2270 Deck Height and CR, Pistons sitting proud of the deck, how many shims is too many shims? Options

[technicalninja]

I'm planning on re-using the original Mahle cylinders and having them bored due to the posts I've seen on here.

The original German stuff is BETTER quality than what is available now. (with the exception of Nickies).

It will actually be MORE expensive to have my cylinders bored out than to just purchase new but I will be able to control P-B clearance better and will end up with a plateau honed surface.

The biggest area that the new cylinders seem to have trouble with is length.
The original German stuff looks to have a variation in length under .001" and the Chinese junk seems to run =/- .005.

On an engine with P to CYL head clearance above .065 this will not matter at all.

I build engines with as tight a quench number (p-cyl or "deck") as I can get away with.

I'll be under .040 on cast and .045 on forged and a .005 variation means DESTRUCTION of engine.

So I'm starting with used parts that will cost more to prepare than just buying new.

[vjb206]

Did some measurements this weekend!

(IMG:http://www.914world.com/bbs2/uploads_offsite/media.giphy.com-23760-1709694116.1.gif)
My combustion chambers are 60ccs. Measured with fluid as well as called the manufacturer. Double confirmed.

(IMG:http://www.914world.com/bbs2/uploads_offsite/media.giphy.com-23760-1709694117.2.gif)
Deck height is -0.090. Got that with a dial indicator.

@cgnj LMK if this is in your range if you recall...

@VaccaRabite great to know re: CR range (and thank you for the details, really)

So here's what I'm thinking, would love opinions...
• Base shim of 0.090
• Copper head shim of 0.08
That'll get an 8.6 CR

...a 0.060 copper shim would have gotten me to an 8.9CR. I would have run with that prior to reading this thread, but maybe not?

[Superhawk996]

Have you fully researched the use of head gaskets? If not, do so then make your own decision.

I don’t want to rehash the topic which is contentious.

The thermal linear coefficients of expansion for aluminium, copper, and steel per degree centigrade are:

Copper 17∙10E-6
Aluminium 23∙10E-6
Steel 12•10E-6

[vjb206]

Have you fully researched the use of head gaskets? If not, do so then make your own decision.

I don’t want to rehash the topic which is contentious.

The thermal linear coefficients of expansion for aluminium, copper, and steel per degree centigrade are:

Copper 17∙10E-6
Aluminium 23∙10E-6
Steel 12•10E-6

@Superhawk996 Looking into this now... Thank you for the heads-up.

[technicalninja]

Did some measurements this weekend!

(IMG:http://www.914world.com/bbs2/uploads_offsite/media.giphy.com-23760-1709694116.1.gif)
My combustion chambers are 60ccs. Measured with fluid as well as called the manufacturer. Double confirmed.

(IMG:http://www.914world.com/bbs2/uploads_offsite/media.giphy.com-23760-1709694117.2.gif)
Deck height is -0.090. Got that with a dial indicator.

@cgnj LMK if this is in your range if you recall...

@VaccaRabite great to know re: CR range (and thank you for the details, really)

So here's what I'm thinking, would love opinions...
• Base shim of 0.090
• Copper head shim of 0.08
That'll get an 8.6 CR

...a 0.060 copper shim would have gotten me to an 8.9CR. I would have run with that prior to reading this thread, but maybe not?

You need a base shim of 0.135 and NO fire ring (Head shim) at all to achieve .045 deck height. This is for forged pistons.

Base shim of 0.130 for cast stuff.

Few use a head shim (fire ring) today due to what Superhawk referred too.

If you create a deck height clearance LARGER than .060 you eliminate the quench action which VASTLY increases the tendency to detonate and reduces your compression ratio.
Bad in two ways...

Less power AND an increased requirement for higher octane fuel.

[930cabman]

Have you fully researched the use of head gaskets? If not, do so then make your own decision.

I don’t want to rehash the topic which is contentious.

The thermal linear coefficients of expansion for aluminium, copper, and steel per degree centigrade are:

Copper 17∙10E-6
Aluminium 23∙10E-6
Steel 12•10E-6

I built a 2056 a couple years ago and was on the fence with regards to the use/no use of a head gasket. I checked and double checked everything including Plastigage at quarter points at the cylinder/head mating surface after torquing everything together. I was pleased with the results and learned mating the heads to the cylinders without any sealing product works well.

[technicalninja]

I missed a critical point!

Check deck height on ALL pistons, don't assume they will be all the same height, they seldom are.

Choose your shims for the cylinder with the most piston height!

I'd also make damn sure the height of the jugs matches per bank.

[Montreal914]

Detail in the grand scheme of things in the current state of discussion, but I don’t see where you have measured the volume of the pockets in the pistons.

I maintain my previous comments. This is not an IKEA kit.

Need to read a lot on building a strocker high power type 4 engine before starting to put parts together!!!!

Good luck with your project!

[r_towle]

I think you need the longer cylinders from AA.

[Jack Standz]

Did some measurements this weekend!

