open deck cylinder towers

[bentvalves]

how important are torque plates when sizing open deck blocks. Headbolts are nowhere near the holes.

[gunt]

on a what ? engine

[bentvalves]

with the headbolts well out of the way of the bores, what difference does it make? No disrespect intended.

[PackardV8]

with the headbolts well out of the way of the bores, what difference does it make? No disrespect intended.

Maybe a critical difference:

The cycling hone head puts a lot of torque and pressure on the inside of the cylinders. On some engines, honing without a torque plate one can actually see the cylinder move. Others, with webbing between the cylinders, not so much.

Then, there's the compressive force of the headbolts pulling down on the free-standing cylinders. Depending on the design, the head gasket and several other factors, it's impossible to accurately hone some open deck engines without a torque plate.

[Schurkey]

with the headbolts well out of the way of the bores, what difference does it make? No disrespect intended.

The "Pontiac" engine has the headbolts anchored to the water jacket, not the cylinders.

Those blocks move around like crazy when you torque the head bolts.

There's no knowing how the block will or won't move under stress from the head bolts, or main bolts--or bellhousing bolts--until you check 'em with instruments.

[bentvalves]

fa20f, subie.

built engine arrived with a blown headgasket mixing coolant with oil. bores looked good until I lightly stroked them with a rigid hone showing the top inch, inch half perfectly all the way around not being touched by the hone.

bore gauge shows this 1" portion to be 5-7 thou oversized. One of the holes is egg shaped 30* off thrust

these were brand new OEM case halves about 5k miles ago. std bore

[BCjohnny]

Detonation .......

[Schurkey]

The way my machinist talks, new Subaru four-poppers should come with extra head gaskets in the trunk. They're practically a maintenance item.

[PackardV8]

Couldn't believe the first time the local repair shop brought in a pair of Subie heads, complete with valves and springs in place and waited. My machinist bolted them on the surfacer, cut both back flat, washed, pressure and vacuum tested them, gave them back and the customer drove his car home that night.

If the head bolts are retorqued at about 50kmi, Subies will run maybe 125kmi. If they aren't retorqued, the gaskets will go at about 75-90kmi.

[Sparksalot]

That's very faint praise Packard V8 and it's well deserved.

[cncguy987]

The dodge nascar r5 block had open cylinder bores and had bore deformation under use. Penske used a wedge at the top of cylinder to keep the bores holding roundness. The wedge was pressed in between the block and the od of the cylinder wall.

[cncguy987]

The dodge nascar r5 block had open cylinder bores and had bore deformation under use. Penske used a wedge at the top of cylinder to keep the bores holding roundness. The wedge was pressed in between the block and the od of the cylinder wall.

[gunt]

that's why i was asking , as i guessed it was the new subi stuff , with the head bolts towers separate tot he block ,

but tou could also ne asking about a diesel , and certain engines have their own issues

[gunt]

ok , so i havn't huge experience on the new range but the old subi stuff ej20-25 , even the std bores new are way off , and you state built engine on std bores , from what i have seen there wouldn't be a hope of putting forged pistons in them std , there was 1 company that did graded pistons for them , but either way the bores could be link a 50 pence piece , the std head bolts are utter crap , we have a few where 1 or 2 bolts rotted away , and destroyed the block as getting the snapped remaining stud out so low down ,

did you check the bores before the pistons were fitted , to the extent you are measuring them now ,

the std also has a taped just at the very top section but not the measurement you describe , is what you find common to all cylinders

did you use arp head bolts or something

[cncguy987]

The new dodge r6 blocks had a closed deck and the redesigned it for a reason. Torque plates work great for machining the block, but if the bores are not strong enough to keep the bores from distorting under use, that's the next problem. Darton mid sleeve are stronger than a common sleeve with top deck built in.