. or Coils. Have had good results using OEM stuff. On my 300 six Truck, i have a 83 Dura Spark Dist. Hooked to a GM HEI 4pin Ign. Module, & a Ford TFI Coil. Its all cheap, and works great. Never messed with a wider Plug Gap. Back in the late 70s, early 80s. GM played with .060 & .080 Gaps. They over worked the HEI parts, & stuff failed. Then they went to a safe .045 Gap. :nod:
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Re: Will I be able to open up the gap on my plugs any?

Post #20 by jamyers » Fri Feb 15, 2013 11:26 am

Wow, how far has this thread expanded (pardon the pun)?

*Generally*, you can open up the plug gap when you upgrade other ignition components. How far? Depends (I know...) Simple answer is .045 for most electronic ignitions. The complicated answer is that the only way to know for sure is to open it up a bit at a time, keeping track of mileage/performance, until you find the point at which it's too far, then go back to the best gap.

Now here's my contribution to the thread-expansion... IMHO, what's WAY more important than plug gap or initial timing is the Timing Curve, or where the timing starts and then how fast and far the ignition timing advances. For a variety of reasons, the factory (Ford and GM at least in my experience) seems to use that's WAY conservative - for example, an stock early 70's Buick 350 typically starts at 0 degrees at idle and goes up to 26-28 at over 3200rpm, and the cam runs out of breath and won't rev much past 4400rpm. Doing nothing else to the engine, you can change the Timing Curve to somewhere around 10-12 degrees at idle, with 32-34 max at 2400 rpm, and the result in throttle response, idle, mileage, and power is simply astonishing - you'd think you put a cam and headers in it! Now, when you do that you also need to re-work (limit) the vacuum advance or it'll be pinging all over the place, but once you get the static, mechanical, and vacuum settings down, that's 90% of the ignition. THEN you start playing around with plug gap, fancy wires, coils, etc...
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Re: Will I be able to open up the gap on my plugs any?

Post #21 by THE FRENCHTOWN FLYER » Fri Feb 15, 2013 12:56 pm

Auto companies have to sell cars that can be driven anywhere.

Take a WOT run across Death Valley (-600 ft altitude) some dry, chilly morning with the timing advanced from stock and you are likely to eat a bunch of ring lands. Those kinds of conditions are what the car makers must protect against. Hence, if you live in a climate where it is moister, warmer, higher and generally has less air density than standard atmospheric conditions then, yes, you will probably benefit from a few extra degrees of spark advance.

But then again, you don't have to eat the warranty bill for the guy who encounters extreme climatic conditions on his drive.
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Re: Will I be able to open up the gap on my plugs any?

Post #22 by 1986F150six » Fri Feb 15, 2013 1:51 pm

THE FRENCHTOWN FLYER wrote:There are several reasons you might want to upgrade ignition systems:

increased compression requires more voltage to fire the plugs
lean or stratified mixtures require more voltage to ignite the charge
the presence of excessive EGR requires a larger gap /more voltage to fire to ignite the charge

By spreading the plug gap you can increase your chances of igniting the charge in the cylinder at the proper time to insure a good burn rate and minimize the chances of a misfire / slow burn.

You didn't mention what state of build-up the engine is. Increasing the plug gap results in a larger flame kernal, the initial fireball that ignites the remaining charge. I you have any of the above conditions it may help. On the other hand advancing the timing a couple of degrees to give the flame kernal a little more time to develop into a larger flame front, assuming it ignites in the first place, does quintessentially the same thing as increasing the plug gap. And it costs a lot less to advance the timing than to install new ignition system components. So if the engine suffered from the above maladies or increased compression then ignition system component upgrades make sense. But an engine that runs well with no mixture distribution issues will not see any benefit to upgrading the stock ignition system. Most Fords with EGR specify about a .055 gap.


As I read and reread this thread [trying to learn and better understand], some things come to mind and I will ask if I am on the right track?

#1. By increasing plug gap, one actually advances timing [point of ignition] in relation to BTDC?
#2. By using higher octane fuel, the timing [point of ignition] is retarded in relation to BTDC?

Thank you for your answers, in advance!

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Re: Will I be able to open up the gap on my plugs any?

Post #23 by BIG 6 farmer » Fri Feb 15, 2013 3:21 pm

jamyers wrote: IMHO, what's WAY more important than plug gap or initial timing is the Timing Curve, or where the timing starts and then how fast and far the ignition timing advances. For a variety of reasons, the factory (Ford and GM at least in my experience) seems to use that's WAY conservative -
Yes on that. Forgot to say on my Truck that i changed the advance springs in my Dura Spark Dist., for a quicker curve. I like the Ford Vacuum Advance, cause most are adjustable. I hook it up to off idle vacuum, so it starts to pull @ 3-4 inches. FTF is SO VERY RIGHT. Imagine some Knuckle dragger, goes and buys a new car/truck. Loads it down heavy on a HOT day, gets it goin in high gear. Puts his fat foot to the floor, & holds it there. Later hes cussin out the Car Dealer, cause hes got busted pistons & rings. Yes the Car/Truck builders have to protect the people from themselves. :nod:
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Re: Will I be able to open up the gap on my plugs any?

Post #24 by jamyers » Wed Feb 20, 2013 5:38 pm

THE FRENCHTOWN FLYER wrote:...
But then again, you don't have to eat the warranty bill for the guy who encounters extreme climatic conditions on his drive.

Well yeah...but we're not the factory, we're talking about tuning our own engines. If I then blow it up, it's on me....
:beer:
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Re: Will I be able to open up the gap on my plugs any?

Post #25 by THE FRENCHTOWN FLYER » Thu Feb 21, 2013 12:04 pm

jamyers wrote:
THE FRENCHTOWN FLYER wrote:...
But then again, you don't have to eat the warranty bill for the guy who encounters extreme climatic conditions on his drive.

Well yeah...but we're not the factory, we're talking about tuning our own engines. If I then blow it up, it's on me....
:beer:

Reminds me of the saying in the early days of Top Fuel drag racing, when we were on our last shot at qualifying:

"Go up 10, 10, and 10."

Meaning 10% more blower drive, 10 degrees more ignition timing, and 10% more nitro. Either qualify or blow up.
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Re: Will I be able to open up the gap on my plugs any?

Post #26 by crash-harris » Mon Feb 25, 2013 6:30 pm

FTF, a few of your posts about our 300's being at WOT got me thinking. I spend a good bit more of my driving time at WOT, I'd say more like 20% (big number, I know). But I'm also carrying a good bit more weight. Heavy offroad fab parts on the suspension, 37" tires + 2 spares, one for the 15's current in the front (D60 going in up front will do away with that) and and mostly driving 65+ mph highways with short on ramps (equipped with inconsiderate drivers) and weighing in with me at around 5500 lbs.

Still using EFI, but wondering if the 12* inital advance may be a bit low for going WOT so much.

PM me so I'm not totally hijacking the thread :mrgreen:

Unless there's a chance of this becoming a sticky one day.
Bruiser - 1990 Ford F150...barely...EFI 300 Big Six, 500K+!, converted to 4x4. 4.10 gears and Sterling FF rear w/ Trac-Lok, 37" meats. Undergoing 1 Ton leaf spring SAS. 6BT in the plans.

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