BOTTLEFED
Enthusiast
345/30-19 Nitto NT05Rs
Project: Bullet-proof V-10
- Thread starter BOTTLEFED
- Start date
KingSnake97
Enthusiast
Damn Now I Want To Sell My 18hres.....!@#$
AndyMac
Enthusiast
Make sure to get the NTO5R's and not the NT05's. I find the NTO5's don't stick worth a damn. I can break them loose in 3rd rolling on it around 60mph.
Awesome thread, love the info, and an excellent read.
DIY FTW!
BOTTLEFED
Enthusiast
A few more updates.
I wanted to calculate the compression ratio, quench clearance, and check for range of motion problems. Since I didn't get any specs on the pistons and rods when I bought them, I didn't know exactly what to expect for the compression ratio, other than the seller told me they were designed for a FI build.
I did these checks myself, and want to share with you guys the procedure, however, it is best if you leave it to a professional engine builder to make them. In fact I had my calculations and measurements verified by my machinist. I'll show you how to calculate these for reference and so you'll understand what your engine builder it talking about. Knowing this stuff will also help you design the parts you will need for your own engine build. There may be some other measurements you need to make on your build. If you feel comfortable with doing these, then go for it
I wanted to calculate the compression ratio, quench clearance, and check for range of motion problems. Since I didn't get any specs on the pistons and rods when I bought them, I didn't know exactly what to expect for the compression ratio, other than the seller told me they were designed for a FI build.
I did these checks myself, and want to share with you guys the procedure, however, it is best if you leave it to a professional engine builder to make them. In fact I had my calculations and measurements verified by my machinist. I'll show you how to calculate these for reference and so you'll understand what your engine builder it talking about. Knowing this stuff will also help you design the parts you will need for your own engine build. There may be some other measurements you need to make on your build. If you feel comfortable with doing these, then go for it
BOTTLEFED
Enthusiast
The first thing was to turn the engine stand so that one bank of the block is level. I chose to work with cylinder #1, but that is not critical at all.
This will be for measuring piston deck height and quench clearance.
I used a dial indicator to find exact top dead center (TDC). I brought the piston up slowly until the dial stopped moving, but before the piston started moving back down. The numbers on the dial are unimportant for this.
Once I got the piston at exact TDC, I laid a straight-edge across the block deck. I used a feeler gauge under the edge to measure the clearance. I kept pressure on the straight-edge as I slid the gauge under to prevent lifting it and getting a false reading. This measurement is the piston deck height. Along with the head gasket thickness, I got my quench clearance.
As you can see from my pic, I have .005" for deck height.
This will be for measuring piston deck height and quench clearance.
I used a dial indicator to find exact top dead center (TDC). I brought the piston up slowly until the dial stopped moving, but before the piston started moving back down. The numbers on the dial are unimportant for this.
You must be registered for see images attach
Once I got the piston at exact TDC, I laid a straight-edge across the block deck. I used a feeler gauge under the edge to measure the clearance. I kept pressure on the straight-edge as I slid the gauge under to prevent lifting it and getting a false reading. This measurement is the piston deck height. Along with the head gasket thickness, I got my quench clearance.
As you can see from my pic, I have .005" for deck height.
You must be registered for see images attach
BOTTLEFED
Enthusiast
Next I moved on to a cylinder head.
I have JM stage3 heads, so your head will probably look a little different. JM states on their site that the stage3 head comes standard with a 75cc combustion chamber volume. I didn't know if my heads were custom ported over what JM usually does with the stage3, so I decided to go ahead and measure the cylinder head combustion chamber volume, commonly known as head cc.
To do this, I first cleaned the carbon out of one of the chambers in the head (cylinder #1 since that was the cylinder I worked on in the block). I used some carb cleaner and a scotchbrite.
These are the things I used to measure the volume. I also measured the piston dish volume as well.
Cut a piece of plexi-glass to fit over the chamber. Not too thin so it doesn't flex. Drill a 1/4" hole in it.
A syringe with cc measurement.
A light oil. I used vegetable oil because it's cheap and the lightest oil I had.
Light grease to seal the plexi-glass to the surface. I use vaseline.
The head needs to be head cc side up and as level as possible. The oil needs to fill the head cc without leaking out.
I coated the edge of the cylinder head chamber with the vaseline.
I placed the plexi-glass on the head and pressed down to seal it to the head with the vaseline.
I used the syringe to measure out 10cc of oil at a time to fill the head cc through the hole in the plexi-glass. I kept track of exactly how much I put in. This is the head cc measurement. I also cc'd the piston dish, which is part of the total cylinder volume, and used to calculate compression ratio.
The head cc measured 75cc (just like the JM site says). I took the head to my machinist and he verified this measurement as well.
The piston dish cc came out to be 8cc.
I have JM stage3 heads, so your head will probably look a little different. JM states on their site that the stage3 head comes standard with a 75cc combustion chamber volume. I didn't know if my heads were custom ported over what JM usually does with the stage3, so I decided to go ahead and measure the cylinder head combustion chamber volume, commonly known as head cc.
