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?
Exactly why they are made that way.
Using Wallace calculator ; .042 gasket 8.96 to 1. or .040 gasket 9.00 to 1
Assuming an unshaven block @ .050 piston to deck.
Assuming an unshaven block @ .050 piston to deck.
That’s fairly close. Is the Wallace calculator a free sw?
YES
Welp I measured 0.065 in da hole. Not good. Also see some side skirt action but no scratches. I thought I had an opportunity to get a rebuilt 360 cheap but wasn’t fast enough. I am currently now looking back at my 340 in my Satellite. I am trying to get the oil pan down to see if my crank is forged or cast as it had been rebuilt by someone.
why are you so concerned about a cast v forged crank?
unless you're going to be hitting it with the giggle gas or spinning it to the moon i'd rock the cast crank and not worry about it. and even then, i'd be more concerned over a multitude of other things before i was even thinking about the crank.
.065 isn't great, but it also isn't .100 down. depending on what you're trying to accomplish it could be just fine.
unless you're going to be hitting it with the giggle gas or spinning it to the moon i'd rock the cast crank and not worry about it. and even then, i'd be more concerned over a multitude of other things before i was even thinking about the crank.
.065 isn't great, but it also isn't .100 down. depending on what you're trying to accomplish it could be just fine.
33IMP
Well-Known Member
.... for brain dead engine assemblers.
33IMP
Well-Known Member
Yep, free. And LOTS of useful stuff on his site. Bookmarked on my phone and tablet.
I've used his cr calculator lots of times. Only thing confusing is his dome volume/dish volume is backwards from the way I would think of them, so care, and following instructions is required.
I purchassed this motor with no build info. Then I put it in my car. I assumed a cast crank for a 73 340 which is correct. I should have verified but didn’t.
I didn’t build this motor. I am getting a vibration at 45mph and up and gets progressively more noticeable with speed. It’s not shuddering but noticeable. I think it’s the motor as I believe it gets better or goes away when I throw it in neutral. But to be sure I balanced all the tires and drive shaft.
Here’s why I am concerned. This is an unknown build of a 73 motor. It has TRW 12:1 pistons. Solid lifters with 273 adjustable rockers. I assumed a 1973 cast crank. BUT IS IT THE STOCK CRANK? If it’s a forged crank then the weighted Harmonic Balancer and Torque converter and flex plate are a problem. If cast then I can rule it out. I can also inspect the rods and even some bearings if I want to as well as measure crank end play. Something is causing the vibration and I am assuming it’s the motor.
Am I off my rocker?
This is in addition to detonating under heavy load and yes I have timing dialed way back and a colder plug. I have 200psi static compression across the cylinders. So this is just another issues I have been working on.
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honestly, at this point i can't keep up with what's going on. so thanks for somewhat clarifying.
the thread is about a 318, then you're on about a 360 and now it's something on a 340. in the future, my suggestion would be if you want pointed advice is to ask clear and concise questions and not muddle up a thread with a bunch of information that's not pertinent to the original ask.
here's my thought: i would eliminate any and every possibility from the drivetrain before suspecting the motor (aside from a bad harmonic balancer).
if it has 12:1 pistons i'd assume a performance build and therefore a forged crank-- factory or otherwise. but like they say: trust but verify
however... the balancer *should* be the tell tale sign.
so you're not off your rocker, it's just a super round-about way of getting there.
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