A
Anonymous
Guest
Well, I am getting it back together finally! I am ready to put the pistons in but was wondering if I should open up the gaps a little. What do you guys think?
Dan
Dan
Dan,
We just installed Kelly's new forged pistons and we used .018" end gap for the top ring and .015" for the second.
Now this is for a boosted motor. A N/A motor would be less gap.
The basic formula that I like to use is .004" x cyl. bore diameter for N/A.
.005" x bore dia. for power adder.
In our case I used the N/A formula for the second ring.
Later,
Will
We just installed Kelly's new forged pistons and we used .018" end gap for the top ring and .015" for the second.
Now this is for a boosted motor. A N/A motor would be less gap.
The basic formula that I like to use is .004" x cyl. bore diameter for N/A.
.005" x bore dia. for power adder.
In our case I used the N/A formula for the second ring.
Later,
Will
A
Anonymous
Guest
Forged pistons!!!! Sweet! What rods are you using? Same motor? Anyway. Thanks for the info on the rings. Why did you use the N/A gap for the second ring?
Dan
Dan
Dan,
Yes it's the same motor. For now anyway! We're still using the stock 250 rods. Although I have been looking at aftermarket 4.6L rods. They are only .056" longer than the 250 rod, and the big end is .040" smaller in diameter. So I'm sure that a little machining on the big end, or better yet offset grind the crank a little so that you'll gain an couple more cubes, and use "off the shelf" H-beam or I-beams and we'll be able to handle 25lbs of boost!
We just fired it up last night. Kelly is racing it this weekend up in Phoenix at the PSCA race.
Bigger turbo, bigger intercooler, and hopefully a cooler running #6! We're shooting for mid 11's.
The reason for the reduced gap on the second ring is that there is not as much heat and pressure on the second one. Basically less thermal expansion means less room needed to grow. If running N/A then both rings can be the same.
Later,
Will
Yes it's the same motor. For now anyway! We're still using the stock 250 rods. Although I have been looking at aftermarket 4.6L rods. They are only .056" longer than the 250 rod, and the big end is .040" smaller in diameter. So I'm sure that a little machining on the big end, or better yet offset grind the crank a little so that you'll gain an couple more cubes, and use "off the shelf" H-beam or I-beams and we'll be able to handle 25lbs of boost!
We just fired it up last night. Kelly is racing it this weekend up in Phoenix at the PSCA race.
Bigger turbo, bigger intercooler, and hopefully a cooler running #6! We're shooting for mid 11's.
The reason for the reduced gap on the second ring is that there is not as much heat and pressure on the second one. Basically less thermal expansion means less room needed to grow. If running N/A then both rings can be the same.
Later,
Will
kirkallen143
Famous Member
Does10s":22hz0qux said:
I am glad you posted that Will, I now have to build-up a new short block for the bronco (rings are shot in half of the engine's cylinders), but I am going to stay with cast pistons. Forged would be nice, but an IRS refund only goes so far. Have a good one.
Kirk
A
Anonymous
Guest
Thanks Will! Yea, I was going to get better pistons this time around but I just could not spend that much on good pistons only to put them on stock(or stock pinto)rods. Remember I am only a 200. Is there room in a 250 to add a little stroke to the crank? I know in a 200 that is not going to happen!
Dan
Dan
Dan and Kirk,
Cast pistons are fine. We just started to burn up the #6 one, hence the reason for the swap. But we're pushing them pretty hard! If we were just going to street drive Kelly's car then we would stick with the cast ones.
There isn't much room for a big strocker crank in a 250. In fact the cam is clearanced somewhat to clear the rod bolts! I was checking that out while the motor was apart. It almost looks like if you turned the crank with rods/pistons installed and didn't have the timing chain on, the rod bolt/nut would hit the cam! It's at least very close!
Good luck you two, and get those rides back up and running!
Later,
Will
Cast pistons are fine. We just started to burn up the #6 one, hence the reason for the swap. But we're pushing them pretty hard! If we were just going to street drive Kelly's car then we would stick with the cast ones.
There isn't much room for a big strocker crank in a 250. In fact the cam is clearanced somewhat to clear the rod bolts! I was checking that out while the motor was apart. It almost looks like if you turned the crank with rods/pistons installed and didn't have the timing chain on, the rod bolt/nut would hit the cam! It's at least very close!
Good luck you two, and get those rides back up and running!
Later,
Will
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