69 Mach 1 – looking for answers about a 390 to 351w conversion:

[mcmenomy]

Hi All,
I purchased a 69 Mach1 S code 390 with a four speed car and I want to replace the drive train for a 351W with an AOD, to make it friendlier for everyday city driving. I already know that I will need another transmission cross member, shifter to replace the four speed, and new pedals, but I’m not sure on the best place to find them. I also would like to know if I can use the mounting brackets for the alternator and power steering from the 390 on the 351. The 351 is out of an 84 bronco.
The reason that I’m replacing the engine is that I’m looking for something that I can drive everyday and not kill me at the pump. I’m also tired of having my toys stay in the garage and want to enjoy my 69 every day I can.
So, does anyone have experience on this conversion and what will be needed?

 

[96 DOHC Cobra]

You DO know that you'll be absolutely ruining the value of a fairly rare car? Anyway, as they say: "It's your car ..."

There's going to be a long list of parts you'll need to replace. Here are some to begin with.
Engine-to-frame mounts.
trans crossmember
driveshaft
shifter
speedo cable
oil pan & pickup
timing cover

You don't really need new pedals. You could just remove the clutch pedal or bury it on the floorboard.
The 390 brakets won't work on the 351W. If you have the brackets on the 351W, your alternator should bolt to them just fine.
I'm sure others will think of more.

 

[D.Hearne]

BAD IDEA !!!!! If you want a 351W, sell the car and buy one with it already. 390 cars are as DOHC said, fairly rare cars, (especially 4 speed big blocks) please don't ruin it by doing a Windsor swap. There are lots of small block cars out there to choose from, you can sell yours and buy a small block Stang and have thousands left over to do mods to the small block car. There are ways of making the 390 more fuel efficient(headers, cam, intake, ignition, rear gear change), at least do that instead of ruining the car with a small block. I used to get nearly 20 mpg with a 427 in one on the highway, and that was with dual fours.

 

[mcmenomy]

Thanks for the bashing, right out of the gate, which I was expecting. My intent is not the chop the car up, just make it friendlier for the stop and go traffic. No free way driving involved. The 390 will go back into the car after my 51 F1 is done in a year or two, so why not have some fun with it.

 

[rnrjunkie]

I really don't think that they were bashing you. The point that they were trying to get across is that all of that work and investment will most likely not accomplish what you are trying to do. A 4 speed is in my opinion more fun to drive than an automatic, and the fuel saving between a 390 and a 351 will probably be minimal.

 

[mcmenomy]

I was also looking for a Honda engine for the economy savings part. I saw in a hot rod magazine that guy placed a Honda engine in a 67 Camaro that was pulling 800 hoarse with 30 mpg. That also sounds like fun. Any thoughts?

 

[D.Hearne]

First of all, you're talking out of both sides of your mouth in this thread. You say you want to "be able to drive the car without having the 390's fuel economy". But you're willing to spend what, about 4 grand to do so ? That 4 grand can buy a LOT of fuel when you compare mileage between the two (which isn't going to be anywhere near the difference you think it is) If you got a 5 mpg difference (could be more, could be less, but that may be the difference in my opinion, having had a 67 GT390 Stang that got 15-18 mpg) divide $4000 by $3 a gallon, then 5 into 4000 and see how many extra gallons you may get with that $4000. That $4000 could be better spent in upgrades tot he 390 that will yeild the same mileage as the 351W will get. And with a LOT LESS work. It's obvious to me that you're either a troll here, or incredibly naive and uninformed on what a 390 is capable of.

 

[mcmenomy]

I guess that I’m the troll in this instance, because I don’t see ever getting 15-18 mpg in bumper to bumper traffic with a carbureted 390 4 speed car. At least not with the dope I’m smoking. Thanks for your input.

 

[D.Hearne]

I guess that I’m the troll in this instance, because I don’t see ever getting 15-18 mpg in bumper to bumper traffic with a carbureted 390 4 speed car. At least not with the dope I’m smoking. Thanks for your input.

