Cast vs. Aluminum heads and bang for buck..
Customer brings me two cleaned, magged cores.
Not much core shift. They’ve been done at least once before.
One head had 3 chambers pretty close with regards to quench area depth....... one .030 lower/deeper.
The other head had the two ends .040 apart, the two in the middle split the difference.
The two deepest ones were .090 and .100 deep.
They’re all about .105-.110 deep now, nominal 67.5cc.
The smallest chamber also had the valve job about .025 closer to the deck.
That whole chamber was just closer to the deck.
Aftermarket closed chamber heads...... zero deck with flat tops....... done.
Better and cheaper.
The target intake flow was 240.
Wasn’t giving that up without trimming the guides and the lump in the roof.
Way more work than 240 out of an X head.
Shooting for 160 from the exhaust.
After new seats installed, vj and a bowl blend, bullet nose the guide boss...... 158.
I’ll clean up the rest of the runner, should get me there.
There is no SSR on the ex port on this vintage of 340/360 heads...... so that extra clean up may or may not pan out.
I converted to 11/32 stem nailhead valves.
I will say this, stock J’s can vary quite a bit.
I had a set of refreshed 915’s in the shop once....... off the same motor.
Looked like nothing special. Flowed one.....215cfm.
Same as what you typically get with a vj and a minor quickie blend.
I looked that head all over..... saw nothing to indicate why it was that good.
Flowed another cylinder...... about the same.
Flowed the other head...... mid-190’s.
Aaahh...... that’s more like it.
I didn’t cc them, but I bet one was bigger.
I tested one pair of ports on the set I’m working on now before I did anything.
I had already replaced the guides so I was able to use the new 11/32 valves.
The previous shop used a valve seat cutter with a big radius on the bottom for both intake and exhaust, along with a little bit of a vertical plunge cut at the bottom.
Flowed 213/137 @.500.
Customer brings me two cleaned, magged cores.
Not much core shift. They’ve been done at least once before.
One head had 3 chambers pretty close with regards to quench area depth....... one .030 lower/deeper.
The other head had the two ends .040 apart, the two in the middle split the difference.
The two deepest ones were .090 and .100 deep.
They’re all about .105-.110 deep now, nominal 67.5cc.
The smallest chamber also had the valve job about .025 closer to the deck.
That whole chamber was just closer to the deck.
Aftermarket closed chamber heads...... zero deck with flat tops....... done.
Better and cheaper.
The target intake flow was 240.
Wasn’t giving that up without trimming the guides and the lump in the roof.
Way more work than 240 out of an X head.
Shooting for 160 from the exhaust.
After new seats installed, vj and a bowl blend, bullet nose the guide boss...... 158.
I’ll clean up the rest of the runner, should get me there.
There is no SSR on the ex port on this vintage of 340/360 heads...... so that extra clean up may or may not pan out.
I converted to 11/32 stem nailhead valves.
I will say this, stock J’s can vary quite a bit.
I had a set of refreshed 915’s in the shop once....... off the same motor.
Looked like nothing special. Flowed one.....215cfm.
Same as what you typically get with a vj and a minor quickie blend.
I looked that head all over..... saw nothing to indicate why it was that good.
Flowed another cylinder...... about the same.
Flowed the other head...... mid-190’s.
Aaahh...... that’s more like it.
I didn’t cc them, but I bet one was bigger.
I tested one pair of ports on the set I’m working on now before I did anything.
I had already replaced the guides so I was able to use the new 11/32 valves.
The previous shop used a valve seat cutter with a big radius on the bottom for both intake and exhaust, along with a little bit of a vertical plunge cut at the bottom.
Flowed 213/137 @.500.