Factory Small Block Heads

[318willrun]

Here is my list, in order, to the best performing factory small block heads as cast from the factory (273, 318, 340, 360).

1. Magnum heads. Speaking strictly of how they perform from the factory, I think these are my #1.
2. X head. Only put this ahead of the 308 because of the 2.02
3. 308 head. Gives up some valve size to the X head on intake side, but I like the exhaust port
4. J head. Really, this head works as well as a X head in my opinion, but most came with 1.88 intakes, thus it falls to #4
5. Smog 360 head, pick the casting. Yep, I put this ahead of the closed chamber 318 heads.
6. 318 heads (non magnum) - and pick your poison. I guess the 920 head may lead the way in performance. The 675 casting is not a bad choice either among the 318 heads. Many go bananas over the 302-swirl port closed chamber. I guess stacked up against the other 318 heads, ok. I think from the factory the 675 flows more.

 

[318willrun]

My preference to run on my engine may vary from the list above. I like rocker shafts. Some of the castings above are notorious for cracking. I like hardened seats. I like LA bolt pattern

 

[TT5.9mag]

So magnum heads, with Hughes shaft paired rockers, drilled for LA intakes. The perfect factory head.

 

[318willrun]

So magnum heads, with Hughes shaft paired rockers, drilled for LA intakes. The perfect factory head.

What I don't know is if they were ported by a professional which head would be best. But as cast, I like the magnum head.

 

[crackedback]

1.88 J opened to 2.02 with a nice throat cut, better than an X. But that takes work.

Lots of early J's got 2.02's

 

[RustyRatRod]

ALL small block open chamber heads are smog heads. Even the X. That's the whole point of an open chamber.

 

[TT5.9mag]

ALL small block open chamber heads are smog heads. Even the X. That's the whole point of an open chamber.

Yea I put my open chamber W2s on to pass California’s strict smog laws.

 

[RustyRatRod]

Yea I put my open chamber W2s on to pass California’s strict smog laws.

That's different, dummy. I meant production stuff. lol

 

[Locomotion]

1.88 J opened to 2.02 with a nice throat cut, better than an X. But that takes work.

Lots of early J's got 2.02's

Agreed. After so many years of popularity, you don't know how many valve jobs an X-head may have had until you get into the rebuild. The extra work required to go from 1.88 to 2.02 would be worth the time & effort instead of gambling on the X. 1.88 heads are usually cheaper too! A sunken, multi-valve job 1.60 exhaust isn't as critical as the intake (within reason).

 

[273]

Too bad Magnum had the cracking problem.

 

[318willrun]

ALL small block open chamber heads are smog heads. Even the X. That's the whole point of an open chamber.

I guess I had in mind the air injection ports. I'm not sure all closed chamber heads are better in the combustion than some open chamber heads.

 

[318willrun]

Too bad Magnum had the cracking problem.

Too bad the Aussie EQ replacements went out of business.....

 

[JDMopar]

I've never had a set of 308's. Are they as prone to cracking as 302's?

 

[RustyRatRod]

I guess I had in mind the air injection ports. I'm not sure all closed chamber heads are better in the combustion than some open chamber heads.

Oh I didn't say one was better than the other. Don't misunderstand me. Just because they were made for better emissions doesn't necessarily make them "bad".

 

[318willrun]

I've never had a set of 308's. Are they as prone to cracking as 302's?

Yes, they crack. Magnums, 302's, 308's are prone to cracking BUT most people don't even know they are cracked and are driving all over with them. Cracks "most of the time" are not in a place that seems to affect them.

 

[318willrun]

Here are remanufactured "302" heads from Jegs. Not a bad price at all.
https://www.jegs.com/i/ATK-Engines/...yKUpGw9R2Go2hAUksz83wwwxZxUE0_1673585_BANNER_

 

[318willrun]

Remanufactured 360 heads from Jegs
https://www.jegs.com/i/ATK-Engines/...m_term=4581596255650123&utm_content=Evergreen

 

[TT5.9mag]

I’d love to see that same list put together by a few different guys here.
1. @Scampin
2. @furrystump
3. @GTX JOHN

Those guys all go really damn fast with factory heads and probably know which ones are best to port.

 

[RustyRatRod]

Remanufactured 360 heads from Jegs
https://www.jegs.com/i/ATK-Engines/...m_term=4581596255650123&utm_content=Evergreen

I wonder if you get the option to get matching casting numbers if you purchase two?

 

[Syleng1]

I wonder if you get the option to get matching casting numbers if you purchase two?

Order in a few sets and send back the ones you don’t like. Lol!
I’ve have a few engines that the heads were mid match. Possibly from warranty or what ever. Ran fine and no issues.
I’ve got a set in my heads from a built 340 I bought - 2.02/1.60 that are ported and the guy went to aluminum heads I bought for $500. Mis matched.
I should had looked at the numbers but got caught up in the heads being already ported. Sorry I do not have the head numbers in front of me but my machine shop told me they are good to go and not worry about it since they were ported identical.

 

[Bobzilla]

For anyone wanting a factory style cast iron LA head, Indy Cylinder supposedly bought up a bunch of unfinished brand new castings and is now offering them in finished form. Looks like they are live on the Indy website now.

New 2.02 LA Heads - Indy Cylinder Head

 

[66fs]

I've never had a set of 308's. Are they as prone to cracking as 302's?

Yes

 

[toolmanmike]

I guess I had in mind the air injection ports. I'm not sure all closed chamber heads are better in the combustion than some open chamber heads.

Yep. It makes a difference what piston you use and how far in the hole it sets.

 

[Locomotion]

For anyone wanting a factory style cast iron LA head, Indy Cylinder supposedly bought up a bunch of unfinished brand new castings and is now offering them in finished form. Looks like they are live on the Indy website now.

New 2.02 LA Heads - Indy Cylinder Head

That should have an interesting story behind it! A "barn find" type discovery in a warehouse? A photo search showed an at least one year old photo from the Indy site but these castings haven't been available from Mopar Performance for decades. Casting # is 4772576, an over-the-counter 308 head replacement with no EGR holes. They also had a wide variety of bare, stock-type assemblies, 2.02, 1.88, ported & T/A versions in the catalog. I doubt it's a previously unknown casting number (4772575). I'm surprised Indy hasn't corrected the number. I know several class racers who like this head for 1.88 valves. But it depends on the class and how they planned to modify them.

10* locks & 74cc chambers???

 

[318willrun]

For anyone wanting a factory style cast iron LA head, Indy Cylinder supposedly bought up a bunch of unfinished brand new castings and is now offering them in finished form. Looks like they are live on the Indy website now.

New 2.02 LA Heads - Indy Cylinder Head

Got to be careful what's under the 2.02's. I personally have taken the valve out and was shocked what was underneath. No bowl blend for the bigger valve.