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PostPosted: Wed Oct 09, 2019 2:49 pm 
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I have a high miles Cleveland in a 71 mach1.

It has one 4V head with a dot, and one without one. I've never seen that before. Has anyone else?

It's a high miles car and the engine is uniformly grungy enough that it doesn't look like it's been cracked open, but who knows, the car's 48 years old.


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PostPosted: Wed Oct 09, 2019 7:08 pm 
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All the 4V heads that passed through my hands were "4-Dot" OC and just "4" CC, so that wouldn't make sense from the factory unless there was something in the "dot" in the mould and the dot didn't get cast. Or the heads have different chambers possibly a replacement that was ordered incorrectly. See if the plugs look different side to side (heat/burn not blowby) and do a compression test side to side as it might have 1-OC and 1-CC head.

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PostPosted: Thu Oct 10, 2019 12:37 pm 
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Dot has no meaning. If it does, it might be to ID a Ford casting line, but it sure doesn't indicate the type of head. Similar with 2V heads - mostly before the 351M they came with a "2". Sometime after 73 or around 75 that was the only head, so they dropped the number. I have a 71 2V OC head with no number. It's exactly the same and the other 71 hear with a 2. Can't remember which one now because I ground the 2 off so they match.

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PostPosted: Thu Oct 10, 2019 9:10 pm 
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Umm, no so from my experience, every set of 4V heads I have seen were dot or no dot matched to the chamber and the number of sets that passed through my hands is in the double digits (that would be a huge coincidence). They only used the 4V until 74 and the dot has nothing to do with a 2V or a 351M-400 ,as I recall there were only OC heads in these varieties in North America, the only 2V CC heads were Australian. Seems like the only reason they numbered the only 2V heads was for easy identification from the outside once installed. This may be a fluke but I would bet the real anomaly would be the set that doesn't fit this.

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PostPosted: Fri Oct 11, 2019 9:39 am 
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We've hashed this out over the last 20 years - feel free to study the list

http://www.351c.net/archive/parts/cleve ... ate-codes/

Sample - CC = "closed chamber":
D1AE GA 0F17 17-Jun-70 no Dot CC Bill Gallagher
D1AE GA 0F17 17-Jun-70 no Dot CC Carl
D1AE GA 0G13 13-Jul-70 Dot CC Lowell
D1AE GA 0G13 13-Jul-70 Dot CC Lowell
D1ZE CA 0G22 22-Jul-70 Dot CC Kieth

Yes, all US 2V heads are OC. Some numbered, some not. After 1975 the exhaust ports on the 2Vs got modified and are virtually unusable. They -all years - are way prone to cracking around the exhaust valve seat.

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PostPosted: Fri Oct 11, 2019 10:25 am 
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Thanks Chris,
It appears like it is a coincidence, maybe geographical in nature as I never seen a set that didn't fit the model. :oops:

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PostPosted: Fri Oct 11, 2019 6:26 pm 
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Location: Orange County, NC
Falcon67 wrote:
We've hashed this out over the last 20 years - feel free to study the list

http://www.351c.net/archive/parts/cleve ... ate-codes/

Sample - CC = "closed chamber":
D1AE GA 0F17 17-Jun-70 no Dot CC Bill Gallagher
D1AE GA 0F17 17-Jun-70 no Dot CC Carl
D1AE GA 0G13 13-Jul-70 Dot CC Lowell
D1AE GA 0G13 13-Jul-70 Dot CC Lowell
D1ZE CA 0G22 22-Jul-70 Dot CC Kieth

Yes, all US 2V heads are OC. Some numbered, some not. After 1975 the exhaust ports on the 2Vs got modified and are virtually unusable. They -all years - are way prone to cracking around the exhaust valve seat.


At some point they started casting the 2v heads with the letter M cast in them instead of the 2. I have a set from '75, but I ground the M off. They have the shitty exhaust port with the extra material around the guide for the smog crap, but surprisingly after porting they actually flowed a little better than a similarly ported early 2v head.

I am pretty sure all the 4v heads I have gone thru were all matched as far as dot or no dot.


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PostPosted: Sat Oct 12, 2019 12:10 am 
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Thank you, folks. When I shake loose some time to check it I'll update to let you know what I found.


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PostPosted: Thu Oct 17, 2019 9:51 am 
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SBFgrudge wrote:
Thanks Chris,
It appears like it is a coincidence, maybe geographical in nature as I never seen a set that didn't fit the model. :oops:


Ya just never know!

What KV and I are talking about on the 75 up 2V heads - the sharpie line approximates the early heads:

Image

I ported the early 2V heads I have here and the bench said 254 intake @ .550, 200 ex @ .500 They have a low floor on the intake and somewhere between .400 and .500 the air can't make the turn into the pocket and about 30 CFM is lost, after which it slowly recovers. Otherwise the intake figures on mine would have been in the 270 range.

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PostPosted: Thu Oct 17, 2019 10:34 am 
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I ported the M heads I have. I was pretty conservative on the intake side, and they only managed to flow 225 cfm. They peaked at .500 and just flat lined. The exhaust also peaked at .500 and flat lined at 189 cfm. The guy that flowed them, at the time was one of the premier nitro Harley head porters in the country, and he calibrated his bench twice while he flowed them because he thought the numbers should have been better.

However, that was good for 10.40's in the qrtr in my car on alchy with just shy of 11-1 compression and a small-ish off the shelf rolller cam.

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