4.6 zero tolerance?
01-05-2006, 03:12 PM
#11
4th Gear Member
Join Date: Aug 2004
Location: Philadelphia, PA
Posts: 1,654
RE: 4.6 zero tolerance?
Quick question. Why is it that some pistons have the groves in them for the valves. Is that because those particular engines open valves when the piston isn't quite down far enough or is that just a safety thing incase the belt/chain breaks?
01-05-2006, 03:17 PM
#12
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Join Date: Aug 2003
Location: United States
Posts: 1,974
RE: 4.6 zero tolerance?
Those typically are high compression pistons and because of valve lift and duration the valve and piston would occupy the same space at the same time.
It is uncommon to see grooves like that on low compression pistons but I suppose of you run enough lift and durationyou could need them in an application like that.
A motor is all about getting as much fuel and air in as possible. The longer you can hodl the valve open the more fuel and air you can try and cram in there.
It is uncommon to see grooves like that on low compression pistons but I suppose of you run enough lift and durationyou could need them in an application like that.
A motor is all about getting as much fuel and air in as possible. The longer you can hodl the valve open the more fuel and air you can try and cram in there.
01-05-2006, 07:22 PM
#13
3rd Gear Member
Join Date: Dec 2005
Location:
Posts: 533
RE: 4.6 zero tolerance?
ORIGINAL: SilverGTV8
All of that equals very bad.
We have the luxuary of running chains and not belts. It is quite uncommon to break a chain but common to break a belt.
It is also not commonly refered to as a "Zero-Tolerance" Motor but an "Interference" motor.
Zero tolerance implies that there is no allowable machine tolerence during assembly. If you built a zero tolerance motor it would lock-up with in minutes due to metal expansion as it heats up.
On a side note. The tolerance for the crank shaft end play is 6 to 11ths (0.006 to 0.011) and that's alot interms of machine tolerance.
All of that equals very bad.
We have the luxuary of running chains and not belts. It is quite uncommon to break a chain but common to break a belt.
It is also not commonly refered to as a "Zero-Tolerance" Motor but an "Interference" motor.
Zero tolerance implies that there is no allowable machine tolerence during assembly. If you built a zero tolerance motor it would lock-up with in minutes due to metal expansion as it heats up.
On a side note. The tolerance for the crank shaft end play is 6 to 11ths (0.006 to 0.011) and that's alot interms of machine tolerance.
01-05-2006, 08:00 PM
#15
Gentleman's Relish
Join Date: Feb 2005
Location: AZ
Posts: 13,090
RE: 4.6 zero tolerance?
something else to consider is that MOST V8's do not share the interference type of design because most are at or below 9.5:1 or 10:1 compression. Interference engines are typically found on 4-cyl engines which is why they usualy have a 9.8:1 and above compression.
That is also why if your timing belt breaks on a 4cyl you're almost always screwed. Piston hits an open valve badda-bam..done.
That is also why if your timing belt breaks on a 4cyl you're almost always screwed. Piston hits an open valve badda-bam..done.
01-05-2006, 09:20 PM
#16
4th Gear Member
Join Date: Aug 2003
Location: United States
Posts: 1,974
RE: 4.6 zero tolerance?
ORIGINAL: VARifleman
Tolerances also refer to the parts, and it is impossible to make a zero tolerance part as machines are not that accurate. You could make them to the 10 or 100 thousandth of an inch if you had the time and money, but to make them to closer tolerances than that is impossible with our technology.
ORIGINAL: SilverGTV8
All of that equals very bad.
We have the luxuary of running chains and not belts. It is quite uncommon to break a chain but common to break a belt.
It is also not commonly refered to as a "Zero-Tolerance" Motor but an "Interference" motor.
Zero tolerance implies that there is no allowable machine tolerence during assembly. If you built a zero tolerance motor it would lock-up with in minutes due to metal expansion as it heats up.
On a side note. The tolerance for the crank shaft end play is 6 to 11ths (0.006 to 0.011) and that's alot interms of machine tolerance.
All of that equals very bad.
We have the luxuary of running chains and not belts. It is quite uncommon to break a chain but common to break a belt.
It is also not commonly refered to as a "Zero-Tolerance" Motor but an "Interference" motor.
Zero tolerance implies that there is no allowable machine tolerence during assembly. If you built a zero tolerance motor it would lock-up with in minutes due to metal expansion as it heats up.
On a side note. The tolerance for the crank shaft end play is 6 to 11ths (0.006 to 0.011) and that's alot interms of machine tolerance.
You said "You could make them to the 10 or 100 thousandth of an inch if you had the time and money". What you said is any where from .010 to .100 and if you said that to a machinest you gave a 90ths window of tolerance. He could do that with his eyes closed. What I think you were trying to say is any where from .001 to .0001 of an inch.
A typical line to line statement meaning the OD of one part nearly matched the mating ID part in dimension BUT will still go together if inserted properly. But a line to line difference is typically just into the tenths.
10ths or .010 is a common tolerance ( +/- .005), I typically work with parts that a toleranced +/- .001 (2thou swing). I have worked in the past in tenths (.0005) which is extremly small.
In the business area I work in it is not uncommon to see specs down in the tenths for critcal applications. I acuatlly use a pump that the tolerance between the drive piston and pressure housing is in to the millionths of an inch.
But you are correct it comes down to time and money.
