Shout out to the 73 351C 4V!

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73inNH

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1973 Convertible, Q code, 4 speed, 3.25, A/C, P/S
Hi all!

Just a feel-good post to say how happy I am with my engine. :)

73 Vert with 351C 4V, 3.25 gears, 4 speed. The engine internals have never been opened, but I've done the following:

Edelbrock 4V Intake (used)
Edelbrock 650 AVS 2 carb (with choke removed)
FPA headers
2.5" exhaust
Pertronix disty and matching ignition components. Recurved advance, timing advanced.


It took me a little while to get things right. I tuned the carburetor with an AFR meter. I had to change every jet, rod and spring on the carb, and drill out the accelerator pump (significantly) to get it right.

It screams. I'm so impressed with this engine in its stock form. I've changed all of the breathing components outside of the heads and she's running so well.

I've done similar breathing improvements on most classic engines I've had, but for whatever reason this one reacted incredibly well.

In the future, I'm likely going to change the heads and cam just to unleash the rest of the engine's potential, but just know that you can make this engine very powerful, fairly easily.

I'd also like to go from 3.25 to 3.5 rear.

That's it - cheers to a great engine!
 

giantpune

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I've been tuning my cars with a vacuum gauge and a timing light with the adjustable advance. I have been interested in using an AFR meter. Is there something you can use that doesn't require drilling a hole in the headers and welding in O2 sensors? That's my hurdle. A vacuum gauge and a timing light I can move from car to car easily.
 

73inNH

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1973 Convertible, Q code, 4 speed, 3.25, A/C, P/S
I've been tuning my cars with a vacuum gauge and a timing light with the adjustable advance. I have been interested in using an AFR meter. Is there something you can use that doesn't require drilling a hole in the headers and welding in O2 sensors? That's my hurdle. A vacuum gauge and a timing light I can move from car to car easily.
I use: https://www.amazon.com/gp/product/B003JZL0ES/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

AND I happened to have one of these in the house: https://www.amazon.com/AutoE-Tailpipe-Aluminum-Universal-Accessories/dp/B08NF62WB1/ref=sr_1_4?crid=S90IFD9O509Z&keywords=exhaust+whistle&qid=1652450563&sprefix=exhaust+whistle,aps,169&sr=8-4&th=1

Yes, I have kids. : ) My oldest took that apart and attached the O2 sensor to that exhaust clamp and viola!

I use a positive and negative wire with alligator clamps and small 12v battery in the car to power the AFR (just + / -). My son sits in the back seat while I'm driving, holding the meter in hand and tells me how we're doing. We then go back to the garage, correct and retest. We did this a few times until we got it right.

I used a vacuum gauge first. I got the car running acceptable, but when verifying via AFR, I found it was lean across the board (idle > WOT). I used the AFR to fix that (one part of the throttle at a time).

No idea why, but setting the idle air screws with the vacuum gauge seemed to be more accurate than the AFR. I turned the screws to get max vacuum and left them there. Everything else I did with the AFR meter.

NOTE: The AFR meter is flaky in that sometimes it won't turn on. No idea why. I have to disconnect it and reconnect a few times it'll turn on. There may be better units out there. I have no preference, it's the only one I've ever used.

Hope that helps!
 

giantpune

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I use: https://www.amazon.com/gp/product/B003JZL0ES/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

AND I happened to have one of these in the house: https://www.amazon.com/AutoE-Tailpipe-Aluminum-Universal-Accessories/dp/B08NF62WB1/ref=sr_1_4?crid=S90IFD9O509Z&keywords=exhaust+whistle&qid=1652450563&sprefix=exhaust+whistle,aps,169&sr=8-4&th=1

Yes, I have kids. : ) My oldest took that apart and attached the O2 sensor to that exhaust clamp and viola!

I use a positive and negative wire with alligator clamps and small 12v battery in the car to power the AFR (just + / -). My son sits in the back seat while I'm driving, holding the meter in hand and tells me how we're doing. We then go back to the garage, correct and retest. We did this a few times until we got it right.

