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[cpyahoo]

Found this thumbing through a small-block engine rebuild book.  They have listed, from 1983-1986, cop-specific cylinder heads.  They list a casting number of 4323345.  They supposedly had 1.88 intake valves and 1.60 exhaust valves.  This is what REALLY caught my attention!  Combustion chamber size... 75.1 cc!  Anyone got any info on these heads?  And if they are real... anyone know where any are at?

[Dippy.org]

[spike]

look up what it says for 360 heads, as all the cop engines were 318s with 360 heads

[79dodge4ever]

Found this thumbing through a small-block engine rebuild book.  They have listed, from 1983-1986, cop-specific cylinder heads.  They list a casting number of 4323345.  They supposedly had 1.88 intake valves and 1.60 exhaust valves.  This is what REALLY caught my attention!  Combustion chamber size... 75.1 cc!  Anyone got any info on these heads?  And if they are real... anyone know where any are at?

the smaller the combustion chamber the higher the compersion, 75 cc really isn't that great compared to older heads 68-70 are the best years it seems and the best is probably either magnum heads or 340

[81SportCoupe]

those late-80's police engines had those heads, but the comp ratio was 8:1 or 8.5:1, really not great. even though the have the desirable valves, they arent great on a 318. You cannot mill enough off to shrink the compression ration to a good level for a short stroke engine like a 318 (been down that road) but the good news is they are great heads for a 360, next best 80's 360 heads to the 308 castings (with the same 1.88/1.60 valves, but raised intake ports)

[cpyahoo]

Interesting!  I can't make heads or tails of why they would put a head on an engine with such an application (police or HP) with that big of a combustion chamber.  Thanks for the info dump guys!

[270SE]

Mags are the best for flat-top motors, 340/360 are the best for dome motors. ('68-'71 340s, '65-'67 273-4s) That's just meaning stock valve no work done motors. The Mags are down on the ints, up on the exhs, and the compression is bumped up by them and the chamber more efficient. The 340/360 heads bleed off compression and flow better on the int side.


The reason for it is the standard '73-'84 head was trash. The head was too small. You may be aware that the cop cars then as well as other cars were not exceptionally quick, however sometimes they could be fast. Extended speed runs in the vicinity of 3500-4000 RPM could see a decent benefit in power at the cost of torque by using the better-flowing larger port/chamber heads with a large 4bbl carb. The same idea was used for 318s towing until the '85 model year.


The 308s have the swirl ports, unleaded seats and are set up for roller cams, those are their main strengths.

[81SportCoupe]

the 302 small valve heads have the swirl ports, but the 308 large valve have a different chamber design... are you sure they are swirl port? The ones i have are open chamber, and i am not sure if they are swirl or not...
the reason the factory used the huge combustion chamber heads is for 2 primary reasons
---they already had the casting for the 360, which needed the large chamber to pass emissions (mostly nox) emissions, and everyone here knows that if chrysler could use a part somewhere else without redesigning it (to save money and time) they would!
---also, any true v-8 performance in the 80s (from the factory) was near impossible before efi because of the crude emissions systems, any increase in compression and aggressive timing would send emissions too high for a production car. so, the high combustion chamber cc's kept emissions under control. by keeping combustion temps low, nox production stays low
i hope thats the answer you're looking for...

[270SE]

the 302 small valve heads have the swirl ports, but the 308 large valve have a different chamber design... are you sure they are swirl port? The ones i have are open chamber, and i am not sure if they are swirl or not...
the reason the factory used the huge combustion chamber heads is for 2 primary reasons
---they already had the casting for the 360, which needed the large chamber to pass emissions (mostly nox) emissions, and everyone here knows that if chrysler could use a part somewhere else without redesigning it (to save money and time) they would!
---also, any true v-8 performance in the 80s (from the factory) was near impossible before efi because of the crude emissions systems, any increase in compression and aggressive timing would send emissions too high for a production car. so, the high combustion chamber cc's kept emissions under control. by keeping combustion temps low, nox production stays low
i hope thats the answer you're looking for...

Swirl ports and closed chambers are two different things.

[8D5 Gran Fury]

I believe the 302 are swirl ports, while the 308's are a "fast-burn" style.

[cbodymoparfan]

I believe the 302 are swirl ports, while the 308's are a "fast-burn" style.

That sounds about right. The fast burn heads were in the 2 Bbl police cars and were producing 9.0 cr  IIRC.

[270SE]

That sounds about right. The fast burn heads were in the 2 Bbl police cars and were producing 9.0 cr  IIRC.

What they were rated for which may have been somewhat optomistic. Closed chambers, but the pistons were also changed to up CR.

[80 Lebaron Coupe]

Anyone ever tried putting the late 80's closed chamber fuel injected heads on a early 80's block to increase the comp ratio?

[270SE]

Anyone ever tried putting the late 80's closed chamber fuel injected heads on a early 80's block to increase the comp ratio?

Yes, lots of people. It'll work fine, you just have to use the old motor's valvetrain.

It won't increase it too much but the flow marginally better. If it runs alright, I wouldn't bother.