Cracked 351 Cleveland Heads

Hi everyone,

I have a 1972 Ford Mustang with a 351 Cleveland 2 valve engine. I recently discovered that both of the heads have a hairline crack in them that need to get welded. I have also been told to look into aluminum heads instead because the cast irons are notorious for cracks. I plan to put an Edlebrock 650cfm 4 barrel carburetor and performer intake manifold on my engine when I put it back together. Do you guys recommend going with the aluminum’s because they will be more reliable in the future? Is this going to be to much power for the stock engine block, pistons, crankshaft and transmission (mine is an FMX automatic transmission)? Taking apart my engine has been unknown territory for me and i’m learning along the way. The last thing i want is to make a fatal mistake. So I’d appreciate all the help I can get please! 

Being only 2V heads I would replace them. If your not doing a complete rebuild get some edlebrocks to match your combustin chamber. It would not be that hard to find some other cast iron 2 V heads and rebuild them.

BTW 2v means two barrel carb, not two valves. The V stands for venturi.

bigfoot72,

What is your budget allow for? Aluminum is not cheap!

Aussie Ford 351 Cleveland cylinder heads 2V Closed Chamber 351C Australian Aus

https://www.ebay.com/itm/Aussie-Ford-351-Cleveland-cylinder-heads-2V-Closed-Chamber-351C-Australian-Aus-/273194526472

Its hard to see on the pict if its a crack caused by stress. Loads of 351c cast heads/blocks are having these and handle the power without probs.

Cast made in Mexico were notorious for getting the palm of best scary looking cracks.

May be you could let them inspected by specialists. Considering the cost of new heads, might be worth it.

bigfoot72,

What is your budget allow for? Aluminum is not cheap!

Aussie Ford 351 Cleveland cylinder heads 2V Closed Chamber 351C Australian Aus

https://www.ebay.com/itm/Aussie-Ford-351-Cleveland-cylinder-heads-2V-Closed-Chamber-351C-Australian-Aus-/273194526472

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About $2k. What is the benefit of Australian heads?

bigfoot72,

What is your budget allow for? Aluminum is not cheap!

Aussie Ford 351 Cleveland cylinder heads 2V Closed Chamber 351C Australian Aus

https://www.ebay.com/itm/Aussie-Ford-351-Cleveland-cylinder-heads-2V-Closed-Chamber-351C-Australian-Aus-/273194526472

Click to expand...

About $2k. What is the benefit of Australian heads?

Click to expand...

Hello Bigfoot,

You have the ports of the 2v heads and the quenched chambers of the 4V heads. It may be better to find a set of modern aluminum heads due to their better flow.

If you're not looking for big horsepower your original heads are fine but will depend on cost to rebuild yours vs a set of Edelbrock alloy heads

At a minimum you would want to replace the valves with one piece collet type and if going with a better camshaft new valve springs

By the time you get your original heads totally rebuilt and welded it might be a better proposition to get alloys.

The Aussie 351 2V CC heads are actually only used on our 302C not the 351. I ended up getting my 302 2V heads rebuilt with extensive CNC porting and other mods which ended up costing more than originally thought so perhaps the CHI 3V would have been a better choice but too late now

Probably best to get a quote to rebuild and weld your heads first then weigh up the options

There is no reason in the world to put money into welding factory iron 2V heads. If the budget doesn't allow for aluminum now, find a pair of good used 2V heads. They are a dime a dozen. If you were closer I would give you the pair I have because I literally can't give them away.

I have a pair I can't give away either LOL

Cleveland heads are cheap. Just make sure you are getting Cleveland heads, not 351M.

There is no reason in the world to put money into welding factory iron 2V heads. If the budget doesn't allow for aluminum now, find a pair of good used 2V heads. They are a dime a dozen. If you were closer I would give you the pair I have because I literally can't give them away

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Are there any cracks in the one you have?

I can tell you one thing,....and this comes from everyday experience for 28 years now,...there's not a damn thing wrong with running the "small valve" 2v open chamber heads on the street. Valve size-wise....the "small" valve heads have valves that compare in size with Chevy's over-emphasized 2.02/ 1.600 "fuelie' valves. Seriously, on the street, there's really no need to go bigger on a 351, and the open chambers unshroud the valves. I drive my 351c 2v EVERYDAY on pump gas, to and from work, everywhere. I TOW my skiboat and dragboats with the Mach 1 and have no problems power-wise or pinging-wise or overheating. It just does it all.

So if you are going to race your car, or, you just want to brag about closed chambers or 4v heads ( which have WAY too big of ports and valves for normal street driving ) then go right ahead and change your heads. You will notice that most aftermarket street aluminum heads have ports smaller than the 4v's, closer to the 2v's.

