Damn bro I don't have any pics of the ports.... I will next time the head is off! Not much help i know but don't want to give bad info.
Vitos Stroker Questions
- Thread starter wwholden
- Start date
No problem man im sure someone will chime in.. Id like to see some pics of how the piston meets the ports on a stock stroke / stock port engine. If anyone can posts some pics of the piston at TDC and BDC - max rep given!! I:I
You don't need pics....
On a stock stroke engine with a stock base gasket, the piston actually never fully uncovers the bottom of the transfer ports. There is approximately .5mm or .020" of the piston crown still blocking the port floors.
If you take that exact top end and drop it down onto a +3 stroke crank, you will have 1mm or .040" of transfer port floor showing above the piston.
That COULD be a cylinder ported for a stroker crank without spacer plate but it looks like there is a "lip" of transfer port floor just above the piston crown. Measure that lip and it will tell you how much it's been lowered (or not lowered) to match the stroke.
On a stock stroke engine with a stock base gasket, the piston actually never fully uncovers the bottom of the transfer ports. There is approximately .5mm or .020" of the piston crown still blocking the port floors.
If you take that exact top end and drop it down onto a +3 stroke crank, you will have 1mm or .040" of transfer port floor showing above the piston.
That COULD be a cylinder ported for a stroker crank without spacer plate but it looks like there is a "lip" of transfer port floor just above the piston crown. Measure that lip and it will tell you how much it's been lowered (or not lowered) to match the stroke.
You can relatively accurately measure the difference with the back end of a digital/dial caliper.
Zero the caliper while rolling the sensor out until the part that sticks out the back hits something solid and square. Once it's zeroed, sit the piece that sticks out against the piston crown and the body of the caliper on the port "ledge".
I may be using the incorrect term (I've been known to do that) but what I am talking about the is the very edge of the piston up against the port.
Zero the caliper while rolling the sensor out until the part that sticks out the back hits something solid and square. Once it's zeroed, sit the piece that sticks out against the piston crown and the body of the caliper on the port "ledge".
I may be using the incorrect term (I've been known to do that) but what I am talking about the is the very edge of the piston up against the port.
Ok so say if its below the transfer ports when I measure it. What is a good measurement. Like a ideal situations tolerance. You dont want to be above the port right? And only worry about the transfer ports and not the exhaust right?
Not exactly. If everything is setup for the +3 and perfect, all of the port floors will be exactly even with the edge of piston at BDC but that's not necessarily absolutely true. There are a lot of different setups that will work well including a small lip either way (just as long as it's not a lot).
Get a degree wheel on that and see what the current port timing is. That'll be the real indication on whether it will run well on that crank or not.
The spark plug thread is 14mm x1.25mm.. At least it is on my head
Have just rechambered my head myself too, can't wait to see the results!
Cheers Al
So whats a lot? As far as lip...
Also I dont have a degree wheel. I dont know anything about them. Do you have a preference on brand, model, where to buy.
The spark plug thread is 14mm x1.25mm.. At least it is on my head
Have just rechambered my head myself too, can't wait to see the results!
Cheers Al
Yeah I researched the meaning of the letters on spark plugs. The first letter (the "B" in BR8es) is for the thread type which is 14mm x 1.25mm pitch. You have a lathe too? Im finishing my arbor up tomorrow.
There is no set number that would be bad, more of a percentage of the total area. Shoot for less than 5% of the corrected area total blocked.
How deep do you want to go into this rabbit hole, Alice?
Port timing isn't about measurements (distances) but about time area. Think of it as how "long" the ports are open as the piston speed increases. As the rpm's increase, the time that the same size port is open grows shorter because the piston is moving faster.
If you are blocking some portion of the port area with a piston (or boggers from casting), you are removing some of your port time. How much is detrimental? I'd guess 5% of the port corrected port area (the actual size of the port including entering angle).
Now, it looks to me like you have the opposite problem, the piston is below the port floor which means you are going to be looking at it from the opposite angle. Instead of how much is being blocked, how much COULD be available if the floor was even. If it's less than 5% of the available area currently, you can run it like that.
Explain area of the port to me? How do I figure that? And any tips on a good budget degree wheel. Sorry Im new to how port timing. Havent looked into it much but I want to learn it.
