Mopar Small Block Head info:
All the guys who just homeported the 302s on this site and didn't have a lot of chamber unshrouding done and I mean a lot ..and a flowbench test...their heads might only do as good as stock 675 heads. Closed chambers are work to implement and not hinder the ultimate power maker=airflow.
The x is its own, came 70cc, has a different intake port floor with a flatter peak to straight wall ssr. The average eye doesn't see it at a glance. The machining of those heads p.r holes are a minute amount wider on the set i have when compared to the sets of 1970 j heads i also own, full ported and the other bone stock. There's probably like 6 versions of the of the 360 J head design.. of which mostly revolved around the exhaust port with the exception of a couple intake port volume revisions. The 3418915, 587, 974, 596, 1978/79 recast 915 full number of '341915 smog version 'notice the 8 is missing' with air injection exh floor. Heck.. even the 308 is a J head intake port... with the 6th or so revision of the exhaust port. There are a handful of casting numbers mixed in between as extension/alternative part numbers of the those revision/changes but we'll focus on the mostly common ones that feature those same characteristics.
The 1st version '915' were used in both the 340 cars and in vans/trucks and came both 1.88/2.02. Cast in 1970 for 71.
The 1st j exh revision came with the 587 with small air injection boss..not an advantage though. In that casting the boss is not big enough or close enough to the seat to really aid in flow and the airhole if not plugged flush to the port floor actually creates reverse Eddie's and hurts the flow numbers on the flow bench when tested.
The #974, really good head. 155 cc J intake port, exh port a hair smaller than previous w/bigger air injection bosses right to the seat, tall exhaust ssr floor. Theres more material removed to get to a ported 915 peak int flow due to the slightly smaller port volume... but great head. The 974 were 72-74cc chambers. After the 974 they went back to an exh port floor design that carried air injection bosses that were cast right between the 587 and 974 in the port floor...in other words..they down graded again where you won'tgain from it incorporating it into the ssr for an increase because they pushed it back from the seat so it's a tease and is marginal in any shaping potential.
The late 70's and the oddities of truck heads where they re introduced the j 915 casting minus 1 digit... a meaty casting... air injection, induction hardened with very wide margin seats small bowls and truck valves...intake port on the small side. Chrysler really started getting sloppy on the castings though the shape was mostly uniform...port windows were not sized well as they were in previous years... tapered.. somewhat smaller... extra thick intake decks.. and big 72cc chambers which if you put early passenger car valves in would be 74cc. Truck valves have flat exh valves fwiw and eat up a lil chamber volume.
There a couple versions/casting of the 302 and 308. 714 for the 302 and some weird one i have lost in my mind atm for the alternative 308.
Many can take and emphasize a unique feature over another quite easily and build upon all that.
Here is a pic of #974 exh port ,ported.
Its WAY taller than any 915,587,596,894 etc and easy to get great exh numbers low to high lift.
I have had all of them at some point, still have most. When i get my hair cut and some time ill post my youtube vid up and show some of that stuff.
273/318 are pretty well known, but reasoning behind him now parroting me about the 302 is obviously not understood by him. Its the chamber, the very thing everyone gushes about is the achilles heel to its air flow. It can be made to work very well...but just like the speedmaster heads it is work and you really need to be able to test and know how much is really enough for it to work like it should. Aka you need to be able to drop a big stone down/cutter and hand blend the chamber below the short turn. The valves that come in those heads are also truck valves, they are big stem to head and heavy af. You want passenger car valves for a 1970 dart/valiant/demon/duster etc..
All the guys who just homeported the 302s on this site and didn't have a lot of chamber unshrouding done and I mean a lot ..and a flowbench test...their heads might only do as good as stock 675 heads. Closed chambers are work to implement and not hinder the ultimate power maker=airflow.
The x is its own, came 70cc, has a different intake port floor with a flatter peak to straight wall ssr. The average eye doesn't see it at a glance. The machining of those heads p.r holes are a minute amount wider on the set i have when compared to the sets of 1970 j heads i also own, full ported and the other bone stock. There's probably like 6 versions of the of the 360 J head design.. of which mostly revolved around the exhaust port with the exception of a couple intake port volume revisions. The 3418915, 587, 974, 596, 1978/79 recast 915 full number of '341915 smog version 'notice the 8 is missing' with air injection exh floor. Heck.. even the 308 is a J head intake port... with the 6th or so revision of the exhaust port. There are a handful of casting numbers mixed in between as extension/alternative part numbers of the those revision/changes but we'll focus on the mostly common ones that feature those same characteristics.
The 1st version '915' were used in both the 340 cars and in vans/trucks and came both 1.88/2.02. Cast in 1970 for 71.
The 1st j exh revision came with the 587 with small air injection boss..not an advantage though. In that casting the boss is not big enough or close enough to the seat to really aid in flow and the airhole if not plugged flush to the port floor actually creates reverse Eddie's and hurts the flow numbers on the flow bench when tested.
The #974, really good head. 155 cc J intake port, exh port a hair smaller than previous w/bigger air injection bosses right to the seat, tall exhaust ssr floor. Theres more material removed to get to a ported 915 peak int flow due to the slightly smaller port volume... but great head. The 974 were 72-74cc chambers. After the 974 they went back to an exh port floor design that carried air injection bosses that were cast right between the 587 and 974 in the port floor...in other words..they down graded again where you won'tgain from it incorporating it into the ssr for an increase because they pushed it back from the seat so it's a tease and is marginal in any shaping potential.
The late 70's and the oddities of truck heads where they re introduced the j 915 casting minus 1 digit... a meaty casting... air injection, induction hardened with very wide margin seats small bowls and truck valves...intake port on the small side. Chrysler really started getting sloppy on the castings though the shape was mostly uniform...port windows were not sized well as they were in previous years... tapered.. somewhat smaller... extra thick intake decks.. and big 72cc chambers which if you put early passenger car valves in would be 74cc. Truck valves have flat exh valves fwiw and eat up a lil chamber volume.
There a couple versions/casting of the 302 and 308. 714 for the 302 and some weird one i have lost in my mind atm for the alternative 308.
Many can take and emphasize a unique feature over another quite easily and build upon all that.
Here is a pic of #974 exh port ,ported.
Its WAY taller than any 915,587,596,894 etc and easy to get great exh numbers low to high lift.
I have had all of them at some point, still have most. When i get my hair cut and some time ill post my youtube vid up and show some of that stuff.
