Milling Head, its effect on compression ratio? (1 Viewer)

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You are 100% correct. I *assumed* a cylindrical combustion chamber. I do not have the combustion chamber geometry. I do have a 3d laser scanner, so if I really cared, I could get accurate data. I was trying to get a feel of the "order of magnitude" of compression ratio change with a 0.010" milled head. I now know it is on the order of .2 gain from 9.0:1.

I will post the corrected calculations below. Taking this into account:
sv = stroke volume
nv = non "stroke volume" volume = combustion chamber volume + head gasket thickness volume + others
compression ratio = cr = (nv+sv)/nv
Therefore nv = sv/(cr-1)

Thanks for finding the error.
 
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I'm feeling a bit lazy so I'm not going to calculate, but shaving a few hundreths of a milimeter off of a 100 mm bore is going to be a fraction of a percent. Landtank's numbers look like they're in the right ballpark.

Pulse's change of about 3% seems way high.
 
With the formula correction supplied by semlin, the estimated compression ratio is now 9.175:1 instead of the incorrect 9.22:1 with a 0.010" milled head.

sv = stroke volume
nv = non "stroke volume" volume = combustion chamber volume + head gasket thickness volume + others
compression ratio = cr = (nv+sv)/nv
Therefore nv = sv/(cr-1)

4477 cubic cm
273.203 engine (cubic inches)
3.937 bore (inches)
3.740 Stroke (inches)
9.0:1 Stock Compression Ratio (cr)

45.534 stroke volume (sv) (cubic inches)
5.692 nv (cubic inches)

12.174 crossectional area insq (assuming cylinder)

0.010 mill head inches
0.122 volume removed cuin

5.570 milled nv (cubic inches)
9.175 milled compression ratio
 
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With the formula correction supplied by semlin, the estimated compression ratio is now 9.175:1 instead of the incorrect 9.22:1 with a 0.010" milled head.

sv = stroke volume
nv = non "stroke volume" volume = combustion chamber volume + head gasket thickness volume + others
compression ratio = cr = (nv+sv)/nv
Therefore nv = sv/(cr-1)

4477 cubic cm
273.203 engine (cubic inches)
3.937 bore (inches)
3.740 Stroke (inches)
9.0:1 Stock Compression Ratio (cr)

45.534 stroke volume (sv) (cubic inches)
5.692 nv (cubic inches)

12.174 crossectional area insq (assuming cylinder)

0.010 mill head inches
0.122 volume removed cuin

5.570 milled nv (cubic inches)
9.175 milled compression ratio
Don't forget to use the volume of the compressed head gasket when calculating, and possibly piston to deck height, which I have calculated to be basically 0 (+0.0006219mm), but I'm not sure I have correct block height (I used 9.585" and can't remember where I found that). If you slightly overshave the head you could use a thicker gasket to regain timing. Cometic makes 5 thicknesses from 0.04 to 0.120. If you include the compressed thickness of a stock gasket you can calculate the combustion chamber size accurately but only if pistons are flat top with no dome or relief.
 
robbie/powederpig has chimed in on this before. shaving .010 is the absolute maximum he recommends without timing issues and he has done this many times. the machine shop i took my head to was very reluctant to go .010 and wanted to take only what they had to based on shaving newer toyota heads in the past and encountering timing issues. as mark says, the compression depends disproportionately on the irregular volume inside the head cavity at the moment of combustion. by reducing this, you are making a much larger change in compression than your calculation shows.
What is the feasibility of using a thicker head gasket, taller piston, Different Rod, Custom crank, etc.? I mean if you absolutely, positively must use that head and shave it too close.
 
That would be fine. On a stock 212hp 1FZ, if the block and head are prepped correctly (appropriate RA finish) and you're using a high quality steel gasket and ARP studs, you can use the head gasket to make up for minor decking and finishing tolerances. But this thread was started 10 years ago so they probably figured it out by now. ;). Lol

Using custom rods and or Pistons to make up for decking a head would be hugely cost prohibitive and complete overkill, not to mention having them made would be 2-3x the cost of buying a good used head and reconditioning it.

What is the feasibility of using a thicker head gasket, taller piston, Different Rod, Custom crank, etc.? I mean if you absolutely, positively must use that head and shave it too close.
 
