Can we talk about Small Block ignition timing?

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Can we talk about Small Block ignition timing?

Rembrant
I wanted to pick the brains of the experts and BTDT crowd with regards to SBF ignition timing.

After I had my little 302 built, we broke it in on the dyno and then tuned it. The guy that built my engine was really good, but I'll admit that their shop spends most of their time building much bigger (higher compression) performance engines. A lot of BBC's.

Anyway, he set my timing at 12/20, for a total of 32 without vacuum advance. He said that he didn't want to go over 32 for fear of causing problems. He did bump it up to 34 for a pull or two and when it didn't make any difference he put it back at 32 degrees.

So I got the engine home and installed it in the truck, and when I checked the timing it was not at 12/20, at least not according to my timing light. I have to apologize, as I don't remember where it was exactly, but I adjusted it a little bit to put it back to 12/20 (again, according to my timing light).

I have been doing some reading, and the article below caught my attention as it says that SBF's work best between 38-42 total timing.

https://www.fordmuscle.com/archives/2000/03/timing/

My engine is not what one would consider high compression. On the upper end it might be 9:1, but it's probably more like 8.9:1 and even with full vacuum advance I haven't heard the engine ping at all.

Anyway, I guess I'm just curious what you guys with similar engines are running for base timing and centrifugal timing?

I know I need to work on getting my ignition curve smoothed out, but that's a separate issue from where the actual start and finish numbers need to be.
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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Re: Can we talk about Small Block ignition timing?

ArdWrknTrk
Administrator
12* is a good start.
With a more efficient engine such as yours you might get away with more, but look out for laboring hot starts.
There's no point in overworking the starter, or drawing so much current.

A lot of factors come into consideration.
Weight.
Gearing.
BMEP. (from your dyno results)
Available fuel (or lack thereof)
if you're on the edge using R+M/2 93 and can only find 91 or even 89 in Podunk, you hopefully have a distributor wrench, and have to deal with the compromised curve.

My heavy truck is all in by 3k and starts just off idle @800, 38* total.

I guess a lot depends on how (and what conditions) you drive it .

Bill Vose is the one who will have the best advice for you, Cory.
 Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.
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Re: Can we talk about Small Block ignition timing?

Rembrant
No issues with starting currently. The truck might as well be EFI in that department...just a touch of the key hot or cold and it starts instantly.

Three levels of gas here...87, 89, and 91 for premium. There may be higher octanes further west, I'm pretty sure I've seen 93 when traveling, but for the most part it's 87-91 where I live. I've been running nothing but 87 in the truck, pretty much since I put the engine in there last year. I'm not sure on the ethanol content...could be zero or 10%, I'm not really sure. (I drive a diesel VW most of the time, so I haven't really been paying close attention to gasoline.) I did run 91 for a few tanks after I put the engine in, but tried 87 to see if it would be OK and I didn't notice any difference between the two, so I left it at 87.

The Dyno work was really more like a nice addition. My reason at the time was to just have the engine broken in and to have the basic set-up done. I'm working in a single attached garage, so installing the engine was enough work on it's own, and I just wanted to drop it in and hit the key and go. Also, it was just like a small bit of warranty for me that the builder test the engine and make sure it didn't leak or have any problems before I hauled it home to install it.

My main issue now is to get it working better in the lower RPM's. The Peak HP/performance was irrelevant at the dyno time and it's pretty much irrelevant now;).

1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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Re: Can we talk about Small Block ignition timing?

85lebaront2
Administrator
In reply to this post by ArdWrknTrk
Damn, here we go again on ignition timing/advance.

First, the centrifugal (mechanical) advance is tailored to what the engine needs and can use under load, the vacuum advance makes up the difference to what the engine needs for best efficiency (fuel economy).

I found with the older Windsor engines that the high compression ones liked a total mechanical advance of 38-40°, but did not want it all too early. My Cobra 289 had only a mechanical advance dual point distributor, advance curve was most of the way in by 3000 rpm, static timing at 12° BTDC would advance 16° by 3000 rpm, which would be 28° total advance then would continue slower to add another 10° for 38° total at 5000 rpm.

