340 X heads
- Thread starter ryan1964
- Start date
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Just wondering if they where good head
Sounds like other than slightly lower compression they will be fine
Sounds like other than slightly lower compression they will be fine
Im just trying to build it as close to stick as possible
The 915 heads may have been worked on?? Larger valves?
As far as compression, I believe 894 vs 915 heads would have very similar compression. The comb chambers as far as I know are the same. The runners are slightly different and valve differences will effect compression.
As far as compression, I believe 894 vs 915 heads would have very similar compression. The comb chambers as far as I know are the same. The runners are slightly different and valve differences will effect compression.
"J" or the other letter heads could be 1.88 or 2.02 intake valves. They are very good heads, 2.02 heads were machined different from the factory for the 2.02 intake valves. For a street car you don't need to 2.02 intake valves to be fast. T/A heads had offset pushrod holes so the intake ports could be opened up for racing. They had mechanical rockers with hydraulic cam and special length pushrods to make them work. The exhaust were on center and the intakes were offset because of the moved pushrod holes. Run what ya got, done right they will work very well.
Dartswinger70
Well-Known Member
I have a set of 915 js with 2.02s I am planning on cc'ing them to figure compression ratio with early pistons. I am hoping at least 10:1
casting ending with 894 68-very early 70. 915 casting are 70-71 with 202 intake valves , 72 and early 73 were 915 casting with 188 int valves. Go by the casting number and valve size not the letter. I have seen 915's with no letter at all.
Yes 202 in mine. Valves almost touch each other ...its what I got with my block
My machinist said it's going to tight to put hardened seats but is doable
Not doing any other work ...stock build
My machinist said it's going to tight to put hardened seats but is doable
Not doing any other work ...stock build
Your heads are fine as long as the valves aren't sunk.
Want a better head? Find a 1.88 915 and put 2.02 valves in it with a nice fresh seat and throat cut.
They are at the machinist now
It a stock build so not many red line shifts
More a cruiser
It a stock build so not many red line shifts
More a cruiser
Swinger 340
Well-Known Member
My 70' Dart had "X" heads on both sides, and they were known as original. I have a 340 out of a 70' Challenger and they have (still have the motor) a "O" on one side and a "U" on the other. Thanks, for the input on possible miss matched heads from the factory. I always thought the motor dropped a head along the way. I didn't know the history of that motor, as I did on the Dart.
Swinger 340
Well-Known Member
Not all "J" heads were 2.02. Trucks and Vans were 1.88 in the "J" head on the 360's. I believe just 70 and 71.
The O and U are the same 915 head. No mismatch there
1.88 intake valves came on all run of the mill 360's starting from the beginning in 1971, cars and trucks had 2 groove keepers. Some trucks used valve rotators and those valves use very short valve springs. We threw those valves away. 2.02 valves only came on 340s. 72 and 73 340's then dropped down to the 1.88 intake valves, but used a different .0005" smaller stem diameter and 4 groove keepers. High Performance 360s also used 1.88 intake valves like the 72-73 340s. Like crackedback posted no real big deal to upgrade any 360 heads to 2.02 intake valves. I personally did not bother, the 1.88 intake valve heads worked plenty good for me.
furrystump
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So i guess unless they are x heads
They can have any size valves and not going to know when they are on the car unless you bore scope it
They can have any size valves and not going to know when they are on the car unless you bore scope it
Ha! I'll see your 2.055s and raise you with 2.08s intakes in my X heads. Those really almost touch.Almost touch? I have 2.055 in my X heads.
PRH
Well-Known Member
If you have auto/light truck “360” heads, and they aren’t equipped with 2.02” intake valves……but you want them to be……they’re easily modified to make the 2.02’s fit.
Swinger 340
Well-Known Member
Is that not the reason for the TA's heads with the angle intakes valves, so they can brought up to the 2.08's? Possibly, the letter heads can accommodate the 2.08 valves if the heads were to be machine with the angle valve stems. All the letter heads were the same, except for that. The blocks had a little more meat for durability.
No, the valve placement remained the same. Only the push rod clearance holes changed. All valve angles and placements are the same on all factory LA small block heads from 273, 318, 340 to 360.
PRH
Well-Known Member
2.02/1.60 valves aren’t really all that close together……..
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