I used a vacuum gauge first. I got the car running acceptable, but when verifying via AFR, I found it was lean across the board (idle > WOT). I used the AFR to fix that (one part of the throttle at a time).

No idea why, but setting the idle air screws with the vacuum gauge seemed to be more accurate than the AFR. I turned the screws to get max vacuum and left them there. Everything else I did with the AFR meter.

NOTE: The AFR meter is flaky in that sometimes it won't turn on. No idea why. I have to disconnect it and reconnect a few times it'll turn on. There may be better units out there. I have no preference, it's the only one I've ever used.

Hope that helps!
So you put the O2 sensor way back at the end of the exhaust and it gives accurate numbers? I thought they wanted o2 sensors way up there by the headers.

I suppose this could be my excuse to install exhaust cutouts. Gotta get that motor dialed in so its burning cleaner. If I need exhaust cutouts to stop global warming and save the penguins, I'll do it.
 

Hemikiller

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The biggest impediment to the 351C-4V's performance potential was always the emissions-friendly tune they shipped with, and the 4300x series carburetor, regardless of the year. It's a pretty common problem with Edlebrock carbs being set lean as shipped, some models are worse than others, with the electric choke models at the top of that heap.
 

73inNH

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1973 Convertible, Q code, 4 speed, 3.25, A/C, P/S
So you put the O2 sensor way back at the end of the exhaust and it gives accurate numbers? I thought they wanted o2 sensors way up there by the headers.

I suppose this could be my excuse to install exhaust cutouts. Gotta get that motor dialed in so its burning cleaner. If I need exhaust cutouts to stop global warming and save the penguins, I'll do it.
Works fine for tuning purposes. :)
 
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My understanding is the O2 sensor is placed near the engine for a couple of reasons.

1. It has to be hot to work, being closer to the exhaust means it heats up faster
2. They don't like moisture so less condensation the further up the exhaust

And, of course, if it is being installed as part of the manufacturing of the car, having it up front and close to the engine means less wiring.

Otherwise my internet searching has indicated that a temporary AFR at the exhaust will work for tuning purposes. (I am no expert)
 
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'73 mustang convt.
BTW, really nice looking car. I love that color combo. I love my Cleveland as well. When I built it the car would have been considered 'fast' but 50 years of technology has caught up with us and while it is still a fast car, there are a lot of things that are much faster.
 
Joined
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NW Pennsylvania
My Car
1972 Grabber Blue Mach One 351 Q code orig 4 speed. Now: 427C Titus
Hi all!

Just a feel-good post to say how happy I am with my engine. :)

73 Vert with 351C 4V, 3.25 gears, 4 speed. The engine internals have never been opened, but I've done the following:

Edelbrock 4V Intake (used)
Edelbrock 650 AVS 2 carb (with choke removed)
FPA headers
2.5" exhaust
Pertronix disty and matching ignition components. Recurved advance, timing advanced.


It took me a little while to get things right. I tuned the carburetor with an AFR meter. I had to change every jet, rod and spring on the carb, and drill out the accelerator pump (significantly) to get it right.

It screams. I'm so impressed with this engine in its stock form. I've changed all of the breathing components outside of the heads and she's running so well.

I've done similar breathing improvements on most classic engines I've had, but for whatever reason this one reacted incredibly well.

In the future, I'm likely going to change the heads and cam just to unleash the rest of the engine's potential, but just know that you can make this engine very powerful, fairly easily.

I'd also like to go from 3.25 to 3.5 rear.

That's it - cheers to a great engine!
The proposed 3.50 gear change will be a nice addition to your current upgrades.
 

