bob58o
SuckSqueezeBangBlow
Now that's a piston!
Arrow down. Points to pushrods.
Arrow down. Points to pushrods.
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Powerland 420cc GAB 2.0
- Thread starter bob58o
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bob58o
SuckSqueezeBangBlow
Well frog snacks!!!
The stock length rods are 4.41" on 390's
They are 4.43" on 420cc's.
The Billet Rods available are 4.41" or 4.45"
My piston is 0.003"- 0.004" in the hole right meow!!!
If I got a a 4.41" Rod, I'd be at 0.023" in the hole.
Need to deck the block?
If I got a 4.45" Rod , I'd have 0.017" pop out.
Need to cut the piston.
Let's play with clay!
---------- Post added at 12:25 PM ---------- Previous post was at 12:23 PM ----------
This must be the source of Joe's Pop out.
20 thou pop out, 20 thou gasket at first right?
That makes two engines with near flush deck heights!!!
Where is the fricken 4.43" Billet Rod, ARC????
The stock length rods are 4.41" on 390's
They are 4.43" on 420cc's.
The Billet Rods available are 4.41" or 4.45"
My piston is 0.003"- 0.004" in the hole right meow!!!
If I got a a 4.41" Rod, I'd be at 0.023" in the hole.
Need to deck the block?
If I got a 4.45" Rod , I'd have 0.017" pop out.
Need to cut the piston.
Let's play with clay!
---------- Post added at 12:25 PM ---------- Previous post was at 12:23 PM ----------
This must be the source of Joe's Pop out.
20 thou pop out, 20 thou gasket at first right?
That makes two engines with near flush deck heights!!!
Where is the fricken 4.43" Billet Rod, ARC????
chancer
ɔ ɥ ɐ u ɔ ǝ ɹ
Feed that cat to your Dog! Before they become friends and the Cat turns the Dog against you!
bob58o
SuckSqueezeBangBlow
So for my Piston to Valve clearance....
I measured with clay, with no head gasket....
And I got 0.275".
For margin of error, let's say 0.255"
With a stock gasket, that would be more like 0.300"
Let's say we want 0.075" P2V clearance.
I've got 0.300 - 0.075 = 0.225" to play and be safe.
Can I run 0.017" pop up/out on the piston with the 0.045"???
That is putting the piston closer than the 30 thou recommended 0.028"
And seems like a lot of pop up.
If I can, now we are talking 0.225" - 0.020" = 0.205"
I could mill 0.100"
Now we are at 0.205" - 0.100" = 0.105"
So here we are left with 0.105" of non - used cam lift area.
Stock lift is like 0.260" IIRC, so I could possibly get the long Rod, mill 0.100", and run a cam with up to 0.365" lift.
Cam timing makes a difference, but this is a starting point!!!
You know what 1.3 ratio rocker arms multiplied by 0.260" lift cam shaft equals?????
0.338" lift cam shaft!
Bullfrog has a set of 1.3 rockers with CR Mo ( cut to length) pushrods for as cheap as I've seen.
I'd like to pair that with the $50 Torque cam (0.260" lift, 240 duration)
And Dual Springs and SS Valves with billet retainers/keepers.
I measured with clay, with no head gasket....
And I got 0.275".
For margin of error, let's say 0.255"
With a stock gasket, that would be more like 0.300"
Let's say we want 0.075" P2V clearance.
I've got 0.300 - 0.075 = 0.225" to play and be safe.
Can I run 0.017" pop up/out on the piston with the 0.045"???
That is putting the piston closer than the 30 thou recommended 0.028"
And seems like a lot of pop up.
If I can, now we are talking 0.225" - 0.020" = 0.205"
I could mill 0.100"
Now we are at 0.205" - 0.100" = 0.105"
So here we are left with 0.105" of non - used cam lift area.
Stock lift is like 0.260" IIRC, so I could possibly get the long Rod, mill 0.100", and run a cam with up to 0.365" lift.
Cam timing makes a difference, but this is a starting point!!!
You know what 1.3 ratio rocker arms multiplied by 0.260" lift cam shaft equals?????