To do this, I first cleaned the carbon out of one of the chambers in the head (cylinder #1 since that was the cylinder I worked on in the block). I used some carb cleaner and a scotchbrite.
You must be registered for see images attach
These are the things I used to measure the volume. I also measured the piston dish volume as well.
Cut a piece of plexi-glass to fit over the chamber. Not too thin so it doesn't flex. Drill a 1/4" hole in it.
A syringe with cc measurement.
A light oil. I used vegetable oil because it's cheap and the lightest oil I had.
Light grease to seal the plexi-glass to the surface. I use vaseline.
You must be registered for see images attach
The head needs to be head cc side up and as level as possible. The oil needs to fill the head cc without leaking out.
I coated the edge of the cylinder head chamber with the vaseline.
I placed the plexi-glass on the head and pressed down to seal it to the head with the vaseline.
I used the syringe to measure out 10cc of oil at a time to fill the head cc through the hole in the plexi-glass. I kept track of exactly how much I put in. This is the head cc measurement. I also cc'd the piston dish, which is part of the total cylinder volume, and used to calculate compression ratio.
The head cc measured 75cc (just like the JM site says). I took the head to my machinist and he verified this measurement as well.
The piston dish cc came out to be 8cc.
You must be registered for see images attach
BOTTLEFED
Enthusiast
Now to use those measurements to calculate the compression ratio.
engine displacement (use metric measurements):
BORE X BORE X STROKE X .0031416 = DISPLACEMENT
101.6 X 101.6 X 98.6 X .0031416 = 3197.5
This is for the stock bore (4") and stroke (3.88") of the 8.0L engine. These specs are from the FSM.
swept volume of a single cylinder:
DISPLACEMENT / 4 = SWEPT VOLUME
3197.5 / 4 = 800cc
quench clearance:
DECK HEIGHT + HEAD GASKET THICKNESS (compressed) = QUENCH
.005 + .054 = .059"
The compressed head gasket thickness was taken from the FSM.
*note that this measurement is in inches compared to the others that are in millimeters*
total deck volume of a single cylinder:
BORE X BORE X QUENCH X .01996 + PISTON DISH CC = DECK VOLUME
101.6 X 101.6 X .059 X .01996 + 8 = 20.156cc
compression ratio:
SWEPT VOLUME + DECK VOLUME + HEAD VOLUME /divided by/ DECK VOLUME + HEAD VOLUME
800 + 20.156 + 75 895.156
20.156 + 75 = 95.156 = 9.40:1 CR
I posted the complete equation so you can see how this formula works. The easiest way to do it though is just to input your numbers into a calculator like this one>
RSR Static Compression Ratio Calculator
Try it out for yourself by entering my measurements into their calculator.
9.4:1 is not much lower than stock, which is 9.6:1. I'm thinking the piston/rod combo I have are setup for the stock compression, and my JM heads are giving me the lower CR. Therefore, since I had these heads before, my CR is not changing from what I was already running, but at least its lower than stock. Since I don't plan to go TT anytime soon, the lower boost (10psi) of the Roe will be just fine. I never planned to run the nitrous much, but this CR will limit my HP shot, and I will probably have to run race fuel when spraying.
engine displacement (use metric measurements):
BORE X BORE X STROKE X .0031416 = DISPLACEMENT
101.6 X 101.6 X 98.6 X .0031416 = 3197.5
This is for the stock bore (4") and stroke (3.88") of the 8.0L engine. These specs are from the FSM.
swept volume of a single cylinder:
DISPLACEMENT / 4 = SWEPT VOLUME
3197.5 / 4 = 800cc
quench clearance:
DECK HEIGHT + HEAD GASKET THICKNESS (compressed) = QUENCH
.005 + .054 = .059"
The compressed head gasket thickness was taken from the FSM.
*note that this measurement is in inches compared to the others that are in millimeters*
total deck volume of a single cylinder:
BORE X BORE X QUENCH X .01996 + PISTON DISH CC = DECK VOLUME
101.6 X 101.6 X .059 X .01996 + 8 = 20.156cc
compression ratio:
SWEPT VOLUME + DECK VOLUME + HEAD VOLUME /divided by/ DECK VOLUME + HEAD VOLUME
800 + 20.156 + 75 895.156
20.156 + 75 = 95.156 = 9.40:1 CR
I posted the complete equation so you can see how this formula works. The easiest way to do it though is just to input your numbers into a calculator like this one>
RSR Static Compression Ratio Calculator
Try it out for yourself by entering my measurements into their calculator.
9.4:1 is not much lower than stock, which is 9.6:1. I'm thinking the piston/rod combo I have are setup for the stock compression, and my JM heads are giving me the lower CR. Therefore, since I had these heads before, my CR is not changing from what I was already running, but at least its lower than stock. Since I don't plan to go TT anytime soon, the lower boost (10psi) of the Roe will be just fine. I never planned to run the nitrous much, but this CR will limit my HP shot, and I will probably have to run race fuel when spraying.
AndyMac
Enthusiast
Awesome write up Tim. Thank you!
Yes, very well done indeed! Love to see these sorts of write ups. Can't wait to see the end result.
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