Since I got my car I have spent a lot of free time freeing up the engine that sat for over 15 years.

My plan was to get it running and then slowly freshen up the car one system at a time instead of doing the complete teardown and not driving the car for a year or more.

I got it moving, then I had to deal with some stuck valves. Then I did a compression test with some cylinders being great and others being awful.

I did the rope in the cylinder trick, removed the springs, and spun the intake valves back and forth in their seats with a right angle drill.

When I was done, all but two of the cylinders were 155-165 psi on compression (dry), which I thought was pretty impressive under the circumstances. I was attempting a do-over on one of the low cylinders when I dropped one of the valve locks into the nether regions of my engine compartment (not the engine thankfully). I can't find it. I have run a magnet everywhere and blown compressed air all around as well. It must have fallen into a frame rail, be sitting in part of the engine mount, or I inadvertently kicked it across the garage. I even dropped the other half on purpose a bunch of times to try and see where it might have gone.

In searching for a replacement valve lock (located one that I can pick up in the morning) I discovered many tales of woe involving the stock valves.

My dad has 2 spare Cleveland blocks in his garage that came out of Mustangs headed for the crusher so I was willing to stick to my plan above and just run what I have until I got fairly strong evidence this morning that this is probably the original block. I don't have either motor or body tag, but apparently this car and others made around the same time never had them. My engine is stamped with a number that is 5 away from the number on a car that is 6 away from my VIN.

If I am keeping it under 6000 rpm and just driving back and forth to cars and coffee type stuff am I risking catastrophic block damage with those valves?

If it matters, I think I have closed chamber heads - 4 on the corner with the dot but the date code shows they were made in December of 1970.
Original Post
The valve heads are brittle. Clamp a normal steel valve in a vise by the stem, grab the valve head with a wrench that has some leverage (large channel locks, pipe wrench, etc) and you can bend the stem. Do the same with a Cleveland valve and the valve head snaps off.

They develop cracks below the section where the valve head is welded to the stem. The cracks start-off very small, microscopic, and grow larger over time. The cracks lead to the valve head breaking completely off the stem and bouncing around inside the cylinder while the engine is running. Often putting holes in pistons, cylinder heads, and/or cylinder walls.

The question is what starts them cracking? For that I have no answer. Now the Cleveland is not the only gasoline engine that has had this problem, others have been plagued by this same malady. I've read all sorts of theories about what starts them cracking ... constituents in fuel for example ... but there is nothing definitive that I'm aware of.

I remember walking into a wrecking yard circa 1974, and inside the office they had not one but two Cleveland engines sitting side by side in the corner. Both engines had one head removed, exposing a cylinder with damage from a broken valve head. Both engines had come in within the last month. They were almost new, no more than 2 or 3 years old. On the other hand I know several guys who put 200,000 miles on a Cleveland without a problem. There are Panteras still today, like yours, equipped with the OEM valves. I know one guy who had a valve head fall off the stem while his Pantera was warming up, idling, in the driveway. I also know guys who raced with the stock valves. RPM doesn't seem to have anything to do with valve failure.

Nobody can guarantee you that out of the 16 valves in your car's engine, one of them won't fail. But nobody can predict if and when they will fail either. A failure is usually quite expensive to repair as at least one of the castings will end-up with a hole or crack in it. Each day you start an engine equipped with the OEM valves is a toss of the dice. That's really the best answer I can give you.

The only sure way to avoid failure is to replace the valves. You don't have to install an expensive set of stainless valves, a good quality set of steel replacements designed for 4 bead locks will suffice for applications up to 6200 rpm rev limits, at a much lower cost than the stainless valves. The last time I checked Speed Pro (Sealed Power) had the 2.04 intake valve and the 1.65 & 1.71 exhaust valves in low cost steel replacements, but not the 2.19 intake valve. But I haven't done an exhaustive search.