If you look at the advance mechanism on a Ford distributor, there are 2 curved weights riding against the upper portion of the distributor shaft, there is a slot in each end of the "advance cam" with a number stamped next to each. The number is the distributor advance in degrees, crank advance is double this number. Example, if the slot has 10 stamped next to it, it will give 20° crank degrees of advance. Originally there would be a small rubber or plastic sleeve over the tab to limit this to the marked amount. These crumble with age and loss of it is roughly 2° crank degrees.

There are two springs on the advance mechanism, a light one and a heavy one, light controls the initial stage, the heavy one serves two purposes, it limits the initial advance, then allows the higher rpm advance to occur.

Most newer electronic ignition systems produce a much hotter spark than the older breaker point systems, that being said, they will fire a leaner mixture by virtue of a wider plug gap (.035 on the Cobra engine, .042 on Darth's 460 with DS-II) the vacuum advance will pull the breaker or pickup plate against the direction of rotation to increase the total advance at cruising speed (light load, high vacuum) this is what helps your gas mileage. Many newer engines can handle as much as 60° advance at 2500-3500 rpm light load conditions. The best way to arrive at that in fine tuning yours is to drive the truck on the highway, and very gently increase the throttle opening, if you get some spark "rattle" that goes away with more throttle, then you have too much vacuum advance. One of the ways Detroit engineers cured this was the EGR system, it weakens the mixture and slows the burn rate in the cylinders. If you eliminate the EGR, then sometimes the vacuum advance will need to be decreased or at least the rate will need adjusting.

Older Ford distributors allowed this adjustment with different springs, shims and a stop sleeve that could be done by removing the end cap on the advance diaphragm, newer ones generally have a hexagonal housing and a 18" Allen wrench inserted in the vacuum tube engages a screw through a plate in the hexagonal portion. Adjustment is: clockwise = more and quicker advance, counter clockwise = less and slower advance. Short of having a distributor machine, this part becomes a trial and error process.

Ford balancers have a dual direction scale from 10° ATDC to 30° BTDC, so a certain amount of the mechanical advance can be checked with a standard timing light, if you have an adjustable advance timing light, you can check it all the way. One warning, do a "sanity check" of one of these by locking it at 0° at run the engine up (use the fast idle cam so it is consistent) and read the scale, then using the adjustment bring the 0 TDC mark in line with the pointer and see if the reading on the light's advance scale matches. I have seen one (a Snap-On) that was way off when checked this way, and it was at idle!
Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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Re: Can we talk about Small Block ignition timing?

Gary Lewis
Administrator
In reply to this post by Rembrant
Cory - My reading, and very limited experience, shows that 38 - 42 degrees is about right on a small-block Ford - for the initial and centrifugal together.  But, as Jim said, Bill's the guru on this.

But if what you are looking for is more low-end torque and a bit better MPG, then it isn't really the total advance that needs to change, but the rate at which it comes in.  I say that because most systems will have the total in by something like 2600 R's.  But that's not "low-end".  So what you want is to have it come in faster - and maybe farther.  However, the Ford dizzy is a pain to change the advance curve on, so if you are in there changing anything, change both the rate as well as the total.

Jim's favorite instructions, and mine as well, are these from Crane.  They show you the order in which to dial in your advance, meaning intial/centrifugal/vacuum, as well as how to do it.  And they have some suggestions on how much and how fast.  
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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Re: Can we talk about Small Block ignition timing?

Rembrant
Thanks for the replies gentlemen,

I will be back with more questions later, but first I have a quick question slightly off the topic of this thread, but still related...

What is the max spark plug gap my stock DSII ignition can handle?
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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Re: Can we talk about Small Block ignition timing?

ArdWrknTrk
Administrator
Try .048"
There's no point in huge gaps. It just has to ignite the charge.
Atomization and swirl or turbulence determine that.
If you get over 50 the charge is going to start breaking down the insulation on even good plug wires.

Scotty's site used to have a GREAT article on recurving the DSII distributors. Including how the notch related to the stamped numbers on the arm (weight)

I'm not sure about his pages now, but a lot of my bookmarks are broken
 Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.
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Re: Can we talk about Small Block ignition timing?

LARIAT 85
In reply to this post by Rembrant
If your timing is late, it will show on a vacuum gauge.  Unless you have a wild cam, you should have 18 - 22 inches of engine vacuum.