0.338" lift cam shaft!
Bullfrog has a set of 1.3 rockers with CR Mo ( cut to length) pushrods for as cheap as I've seen.
I'd like to pair that with the $50 Torque cam (0.260" lift, 240 duration)
And Dual Springs and SS Valves with billet retainers/keepers.
bob58o
SuckSqueezeBangBlow
Forgot pics
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image.jpg
bob58o
SuckSqueezeBangBlow
And
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image.jpg
bob58o
SuckSqueezeBangBlow
Sitting on toilet, Wishing and Hoping with Both Hands Full
Well I may have found a solution to my deck height issue.
I found a $20 Aftermarket 90mm piston for the 420cc clones.
Here it is.
http://www.nrracing.com/product-p/420pistonkit.htm
90mm Aftermarket Flat-top Piston for big bore GX390s. Fits stock bore on 420 Predators.
And I think this is a similar 88mm version
http://www.nrracing.com/product-p/390flattop.htm
THE FOLLOWING COMMENT IS ONLY ON THE 88mm ONE, BUT HOPEFULLY THEY JUST DIDN'T MENTION IT ON THE 90mm
Pistons has approx. .020 shorter compression height. However, they will still raise the compression approx .5 points.
NOW if the 90mm piston also has -0.020" Compression Height (top of piston to center of pin),
THEN I can used the 4.45" Rod (+0.020" I THINK) and the flat top piston (-0.020" I HOPE) to give me a billet rod and flat-top piston combo that sits 0.004" In the hole with no machining!
I wish Russel at NR was easier to get on the phone!
I'll send an email now!!
Well I may have found a solution to my deck height issue.
I found a $20 Aftermarket 90mm piston for the 420cc clones.
Here it is.
http://www.nrracing.com/product-p/420pistonkit.htm
90mm Aftermarket Flat-top Piston for big bore GX390s. Fits stock bore on 420 Predators.
And I think this is a similar 88mm version
http://www.nrracing.com/product-p/390flattop.htm
THE FOLLOWING COMMENT IS ONLY ON THE 88mm ONE, BUT HOPEFULLY THEY JUST DIDN'T MENTION IT ON THE 90mm
Pistons has approx. .020 shorter compression height. However, they will still raise the compression approx .5 points.
NOW if the 90mm piston also has -0.020" Compression Height (top of piston to center of pin),
THEN I can used the 4.45" Rod (+0.020" I THINK) and the flat top piston (-0.020" I HOPE) to give me a billet rod and flat-top piston combo that sits 0.004" In the hole with no machining!
I wish Russel at NR was easier to get on the phone!
I'll send an email now!!
bob58o
SuckSqueezeBangBlow
E^2 will be happy to know I will start fixing said "broken" engine.
It is not making 30HP,
So ya, it is broken.
Today we port.
---------- Post added at 10:03 AM ---------- Previous post was at 10:01 AM ----------
The guy at HOPE said he is pretty sure I want the 4.45" Rod with that above mentioned 90mm flat top.
He says I won't have pop out, it should be ok.
He also may be giving me a three angle valve jobber.
B jobbers and H jobbers are more expensive than V jobbers.
Z jobbers are not for beginners, sorry.
---------- Post added at 10:55 AM ---------- Previous post was at 10:03 AM ----------
Step 1.
Procure Needed Materials.
Step 2.
Re-Research P&P.
2nd Rodeo this time Cowboys!
Got to find the math for the throat size and stuff.
Pretty pictures on Google Images will be my guidelines.
(Off topic, it is weird when I search stuff on Google and SEE my own images. I guess nobody else posts pics and videos of TS-500 minibikes?)
3. Hot dog down a hallway.
It is not making 30HP,
So ya, it is broken.
Today we port.
---------- Post added at 10:03 AM ---------- Previous post was at 10:01 AM ----------
The guy at HOPE said he is pretty sure I want the 4.45" Rod with that above mentioned 90mm flat top.
He says I won't have pop out, it should be ok.
He also may be giving me a three angle valve jobber.
B jobbers and H jobbers are more expensive than V jobbers.