It's not that hard to do for someone who's developed a "feel" for their car. You won't get that either with a 351W. Why not just drive the car and enjoy it and use the money you'll spend in the conversion to buy the little extra gas it may use ? I'll bet it's also got a double pumper Holley sitting on it too. Just replacing that will net you 3-4 MPG if that's the case. A more efficient cam will as well. Plus headers and a good electronic ignition.

 

[Max Power]

Wow, buy a car, try and use it for something other than it's intended purpose, only to allegedly return it to form in a year or two? I will ignore the Honda engine comment as bait.

I pray that this rare big block 4 speed muscle car survives you. It deserves better.

 

[mcmenomy]

Thanks for up lifting comments Max, which I will add is coming from someone that has butchered their own car. that's the pot that is calling the kettle black!

Isn’t the intent to restoring an old car, to enjoy it? Or does that only mean to restore it back to it’s original state. I think some of you need your head examined. Look at all the Shelby clones that you drool over and dream of trying to make your cars look just like them, big block or not. Pretty hypocritical!

Since I can drive my car all year round without rusting out, my intent is to enjoy it as I see fit.

 

[mroed]

I guess you know that what you just asked, was kind of an untraditional question, and personally I don't know anyone who would consider this kind of swap, and then you mention a Honda engine... What do you expect?

But I do agree with you on one thing, the intent of restauring a car is to enjoy it!

 

[2+2GT]

The stock 390 was known for surprisingly good fuel economy. My guess is it is far from stock right now, probably as suggested wearing a too-large Holley double pumper. The original was an Autolite 4300. You could reasonably expect 14-17 mpg, while the 351W might get as much as 15-20. Frankly, I think it would be nutz to spend the better part of ten grand to switch to a 351W to save 3 mpg for a year. For 6-8 grand you could buy a lotta gas. A LOTTA gas.

Oh, and I drool over both big and small engine Shelbys and Mustangs. Especially my own 289HP.

 

[ic237]

How rare would you guys say a 69 fastback with a 390 is? I got a family member who wants to buy this on ebay

http://cgi.ebay.com/ebaymotors/MUST...iewItem&pt=US_Cars_Trucks&hash=item414fadde42

I am not a 100 percent sure but I think its about at its peak if not more. We arent sure if thats worth the money?

Thanks guys.

 

[2+2GT]

It's a well-polished parts collection. The engine compartment is so-so, and the undercarriage is "daily driver". Parts collection, because it's not a 390 car, it's 250 6 cylinder car. Unless it really lights your fire, it's overpriced.

 

[ic237]

It's a well-polished parts collection. The engine compartment is so-so, and the undercarriage is "daily driver". Parts collection, because it's not a 390 car, it's 250 6 cylinder car. Unless it really lights your fire, it's overpriced.

Thats what I fugured. I mean the body work is nice. But 38 is too much. I told him 25 tops

 

[ic237]

You caught me off gaurd with the 6 cylinders. Yup, I crossed the vin too. It sure was a 6.

 

[D.Hearne]

Thanks for up lifting comments Max, which I will add is coming from someone that has butchered their own car. that's the pot that is calling the kettle black!

Isn’t the intent to restoring an old car, to enjoy it? Or does that only mean to restore it back to it’s original state. I think some of you need your head examined. Look at all the Shelby clones that you drool over and dream of trying to make your cars look just like them, big block or not. Pretty hypocritical!

Since I can drive my car all year round without rusting out, my intent is to enjoy it as I see fit.

The by all means go ahead and butcher the car. It's your car and your money. Just don't be surprised to end up with a severely devalued car that you'll never recoup the money you spent on it. And when you're done with the conversion and find that you netted a 2 mpg increase in mileage, we'll all have a good laugh at your expense. As for the Shelby clones, most are done starting with common, small block cars that aren't worth that much to start with.

 

[2+2GT]

As for the Shelby clones, most are done starting with common, small block cars that aren't worth that much to start with.

Most of the "clones" I have seen were originally six cylinders.

 

[68RestoMod]

I think some of you need your head examined. Look at all the Shelby clones that you drool over and dream of trying to make your cars look just like them, big block or not. Pretty hypocritical!

That would only be hypocritical if we were drooling over Shelby GT-500KR convertibles being turned into standard 6-cylinder coupes. I don't think you will find anyone on this forum doing that.