I've never had a blocked squared before. I thought that having the main bearing bore alignment checked first would be a good idea. Are mopars known for main bearing bore alignment problems? Then the block deck height could be checked, am I going in the right direction for the purpose of squaring up the block? Are small block mopars known for their block deck height being way off? My goal is to have the block zero decked. What pistons would be best to use, I found a set of speed pros and Keith Black. The speed pros would require a 0.027" cut, is this acceptable?
Machining a mopar small block
- Thread starter Dan the man
- Start date
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Bobzilla
Well-Known Member
All factory engine blocks can have some degree of variation from design spec. If you have a really good machine shop to work with, none of this will be a problem unless the block happens to be really bad, which is mostly rare.
If I recall correctly, the block is indexed or mounted by the cam bearing bores, then crankshaft bores are addressed to line up with the camshaft bores. After that the decks can be squared and set.
Check out the compression calculator on the Diamond Pistons website. Play with numbers to see which pistons (compression height) and combustion chambers get you the compression ratio you want with the least material removed from the decks as possible.
Rat Bastid
Dunamis Metron
There isn’t a block out there that doesn’t need the mains line honed. That’s like saying the bores are good enough.
Get the main line in it and then deck it.
There isn’t a production block out there with any name on the valve cover that has a flat, true, square deck. How far off they are depends largely on how much they had to machine off the casting to start with and how accurately the block was stuffed onto the fixture.
You cut the deck as far as you have to so you end up with the deck clearance you need. I’ve had to take .060 off to get it.
Of course, the intake will most likely not fit if you have to take that much off so it will need to be machined as well.
When I built my motor in 2020, I bought a set of icons that were .027 in the hole. They were doing the whole thing, align hone mains, deck, bore, home.
I told the machine shop to try and deck it to 9.582 so I could run a .027 cometic and end up with a .036 quench and a little under 11:1. I also said to call me if that didn't work. That would allow me to deck it again in the future and run a thicker gasket.
Block needed to go down more to clean and ended up zero decked with a .036 gasket. Your best bet, in my opinion, is to figure out what gasket you plan to run, do the mains, and then deck as little as possible.
$1000 back in spring 2020.
I told the machine shop to try and deck it to 9.582 so I could run a .027 cometic and end up with a .036 quench and a little under 11:1. I also said to call me if that didn't work. That would allow me to deck it again in the future and run a thicker gasket.
Block needed to go down more to clean and ended up zero decked with a .036 gasket. Your best bet, in my opinion, is to figure out what gasket you plan to run, do the mains, and then deck as little as possible.
$1000 back in spring 2020.
MOPAROFFICIAL
If it has tits, it's a liabilititty.
The mains are usually straight.
The deck height always varies up to .008 or so front to back & across
The deck height always varies up to .008 or so front to back & across
The whole operation takes place at the machinists. Tell him you want the block squared up and what compression you want to run.
MOPAROFFICIAL
If it has tits, it's a liabilititty.
Aka pin height and once he has the rods done. 1st.
He can dial it some and or work around a gasket.
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