73inNH

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Messages
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My Car
1973 Convertible, Q code, 4 speed, 3.25, A/C, P/S
The biggest impediment to the 351C-4V's performance potential was always the emissions-friendly tune they shipped with, and the 4300x series carburetor, regardless of the year. It's a pretty common problem with Edlebrock carbs being set lean as shipped, some models are worse than others, with the electric choke models at the top of that heap.
Agreed. And there does seem to be something different about the Cleveland and Eddy carbs. I've installed Edelbrock carbs out the box on two Chevy 350s and 1 Pontiac 350 with minimal adjustment. For whatever reason, the 351C likes a bit more TLC. :)
 

Greg

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I have a 71 Mach 1 grabber blue and white, a 73 Mach 1 Copper and White with power sunroof and a 73 Convertible all loaded
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My Car
1972 Mustang convertible, 351C 2V with FMX (#'s matching)
Currently equipped with 351C 4V 4BM, .060 over, roller cam, Sanderson block huggers, -AC
73inNH made engine upgrades that call for the ditching of the lame 3.25's
Today I had her out and with Chicago tourists infiltrating my town and the radar signs out I did some verifying on my speedo after I put in the trac-loc 3:50’s and the C4 after pulling out the FMX w/2:75 open. I have a 23 tooth gear in trans, recording 4mph under actual, 60 mph at 3k rpm, 3600 rpm at 70. Maybe, just maybe when I smoke the C4 I will think of an OD but where I live I take the backroads to Milw area if I ever feel like going there which after last nights gang bang-up party with 17 shot I’m cool with staying away…
 
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Roland

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1972 Mach1 351C Q-code gold glow, black interior
on my 72 Q-code I just replaced the original intake and carb with an original OEM 70‘ M-code intake and put on a 625cfm Street Demon carb., also exchanged the mufflers with Flowmasters! Result, great sound and an awaked engine with great driveability and still looking stock! like it.
 
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My all time favorite vehicle is our 1969 Shelby GT500
I don't like the 3.50 for highway. Feels like you would need another gear or overdrive
We have a 3.5:1 TractionLok set of gears in our 73 Mach 1 (351W, not C) street/strip engine. The gears and engine transplant were done by the prior owner. With the original C4 in 3rd/Top Gear we were turning about 2,900 RPM at 60 MPH. Although not intolerable, after about 20 minutes the sound of the engine at that RPM would begin to grate on me. Much later on (like the next year) the C4 began to slip in its 1-2 upshift, and rather than rebuild the tranny we transplanted an AOD into the Mach 1. That worked out great. Now in 4th/OD/Top Gear we are only turning about 1,900 RPM at 60 MPH. and the car is now a really nice vehicle to cruise in even at highway speeds.

That said 3.5:1 is about the lowest rear axe ratio I personally would do in a vehicle that does not have an OverDrive transmission. A ratio that is lower than 3.5:1 will spin the engine at more than 3,000 RPM at 60 MPH, making it sound like it is about to grenade at any moment. For a vehicle driven on the public roads that is not as cool to have to live with as it sounds. For me, the 3.5:1 is a near ideal compromise between spirited performance and practical driving on public roads. Using an OverDrive tranny or GearVendors OD provides the best of both worlds. Decent low end performance and a nice cruising experience at 60 MPH. It seems that with an OD Unit I feel I could go to 4.11 rear axle gears and still have my engine RPM running at a comfortable 2,250 RPM or so.

In our case I opted for an AOD vs a GearVendors solution as I had to rebuild or replace the tranny anyway. If my tranny not in need of rebuilding the GearVendors bolt on solution would have been fine. If anyone is interested in getting our list of AOD vendors and parts, and the links to the YouTube video showing step by step how we did our AOD transplant into our 73 Mach 1 just download the attached files. The YouTube videos are included in the 1973Mach1_AOD_Transplant_Chronology_20210619.pdf file. One of the YouTube videos shows how I did the wiring harness splice to use the AOD Neutral Safety/Backup Light Switch:

 

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  • 1973Mach1_AOD Transplant Parts List_20210728.pdf
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  • 1973Mach1_AOD_Transplant_Chronology_20210619.pdf
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