Z jobbers are not for beginners, sorry.
---------- Post added at 10:55 AM ---------- Previous post was at 10:03 AM ----------
Step 1.
Procure Needed Materials.
Step 2.
Re-Research P&P.
2nd Rodeo this time Cowboys!
Got to find the math for the throat size and stuff.
Pretty pictures on Google Images will be my guidelines.
(Off topic, it is weird when I search stuff on Google and SEE my own images. I guess nobody else posts pics and videos of TS-500 minibikes?)
3. Hot dog down a hallway.
ezcome-ezgo
G'me sumthin to write on
Put a little relish on that dog.
You can't run any pop out. If it doesn't hit the head I promise you it will hit the gasket !
You can buy a preshaved lip piston from nr for $20. And run the MLS .020 gasket and the arc long rod 6274 and It is under deck for future milling of the head.
You can buy a preshaved lip piston from nr for $20. And run the MLS .020 gasket and the arc long rod 6274 and It is under deck for future milling of the head.
bob58o
SuckSqueezeBangBlow
Here's the relish, onions, mustard, tomatoes, pickle, peppers, and celery salt....
https://www.cartechbooks.com/techtips/cylinder-head-math-for-engine-performance/
https://www.cartechbooks.com/techtips/cylinder-head-math-for-engine-performance/
bob58o
SuckSqueezeBangBlow
Valve Curtain Area
Valve Curtain Area
https://www.cartechbooks.com/techtips/cylinder-head-math-for-engine-performance/
"When contemplating engine combinations and camshafts in particular, it is often useful to calculate the valve curtain area for a given valve lift and compare it to proposed changes by percentage. The valve curtain area is the area of the flow window that opens when the valve is lifted off its seat. Say you have a 2.02-inch intake valve that opens to 0.500-inch lift. What is the valve curtain area and how much will it increase if you open the valve to 0.535 inch?
To perform the calculation correctly you can’t go by the valve diameter itself. You have to go by the flow diameter, which is where the actual valve seat begins. This is usually about 0.040-inch smaller than the average valve diameter. For most calculations it’s pretty accurate to simply multiply the valve diameter by 0.98. The calculation then becomes the valve diameter times 0.98 times pi times the lift value. The result is the total available flow area for the valve’s flow diameter at the given valve lift.
Valve curtain area = valve diameter x 0.98 x 3.14 x valve lift or per our example: 2.02 x 0.98 x 3.14 x 0.500 = 3.107 square inches"
---------- Post added at 01:45 PM ---------- Previous post was at 12:54 PM ----------
Powerland 420cc Intake Valve Curtain Area
Intake = 35mm or 1.38"
1.38" * 0.98 = 1.35"
1.35" * pi = 1.35" * 3.14159 = 4.25"
A 35mm valve has an effective flow circumference of 4.25"
So a 0.260" lift cam (stock?) has Valve Curtain Area of ...
4.25" * 0.260" = 1.105 sq inches.
A 0.275" cam
4.25" * 0.275" = 1.169 sq inches
A 0.310" lift cam has Valve Curtain Area of....
4.25" * 0.310" = 1.317 sq inches.
A 0.360" lift cam has a Valve Curtain Area of ....
4.25" * 0.360" = 1.530 sq inches
The Intake port has a 1.25" Diameter.
Intake port opening cross-sectional area = Pi*r*r
r= 1.25"/2 = 0.625"
Port CSA = 3.14159*0.625*0.625 =
1.227 sq inches.
To find max camshaft lift that will work with that port CSA and Valve size,....
Divide 1.227 sq inches by the 4.25" Effective valve flow Circumference
to get...
1.227 sq inches / 4.25" = 0.289" Lift.
Anything over a 0.290" lift cam might require opening up the port more.
Perhaps a 0.290" lift cam is perfect for this port size?
Valve Curtain Area
https://www.cartechbooks.com/techtips/cylinder-head-math-for-engine-performance/
"When contemplating engine combinations and camshafts in particular, it is often useful to calculate the valve curtain area for a given valve lift and compare it to proposed changes by percentage. The valve curtain area is the area of the flow window that opens when the valve is lifted off its seat. Say you have a 2.02-inch intake valve that opens to 0.500-inch lift. What is the valve curtain area and how much will it increase if you open the valve to 0.535 inch?