351-C valve breakage has to do with metallurgy and that is not visually ID-able. The safest thing is to replace the stock valves with one-piece valves. Being one piece, they will NOT be 45-yr old OEM (which is good) and will not have been welded. Warning: cheap stainless steel valves can also be made by welding a head and stem together, and whether the cheap alloy or the welding is to blame for breakage is irrelevant. YOU are the one that has to sweep up your engine and start over. The offshore valve makers will not care either. Good luck- you've been warned.
So if someone (OK, me...) was planning to replace the stock original valves with good steel or stainless-steel valves, what specific valves (make/part numbers?) would you recommend for an original '71 high-compression Cleveland?

What's the cost/benefit differential between stainless and regular steel?

stock replacement valve lengths are listed as;


MELLING V1172 4 groove, Head Dia 2.19", 5.234" OAL

MELLING V1174 1 groove, Head Dia 2.19", 5.234" OAL

SEALED POWER V2075 4 groove, 2.04" Head Dia, 5.231" OAL


SEALED POWER V1879 Head Dia 1.71", 5.05" OAL

SEALED POWER V2030 4 groove, Head Dia 1.65", 5.05" OAL


Ferrea 5000 series are popular 1 piece single groove SS upgrade valves

F5037, Head Dia 2.19", 5.30" OAL

F5045, Head Dia 1.71", 5.06" OAL

size variations, 6000 & Competition series also


Si Valves came up the other day too,

Alex's Parts has a good reputation on the Old Cleveland Forum


FWIW it may be a good idea to let the shop take a look & see what you're working with before buying anything. you could have or need oversized guides and valve stems, and/or you may want an oversized valve head diameter to avoid having to replace seats. there's all kinds of repair tricks available. then you can source proper springs, retainers and locks the first time or better yet let the shop order the smalls in case they need to be returned / swapped for a different part number. it can take some jumbling on the bench to get all the clearances right, let the man work LOL. 'homers' get into all sorts of twists & fits trying to beat the learning curve

Originally posted by Mark Charlton:

... What's the cost/benefit differential between stainless and regular steel ...

Everybody wants guide lines. So for folks who need benchmarks, guidelines, and limits I tell them 400 horsepower and/or a 6200 rpm rev limit. If you want to have more horsepower or a higher rev limit you'll need to spend the money on ALL the parts needed for higher rpm.

If your Panteras engine is to be rev-limited to 6200 rpm it doesn't need stainless valves. Sealed Power has 2.041/1.655 steel valves (p.n. V-2075 and p.n. V-2030) for $136 USD per set. Sealed Power has no current listing for the steel 4V intake valve, I've found steel 2.19 intake valves to be currently hard to find amongst my normal sources. The Melling V1172 listed by 4V&Proud would be a good recommendation if you can find it. But the 1.710 steel exhaust valves, Sealed Power p.n. V-1879, are available for $128 USD per set of 8.

If your Panteras engine is to be rev-limited at higher rpm it DOES need stainless valves because (1) they are lighter weight and (2) their stems are designed for tight fitting single key locks. The valves are just one set of several parts that must be upgraded to operate the engine reliably at higher rpm.

But those are only two of the reasons for choosing stainless valves. Stainless intake valves (3) are available as “Racing” valves which are equipped with valve heads which increase air flow and are lighter than standard stainless valves. If the cylinder heads are equipped with 2.04 intake valves then (4) stainless valves make it possible to substitute 2.12 diameter valves in place of the 2.04 diameter intake valves. Manley 2.125/1.655 stainless steel valves (p.n. 11344-8 and 11807-8) are $438 USD per set; Manley 2.19/1.71 stainless steel valves (p.n. 11872-8 and 11805-8) are $390 USD per set. All these prices are from Summit Racing.
Gentlemen, thank you very much for your detailed and clear responses. I don’t push my stock 22,000 mile engine much, but really don’t like the thought of it grenading itself on a diet of valves. Since I’m contemplating pulling it out of the car to deal with replacing oil seals, valve guide seals and the timing assembly, it seems it might be worth doing the valves as well. I appreciate your input and suggestions.

I bought at Realstreet Performance:

- Intake: 8 Manley 11872 at $139.20

- Exhaust: 8 Ferrea 6000 F6124 at $153.92 instead of $238 for the Manley 11805 which weighs the same weight (108 gr).

The Ferrea 6000 for intake are more expensive (155/139.2 $) and heavier (145/129gr) than the Manley.

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