My distributor was calibrated very similar to yours:  12 degrees initial and 20 degrees mechanical/centrifugal @ 3000 RPM.  When I installed it in my truck, I adjusted the initial by using a vacuum gauge.  I loosened the hold down bolt and slightly turned it (by the vacuum canister) until I reached the highest reading on the vacuum gauge. Then I took it for a test drive and listened for pinging.  It pinged only a little, so I retarded it back by about two degrees.  Then I checked for kick-back on a hot re-start.

I ended up at 16 degrees initial.  It is noticeably quicker on the bottom end here than when it was set at 12 degrees.  

My normal vacuum reading is 21 degrees at idle in PARK.
Lucille:  1985 Ford F150 XLT Lariat

*Colors:  Dark Canyon Red exterior, Canyon Red interior
*Engine: 5.0, CompCams 31-230-3, "Thumper" E7 heads, Edelbrock Performer intake, Autolite 4100 carburetor, DuraSpark II ignition, Thorley Tri-Y headers, Flowmaster dual exhaust, H-pipe.
*Drivetrain:  AOD transmission, 3.55 gears, 2wd.



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Re: Can we talk about Small Block ignition timing?

Rembrant
Thanks for the replies here guys. I am going to adjust the timing and get it dialed in better than it is, but I'm starting to realize here that (I think) I am chasing several issues at the same time.

My timing, whether it is set at an optimal point or not has still been pretty consistent.

The truck definitely has a miss, and I need to take a step back and give things the KISS treatment...keep it simple stupid...

Up until this point I have been totally ignoring the plugs, wires, cap, and button because they're all fairly new and don't have many miles on them (3500 miles maybe?). I'm going to replace a bunch of this stuff before going any further.

Something I'm curious about however...along the same topic of this thread, is the upper advance shaft in the distributor? How much play/wiggle is OK here? I pulled the rotor button off last night and noticed it has some wiggle.

1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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Re: Can we talk about Small Block ignition timing?

ArdWrknTrk
Administrator
I would always start with a 'tune up'.
3500 miles seems like nothing though.

Although a tune up with Autolite plugs is what put me off them.
Changed plugs, rotor and cap.
Had a miss that wasn't there before.

Changed the rotor back. Still there.
Changed the cap back. Still there.
Pulled the plugs and TWO insulators were not crimped tightly.

So NEW is not necessarily GOOD.
I'm sticking with NGK until they bite me too.

Axial play, or torsional play?
Any side to side wiggle of the shaft is a problem.

This was mentioned in reference to a DUI dizzy recently, where the guy went to an old points distributor and a Pertronix unit because poor oiling ate the shaft bushings.
 Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.
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Re: Can we talk about Small Block ignition timing?

ArdWrknTrk
Administrator
This post was updated on .
Pages 1 & 2 of Scott's recurve instructions.

http://www.reincarnation-automotive.com/Duraspark_distributor_recurve_instructions_index.html

http://www.reincarnation-automotive.com/Duraspark_distributor_recurve_instructions_page-2.html
 Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.
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Re: Can we talk about Small Block ignition timing?

Gary Lewis
Administrator
Good find on Page 1, Jim.  Together that's a good resource.  Where should we book it, Dano?

Cory - Before you do your tuneup you might try running the engine at night w/o lights on.  Sometimes a bad plug wire will show up.  I've seen the engine compartment look like Las Vegas with all the sparks.  But sometimes it takes spraying the wires with water to get the action started.

And don't forget to adjust the idle air/fuel mix on the carb.  Perhaps that's off.

Last, see if you can dial in more initial advance w/o the engine kicking back when you start it or with pinging under load.  More initial will help the bottom end power.
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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Re: Can we talk about Small Block ignition timing?

ArdWrknTrk
Administrator
Gary,

I would ask Scott if he's okay with hosting it here, with accreditation and a link back at the very least.
Scott works hard to be the best there is (as you do) he deserves to be rewarded for his efforts.

Another document you need is the Crane adjustable advance instructions.
Jegs has them on their site.
It's important to follow them to the letter.
 Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.
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Re: Can we talk about Small Block ignition timing?

Gary Lewis
Administrator
I need to call Scott tomorrow anyway, so I'll ask him why he hasn't joined.  He said he would.  But his pages are just that, HTML/CSS pages, so don't lend themselves to embedding here.  In other words, I think the best thing we can do for Scott is to link to them.