To perform the calculation correctly you can’t go by the valve diameter itself. You have to go by the flow diameter, which is where the actual valve seat begins. This is usually about 0.040-inch smaller than the average valve diameter. For most calculations it’s pretty accurate to simply multiply the valve diameter by 0.98. The calculation then becomes the valve diameter times 0.98 times pi times the lift value. The result is the total available flow area for the valve’s flow diameter at the given valve lift.
Valve curtain area = valve diameter x 0.98 x 3.14 x valve lift or per our example: 2.02 x 0.98 x 3.14 x 0.500 = 3.107 square inches"
---------- Post added at 01:45 PM ---------- Previous post was at 12:54 PM ----------
Powerland 420cc Intake Valve Curtain Area
Intake = 35mm or 1.38"
1.38" * 0.98 = 1.35"
1.35" * pi = 1.35" * 3.14159 = 4.25"
A 35mm valve has an effective flow circumference of 4.25"
So a 0.260" lift cam (stock?) has Valve Curtain Area of ...
4.25" * 0.260" = 1.105 sq inches.
A 0.275" cam
4.25" * 0.275" = 1.169 sq inches
A 0.310" lift cam has Valve Curtain Area of....
4.25" * 0.310" = 1.317 sq inches.
A 0.360" lift cam has a Valve Curtain Area of ....
4.25" * 0.360" = 1.530 sq inches
The Intake port has a 1.25" Diameter.
Intake port opening cross-sectional area = Pi*r*r
r= 1.25"/2 = 0.625"
Port CSA = 3.14159*0.625*0.625 =
1.227 sq inches.
To find max camshaft lift that will work with that port CSA and Valve size,....
Divide 1.227 sq inches by the 4.25" Effective valve flow Circumference
to get...
1.227 sq inches / 4.25" = 0.289" Lift.
Anything over a 0.290" lift cam might require opening up the port more.
Perhaps a 0.290" lift cam is perfect for this port size?
Poboy kartman
Senior Moments Member
That paticular feature is so the "Venturi Effect" can be employed. Many beginning porters remove that...to the detriment of air flow.
Just one of the many mistakes the semi-informed make because they are not privy to the hidden secret information here.
BTW: I think it was Jim Carey that coined that "Venturi" connotation....it was one of his "Pet" things...IIRC.
Just one of the many mistakes the semi-informed make because they are not privy to the hidden secret information here.
BTW: I think it was Jim Carey that coined that "Venturi" connotation....it was one of his "Pet" things...IIRC.
bob58o
SuckSqueezeBangBlow
Remember trying to keep RPMs low and a fairly mild engine that will last.
Here is the cam I like.
Camshaft, 280 Series - (GX240s to GX390s)
Our Price: $109.99
http://www.nrracing.com/product-p/390cam-280.htm
Approx .280 lift and 220 duration (at .050). This is a nice cam that works well on both stock and modified motors. This cam produces lots of low end torque. One of the best all around cams we offer. HD springs required. Bored or Aftermarket carb needed.
TQ Grind - Serious Torque for Small Tracks 6000 max RPM. 9.0 to 1 compression or more, HD Springs Required.
Or maybe I like the Black Mamba Jr for gx390!
0.275" Lift, 230 degree duration, 104 LSA.
http://smallenginecams.com/
---------- Post added at 02:08 PM ---------- Previous post was at 02:02 PM ----------
I haven't yet got the math of the throat of the port. Geez.
This was just the port opening and "runner?".
I was just about to re-read up on the optimized throat diameter.
I think it SHOULD BE MORE NARROW,
to speed up the air like a Pet Detective.
---------- Post added at 02:10 PM ---------- Previous post was at 02:08 PM ----------
https://www.youtube.com/watch?v=NarFUj80HfY
https://www.youtube.com/watch?v=lut9QPNAPhU
---------- Post added at 02:16 PM ---------- Previous post was at 02:10 PM ----------
SEE It was the very next section.
