[racerboy]

Just for fun I was messing around with the CR Calculator on the Butler website and if I wanted to use the 4.00 stroker assembly on my 400, and run my #12 heads, I would need a 24cc dish in the piston to get my CR down to 9.5:1. I entered 72cc for the heads, zero-deck, and .040 head gasket. Even if I went with the stock 3.75 stroke, and input the 14cc dish, it still puts the CR at 9.8:1. I thought the whole purpose of this 14cc-dish piston was to allow people to run the stock cast-iron heads. What am I missing here?

[Vid]

Originally Posted by geeteeohguy

Those are the dreaded '8 relief' jobber pistons which have a rounded shoulder as well. They provide low compression AND detonation as well as being fragile. You will be money ahead to replace them with pretty much anything else.

Yeah agreed. I had a .030 over 400 with those 8 eyebrow relief suckers and #16 heads. Not only was detonation a constant problem but the car just never ran as good as it should have. X2 on voting those pistons out of office, LOL


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[Gary H]

Originally Posted by racerboy

Just for fun I was messing around with the CR Calculator on the Butler website and if I wanted to use the 4.00 stroker assembly on my 400, and run my #12 heads, I would need a 24cc dish in the piston to get my CR down to 9.5:1. I entered 72cc for the heads, zero-deck, and .040 head gasket. Even if I went with the stock 3.75 stroke, and input the 14cc dish, it still puts the CR at 9.8:1. I thought the whole purpose of this 14cc-dish piston was to allow people to run the stock cast-iron heads. What am I missing here?

Icon Pistons website calculator shows 9.6 compression ratio for 4.120 bore, 14 cc pistons, .039 gasket at 4.250 diameter, and 72 cc heads, and 3.75 crank

[racerboy]

Originally Posted by Vid

Yeah agreed. I had a .030 over 400 with those 8 eyebrow relief suckers and #16 heads. Not only was detonation a constant problem but the car just never ran as good as it should have. X2 on voting those pistons out of office, LOL


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Thanks Vid. That decision has been made. The RA III 400 js coming out, Just trying to figure out what the next steps should be. Build up the 400 straight away, and if so, how much of a build up (stock, with good forged rods/pistons -or- a stroker kit?) or just drop in a 428 that I have laying around and run that for a while until I can decide what to do with original WS motor.

[racerboy]

Originally Posted by Gary H

Icon Pistons website calculator shows 9.6 compression ratio for 4.120 bore, 14 cc pistons, .039 gasket at 4.250 diameter, and 72 cc heads, and 3.75 crank

Thanks Gary. Is 9.6 borderline for pump gas?

[4zpeed]

It's perfect, enough to allow a safety if it where to ever go lean on you.

You could even run low grade fuel, I don't because I'd just rather not.


Frank

[tooski]

Originally Posted by Gary H

Icon Pistons website calculator shows 9.6 compression ratio for 4.120 bore, 14 cc pistons, .039 gasket at 4.250 diameter, and 72 cc heads, and 3.75 crank

That is with .000 deck height.

I had to have .025 shaved off the deck to get to zero deck with the forged Speed Pro pistons with a compression height of 1.714.
The previous engine had the eight eyebrow cast pistons with a compression height of 1.70. That block was not decked as the pistons were .040 in the hole. With the 71 cc heads and assuming about 14 cc for the valve reliefs it came out at 9.1 CR. Detonated badly.
To get to zero deck, the block will have to be decked the appropriate amount or the pistons will have to have to have the appropriate compression height. Read that as a custom piston.

[racerboy]

Originally Posted by tooski

That is with .000 deck height.

I had to have .025 shaved off the deck to get to zero deck with the forged Speed Pro pistons with a compression height of 1.714.
The previous engine had the eight eyebrow cast pistons with a compression height of 1.70. That block was not decked as the pistons were .040 in the hole. With the 71 cc heads and assuming about 14 cc for the valve reliefs it came out at 9.1 CR. Detonated badly.
To get to zero deck, the block will have to be decked the appropriate amount or the pistons will have to have to have the appropriate compression height. Read that as a custom piston.

Tooski
This sounds like my situation. If the shop that did the build for the PO went with these low-budget 8-eyebrow pistons and the small cam, I doubt they zero-decked the block.


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