need help identifying heads

jerthemost

Member
Sep 9, 2012
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I have a 68 mustang stock 289, auto tranny, came with 2v. I installed an edelbrock 2121 performer 289 intake with an edelbrock 1403 500 cfm 4v. I used all edelbrock recommended parts, gaskets, bolts, sealers, gascasench etc. put ultra black rtv around water ports on both sides of gaskets. gaskets are not slipping because gascacinch holds very well. also used rtv across ends instead of gaskets there as recomended by edelbrock. no leaks on ends.

Have done install 4 times and leaking water into oil all 4 times. No leaking with old intake. Cast code on old intake says it is from a ’68. Noticed that original intake covered apprx ¼ to 5/16 more on sides where intake meets heads. Didn’t think much about it at first until kept having contamination of oil. Upon closer inspection actually found tiny bit of top of exhaust port exposed. Was hidden behind gasket overlap. So based on this I assume intake is maybe not the right one for this engine or at least with these heads. Although, other than coverage as just described, the new intake appears to fit perfectly.

Also my mechanic brought up interesting point, this engine requires small spark plugs although book says plugs should be the large ones. So based on this I investigated heads. I assume heads must not be original since they use small plugs. I removed a valve cover to look for info on head. I only found 2 markings. One appears to be “ILII” and another that is a letter “C” and letter “P” in a circle. I did not find 289 or 302 in the head. I have attached a drawing describing everything.

The heads have valves in-line not offset and 6 bolt valve covers. They appear to be 289 or 302 heads from photos I saw. Or could they be 351w heads? Can’t find photo of those. If they are 351w heads would that explain why intake not high enough? And would intake height cause water leak?

This is a real mystery. I cannot drive my car and it has cost me double what the upgrade should have cost. If I can’t figure this out my only choice will be to go back to old 2v and lose at least $1200 on this deal. I don’t even want to think about that option. I suppose I could have it towed to another garage but I just don’t trust most average mechanics to have the tech knowledge to fix something out of the ordinary. The guys in this forum do seem to have the knowledge so I am appealing to you all for help and suggestions. All help will be greatly appreciated.

Oh, also any ideas on how to remove stuck intake? This time end seal rtv seems to have it really stuck down. I have tried prying it up but will not budge and don’t want to break it.
 

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Do you have casting numbers off of your original intake? Or even your engine block? The casting numbers for the engine block is down by the starter. I think there should also be a 289, 302, or 351 cast in the lifter valley, you should be able to see once the intake is off.
 
cast code on old intake is C8AE 9425-B A
CAN'T get to engine code right now, too wet and cold outside. could the code in the heads that i think is lLll really be upside down and be 71 instead indicating heads made in 71? someone showed pic of 351 w head and water port is L shaped. mine are rectangular. so i assume mine are 289 or 302 from maybe a later year like 71. i believe ford went to small plugs in 70, right?

so could these heads and old intake be milled? if so how can i tell? wouldn't that explain my new intake leaking? or not? i don't really understand milling, which surfaces are milled on intake and heads?