"Calculating Optimum Port Area from Valve Size
The primary objective of all performance cylinder heads is to produce the maximum possible volumetric efficiency across the broadest possible range of engine speed. That’s why port and valve sizes are so critical and so easy to mess up without careful deliberation. The intake port crosssectional area (c/s) describes the smallest area of a port in a perpendicular plane to the flow upstream of the valve. There are two schools of thought on this. Depending on the cylinder head, the smallest cross section may actually be the venturi diameter or throat area directly above the valve seat. This is particularly true if you also consider the additional obstruction of the valve guide and valve stem. Others define cross-sectional area as the choke point farther upstream near the bump in the port wall adjacent to the pushrod. To determine this you measure the vertical and horizontal dimensions at that point and multiply to find the area."
---------- Post added at 02:29 PM ---------- Previous post was at 02:16 PM ----------
The throat (difficult to measure) my best guess is 1.185 sq inches +/- 0.125 square inches.
So If we use this number then....
1.185 sq inches / 4.25" = 0.279"
I still like my cam choices!
---------- Post added at 02:42 PM ---------- Previous post was at 02:29 PM ----------
"Head porters contend that the upstream cross-sectional area (in the port itself) should be 90 percent of the flow diameter of the intake valve for a race engine and 0.85 percent for a street engine. Some feel that 90 percent is good across the board. This is based on the valve’s flow diameter at the inner edge of the valve seat. It’s a reasonable assumption although the throat diameter directly above the valve seat may be even smaller and that is what the air actually sees. And it doesn’t account for the partial blockage caused by the valve guide and stem. For now however, we are simply relating port cross-sectional area in the port itself to the flow diameter at the valve seat.
For example, a 2.02-inch intake valve has a flow diameter of 1.717 inches if we’re going by the 85-percent rule."
My intake valve is 35mm.
35mm / 25.4mm/in = 1.38"
They say use 85 or 90.
I'll use 87.5.
1.38" *0.875 = 1.21" (87.5% Valve flow diameter)
1.21"/2 = 0.605" Radius
87.5% Valve Flow Area =
0.605" * 0.605" * 3.14159 =
1.150 sq inches
I measured 1.185 sq inches
= 3.14159 *r*r
r*r = 0.377
r = 0.614
Diam = 1.228"
1.228"/ 1.38" = 89% of Valve Diameter
SWEET!!
Everything looks really good on this engine so far. At least to me.
Good but very Broken!
---------- Post added at 02:49 PM ---------- Previous post was at 02:42 PM ----------
So what does this show me???????????????
Don't make anything much bigger!!!!!!!!!
Just clean it up!!!!!!!!!!
Then look at it after and wonder where all the material has gone!!!
Here is the cam I like.
Camshaft, 280 Series - (GX240s to GX390s)
Our Price: $109.99
http://www.nrracing.com/product-p/390cam-280.htm
Approx .280 lift and 220 duration (at .050). This is a nice cam that works well on both stock and modified motors. This cam produces lots of low end torque. One of the best all around cams we offer. HD springs required. Bored or Aftermarket carb needed.
TQ Grind - Serious Torque for Small Tracks 6000 max RPM. 9.0 to 1 compression or more, HD Springs Required.
Or maybe I like the Black Mamba Jr for gx390!
0.275" Lift, 230 degree duration, 104 LSA.
http://smallenginecams.com/
---------- Post added at 02:08 PM ---------- Previous post was at 02:02 PM ----------
I haven't yet got the math of the throat of the port. Geez.
This was just the port opening and "runner?".
I was just about to re-read up on the optimized throat diameter.
I think it SHOULD BE MORE NARROW,
to speed up the air like a Pet Detective.
---------- Post added at 02:10 PM ---------- Previous post was at 02:08 PM ----------
https://www.youtube.com/watch?v=NarFUj80HfY
https://www.youtube.com/watch?v=lut9QPNAPhU
---------- Post added at 02:16 PM ---------- Previous post was at 02:10 PM ----------
SEE It was the very next section.