The 2v castings are plentiful and you should have no problems acquiring another set of cores to work up, and compression ratio makes more sense with today's low-octane gas.

Just my .02 cents, ….

I can tell you one thing,....and this comes from everyday experience for 28 years now,...there's not a damn thing wrong with running the "small valve" 2v open chamber heads on the street. Valve size-wise....the "small" valve heads have valves that compare in size with Chevy's over-emphasized 2.02/ 1.600 "fuelie' valves. Seriously, on the street, there's really no need to go bigger on a 351, and the open chambers unshroud the valves. I drive my 351c 2v EVERYDAY on pump gas, to and from work, everywhere. I TOW my skiboat and dragboats with the Mach 1 and have no problems power-wise or pinging-wise or overheating. It just does it all.

So if you are going to race your car, or, you just want to brag about closed chambers or 4v heads ( which have WAY too big of ports and valves for normal street driving ) then go right ahead and change your heads. You will notice that most aftermarket street aluminum heads have ports smaller than the 4v's, closer to the 2v's.

The 2v castings are plentiful and you should have no problems acquiring another set of cores to work up, and compression ratio makes more sense with today's low-octane gas.

    Just my .02 cents, ….

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Thanks man! I don’t plan on racing my car really, I just want something that can take the power from an Edelbrock 650cfm 4 barrel carburetor w/ performance intake manifold while not blowing up on the street haha. So should i go aluminum then or just weld the current cast irons? Welding is cheaper but I know aluminum is more reliable, right?

Bigfoot,

It's really a very pragmatic question of money , I think. I know , at the engine shop that I work at, we get $100 per hour labor rate. I'm not sure , as I sit here just what the cost of "pinning " cracks per inch, plus the cost of the pins, would be, ( and I don't think in your case welding is the direction most shops would go ), but it seems it would not be cost effective to repair your cracked heads over replacing them with good cores. Even if the labor charge was low, you'd still end up with a repaired part , but seeing as that the 2v heads are plentiful, I would recommend replacing the castings if you stay with cast iron. Aluminum heads are much more expensive, so it's not an apples-to-apples question. Most will come with heavier springs which you may not require, and most aluminum heads will use guide plates and rocker studs....so add the cost of hardened pushrods and a completely new set of aftermarket rockers to your cylinder head swap. If you use poly-locks to hold the rockers down , you're going to toss your stock valve covers away and purchase new taller aluminum ones, oh...and likely breathers to fit them too. Now, your spark plug wires may not be long enough to adequately go over the covers. Suddenly those aluminum heads got much more expensive than you thought! The rocker geometry may also change slightly with different aluminum heads, and cause a pushrod length change and should be checked always when swapping heads, regardless of what the advertiser claims. Its simply good engine building. As the head engine assembler at our shop, I try to help the customer understand their engine's requirements. Just as when running an engine on the dyno for tuning purposes, the tech understands the concept of " giving the engine what it wants, NOT what you want to give it" for it to run it's best. If a racing grind of over .500" or more than 230 degrees at .050 duration is going to be used in your engine, then the aluminum heads better breathing potential may be what is NEEDED to utilize the new cam's requirements, but for a stock 2v or 4v cam ( they're different grinds, stock ), or a mild grind cam , the factory heads will do the job. You could go further and enhance the iron heads breathing with dual exhausts, headers, if you feel the need, along with your aftermarket 4v intake and carb, but that's for you to combine the costs, and compare . With my own Mach 1, even with 3.50s in the rear and a shift-kitted trans that really gets with it, if I tromp the pedal, even with a passing gear shift, it will upshift before 5000 rpm and I'm hauling freight at that point. If you're not building a race car, you shouldn't see rpm over 5000 either, realisticly.

...4v heads ( which have WAY too big of ports and valves for normal street driving )

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No they do not.

and who want's to be normal anyway?

and who want's to be normal anyway?

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Certainly not you lollerz

Barnett 468,

Yes ,...…..the Factory 4v heads ARE too big for the street, and there's lots of proof, in almost every aftermarket head made for the Cleveland, and in any good head shop's flow bench and porting room. Back in the sixties and seventies head porters just hogged the ports out to whatever maximum shape they could, at the same time, there wasn't any available knowledge regarding flow along the port roof, or the port floor. Flow benches today, don't pull any punches, and 4v headed Cleveland owners are getting more power by restricting the 4v's ports. I don't make this stuff up, and I have nothing to gain by bullshitting anyone here, or at work.

Just to feed anyone's interest here, I am attaching a couple of pages from an information sheet from another company, and I am in no way affiliated with them, however their info reinforces what I've said here.