351 2V ---> 4V

Hey guys,

I got a question for 351 guru. Ive searched in the forum post, and still cant be satisfied. I order the book "Ford Small-Block Engine Parts Interchange", and im waiting for it. Im also sure this question have been asked hundred times before.

I own a 1973 2V engine, and i want to move to 4V. I know i need to change heads, intake & exhaust manifold and of course the carburetor.

Following this, i bought 1970 heads DOAE-N, and D0AE-9425-L intake manifold. (still need to find the exhaust and carbs)

Now my questions is, what about the pistons & the cam ? Are they exactly the same for 1970-1973 ?

Also, is there anything else i forgot to take in consideration ? I want factory parts, not a build with aftermarket to gain power.

Is there a place where i can get all the P/N from the 1970 and the 1973 engines ?

im still a newbie, just bought the car in september so im learning.

Thanks !

73 will have dished piston further lowering the compression. As for the cam it will be different. There were different cams used in different Cleveland set ups. M codes, differ from R codes, differ from Q codes and differ from H codes as well as differing based on year. A 73 H code will have the least aggressive cam. These changes were made due to unleaded fuels and emission requirements.

What are your plans for the power? Are you wanting a high-revving engine, or more low-end grunt? The only differences between a 2V and 4V is the intake and heads, which make the 4V make more power higher in the power band.

Do you actually need a 4V set-up for more power up-high (like on the track)? Or are you just looking to make more street power with a 4bbl carb? If so, there are plenty of 2V 4bbl intakes and performance goodies that'll wake up your engine. Otherwise, there are lots of guys running 4Vs making gobs of power who can advise as well.

Click on my Garage button below for more information on how I built my '71 H-Code with the factory 2V heads - that'll give you an idea of what you're up against, regardless of which way you choose, since you'll need to dump the anemic factory cam and pistons anyway.

I dont want a build with edelbrock, comp cam stuff to gain power.

I have a factory 2V, what would be the exact partlist to go to factory 4V ?

Would it be more simple to buy a 4V complete engine instead of modify a 2V ?

Well, that's a different story. You'll want to look up 1973 Q-Code specs to make that work, unless you're not particular about the year model... which, in that case, could be M-, Q-, or R-Codes for '71, or Q- & R-Codes for '72.

Hopefully, one of the others can help you out. I just said, "What the Hell," since mine was seized and rusty when I got it.

Not to muddy up the water, but it you were to look up on Power Nation dot com. The TV show is horsepower. you should be able to lookup the 351 Cleveland 2v versus 4v rebuilds they did with junkyard engines a couple of years ago. They actually generated more horsepower with a 2v than with a 4v. something to look into before you dump all that cash into a change so to speak. Just trying to help out a fellow member.

Wootdog in Virginia Beach, Virginia.

I'm not an expert, but I'm trying to work my way thru this as well.

I presume you are wanting to basically build a 70-71 M-code motor. This is the closed chamber, flat top piston 10:1 to 11.1:1 compression ratio motor.

If you build it like that it may have issues on modern pump gas. A cam to bleed off a little compression would help with that. Or, since you may have to replace pistons anyway, a slightly dished aftermarket piston to get the compression down just a little. Make sure your heads have not been ported or milled. Either/both of these may cause problems with a stock type build.

Replace your valves. General consensus is that the OEM Ford valves tend to break, especially after all these years. Install new hardened valve seats. The old ones are old and modern oil has very little ZDDP (zinc) to protect the seats.

When you go to buy exhaust manifolds, beware of sellers that think a drivers side 70 351c 4v manifold is the same as 71-73. It is not! The 70 turns up at the h-pipe outlet, 71-73 stay pointed down. Passenger side is the same 70-73, but they do tend to crack between 2-3, look for repairs.

The same exhaust manifolds were used thru 74 at least, but on Torinos/Montegos/Cougars etc.

Also, there are at least two, maybe three manifold outlet diameters; 4V and Boss351/HO for sure, not sure about 351CJ.

There are two or three oil pans. Stock 2v (maybe 4v, too) type and possibly two others. One for sure has an oil baffle around the pickup and a windage tray of sorts. The third might be baffle and no windage tray.

If you haven't read it yet, do a search on George Pence and 351 Cleveland. There is a link somewhere to his posts on a Pantera forum. Probably everything you want to know is on there, including engine recipes using only Ford parts.

There's tons of information on the net about the differences on 2V and 4V engines year by year. There's more than just heads and intake though in factory form. I don't why Ford ever advertised the 351 4V engines as 11:1 (70) and 10.7 (71) and now people take these figures as gospel, because there's no way with a 3.5" stroke, 4" bore a piston sitting down the bore at the very least least .020 with 6cc valve reliefs and the top ring sitting .250 (I think) from the crown, head gasket compressed at .045-.047 with a 4.080 bore and 63cc (70) and 66cc (71) chambers. Do the math and you'll find it's not even close, the only 351 Cleveland close to those numbers is a 71 Boss. I couldn't imagine running an 11:1 comp engine on the street with the standard 4V camshaft specs. A 72 CJ, 72/73 4V cam may have been a little better at those comps, but Ford ran that camshaft low compression open chambered 4V engine and no matter what some think, those Ford engineers knew exactly what they were doing even in those crazy changing world of emission engines, just look at their record at their achievements.