I just had the head milled, block decked used an oem gasket and didn't care. A slight (and .1 is slight) bump in compression isn't going to cause detonation.
 
Ok, resurrecting a thread that's older than my oldest child as this was the most relevant hit for the Google search "1FZFE Cylinder Head Volume"

I'm about to get my head and block from the machine shop and he's recommending a head gasket that's .020 over stock compressed in order to restore compression to 9:1 based solely on what they took off the block and head. Since it was also bored to 101.5, I wanted to double check his math if I'm going to buy a (another) high $ gasket by using Summit's calculator.
Bore (now) 101.5mm
Stoke: 95mm
Cylinder Head Volume: 82.922cc (Stock 9:1 less .010'. I understand from the previous posts this is accurate-ish but I don't have any other way to get there)
Effective Dome Volume: 0? as its a flat head piston
Deck Clearance: To be measured by machine shop but slightly negative, now (anyone tell me what stock is for grins?)
Compressed Gasket Thickness: .040 stock This is the variable to get back to 9:1
# Cylinders: 6 glorious ones.

Throwing this out to the group for feedback, critiques, flames and general entertainment.
 
Buy the correct thickness Cometic HG.
I was able to get back to factory clearances with Cometic.
I felt it was importance since I installed a turbo.
 
Buy the correct thickness Cometic HG.
I was able to get back to factory clearances with Cometic.
I felt it was importance since I installed a turbo.
Thats what I'm trying to back into given my calc above.
 
Ok, resurrecting a thread that's older than my oldest child as this was the most relevant hit for the Google search "1FZFE Cylinder Head Volume"

I'm about to get my head and block from the machine shop and he's recommending a head gasket that's .020 over stock compressed in order to restore compression to 9:1 based solely on what they took off the block and head. Since it was also bored to 101.5, I wanted to double check his math if I'm going to buy a (another) high $ gasket by using Summit's calculator.
Bore (now) 101.5mm
Stoke: 95mm
Cylinder Head Volume: 82.922cc (Stock 9:1 less .010'. I understand from the previous posts this is accurate-ish but I don't have any other way to get there)
Effective Dome Volume: 0? as its a flat head piston
Deck Clearance: To be measured by machine shop but slightly negative, now (anyone tell me what stock is for grins?)
Compressed Gasket Thickness: .040 stock This is the variable to get back to 9:1
# Cylinders: 6 glorious ones.

Throwing this out to the group for feedback, critiques, flames and general entertainment.
I think you are over thinking this. If the machine shop took 20 thousandths off in block and head, I would get a 60 thousandth head gasket. The actual compression change is going to be very negligible this is a tractor not a race car. IMO
 
I think you are over thinking this. If the machine shop took 20 thousandths off in block and head, I would get a 60 thousandth head gasket. The actual compression change is going to be very negligible this is a tractor not a race
Even with a larger bore?

Re: overthinking...trying not to....
 
Most likely the reason toyota doesn't want the head machined is because it affects timing chain length. With my LS motor I can machine the head without worrying about that. If you have slotted cam gears you can offset the length. Thus affecting when the valves open/close in relation to the piston position. I don't have much experience here but that's me just thinking about the effects it would have in theory.
 
Why is anyone worried about 20 thousandth And it’s minuscule affect on compression.

We aren’t building race engines here
 
Yep I would be less concerned with compression and more concerned with valve timing, just get the proper thickness MLS gasket to restore it back to stock.


Or set the timing where it is happiest.

My rocks hard for a stock 1FZFE.

Cheers
 
Timing is adjustable so it's not a worry. And its tensioned sooooo.... If we were zinging these engines past 6k rpm to like 7k I'd take more precautions but a low revving 1fz-fe is not going to have any issues with a little off the top.

I have 20 thousandths off my head and deck (total of 40 thousandths reduced) and am only running the OEM gasket. The engine has been bulletproof and running strong for the last 60,000mi.
 
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Ignition timing and valve timing are not the same. But it is not a big deal. To get valve timing correct after milling the block and head without replacing that material with a new gasket you would need adjustable cams gears.
 
ah yep that is true, good catch. I agree though on an engine with this low of a redline and the tolerances we are dealing with here it's not a bid deal. It's still more or less a fancy forklift motor at the end of the day.
 

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