Mercury Cougar Owners banner

1 - 4 of 4 Posts

·
Contributing Sr Motorhead
Joined
·
5,470 Posts
73 351C-2V and -4V used the same D2AE-CA block casting, but the 4V was drilled for four-bolt maincaps.

Yes, you can put 4V heads on a 2V, but there really isn't all that much gain in doing so. 72-74 4V heads have open chambers for low compression. 70-71 4V heads are closed chamber or 'quench' heads for higher compression. All US production 2V heads are open chamber. 4Vs use bigger intake and exhaust ports, so if you're putting a four-barrel intake on the motor, make sure it is for the 4V heads or there is really no value in using the 4V heads. Really, the ports and valves of a 2V are plenty for a hot street engine provided you pick a good camshaft.

70-74 2V heads - open chamber, 2.06/1.66 valves
70-71 4V heads - closed chamber, 2.19/1.71 valves
72 4V heads - open chamber, 2.19/1.71 valves
73-74 4V heads - open chamber, 2.06/1.66 valves.

Then there's the Australian 2V head -- closed chamber and 2.06/1.66 valves... These appear from time to time on eBay... imported from junkyard Australian cars, so most will need to be refurbished.

The casting number on Cleveland heads is found on the underside of an intake runner, only visible if the intake is removed and you use a mirror!!!
 

·
Premium Member
Joined
·
13,577 Posts
Interesting on the 73-74 heads Milo, 2V valves, 4V ports, I was unaware of that. Just wanted to add that 4V heads usually have "4" cast into the upper corners by the valve cover surface, 2V heads usually have "2".
 

·
Contributing Sr Motorhead
Joined
·
5,470 Posts
Interesting on the 73-74 heads Milo, 2V valves, 4V ports, I was unaware of that. Just wanted to add that 4V heads usually have "4" cast into the upper corners by the valve cover surface, 2V heads usally have "2".
The small valve 4V heads required a different casting from the early big valve heads (bowl area under the valves needs to be smaller... This is why the 73-4s use the D3ZE-AA casting.
 
1 - 4 of 4 Posts
Top