Quote:

---

To clear up a few things, that have been posted a hundred times at least, the stock 68-69 383 HP piston has a CH of 1.932, on a factory blueprint deck of 9.980 it sits .0025-.003 in the hole. If you build a 69 383HP to NHRA BLUEPRINT you get close to 11.0 compression, the NHRA spec has the piston .021 ABOVE the deck and it uses a 79.5 CC head chamber volume, NEITHER is factory actual build spec. I have an untouched 56K mile 69 383HP in my 69 GTS Dart and this is how it , and another 69 383HP I have on an engine stand, are built as were others I have disassembled with original pistons and uncut decks.

---

Quote:

---

Why wouldn’t I get the 400’s and have the 8.4:1 compression?

---

Quote:

---

What is the compression height of a stock 383 2-brl piston? Are the KB 162 and 400 the same compression height?

My stock pistons are .080" in the hole, is that normal for a stock 2-brl 383?

---

Quote:

---

Quote:

---

What is the compression height of a stock 383 2-brl piston? Are the KB 162 and 400 the same compression height?

My stock pistons are .080" in the hole, is that normal for a stock 2-brl 383?

---

What year is your 383?

A 68-69 383 2 bbl has the same compression height piston as the 4 bbl engine it just has a dish in it , I have not CC'd the dish to see what it is.

I'm going to ask the STUPID question...

Why are you dead set against milling the deck of the block ... it's CROOKED ... or the heads ... NOT FLAT ...

The dome hinders flame travel in Chrysler poor combustion chamber design ... open chamber head .

Use the 162 with a 516 head and a steel shim gasket , problem solved on both comprewssion and quench ...

If anything you will have a higher compression ratio , ASSuMEing that your 383 had 906s or 346s on it .

---

Quote:

---

I have a 383 that will be .030” over and will be used for a daily driver. 650 carb, stock exhaust manifolds and gas friendly cam. Thinking maybe 300-330 horse. Looking at what pistons to get and have narrowed it down to the Keith Black 162’s or 400’s. Seems like most folks go with the 162’s but I’m not sure why since the compression is so low. I do not want to deck the block or mill the heads so what to do???

Facts:

4.280” bore
3.38” stroke
4.5” head gasket bore (estimated)
.020” head gasket thickness
90 cc heads (measured- 906)
.080” depth to stock piston (measured)

Using Keith Black KB-162 pistons (5cc dish with stock compression distance of 1.908” puts compression at 7.69:1

Using Keith Black KB-400 pistons (6cc dome with stock compression distance of 1.908” puts compression at 8.37:1

The KB-162’s are supposed to be stock replacement pistons though stock pistons don’t have the valve relief so does that mean they have a 0cc dish/dome? If so the compression would have been 7.99:1 with stock pistons.

Why wouldn’t I get the 400’s and have the 8.4:1 compression? Am I missing something?

---

Quote:

---

It's a '71 383 with 906's. I have no dish in my pistons.

I didn't want to deck the block/heads to save money (machine work here is very expensive) and so I didn't have to shave intake manifold. Also, don't want to buy 516 heads. If I could get the engine to come out with stock horsepower and torque I would be fine with it. I was hoping for a re-ring and new bearings after a hone but I have .006"-.008" piston to wall clearance.

I am just trying to find "free" power (pistons are the same cost) if possible and I thought bumping the compression up a little would do just that.

---

Quote:

---

Quote:

---

It's a '71 383 with 906's. I have no dish in my pistons.

I didn't want to deck the block/heads to save money (machine work here is very expensive) and so I didn't have to shave intake manifold. Also, don't want to buy 516 heads. If I could get the engine to come out with stock horsepower and torque I would be fine with it. I was hoping for a re-ring and new bearings after a hone but I have .006"-.008" piston to wall clearance.

I am just trying to find "free" power (pistons are the same cost) if possible and I thought bumping the compression up a little would do just that.

---

I'm going to try and reuse my factory 69 HP pistons if at all possible. Yes they're heavy but are supposed to be plenty strong for a typical performance street build and have a better compression distance than anything the aftermarket has to offer short of a semi-custom forged piston $$$$. I haven't had a chance to measured my block or piston clearances yet but either way if the old pistons can be used I'm thinking about Swain Coatings for at least the piston skirt and maybe a thermal barrier on top too. Not sure how much money I want to sink into a set of old pistons but they can do a heavy coat to the piston skirt to build up as much as 0.004" to bring clearance back into spec. Just something to consider...

Swain Tech Coating Price Sheet - Link

---

Quote:

---

What happens if the coating wears off ?

---

Quote:

---

How much is it going to cost to coat the pistons?

---

Quote:

---

My stock pistons are .080" in the hole, is that normal for a stock 2-brl 383?

---

Quote:

---

Quote:

---

My stock pistons are .080" in the hole, is that normal for a stock 2-brl 383?

---

Are they all exactly 0.80 in the hole? Mine varied from about .030 to .050. I'd be surprised if yours are all the same because most blocks weren't square from the factory.

---

Quote:

---

Are they all exactly 0.80 in the hole? Mine varied from about .030 to .050. I'd be surprised if yours are all the same because most blocks weren't square from the factory.

---

Quote:

---

Quote:

---

I have a 383 that will be .030” over and will be used for a daily driver. 650 carb, stock exhaust manifolds and gas friendly cam. Thinking maybe 300-330 horse. Looking at what pistons to get and have narrowed it down to the Keith Black 162’s or 400’s. Seems like most folks go with the 162’s but I’m not sure why since the compression is so low. I do not want to deck the block or mill the heads so what to do???

Facts:

4.280” bore
3.38” stroke
4.5” head gasket bore (estimated)
.020” head gasket thickness
90 cc heads (measured- 906)
.080” depth to stock piston (measured)

Using Keith Black KB-162 pistons (5cc dish with stock compression distance of 1.908” puts compression at 7.69:1

Using Keith Black KB-400 pistons (6cc dome with stock compression distance of 1.908” puts compression at 8.37:1

The KB-162’s are supposed to be stock replacement pistons though stock pistons don’t have the valve relief so does that mean they have a 0cc dish/dome? If so the compression would have been 7.99:1 with stock pistons.

Why wouldn’t I get the 400’s and have the 8.4:1 compression? Am I missing something?

---

I just reran these numbers and I get higher compression ratios even with the overestimate bore size of the head gasket , which is actually 4.410 and .021 thick. The KB is .027 in the hole ASSuMEing the block is at factory 9.98 deck.

Flat top is 8.38 with your head gasket or mine

Dome is 9.22, mine is 9.21 ???

I use the calculator at www.Diamondracing.net/tools

Your compression will be higher than original , flip a coin and use which ever you want.

---

Quote:

---

.010" cut off the block with Speed Pro 2315's.

---