As for the Crane document, that is a PDF so is easily downloaded and then embedded in either a post or a page.

One approach for both would be to create an Ignition folder in the Resources folder/section of the forum.  Another approach would be to add another tab to the Documentation/Electrical/Ignition page and capture both the Crane doc as well as links to Scott's pages.

(Or, we could do both - create an Ignition entry in the Resources and have a link to a page in Documentation.)

Thoughts?
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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Re: Can we talk about Small Block ignition timing?

ArdWrknTrk
Administrator
The URL is the old RHP domain.
I don't think he even has them on the Parkland Performance site.

Inquire why not.
Ask him if he would move them, and if you could then link it and drive some traffic to his site.
I would gladly pay $155 (or whatever it is) for a custom curved distributor, if I had to replace it anyhow.

I like the idea of having both another folder, and a tab for ignition.
Anything to make those resources more available.
 Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.
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Re: Can we talk about Small Block ignition timing?

Gary Lewis
Administrator
I think there's a way to clone the whole page and put it on our site if he doesn't want to migrate it to his new site. But of course we'd give him credit. I'll ask.

And let's plan on doing both the belt and braces approach - add the info to the Documentation/Electrical/Ignition page and put a link to it in the Resources/Electrical folder on the forum.
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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Re: Can we talk about Small Block ignition timing?

LARIAT 85
In reply to this post by Rembrant
Rembrant wrote
The truck definitely has a miss, and I need to take a step back and give things the KISS treatment...keep it simple stupid...

Make sure your spark plug wires are routed correctly.  As strange as that sounds, it makes a difference.  If certain wires are too close to each other, they can crossfire and cause an engine miss.

There are two different firing orders for a 5.0/302:  there is the standard firing order and the 5.0 H.O./351 firing order.  The spark plug wires are routed slightly different between the two.
Lucille:  1985 Ford F150 XLT Lariat

*Colors:  Dark Canyon Red exterior, Canyon Red interior
*Engine: 5.0, CompCams 31-230-3, "Thumper" E7 heads, Edelbrock Performer intake, Autolite 4100 carburetor, DuraSpark II ignition, Thorley Tri-Y headers, Flowmaster dual exhaust, H-pipe.
*Drivetrain:  AOD transmission, 3.55 gears, 2wd.



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Re: Can we talk about Small Block ignition timing?

Rembrant
Rick,

Wires are all routed OK and firing order is checked and correct. All good there. I replaced all the plugs, wires, cap and button this morning and it was running a little better for sure. I then bumped the base timing up to 16btdc, and it works better here too. The problem I'm having now though is that the idle is not as smooth as it was. Before, my tach needle was rock solid. Now it's bouncing a little bit.

I put the timing light back on, and you can see that the timing it bouncing way advanced. It reads on the 16, but bounces way ahead. I should note here also that I put some oil in the upper advance shaft in the distributor (below the little felt that's in there).

Vacuum is reading 16" at idle. That was with no air cleaner on it. When I put the 5.0 dual snorkel intake back on it, the idle goes from 800 up over 900.

So my base ignition jumping way ahead...is that my centrifugal advance? When I've checked it previously, when set at 12btdc, it was always pretty steady.
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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Re: Can we talk about Small Block ignition timing?

Gary Lewis
Administrator
It seems that your curve starts coming in just above 800 RPM, so any increase in idle speed gets more advance, which may increase the idle speed.

And where do you have your vacuum advance connected - ported or manifold vacuum?

But the increase in RPM with the air cleaner on suggests that your air/fuel ratio is lean.  The air cleaner tends to enrichen the mix slightly.  And your vacuum at idle should be closer to 20", which may also be due to a lean air/fuel mix.
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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Re: Can we talk about Small Block ignition timing?

Rembrant
Gary,

Vacuum advance is currently disconnected.

Right, so I'll play around with the idle speed and adjustments to see if I can get it to stop bouncing.

I wonder if the centrifugal advance is now moving too easily since I oiled it? Any time I played with it previously it wasn't advancing until a much higher RPM. Maybe it was sticking before and now that it's lubed up it's swinging out to full advance at too low an RPM?
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

12