What F'n head do I have? Seriously...

[unclebilly]

OK, I have a 71 FJ40 that i bought from the original owner. The engine is original, it has flat top pistons (I've had the engine apart).
I am going to rebuild the bottom end and happened to get 2 F cylinder heads. They both are similar but appear to be different from mine. Mine has no exhaust manifold bolts at the front or back of the head, these both do. These heads are both F heads. One has pre 71 written on it, the other is freshly rebuilt. The rebuilt head has an oil hole in one of the valve train mounting points, the other does not. What head is the rebuilt head (both have kidney shaped combustion chambers)? Will using this head lower the combustion of my engine?

What are the differences in the various F heads? My valve cover has an original sticker that says 155 HP - could this be why my head is different?

 

[unclebilly]

upon further inspection, my head also only has 2 threaded porst into the cooling jacket (the other heads have 3) and my head has no ports for air injection.

Anu ideas why mine would be different? Will the combustion chambers be the same?

 

[Adventure Teq]

Pics?

 

[65swb45]

Chambers should be the same as your 71. Yes, the newer heads had the extra bolt holes at the ends that the earlier ones didn't.

The third coolant port on the head was for a thermal sensor for the emissions equipment.

The head with the extra hole under the rocker arm stand would most likely be from a '74.

73 and 74 heads had air injection ports.

Run whichever one looks to be in the best condition.

Hth

Mark A.

 

[Mark W]

'68 -'72 F heads have closed chambers (oval shaped). '73-'74 F heads have open chambers (roughly circular). '74 heads have the oil port under the rockerarm pedestal. Some (many) '73s will too.

The '73 and '74 heads are easy to confuse with 2F heads at a glance. I don't have any info on casting numbers in front of me right now, but these numbers will definitively identify the heads. What are they?


Mark...

 

[unclebilly]

Hi guys,

Thanks for responding. The casting numbers are as follows:

The head in my 71 cruiser (stock) 60031,
The rebuilt head (missing one valve) 60051,
The spare head (rebuilt and run) 60050.

I do not have photos of my combustion chambers (the head is still installed) but here are some photos of the head in my cruiser and the head I plan to install:

Will I be taking a hit in compression ratio by switching heads?

 

[unclebilly]

This is the other head:

I hope you have a magnifying glass...

 

[Mark W]

Neither of those heads pictured are heads that you want to run on a '71 F. They have open combustion chambers. You will definitely take a hit to your compression. Loss of power for sure.


Mark...

 

[Dianna]

I'm proud of you guys, I really thought this thread would head off in another direction!

 

[unclebilly]

Great - thanks. Anyone want a rebuilt late F head?

 

[Degnol]

Mark W....

How much does it raise compression to run a '74 F head on say a '77 2F with domed pistons?

Thanks,

Ed

 

[Mark W]

I need to measure a couple of combustion chambers one of these days to quantify it with confidence. But for now I'd say abouy your compresion would be about 9:1 with a '73-'74 F head on a domed piston 2F shortblock.


Mark...

 

[Mace]

That sounds like an improvement to me

 

[Degnol]

I need to measure a couple of combustion chambers one of these days to quantify it with confidence. But for now I'd say abouy your compresion would be about 9:1 with a '73-'74 F head on a domed piston 2F shortblock.


Mark...

Would that still run on 87 octane?


Ed

 

[unclebilly]

This head has new seats (both intake and exhaust and new guides).

 

[unclebilly]

I still have these apare heads and am motivated to sell them.

$300 OBO for the 60051 head and $175 OBO for the 60050 head.

Offered here first, Ebay next week...

ssherman(at)me.uvic.ca if interested.

 

[Ziffdaddy]

Would that still run on 87 octane?


Ed

I wouldn't mind finding that out either? With that bump in compression, would there be any drawbacks?

 

[unclebilly]

9:1 compression would be just fine with 87 octane. This is normal CR for late 80's / early 90s vehicles.

With higher compression, you get more HP and better gas mileage because the efficiency of the engine is better. The 7.8:1 compression these things came with is pretty doggish but was done so they could run on gas anywhere in the world.

 

[Ziffdaddy]

Sounds good.....sorry for the highjack, but what's the best way to bump the compression up on a 74' F engine? Different pistons, shave the head? If it's not a fortune to do, it seems like a great way to get a better running stocker. Any issues with doing that?

-Steve

 

[unclebilly]

Sounds good.....sorry for the highjack, but what's the best way to bump the compression up on a 74' F engine? Different pistons, shave the head? If it's not a fortune to do, it seems like a great way to get a better running stocker. Any issues with doing that?

-Steve

On a 74, you may be able to get higher compression pistons or install the pre 73 head provided it will clear your domed pistons. The combustion chambers on my 71 head cc'd at 80 cubic centimeters each yesterday which gives 8:1 compression ignoring the head gasket.

You could also shave your head.