(IMG:http://www.914world.com/bbs2/uploads_offsite/media.giphy.com-23760-1709694116.1.gif)
My combustion chambers are 60ccs. Measured with fluid as well as called the manufacturer. Double confirmed.

(IMG:http://www.914world.com/bbs2/uploads_offsite/media.giphy.com-23760-1709694117.2.gif)
Deck height is -0.090. Got that with a dial indicator.

@cgnj LMK if this is in your range if you recall...

@VaccaRabite great to know re: CR range (and thank you for the details, really)

So here's what I'm thinking, would love opinions...
• Base shim of 0.090
• Copper head shim of 0.08
That'll get an 8.6 CR

...a 0.060 copper shim would have gotten me to an 8.9CR. I would have run with that prior to reading this thread, but maybe not?

You need a base shim of 0.135 and NO fire ring (Head shim) at all to achieve .045 deck height. This is for forged pistons.

Base shim of 0.130 for cast stuff.

Few use a head shim (fire ring) today due to what Superhawk referred too.

If you create a deck height clearance LARGER than .060 you eliminate the quench action which VASTLY increases the tendency to detonate and reduces your compression ratio.
Bad in two ways...

Less power AND an increased requirement for higher octane fuel.

Might want to check the deck height for all cylinders, don't assume they're the same.

In addition, you might want to skip the copper head gasket, unless you're racing the car and will re-torque the heads regularly. And using your numbers, you're aiming for zero deck height? If you use a head gasket and zero deck height and you've measured even a little off (again, check the deck heightfor all cylinders), you might end up hitting the piston crown on the head gasket, if it encroaches into the cylinder. Might get away with it, might not. Better to figure it out now before the mock-up. No matter what, plan to mock things up a bunch of times before the final assembly.

[Jack Standz]

I think you need the longer cylinders from AA.

AA Pistons only lists longer cylinders for 103, 104 and 105mm cylinders.

[crash914]

Also don't forget:
Pushrods will not be stock. Buy cut to length and determine the valve geometry.
Since the head spacing will be further apart, there might be some fitment issues depending on the induction system used.
Pushrod tubes will need to be either modified or spaced out slightly for the additional length.
Rod/case/cam clearance will need to be checked and verified.
Not too major, just a lot of "this" will change "that"

[vjb206]

Definitely planning on getting deep into the valvetrain geometry, but want/need to install the heads 1st.

Also don't forget:
Pushrods will not be stock. Buy cut to length and determine the valve geometry.
Since the head spacing will be further apart, there might be some fitment issues depending on the induction system used.
Pushrod tubes will need to be either modified or spaced out slightly for the additional length.
Rod/case/cam clearance will need to be checked and verified.
Not too major, just a lot of "this" will change "that"

[vjb206]

If I'm 90 under and get a 90 shim I'll be at 0. Then the head gasket = my deck height. based on the thread above, I might not want to go that route in the end (still doing some reading per @superhawk's recco).

Can / should multiple cyl base shims be stacked to achieve desired deck height (rather than doing a cyl shim + head gasket)?

Did some measurements this weekend!

(IMG:http://www.914world.com/bbs2/uploads_offsite/media.giphy.com-23760-1709694116.1.gif)
My combustion chambers are 60ccs. Measured with fluid as well as called the manufacturer. Double confirmed.

(IMG:http://www.914world.com/bbs2/uploads_offsite/media.giphy.com-23760-1709694117.2.gif)
Deck height is -0.090. Got that with a dial indicator.

@cgnj LMK if this is in your range if you recall...

@VaccaRabite great to know re: CR range (and thank you for the details, really)

So here's what I'm thinking, would love opinions...
• Base shim of 0.090
• Copper head shim of 0.08
That'll get an 8.6 CR

...a 0.060 copper shim would have gotten me to an 8.9CR. I would have run with that prior to reading this thread, but maybe not?

You need a base shim of 0.135 and NO fire ring (Head shim) at all to achieve .045 deck height. This is for forged pistons.

Base shim of 0.130 for cast stuff.

Few use a head shim (fire ring) today due to what Superhawk referred too.

If you create a deck height clearance LARGER than .060 you eliminate the quench action which VASTLY increases the tendency to detonate and reduces your compression ratio.
Bad in two ways...

Less power AND an increased requirement for higher octane fuel.

Might want to check the deck height for all cylinders, don't assume they're the same.

In addition, you might want to skip the copper head gasket, unless you're racing the car and will re-torque the heads regularly. And using your numbers, you're aiming for zero deck height? If you use a head gasket and zero deck height and you've measured even a little off (again, check the deck heightfor all cylinders), you might end up hitting the piston crown on the head gasket, if it encroaches into the cylinder. Might get away with it, might not. Better to figure it out now before the mock-up. No matter what, plan to mock things up a bunch of times before the final assembly.

[930cabman]

My vote goes to NO head gasket

[Superhawk996]

Can / should multiple cyl base shims be stacked to achieve desired deck height (rather than doing a cyl shim + head gasket)?

Can they be stacked - yes

Should multiple shims be stacked - no.

Each time you add a head gasket or stack shims you are creating potential leak paths by adding unnecessary interfaces between parts.