"Calculating Optimum Port Area from Valve Size
The primary objective of all performance cylinder heads is to produce the maximum possible volumetric efficiency across the broadest possible range of engine speed. That’s why port and valve sizes are so critical and so easy to mess up without careful deliberation. The intake port crosssectional area (c/s) describes the smallest area of a port in a perpendicular plane to the flow upstream of the valve. There are two schools of thought on this. Depending on the cylinder head, the smallest cross section may actually be the venturi diameter or throat area directly above the valve seat. This is particularly true if you also consider the additional obstruction of the valve guide and valve stem. Others define cross-sectional area as the choke point farther upstream near the bump in the port wall adjacent to the pushrod. To determine this you measure the vertical and horizontal dimensions at that point and multiply to find the area."
---------- Post added at 02:29 PM ---------- Previous post was at 02:16 PM ----------
The throat (difficult to measure) my best guess is 1.185 sq inches +/- 0.125 square inches.
So If we use this number then....
1.185 sq inches / 4.25" = 0.279"
I still like my cam choices!
---------- Post added at 02:42 PM ---------- Previous post was at 02:29 PM ----------
"Head porters contend that the upstream cross-sectional area (in the port itself) should be 90 percent of the flow diameter of the intake valve for a race engine and 0.85 percent for a street engine. Some feel that 90 percent is good across the board. This is based on the valve’s flow diameter at the inner edge of the valve seat. It’s a reasonable assumption although the throat diameter directly above the valve seat may be even smaller and that is what the air actually sees. And it doesn’t account for the partial blockage caused by the valve guide and stem. For now however, we are simply relating port cross-sectional area in the port itself to the flow diameter at the valve seat.
For example, a 2.02-inch intake valve has a flow diameter of 1.717 inches if we’re going by the 85-percent rule."
My intake valve is 35mm.
35mm / 25.4mm/in = 1.38"
They say use 85 or 90.
I'll use 87.5.
1.38" *0.875 = 1.21" (87.5% Valve flow diameter)
1.21"/2 = 0.605" Radius
87.5% Valve Flow Area =
0.605" * 0.605" * 3.14159 =
1.150 sq inches
I measured 1.185 sq inches
= 3.14159 *r*r
r*r = 0.377
r = 0.614
Diam = 1.228"
1.228"/ 1.38" = 89% of Valve Diameter
SWEET!!
Everything looks really good on this engine so far. At least to me.
Good but very Broken!
---------- Post added at 02:49 PM ---------- Previous post was at 02:42 PM ----------
So what does this show me???????????????
Don't make anything much bigger!!!!!!!!!
Just clean it up!!!!!!!!!!
Then look at it after and wonder where all the material has gone!!!
Poboy kartman
Senior Moments Member
Save that grinding for camshafts (not for beginners, tho...)
bob58o
SuckSqueezeBangBlow
Don't these ports look pretty.
Looks pretty basic to me.
This is what I was going to base my porting off of.
Nothing major changed.
Some Valve Guide taken down.
Some of the Valve Guide boss taken away. (most work here)
Remove some of the lip where the port runner? meets the bowl (on sides).
Lightly work the short radius.
Blend seats into bowl.
Looks pretty basic to me.
This is what I was going to base my porting off of.
Nothing major changed.
Some Valve Guide taken down.
Some of the Valve Guide boss taken away. (most work here)
Remove some of the lip where the port runner? meets the bowl (on sides).
Lightly work the short radius.
Blend seats into bowl.
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Goals.jpg
bob58o
SuckSqueezeBangBlow
Just in case I have shared this video enough.
http://www.powerblocktv.com/episode...port-and-polish-for-power-how-to#.VvF_feIrLIU
---------- Post added at 03:24 PM ---------- Previous post was at 03:22 PM ----------
Here we go. I'll get some lights set up and take some before pictures.
http://www.powerblocktv.com/episode...port-and-polish-for-power-how-to#.VvF_feIrLIU
---------- Post added at 03:24 PM ---------- Previous post was at 03:22 PM ----------
Here we go. I'll get some lights set up and take some before pictures.
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