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Contributing Sr Motorhead
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Discussion Starter #1
I was over my buddy's the other day and happened to be looking through their pile of engine parts. I was looking at a bunch of their Cleveland 4V heads and learned something!

Remember me telling y'all about the 1/4" round bump next to the '4' on the upper corners of the 4V heads signifying that they were open chamber heads? Well, in that pile of heads were two sets of 'bump-4s' that are closed chamber. There shoots that theory all to heck! Now that's got me thinking what that bump could possible be signifying. :confused:

Grumble....grumble...grumble...and I thought I was a Cleveland know-it-all, grumble...grumble...grumble... :uhoh: :redface:
 

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The round bumps are indicative of closed chamber 1970 heads.

No open chambers have bumps -- nor do 71 closed chamber which are slightly larger CC than 70.

Who said the bumps were open?
 

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Contributing Sr Motorhead
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Discussion Starter #3
bump 4 vs. no bump 4

Until this past weekend, every set of the 'bump-4' heads I've seen have been open chamber. In fact, I have two sets of bump-4s in the garage right now that are open chamber. AlphaCat's small valve bump-4 73 original heads are open chamber have the casting number & date of D3ZE-AA & 2L8, and the spare heads I have from a 72 are also bump-4s with big valves and open chamber are D1ZE-DA & 2C18.

My wife's 70 Mach (a 351C-4V car) has the closed chamber 4V heads and no bump next to the 4. Sorry, I'm not gonna pull her motor apart to see what the casting number & date are.

I have a set of closed chamber 4V heads on BetaCat's engine and they don't have a bump either -- nothing next to the 4. (don't know the casting number or date from these either!)
 

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eh?? what bump? these are closed chamber D0AE heads btw
 

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Re: bump 4 vs. no bump 4

Oops. My bad. My head, the real one, was screwed on backwards.

After seeing the other poster's photo I realized I had it backwards. So I went and looked at my collection of vintage '70 CC heads. All no-bump, as you state. But now my memory is telling me that in '71 they added the bump. They're still CC heads but *larger* than the '70. Beyond that, I do believe the bump remained, even for OC heads.

Were you looking at '71 heads?

Sorry for the corn-fusion.


Cougrrcj said:
Until this past weekend, every set of the 'bump-4' heads I've seen have been open chamber. In fact, I have two sets of bump-4s in the garage right now that are open chamber. AlphaCat's small valve bump-4 73 original heads are open chamber have the casting number & date of D3ZE-AA & 2L8, and the spare heads I have from a 72 are also bump-4s with big valves and open chamber are D1ZE-DA & 2C18.

My wife's 70 Mach (a 351C-4V car) has the closed chamber 4V heads and no bump next to the 4. Sorry, I'm not gonna pull her motor apart to see what the casting number & date are.

I have a set of closed chamber 4V heads on BetaCat's engine and they don't have a bump either -- nothing next to the 4. (don't know the casting number or date from these either!)
 
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