[vjb206]

Just going to do some more reading before pulling the trigger on the Type 4 store .150 Blanch Ground Cylinder Shims. Soon. This will get me me an 8.9 : 1 CR. Type 4 Store 2270 page says, "Target compression ratio is 9.0:1 using pump 91 octane or 9.5:1 using pump 93 octane (R+M)/2." So that's just giving me pause that perhaps I need .140. Either way, single shim. No fire ring. I'm in NJ (no altitude, and not mountain climbs) and will run 93 octane at all times.

Also will measure my valve pockets, and factor that into the CR calculations / internal debate.

While I'm mulling that over the plan is to take apart my feeler gauge to set the deck height approximating a big .150 shim. While the deck is mocked up, I'll start playing with the valvetrain geometry. I have an adjustable pushrod so I can start to get the feel. This is the 1s time I'm doing this so I want to have time to explore....

Thanks again for all who have weighed in!

Can / should multiple cyl base shims be stacked to achieve desired deck height (rather than doing a cyl shim + head gasket)?

Can they be stacked - yes

Should multiple shims be stacked - no.

Each time you add a head gasket or stack shims you are creating potential leak paths by adding unnecessary interfaces between parts.

[technicalninja]

Proper quench distance is far more important than staying under a specific compression ratio number.

You take an engine with no quench that requires 93 and INCREASE the compression ration by decking the block (adjusting shim size on a T4) to achieve optimal quench and the engine can now run regular without detonation.
The really wild thing is the higher compression engine will also require 5-7 degrees LESS timing to achieve MBT.

MBT stands for Mean Best Torque and is how a steady state dyno tunes.
You continue to add timing (at a specific rpm) until either the engine detonates (detonated limited timing) or you see no further increases in torque for additional timing.

Also, your compression ratio is low enough already that a decrease of 1-2cc in compressed volume is only worth .1-.2 increase in compression. IE you end up with a 9.0 or 9.1 engine instead of an 8.9...

Do some reading involving "quench".
IMO it's the MOST important clearance to get right.
Getting this wrong can be worth 10% less power and a requirement for higher octane fuel.

For a customer job on a sub 4" bore with decent rods (h-beams) and forged pistons I want to hit .045.

On my personal stuff I might go a tiny bit tighter. I'd run as tight as .041-.042.

This clearance must be verified for all cylinders and the tightest used as the reference point for shim selection.

Just noticed the baby syringe in the video. A real burette is far more accurate!
I use a cow syringe in a pinch. They are really handy for chambers at or under 60cc as the cattle syringe is a 60cc unit.
The cow syringe is also not as accurate as a burette but getting the measurement in a single syringe load helps accuracy and if you use the same syringe for each cylinder measurement you will be fairly balanced between cylinders when you are finished.



What cam will you be using?

Induction?

Exhaust?

[cgnj]

@vjb206

I used a .140 shim. No head gasket. I lapped the cylinders to the head. Rods were machined as described in #5 in attached Tech Bulletin. I used Manton CrMo pushrods. Buy n extra pushrod and make your own adjustable push rod. The tips on the adjustable push rod that I used were not the same and caused measurement error. It is possible to stack washers in the pushrod tube bore to space out stock pushrods. EMS sells stroker tubes.

 techbull.pdf ( 141.2k ) Number of downloads: 49

[Jack Standz]

Proper quench distance is far more important than staying under a specific compression ratio number.

You take an engine with no quench that requires 93 and INCREASE the compression ration by decking the block (adjusting shim size on a T4) to achieve optimal quench and the engine can now run regular without detonation.
The really wild thing is the higher compression engine will also require 5-7 degrees LESS timing to achieve MBT.

MBT stands for Mean Best Torque and is how a steady state dyno tunes.
You continue to add timing (at a specific rpm) until either the engine detonates (detonated limited timing) or you see no further increases in torque for additional timing.

Also, your compression ratio is low enough already that a decrease of 1-2cc in compressed volume is only worth .1-.2 increase in compression. IE you end up with a 9.0 or 9.1 engine instead of an 8.9...

Do some reading involving "quench".
IMO it's the MOST important clearance to get right.
Getting this wrong can be worth 10% less power and a requirement for higher octane fuel.

For a customer job on a sub 4" bore with decent rods (h-beams) and forged pistons I want to hit .045.

On my personal stuff I might go a tiny bit tighter. I'd run as tight as .041-.042.

This clearance must be verified for all cylinders and the tightest used as the reference point for shim selection.

Just noticed the baby syringe in the video. A real burette is far more accurate!
I use a cow syringe in a pinch. They are really handy for chambers at or under 60cc as the cattle syringe is a 60cc unit.
The cow syringe is also not as accurate as a burette but getting the measurement in a single syringe load helps accuracy and if you use the same syringe for each cylinder measurement you will be fairly balanced between cylinders when you are finished.



What cam will you be using?

Induction?

Exhaust?

+1

We use a 100 ml burette with a three finger clamp for accuracy and repeatability. BTW you can fly cut the heads to reduce chamber volume and increase compression ratio among other ways.