440 deck height

[ksurfer2]

I have a 440 based 512 that was put together with 440 source parts. With the spec'd parts, the pistons should be .010 in the hole. The crank is a 4.250 stroke, rods are 7.100, and the compression height of the pistons is 1.485. This equates to 10.71. The deck height of a 440 is listed as 10.725 which adds up. However, when I measure my block, the pistons are .080 in the hole. I confirmed this with both a dial indicator and straight edge with feeler gauges. The top of the bore, above TDC there is an obvious bevel the makes up this .080. My question is, how much of the deck can be milled to remove this extra deck height before running into issues with the block or alignment issues between the heads and intake?

 

[PROSTOCKTOM]

Long story short you could mill all of it off, as I've milled dozens of blocks .100" to add some compression for the late 70's engine that had the pistons .156" in the hole.

However, just be aware that a zero decked 512" is going to produce lots of compression and just small amount of alterations make a huge change on an engine this size.

As far as intake alignment I like the intake sitting higher up on the heads for many reasons.

Most heads have a lip at the top of the head intake port that curves down not allowing the roof to be straight, by sitting the intake manifold higher up on the head you

are able to grind that lip out and get the roofs of both in perfect alignment.

The worst thing you might have to do is file out the intake manifold bolt holes a touch and buy pushrods.

In my opinion all of this is just part of building a sorted performance engine.

FYI: I have a 512" that I purposely left the pistons .035" in the hole to control the overall compression ratio.

You go this!!!

Tom

 

[BSB67]

I have a 440 based 512 that was put together with 440 source parts. With the spec'd parts, the pistons should be .010 in the hole. The crank is a 4.250 stroke, rods are 7.100, and the compression height of the pistons is 1.485. This equates to 10.71. The deck height of a 440 is listed as 10.725 which adds up. However, when I measure my block, the pistons are .080 in the hole. I confirmed this with both a dial indicator and straight edge with feeler gauges. The top of the bore, above TDC there is an obvious bevel the makes up this .080. My question is, how much of the deck can be milled to remove this extra deck height before running into issues with the block or alignment issues between the heads and intake?

My limited experience is the deck is 0.020. - 0.025” above blueprint spec. Your 0.080” seems very high.

 

[silversedan]

did you double check the rod length, and piston height? we got a 470 from them last year and had the same problem, called them and he said some rods came in marked wrong, checked a sure enough the rods weren't the length listed, they made it right with no problems , just some food for thought

 

[68-500]

As above check rod length and crank throw. Either way I think you need some reverse dome pistons if you have pump gas in mind.

 

[RemCharger]

What's the goal? More power?

 

[RemCharger]

. My question is, how much of the deck can be milled to remove this extra deck height before running into issues with the block or alignment issues between the heads and intake?

Iirc it's. 010 for the deck and .0123 for the intake surface.

 

[451Mopar]

It is pretty normal for the blocks to be taller than spec. Even common for them to be different heights front to back and side to side. The 0.080" seems excessive though?
I have the machine shop deck the block to near zero piston to deck. Usually it comes back with the piston 0.002" below the deck at TDC.
I think it may have been mentioned to mock up the heads and intake on the block to check for intake alignment before torquing down the cylinder heads. Decking the block and/or head chamber side lowers the ports in the block "V" so they get closer. The width between them gets narrower for the intake manifold.
If you need to correct this, milling the intake side of the cylinder head for fitment is a good choice as it lets you swap intake manifolds.
You could mill the intake manifold to fit. but then the manifold fitment is specific to that engine (although you might be able to double up gaskets to fit un-milled engines.)
Question? are the pistons dished or flat tops? Just trying to get an idea of compression ratio.

 

[gkent]

If it were me I'd have the decks machined to the stock height. I wish I'd had your problem, once I got my decks straight and square my pistons that were supposed to be .009 IN the hole were .016 ABOVE the decks !!

 

[ksurfer2]

The pistons are flat top (with valve reliefs). The advertised compression ratio for the set up is 12.7:1. This is in a nss race car, it is not a pump gas car. The ultimate goal is to find more hp. I feel the set up is missing a substantial amount of power from where it should be.

 

[Cranky]

If it were me I'd have the decks machined to the stock height. I wish I'd had your problem, once I got my decks straight and square my pistons that were supposed to be .009 IN the hole were .016 ABOVE the decks !!

Got to measure everything BEFORE doing the final assembly....

 

[gkent]

Got to measure everything BEFORE doing the final assembly....

So you get your fully machined block home and the decks are short ... what do you expect the shop to do, weld material back on ??

I expected them to check the deck height FIRST and I would have had the option of finding another block.

I ended up using SCE copper head gaskets to correct things. No problems.

 

[33 IMP]

This is a stupid question, don't be offended.
Sure the crank isn't 4.150 ? (Piston an extra .050 in the hole)

 

[ksurfer2]

While I did not measure the crank, the 440 source website lists the crank as a 4.250.

 

[33 IMP]

It's time to double check all the measurements mentioned above : compression height, rod length, crank stroke.
If all check out correct..... deck the block.
I'd deck the block anyway if you have a machinist you trust. As mentioned above, frequently they are over spec height, out of square front to back, and unequal side to side.
Now is the time to fix it.

 

[PRHeads]

Imo, “something” is way out of spec(and should have been caught during the first trial assembly), and in my mind, the block being that much too tall is the least likely culprit.

If you’re going to move forward with correcting whatever the issue is, the rotating assy needs to be removed anyway, and when it’s apart, the rod length and piston C/H can be verified.

However, before taking the bottom end apart, measure the stroke first.
It should be easy to tell if it’s noticeably shorter than 4.250”.

Btw, .080” of deck clearance with a 4.375” bore is 19.7cc worth of volume.
That’s going to lower the CR about 2.0 points.

*making the assumptions:
-75cc chambers and .040” head gaskets, 4.375” bore

With the extra 19.7cc volume, If the stroke is actually 4.25 the CR would be 10.4.
If the stroke turned out to be 4.15”, you’d lose 12 cubes and the CR drops to 10.2.

 

[dvw]

Could be they sent a 4.150" stroke crank. With .080" in the hole that would be a deck of 10.740". Which with an untouched deck might be possible.
Doug

 

[ksurfer2]

Please excuse my very crude diagram. I am trying to wrap my head around where the issue ultimately lies either with the block or with the crank/rod/piston. In this diagram, the piston (blue), is at TDC, the bore begins a very pronounced taper above the piston to deck height. If the issue is with the crank stroke, rod length, or compression height of the piston, the top of the piston would no longer be tight in the bore as it would now be in the tapered area of the cylinder. That doesn't seem like it would be correct, or am I mistaken?

That leaves deck height as the issue. As Prostocktom mentioned decking the block would be a viable option with some other necessary work to the intake/heads. Wouldn't this also cause an issue with valley pan fitment. One way or another, the motor is coming out and coming apart.

 

[Cranky]

So you get your fully machined block home and the decks are short ... what do you expect the shop to do, weld material back on ??

I expected them to check the deck height FIRST and I would have had the option of finding another block.

I ended up using SCE copper head gaskets to correct things. No problems.

I didn't say it was your fault. That said, being a machinist, I have the tools (many are home made....) at home to check a block before sending it out for any machine work.

 

[ksurfer2]

Here is a close up photo of the piston (at TDC) in the bore. The taper at the top of the bore is very noticeable as is the depth of the piston in the bore.