Is it okay to deck the block?

[jenkins71]

Hey guys, me again. I will probably be dropping my 440 block off at the machine shop tomorrow.

My plans are to have the cylinders honed, the main cap alignment check and honed if needed, and the deck milled .025".

I am using a gasket that's .045" versus the steel shim that was in there of .020". I am milling the deck to keep compression up as it is cheaper than fitting new pistons, and more cc's removed than milling the heads.

I am also planning on capping it off with a set of 440source Stealth Heads.

So, the question is, will the intake fit with that much milled off? I feel since its just the difference between the stock gasket and the new composite gasket I should be fine. And pushrods, will that be okay?

Thanks for any quick response before I drop off the block tomorrow morning!!!!

 

[Xp29h]

I found out the hard way, not told by p.o. But block and heads had been done. New intake bolts wouldn't line up. I had to have the intake shaved as well to get a good tight fit. Doesn't take long for them to do the intake. You can mock it up after getting block back back and heads on just to see if you need and how much.

Good luck.

 

[69Bee]

If you are going to mill the block anyway, make sure your shop uses a BHJ Blok-Tru and square the block. I just did a 440, and removed about 0.020" just to clean and square it, and the pistons were still 0.079" in the hole. Run the numbers, and figure out how much to mill off of the block, and maybe even the heads, to arrive at your compression you want.

1) To reduce the head chamber volume on open chamber heads, mill 0.0042" per CC.
2) Mill 0.0123" off of the intake side of the HEADS for each 0.010" from the head/block.
3) I would clean up the valley rails only as you do not need to remove an amount because of the head/block milling.

I would NEVER remove material from the intake, as it then marries it to the engine.

 

[383man]

I would only deck it enough to clean it up first. Then after you mock it up with the four corner pistons you can check all the specs and if it needs more you will know just how much to take off. And if its good you will be glad you did not take anymore off. Ron

 

[jenkins71]

I would only deck it enough to clean it up first. Then after you mock it up with the four corner pistons you can check all the specs and if it needs more you will know just how much to take off. And if its good you will be glad you did not take anymore off. Ron

I'm re-using the pistons... They were .099 in the hole.
Guys if I mill .025" do you think my pushrods will be OK?

 

[HT413]

Seems like a lot of effort to gain what, 1/4 point of compression? according to IQ52 here on FBBO, that's worth about 1% HP gain.

 

[jenkins71]

Seems like a lot of effort to gain what, 1/4 point of compression? according to IQ52 here on FBBO, that's worth about 1% HP gain.

With my planned setup without decking the block, I'm at 8.94:1.
With decking the block .025" I'm at 9.38:1.
So that's a little over half a point of compression.... Worth $250? (my shop's rate for decking the block)

 

[demonram]

I'd have it decked just to clean it up. Mine was only off .010", I didn't do it for compression.

 

[HT413]

With my planned setup without decking the block, I'm at 8.94:1.
With decking the block .025" I'm at 9.38:1.
So that's a little over half a point of compression.... Worth $250? (my shop's rate for decking the block)

I guess if the deck needs a cleanup anyway, maybe the cost is justified to go a bit more. What are your future plans? This much removal will put most all performance pistons above that new deck height and will cost you if you swap pistons in the future. I guess it all depends.

 

[jenkins71]

Good point about future pistons.... When you're buying pistons on say Summit, will it tell you har deep in the hole the piston will go up?

 

[Meep-Meep]

Chryslers are typically really bad when it comes to the block deck. Meaning it's rarely parallel to the crank CL, so you will be better off squaring it up. Do what 69Bee said.

 

[HT413]

Good point about future pistons.... When you're buying pistons on say Summit, will it tell you har deep in the hole the piston will go up?

They generally list compression height, so you'd have to figure out the distance below (or above) the deck.

 

[HT413]

I guess to answer your question, most pump gas pistons that I looked at when planning my 440 build (I've since switched to a 451) are somewhere between 0.000 and 0.020 in the hole based on standard deck height, with the majority being like 0.010 to 0.020ish. But like is said above, who knows where that really leaves you.

You really need to ask the machine shop how far you need to go to square it up and compare that to where you would be if you went 0.025. I'd bet you are talking 1/4 point of compression.

 

[Longroof]

Chryslers are typically really bad when it comes to the block deck. Meaning it's rarely parallel to the crank CL, so you will be better off squaring it up. Do what 69Bee said.

Getting the decks square is one of the basics of a good blueprinted build. It is essentially free horsepower. Why do you think class racers (stock/Super stock) do it? Well worth the money and effort if you are doing more than a basic rebuild on a daily driver.

 

[62 Dart Convertible]

Why not use a thinner gasket like steel shim or cometic? Probably cheaper and less permament...

Pushrods - you won't know until you mock up as there are so many variables...

 

[HT413]

Here are the pistons I considered when planning my 440 build. Notice most pistons are designed for 0.015 to 0.017 in the hole. While planning, I made a spreadsheet to keep it all straight. Use this for your reference, but all numbers should be verified, as i easily could have made a mistake.

 

[jenkins71]

Thanks for the advice guys. Not going to mill the block now!

 

[Meep-Meep]

Getting the decks square is one of the basics of a good blueprinted build. It is essentially free horsepower. Why do you think class racers (stock/Super stock) do it? Well worth the money and effort if you are doing more than a basic rebuild on a daily driver.

Aside from these obvious benefits, I'll add that blueprinting for the stock class guys means to cut the block and heads to the exact "as per blue print" specifications to make sure they can get the advertised "real" compression ratio.