I'm all for people wanting to run factory parts, but sometimes those parts aren't worth their weight in crap, let alone 40+ years of use.

That's why I referred to the George P. article. He covers the compression issue fairly well I think.

In my mind, even with the over rating of the CR, they were running the right gas back then. Now, along with the lower octane and alcohol, you have a potential overbore (more compression) and possible block decking (more compression) and maybe head milling (yet more compression) to get things right again. So even if the original CR was really 10:1, by the time you do the machine work to get true, you could be higher than you want to be.

I see ... thanks for all your advice. Like detritusmaximus guess right, my goal is to build 70-71 M-code motor. I was in my thinking that i can simply take my 2V engine and replace with the 4V heads - intake exhaust manifold - carbs, and keep the 2V piston - crank - cam.

I see now that this is way more complicated than this, and as im a newbie in engine building, i think it will be more wise to take a 4V stock engine, instead of trying to get parts to modify a 2V.

I will then sold my 2V engine, and my 1970 4V closed chamber heads, and use my father 1973 4V engine.

Thanks !

?? It is not overly complicated. Replacing the cam is pretty straight forward and frankly where you are going to see the most performance gains. Also the 73 4V engine will have open chamber heads and I believe dished pistons as well and not a very aggressive cam.

So you are saying that my 2V pistons will fit with the D0AE-N closed chamber heads ?

The pistons will work just fine, your compression will be a little lower than with flat tops. I am building a 73 2v right now and using the stock 2v pistons with closed chamber 2v heads from Australia, just upgrading the cam and such as well. You will want to make sure your bottom end is in good shape though.

I'm not throwing rocks, but rather genuinely curious: why attempt to build an M-Code to factory specs, if your car is an H-Code? You're voiding out the pedigree (somewhat, although not important if you're building for performance), but by the same token insisting on factory power, appearance, etc.

Obviously, you want more power... but apparently, not all that much more power... which is weird. A '71 M-Code certainly makes more power than a '73 H-Code, but why stop there and limit yourself - go for R-Code specs and have the most 351C factory power available. For that matter, going with a performance build (like mine, and so many others) will give you more power than even the R-Codes... while maintaining your numbers-matching status and nobody has to know what's under there aside from your factory-appearing and correct for your car H-Code (giving a 'sleeper' appearance as well).

If factory appearance is so important, use factory valve covers, oil pan, etc., and paint everything corporate blue.

Sorry, but I guess I'm lost as to what your end-game is. :chin:

Hahaha eric, its ok if you are lost, as i dont have any idea on which direction to take with my project . Going for R code could also be a good idea, but the thing is i dont have any idea how to do such a build. Aftermarket has soooo much part to offer and i dont know how to put them right to build a proper engine. Factory parts are meant to work with each others so it is easier for me to find the right combination.

But you brought a good point, stick with 2V as i got all the parts and the car is a H, im also thinking about it.

Thanks for all the ideas, suggestions and opinions guys, it help myself to choose a direction to take

Erik

You can call comp cams and talk to a tech. I would personally call them tell them you want to use th 4v closed chamber heads and make sure you have additional information ready such as what your gear ratio is, what trans you are running and what you want out of the car and they can help you choose a proper cam and get you rolling

Fair enough, Erik. I was "lucky" mine was such a mess when I got it, that I pretty much had made up my mind to just go for it.

I'd actually run across an almost identical car to mine right after I bought it, but it was a '71 M-Code Mach 1. It was gorgeous, and absolutely faithfully restored... down to daub marks and factory assembly stickers and whatnot. I marveled over it for about an hour, but refused to drive it or even consider purchasing it, basically because it was 'too nice' for me. I wanted a car I could put my own stink on... not a collector car I'd be afraid to drive or customize (which is what a lot of others prefer, and that's fine too).

Do what makes the most sense to you, and have fun doing it. We're here to help in whatever way we can - we're also happy to have you and another cool '73 in our 'stable.' ::thumb::

Ok here's my take, replacing 2v heads with 4v and changing cams can have a knock on affect with gearing ,torque convertors etc as well, just remember that when factoring costs. Personally I wouldn't care if I had closed or open chamber heads , but then I would stick with the 2v .A lot of stuff sounds good as far as hp numbers etc but doesn't translate well to the street.

Have fun whatever you decide.

Hello erikroy57,

My first question is "What is your budget?"

mustang7173

Hey guys,

I got a question for 351 guru. Ive searched in the forum post, and still cant be satisfied. I order the book "Ford Small-Block Engine Parts Interchange", and im waiting for it. Im also sure this question have been asked hundred times before.

I own a 1973 2V engine, and i want to move to 4V. I know i need to change heads, intake & exhaust manifold and of course the carburetor.

Following this, i bought 1970 heads DOAE-N, and D0AE-9425-L intake manifold. (still need to find the exhaust and carbs)

Now my questions is, what about the pistons & the cam ? Are they exactly the same for 1970-1973 ?

Also, is there anything else i forgot to take in consideration ? I want factory parts, not a build with aftermarket to gain power.

Is there a place where i can get all the P/N from the 1970 and the 1973 engines ?

im still a newbie, just bought the car in september so im learning.

Thanks !

Click to expand...