1970 “J” heads

[go-fish]

188 valves are all you need with a closed factory exhaust. Raising the compression would be the better choice. Have the heads milled a little and install thinner head gaskets, Don't over cam the Engine.

Thanks for sharing. I do want my 73 Duster to be similar to the form it would have had if a gearhead had it in the early/ mid 70's.
It is in original form as of now except for a cam change. .468 lift, 224 duration at .050.
I plan to throw my LD340 and TTi step headers on it. I have a spare set of 915 heads that I can work with.
Trying to figure out 2.5" or 3" exhaust with these heads.

 

[B3422w5]

Thanks for sharing. I do want my 73 Duster to be similar to the form it would have had if a gearhead had it in the early/ mid 70's.
It is in original form as of now except for a cam change. .468 lift, 224 duration at .050.
I plan to throw my LD340 and TTi step headers on it. I have a spare set of 915 heads that I can work with.
Trying to figure out 2.5" or 3" exhaust with these heads.

2.5 is plenty fine

 

[rumblefish360]

Since Rob has been kind to me and my family, I'm sending him a set of 915 "Z" heads from my collection. These are real, no photoshop BS involved.

My friend, you humble me once again.
It was a pleasure meeting you at the “End of the Island” for you family gathering. If only I was there for your next arrival as to be a better and proper guide around for the gaggle times 10 of places to see, eat, enjoy and party at!

It would’ve been my upmost pleasure and honor to escort your family around from site to site without falling into the tourist pitfalls and traps.

Thanks for sharing. I do want my 73 Duster to be similar to the form it would have had if a gearhead had it in the early/ mid 70's.
It is in original form as of now except for a cam change. .468 lift, 224 duration at .050.
I plan to throw my LD340 and TTi step headers on it. I have a spare set of 915 heads that I can work with.
Trying to figure out 2.5" or 3" exhaust with these heads.

Agreed with the above. But not just any muffler please!

 

[go-fish]

Agreed with the above. But not just any muffler please!

Glass packs! Day 2 sound.

 

[70dart340]

You went out or your way, Rob, to drive an hour out of your way to meet me and my family. Much respect and thanks sent. We still plan on heading back to Gator Country next year, so you're saving me the 100 pounds in the moving van. I'm a big believer in Karma Points, too. I just me another member from FABO yesterday, and bought and old Edelbrock LD340 intake. Puny ports, but it might be a good retro intake for the Rumble Fish. I'll send you a PM when I get it cleaned up.

 

[70dart340]

don't go by the letter. but by the last 3 of the casting number. 894 or 915. If you look at a set of J's? They are usually U's cut off by the spark plug hole.

894 202 valves in 68-69-70 are 10.5 compression. with 9.56 deck

915 202 valves in 70-71 10.3 compression . with 9.56 deck

Cut a set of 915's and you have 10.5 on 70-71 piston engine

915 188 valve heads came on 72 8.5 compression with 9.56 deck

These are 915"B" heads. They are 2.02/1.6 valves, with what appears to be a 3 angle valve job. I had them pressure checked and magged. All good. Ask Rumblefish for more details in January.

 

[rumblefish360]

You went out or your way, Rob, to drive an hour out of your way to meet me and my family. Much respect and thanks sent. We still plan on heading back to Gator Country next year, so you're saving me the 100 pounds in the moving van. I'm a big believer in Karma Points, too. I just me another member from FABO yesterday, and bought and old Edelbrock LD340 intake. Puny ports, but it might be a good retro intake for the Rumble Fish. I'll send you a PM when I get it cleaned up.

I have intakes for the fish. Thanks very much, but it is unnecessary for I have a OE intake for it and a LD-340 as well.

Next item needed when funds allow are exhaust manifolds for the 340.

 

[Dartswinger70]

for the sake of the conversation what is the actual difference between the X and J casting...? I have a set of Xs on my 340 in my car and my spare engine has a set of 2.02 Js waiting to go on. I have no issue with either. I did have Js with 1.88s but wanted the 2.02s. so I sprung for a set. It was either that or have the machine shop install 2.02s in the 1.88 set that i have.

 

[go-fish]

for the sake of the conversation what is the actual difference between the X and J casting...? I have a set of Xs on my 340 in my car and my spare engine has a set of 2.02 Js waiting to go on. I have no issue with either. I did have Js with 1.88s but wanted the 2.02s. so I sprung for a set. It was either that or have the machine shop install 2.02s in the 1.88 set that i have.

And a Z, O, & U?

I would think it comes down to compression and combustion chamber volume. Possibly, the letter designates what spring pressures it may have been loaded with from the factory? I don’t know, we’re all LA valves the same #’s from 1974 318 2bbl all the way to a 70 T/A?

 

[rumblefish360]

*I Think* I’m right in saying the letter heads all have the same cc chamber. The ports have differences and they are small. A non factor on a factory engine as made when new. As in you would never know what head is on the engine when driving an otherwise stock engine and car.

Actual flow numbers vary per head and sometimes a good bit even in the same letter family. An example could be (enter any letter and valve size) 10-15 cfm variance on any set tested.

 

[EL5DEMON340]

I would rather install a set of 2.02 valves in a 1.88 j head and bowl blend, over a 2.02 head that has 75K to 150K on them and sink the 2.02 even farther.

 

[70dart340]

*I Think* I’m right in saying the letter heads all have the same cc chamber. The ports have differences and they are small. A non factor on a factory engine as made when new. As in you would never know what head is on the engine when driving an otherwise stock engine and car.

Actual flow numbers vary per head and sometimes a good bit even in the same letter family. An example could be (enter any letter and valve size) 10-15 cfm variance on any set tested.

I started on your shipping boxes today. You'll soon have a chance to measure a set of real "Z" heads for your self. I have the 3/4" plywood, I need to clean off my table saw and start cutting. Happy 2022 to all.