But think about it this way. If you were to build a zero-tolerance part. Where would you fluid path be for you lubricant? But the ulitmate reason for not going line to line or zero tolerance is that metal expands and it can expand a lot when it gets hot. Making things to close tolerance often involves heat management to get the part accruate.
01-06-2006, 12:52 AM
#17
3rd Gear Member
Thread Starter
Join Date: Apr 2005
Posts: 607
RE: 4.6 zero tolerance?
Geez! Inteference...tolerance...whatever. I should have better selected my words it looks like. I did mean interference motor...like ever other 4-cyl OHC engine is setup. Tolerance isn't the right word...I am very very very sorry!
I typed up that question/post in like 2.153 seconds.
I typed up that question/post in like 2.153 seconds.
01-06-2006, 05:58 AM
#19
4th Gear Member
Join Date: May 2003
Location: Chi-town!!!
Posts: 1,205
RE: 4.6 zero tolerance?
ORIGINAL: SilverGTV8
Don't know how to say this but your statement is a bit flawed. There is far better technology then your local mom and pops machine shop has.
You said "You could make them to the 10 or 100 thousandth of an inch if you had the time and money". What you said is any where from .010 to .100 and if you said that to a machinest you gave a 90ths window of tolerance. He could do that with his eyes closed. What I think you were trying to say is any where from .001 to .0001 of an inch.
A typical line to line statement meaning the OD of one part nearly matched the mating ID part in dimension BUT will still go together if inserted properly. But a line to line difference is typically just into the tenths.
10ths or .010 is a common tolerance ( +/- .005), I typically work with parts that a toleranced +/- .001 (2thou swing). I have worked in the past in tenths (.0005) which is extremly small.
In the business area I work in it is not uncommon to see specs down in the tenths for critcal applications. I acuatlly use a pump that the tolerance between the drive piston and pressure housing is in to the millionths of an inch.
But you are correct it comes down to time and money.
But think about it this way. If you were to build a zero-tolerance part. Where would you fluid path be for you lubricant? But the ulitmate reason for not going line to line or zero tolerance is that metal expands and it can expand a lot when it gets hot. Making things to close tolerance often involves heat management to get the part accruate.
ORIGINAL: VARifleman
Tolerances also refer to the parts, and it is impossible to make a zero tolerance part as machines are not that accurate. You could make them to the 10 or 100 thousandth of an inch if you had the time and money, but to make them to closer tolerances than that is impossible with our technology.
ORIGINAL: SilverGTV8
All of that equals very bad.
We have the luxuary of running chains and not belts. It is quite uncommon to break a chain but common to break a belt.
It is also not commonly refered to as a "Zero-Tolerance" Motor but an "Interference" motor.
Zero tolerance implies that there is no allowable machine tolerence during assembly. If you built a zero tolerance motor it would lock-up with in minutes due to metal expansion as it heats up.
On a side note. The tolerance for the crank shaft end play is 6 to 11ths (0.006 to 0.011) and that's alot interms of machine tolerance.
All of that equals very bad.
We have the luxuary of running chains and not belts. It is quite uncommon to break a chain but common to break a belt.
It is also not commonly refered to as a "Zero-Tolerance" Motor but an "Interference" motor.
Zero tolerance implies that there is no allowable machine tolerence during assembly. If you built a zero tolerance motor it would lock-up with in minutes due to metal expansion as it heats up.
On a side note. The tolerance for the crank shaft end play is 6 to 11ths (0.006 to 0.011) and that's alot interms of machine tolerance.
You said "You could make them to the 10 or 100 thousandth of an inch if you had the time and money". What you said is any where from .010 to .100 and if you said that to a machinest you gave a 90ths window of tolerance. He could do that with his eyes closed. What I think you were trying to say is any where from .001 to .0001 of an inch.
A typical line to line statement meaning the OD of one part nearly matched the mating ID part in dimension BUT will still go together if inserted properly. But a line to line difference is typically just into the tenths.
10ths or .010 is a common tolerance ( +/- .005), I typically work with parts that a toleranced +/- .001 (2thou swing). I have worked in the past in tenths (.0005) which is extremly small.
In the business area I work in it is not uncommon to see specs down in the tenths for critcal applications. I acuatlly use a pump that the tolerance between the drive piston and pressure housing is in to the millionths of an inch.
But you are correct it comes down to time and money.
But think about it this way. If you were to build a zero-tolerance part. Where would you fluid path be for you lubricant? But the ulitmate reason for not going line to line or zero tolerance is that metal expands and it can expand a lot when it gets hot. Making things to close tolerance often involves heat management to get the part accruate.
!
01-06-2006, 06:03 AM
#20
4th Gear Member
Join Date: May 2003
Location: Chi-town!!!
Posts: 1,205
RE: 4.6 zero tolerance?
ORIGINAL: Jglisson
Geez! Inteference...tolerance...whatever. I should have better selected my words it looks like. I did mean interference motor...like ever other 4-cyl OHC engine is setup. Tolerance isn't the right word...I am very very very sorry!
I typed up that question/post in like 2.153 seconds.
Geez! Inteference...tolerance...whatever. I should have better selected my words it looks like. I did mean interference motor...like ever other 4-cyl OHC engine is setup. Tolerance isn't the right word...I am very very very sorry!
I typed up that question/post in like 2.153 seconds.