Linc's 200":2q4a0twk said:
There is a huge amount of wrong information. All 351C Aussie engines used open chanmber, 75 cc 2V heads. All 302C engines used closed chamber 57 cc 2V heads.
Imported 351C 4v heads were always 57 cc, except a few very rare rpo 083 items destined for the fabled 1972 Phase 4 Falcon GT HO.
Here's a rundown.
Aussie V8's got 4-bbl carbs, except for all early 302C's from 1972-1976, and some 351's for LTD's and Fairlanes to 1976. So whwn an Aussie says 4V heads, he may not know that you are thinking 4V big port heads. In NZ, all 302's untill 1979 got 2-bbl carbs, yet the 1979 XC Fairmont was called a 4.9 4V V-8 on the air cleaner. It wasn't a 4V, it was a 2v head with a 4-bbl Carter carb. So there is a lot of general statements whcih are factually incorrect which takes an age to correct. The more we say, the more confusing things get with Ford's Aussie Clevelands!
I used to think that Aussie 2V 302 heads were the bees knees too untill 1990 when I read a Tough 302 and 351's Volume 2, an article by Street Machine Australia. Four engine builders said that in stock form, the 302 closed chamber heads were bad news. Bob Pinnell, Mike Webb, Kevin Bartlett and Steve Walker. In 2004, my thoughts were confirmed when Bill added his comments .
The main reason for the apperent advantage of the more common 2v 302C head is compression. The 57 cc closed chamber head creates more compression than a 75 cc open chamber head, and people think that is power. Compression on a stock Aussie 4-barrel carbed, 2v headed 351 was about 9.2:1 with 75 cc heads, but 10.7:1 with 57 cc 302 heads or the 57 cc 4V heads. However, any of the 57 cc heads are vastly more prone to detonation than the 75 cc head. To the point of being dangerous unless steps are made to reduce advance, increase chanber volume to 64 cc, or unless a 105 octane fuel is used. Even in 1988, a 351 running leaded 96 RON fuel wouldn't switch off when fitted with 302C heads. Bob Matic (Ford Muscle parts and Detomaso owner) said "half the time, you can't turn the things off becasue they run-on (deisel) due to the high compression".
In 1990, I read from 1974 Bathurst 621 mile winner Kevin Bartlett. He said, and I quote
"Avoid closed chamber 2V 302 heads on 351's. They don't carry much compression, and suffer poor incoming flow. On todays fuels, you definately need to avoid the big bang".
Then Bill discussed in Australian Street Machine last year that the 351 4V HO spec (Boss) closed chamber head created incipient detonation which was not heard, and then lead on to major detonation. Since there was no audible lead in to the onset of total detonation with these heads, people assumed the problems with big end bearings was related to the oiling system. Bill and Mick Webb did all the Ford Special Vehicles race engines.Another racer, Johny Goss was adamant the big end bearings moved around a lot. Taken together, it was detonation caused by the closed 57 cc 4V 351C heads. When the factory RPO 83 engine was dyno tested, they opended the quech area out to 62-64cc, lowering the compression, yet they found extra safe power, becasue there was less detonation.
There is a second reason for the delight Aussies have in selling closed chamber 302 2V heads. They out number open chamber 351 heads 5 to one. If you were selling them, you'd sell all the advantages if they were on sold on 425 000 vehciles from 1972 to 1982. We can't even find open chambered 351 C heads these days, but you've got stakes of them!
Last item was that Aussies never made 4V 75 cc heads in any fasion. The total production of true 4V heads per annum from 1970 to 1976 was via American tools, and in 1974, the 4V got an Australian block, and , reputedley, the last 1200 XB GT Falcons got smaller port 4V heads which are rare as hens teeth. All had 2.19" valves, not the 2.25" items of the 302 Boss heads. The amount of GT Falcons sold with 4V Cleveland heads was very small, something like 3000 over four years.
Americans never got 57 cc 2V heads, but there isn't much meat in them, and they only have the little 2.04" valves, and if they are gasflowed, the maximum chamber size is 64 cc's a s the quench area is very thin and theres no room for good pocket blending as there are in the 4V heads.
Sorry fellas. I love Clevelands...could talk for hours.
