do so. anything else is just a guess.
318 std piston quench with aluminum heads?
- Thread starter 340inabbody
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Can somebody tell me what type of pistons these are?
H403?
Why are they double dished? Would they be at zero deck height?
I found a 360 with these in them????? Wth?
They are a replacement piston. (double valve reliefs) It looks like .035 over?
I think this is the piston. H405-CP 30
If So what heads would these fit?
If So what heads would these fit?
The part number heads I run are open chamber.
But I seem to recall somewhere around 66/67 or so,
some of the heads on the 273/318 were closed chambers.
I am not near the shop where we have 100 plus pairs of heads
and I could take a look.
Maybe someone who is more familiar with the 273/318 early stuff
can tell us.
Yes and the piston head volume I just fount is 10cc’s.
Chrysler 360 with the overbore, the swept volume per cylinder is approximately 57 cubic inches, which is roughly 934 cubic centimeters.
Now, the compression ratio is the sum of the swept volume and the piston head volume, divided by the piston head volume.
So, in cubic centimeters, the swept volume is about 934 cc, and the piston head volume is 10 cc.
So, the compression ratio is (934 plus 10) divided by 10, which is 944 divided by 10, giving us about 9.4:1.
As I recall the early 318 came with a double dish piston until
sometime in the mid 70's or so.
However, I believe they still had the exact same compression
height and would not do anything to help the compression.
All production 360 that I have every seen had a dished
piston and no valve reliefs. That is the only configuration
that NHRA recognizes as coming on them.
Yeah I moved the conversation over to 360 as I am looking at one with these pistons and trying to understand the compression and quench effect of a double dish.
Wonder if the double dish is to make the Pistons compatible either direction? Otherwise I can’t explain why they would have it on both sides
That is a stroked B engine (usually 4.25).
Myself, I have had bad luck trying to seal the aluminum
heads on an iron block. I have to use a composite gasket.
I do not know anyone else's experience.
If I assume a 64cc head volume and a .035 gasket I calculated a cr of 9.3:1
Here is a run using a 0.40 gasket——
If we use a 0.040-inch head gasket, that’s about 1.02 millimeters in thickness.
Using the same bore area of approximately 78.5 square inches, we multiply that area by the 0.040 inches of thickness. That gives us an additional clearance volume of about 3.14 cubic inches, which is roughly 51 cc.
So, the new clearance volume would be the original 74 cc plus the 51 cc, giving us about 125 cc of clearance volume.
Now, the compression ratio would be the swept volume plus the new clearance volume, divided by the clearance volume.
So that’s (934 plus 125) divided by 125, which is 1059 divided by 125, giving us about 8.47:1.
So, with a 0.040-inch head gasket, the compression ratio would be around 8.5 to 1,
or a 0.30 gasket 9.1:1 .
Can anyone check any of my numbers?
Here is a run using a 0.40 gasket——
If we use a 0.040-inch head gasket, that’s about 1.02 millimeters in thickness.
Using the same bore area of approximately 78.5 square inches, we multiply that area by the 0.040 inches of thickness. That gives us an additional clearance volume of about 3.14 cubic inches, which is roughly 51 cc.
So, the new clearance volume would be the original 74 cc plus the 51 cc, giving us about 125 cc of clearance volume.
Now, the compression ratio would be the swept volume plus the new clearance volume, divided by the clearance volume.
So that’s (934 plus 125) divided by 125, which is 1059 divided by 125, giving us about 8.47:1.
So, with a 0.040-inch head gasket, the compression ratio would be around 8.5 to 1,
or a 0.30 gasket 9.1:1 .
Can anyone check any of my numbers?
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