What are the differences or the Pros and Cons of old (1966) vs. new (1980's -1990's)?

 

I have an 86 f150 with a carter tps carb. When calling around looking for donor engines, I always get asked if the A.I.R. is in the head or exhaust. When I tell them exhaust they say they don't have one. Is the head I have rare? Can it be replaced with a head from an older engine?

 

All carbed heads are basically the same in terms of port and combustion chamber design. There are minor differences in rocker arm / pushrod mounting and design.
Early heads have slots to guide the pushrods. Later heads have large pushrod clearance holes, depending on the style of rocker arm employed. And the above mentioned A.I.R. differences.

EFI equipped engines used a redesigned head with different combustion chamber shape which gave it desireable fast burn properties. It also had two additional attachment points for the cast dual exhaust manifold attachment. Engines with these heads require a different spark schedule than carbed engines.

Pros of the carbed head: More potential to make power due to less valve shrouding in the chamber.
Cons of the carbed head: Requires more spark advance for optimum performance and is more prone to detonation.

Pros of the EFI head: More efficient, better choice for max mileage.
Cons of the EFI head: The performance potential is limited due to the shrouded intake valve. If you try to remove the shrouding you will quickly lose the fast burn qualities of the combustion chamber which make it more efficient and also the engine will need more spark advance from the computer. I've also heard stories that they are prone to cracking around the valves, especially if the engine has been overheated.

In general replace a carbed head with another carbed head; replace an EFI head with another EFI head.

 

I think a couple of variations of the carbed head should be noted: There is the head with pedestal mount rockers, and the later 80's head with bolt down rockers. On the later type head Ford also changed the valve lengths. I have read on the forum that it is possible to convert the bolt down type to pedestal mount rockers.

Older type carbed heads: Ford made some of these with the fast burn ridges in the combustion chamber.

 

I was thinking about getting a different head and getting it built before rebuilding the rest f the engine. I don' t have any smog currently, but if I go to the a.i.r. in the head version won't I have to put the different a.i.r. system on? Can I just plug the holes in the head somehow?

 

Thanks Gentlemen, that is exactly the info I was looking for.

 

You can plug the holes with bolts; can't remember off the top of my head what thread they are.

 

To complicate matters more, a 240 head interchanges with a 300 head. The 240 head has smaller combustion chambers (68cc vs. 76cc on the carbed 300, IIRC) but is otherwise pretty much identical.

The oldest heads may not have any of the smog casting in the exhaust. I've got a '66 240 head and the roof of the exhaust port is smooth, no hump for the EGR like you see on the later model heads. Not sure if 300 heads ever came without the funky humps/dips in the exhaust port. If you're going for max flow from a 300/240 head not having to grind down that cursed EGR hump is nice.

 

The reason I put the question out there was this:

I have a 300 with a 240 head. When I pulled the head I found the exhaust valave in the no.1 Cylinder was cracked. (see photo) It needs a complete rebuild which at this time, the $600 is not in budget. What I can do is get a head from PnP for les than $50 and slap it on and it will already have hardened seats for unleaded gas. The bottom end is getting new pistons, rings and bearings. I am moving to Australia next summer and need to tie up this project (along with 2 other cars) before I go. After I get settled I will bring the truck and my other project over with all my other stuff. The truck must be in stock form to enter the country as a classic. Once it's down and registered I can do my modifications to it which includes swapping in a 4.6L DOHC Cobra engine. Thanks for all the info on the head differences. I feel confident enough with a late model head to go get one fro PnP now. The 300 will eventually go in another truck and I will do it up right at that time.

 

Correct.

I have a '68 and a '76 300 head and neither has the hump.

 

FWIW, every 240/300 head had factory hardened seats. So no worries there, mate.

 

I may be mistaken, but I'm not sure that is correct. CMIIW, but 240 and 300 heads made prior to unleaded gas, don't they require hardened exhaust seats?

Also, the other member stated that neither 240 nor 300 had the bumps/divots in the exhaust port (runner). I have read that that divot is a common issue for porting of 300 heads. (Not certain about 240 heads.) My 300 head has them, and I have seen photos of other heads with them on Ford6 forum. Is there something I have misunderstood?

 

Yeah, I was just gonna say... why would a 1966 engine, for example, have hardened seats?

I can give you photographic evidence if you need, but neither my 240 or 300 heads have these EGR bumps. I didn't even know they were a thing until you guys started talking about them.

 

Trozei--If you say your head(s) don't have it I believe you. I'm merely interested to learn that some heads don't have it. Because mine does, and b/c I had read about others dealing with them during porting, I assumed all 300 heads had it. I'm always interested to learn.

 

No wonder I can't find a 300 Six donor...you guys got em' all.

I've been trying to trade my 460 In my 77 f-150 for a 300 Six for soooo loooong now.

I'm afraid if it don't happen soon, all the 300's will be recycled!