Large dish pistons w/small chamber head vs small dish pistons w/ large chamber head
05-17-2007, 10:36 AM
#1
Large dish pistons w/small chamber head vs small dish pistons w/ large chamber head
I've pretty well decided that the source of my oil burning problem is the gapless stainless top ring I bought for my motor, which means that I'm going to have to have the engine torn down and rebuilt to fix it.
I currently have a 28cc dish piston in there with small chamber 5.3 heads. I'm wondering if there is an advantage to going back to a smaller dish piston with something larger like 317 heads. If I'm going to change pistons now is the time to do it, since I have to have the motor torn down anyway. What do you guys think? Is there any advantage to going one way or the other?
I currently have a 28cc dish piston in there with small chamber 5.3 heads. I'm wondering if there is an advantage to going back to a smaller dish piston with something larger like 317 heads. If I'm going to change pistons now is the time to do it, since I have to have the motor torn down anyway. What do you guys think? Is there any advantage to going one way or the other?
05-17-2007, 11:46 AM
#4
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Small head chambers that do not unshroud the valves would be best. The C5-R head is an example, with something like a 36cc chamber. I think the best option is a dish in the piston to match the chamber shape.
I think there is a thread over on tech in the advanced performance section about this topic.
I think there is a thread over on tech in the advanced performance section about this topic.
05-17-2007, 12:08 PM
#6
Originally Posted by thunder550
Any chance you have a link? I looked and didn't see anything like that.
https://ls1tech.com/forums/showthrea...ish+head+valve
05-17-2007, 12:21 PM
#7
OK so I understand the arguments for an actual dish and matching the combustion chamber shape. My pistons look like these:
Which means that it's not really possible for me to match or even get close. I'm currently at 9.7:1 SCR. Any other thoughts?
Which means that it's not really possible for me to match or even get close. I'm currently at 9.7:1 SCR. Any other thoughts?
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05-17-2007, 01:30 PM
#9
Originally Posted by 1slow01Z71
I would talk to Rex at WCCH, they figured out the problem with my oil burner too, and they are going with Wiseco pistons this time that are supposedly better designed for a stroker FWIW.
05-17-2007, 03:05 PM
#10
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Lots of reasons why an engine is an oil burner. Just considering the piston/ring seal area, oil consumption can be caused by piston design, ring design/material, hone finish, cylinder wall prep., start up and break in proceedure. Generally the top rings aren't responsible for oil control. That's up to the oil ring and 2nd rings. The top ring controls cylinder pressure as does the second ring.
In the past we had lots of problems with Diamond pistons when they changed up the diameter of the oil relief holes just below the oil ring land. We saw lots of oil burners with these pistons. We machined the holes larger and the comsumption problems ceased. Diamond denied the problem was a result of their change yet when we changed the hole sizes the problems went away. Now we sell Probe Pistons and Wiesco's and have never had a single issue with oil consumption. We also sell Ackerly and Childs rings sets and have had good success with them. They have a napier groove in the bottom of the second ring. This groove helps scrape and store residual oil that seeps past the oil rings. Ring end gaps on the oil rails should be checked before installing on the pistons. Too much gap and you're going to have an ooil burner. It's not entirely uncommon for the oil rails to have too much end gap. We like to see both iron and aluminum blocks hone finished with a torque plate to control bore distortion when the head botls/studs are torqued. It's also important to folow the ring manufacturers recommendation for hone finish.
We'll be happy to go over your situation with you. If we can't get to the phone when you call, leave a message and we'll get back to you as soon as we can.
Richard
In the past we had lots of problems with Diamond pistons when they changed up the diameter of the oil relief holes just below the oil ring land. We saw lots of oil burners with these pistons. We machined the holes larger and the comsumption problems ceased. Diamond denied the problem was a result of their change yet when we changed the hole sizes the problems went away. Now we sell Probe Pistons and Wiesco's and have never had a single issue with oil consumption. We also sell Ackerly and Childs rings sets and have had good success with them. They have a napier groove in the bottom of the second ring. This groove helps scrape and store residual oil that seeps past the oil rings. Ring end gaps on the oil rails should be checked before installing on the pistons. Too much gap and you're going to have an ooil burner. It's not entirely uncommon for the oil rails to have too much end gap. We like to see both iron and aluminum blocks hone finished with a torque plate to control bore distortion when the head botls/studs are torqued. It's also important to folow the ring manufacturers recommendation for hone finish.
We'll be happy to go over your situation with you. If we can't get to the phone when you call, leave a message and we'll get back to you as soon as we can.
Richard