Random Restomod Questions - Volume 1

GERMYS_72 · Sep 11, 2024

1. I'm putting a 351C 4V D0AE engine from a 70 Mach 1, into a 1972 fastback. Should I be using the 1971-73 "Q" code air cleaner ?

2. I am switching from the stock FMX to Toploader RUG-BJ1. Will my existing driveshaft work, or will I be needing longer one ?

3. how can find the original autolite carburetor model that marries up to my engine, or since I'm not doing a numbers matching build, should I just move on and get a new holley. I would like to keep the engine true to the 70 M code if possible.

4. I have read the 351C 4V from this era do not like unleaded pump gas 87-93 octane. What are you doing as a workaround ?

Hemikiller · Sep 11, 2024

1 - you can run whatever air cleaner you want

2- The factory 351/FMX driveshaft is 51 3/32" ctr to ctr of the u-joints, the one for the toploader is 50 13/16". That's "fairly" close and may work, depending upon the yoke you use. The FMX is 31 spline, the toploader is 28 spline.

3 - I personally wouldn't run an Autolite 4300A. A simple Holley 1850 600cfm or a 3310 750cfm will do the trick for a stock engine. I'd also much rather get an older Holley and rebuild it than roll the dice on a new one.

4 - I've only ever run unleaded in my 351C engines, 2V or 4V. I run 93 in the 351C in my 71 which has a *true* 10.5:1 compression ratio. 16° initial and a conservative 18° curve in the mechanical, with heavy springs to slow the advance. The stock as-built ratios were much lower than what Ford advertised, so that "11:1" 1970 engine is really only around 9.8:1.

GERMYS_72 · Sep 12, 2024

Hemikiller said:
1 - you can run whatever air cleaner you want

2- The factory 351/FMX driveshaft is 51 3/32" ctr to ctr of the u-joints, the one for the toploader is 50 13/16". That's "fairly" close and may work, depending upon the yoke you use. The FMX is 31 spline, the toploader is 28 spline.

3 - I personally wouldn't run an Autolite 4300A. A simple Holley 1850 600cfm or a 3310 750cfm will do the trick for a stock engine. I'd also much rather get an older Holley and rebuild it than roll the dice on a new one.

4 - I've only ever run unleaded in my 351C engines, 2V or 4V. I run 93 in the 351C in my 71 which has a *true* 10.5:1 compression ratio. 16° initial and a conservative 18° curve in the mechanical, with heavy springs to slow the advance. The stock as-built ratios were much lower than what Ford advertised, so that "11:1" 1970 engine is really only around 9.8:1.

View attachment 92959

Great feedback Hemikiller, I will look out for a stock 28 spline yolk. that small difference of driveshaft length won't be a big deal, even if the machine tolerance is exact, I would just need the yolk to be roughly a quarter of an inch shorter to fit my stock shaft.

I prefer not to use ethanol gas in this car, or any engine whatsoever, but it sounds promising if 93 octane will work with no pinging and minor adjustment to initial timing.

Alexei · Sep 12, 2024

I do suggest you not to use a Carb. Go EFI, it´s much better on every day use.

pedstagn71 · Sep 12, 2024

I’d stick with the carb. More period correct and it’s a lot easier to grab a screwdriver to adjust it than get on a computer and tune it. Just depends if you’re a mechanic or a tuner. I have a Holley 750 and have had 0 problems with it starting or performing

GERMYS_72 · Sep 12, 2024

Alexei said:
I do suggest you not to use a Carb. Go EFI, it´s much better on every day use.

Thanks for the suggestion. since I will drive very few miles , I want to stick with old school carb.

GERMYS_72 · Sep 12, 2024

pedstagn71 said:
I’d stick with the carb. More period correct and it’s a lot easier to grab a screwdriver to adjust it than get on a computer and tune it. Just depends if you’re a mechanic or a tuner. I have a Holley 750 and have had 0 problems with it starting or performing

Yes, that's what I intend to do. I just want to make sure and get the right carb the first try, I don't want to be troubleshooting through a bunch of different setups.

EdM · Sep 12, 2024

I am in Boerne and believe I have an original Q code air cleaner as well as an original Q code air cleaner for the ram air hood (NACA?). PM me if interested.

rcadd1ct · Sep 13, 2024

Alexei said:
I do suggest you not to use a Carb. Go EFI, it´s much better on every day use.

Both have their pros and cons.

EFI is not as self tuning as they advertise.

You are just trading hand tools for a laptop.

But once you get EFI tuned it will have better manners for a wider range of situations (altitude for one ).

EdM · Sep 13, 2024

My Edelbrock Pro-Flow 4 has been a game changer for me. Instant throttle response with improved gas mileage. Zero issues and zero screwdrivers.

Alexei · Sep 14, 2024

There is always some EFI set-up, but once done its much better. Mine is Sniper.

Cleveland Crush · Sep 14, 2024

Alexel,
That means one does not know how the set up a carb properly...

rcadd1ct · Sep 14, 2024

Cleveland Crush said:
Alexel,
That means one does not know how the set up a carb properly...

Agree, but if you drive from sea level to altitude it won’t adjust for you.

Most people aren’t doing that though.

c9zx · Sep 14, 2024

The 70-71 M code is not a bad intake at all. I've seen people make 450+ hp with that intake with stock stroke. I would suggest making it a true square bore (primary side bore is smaller than secondary bore). I would use a heat insulating gasket of some kind. Depending on use, I'd consider blocking the carb heat crossover. Again, depending on use, I'd look at the adjustability of whatever carb you select. The old school carbs have no direct way to adjust air bleeds or idle channel restrictors (you can drill them larger but, making them smaller is far more challenging). Main jet changes have little to no effect on idle quality and "mixture" screws do not change the air to fuel ratio of the idle mixture, only the amount of the air fuel mixture set by the idle channel restrictor and the idle air bleeds (same with the transfer slots). Drilling and tapping the old school carbs to make them adjustable is something I've done for many years but, requires a fair amount of precision, patience, and skill.
As far as fuel octane goes, in the 1960s and 1970s the octane number was based on the "RON' method. Today, in the US, it is based on the Anti-Knock Index or R+M/2 method. A 1970 octane number of 95 is equivalent to an octane number today of 91-92 (depending on seasonal blending). In short, "Build it and you will have fun". Chuck

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