Flat top or domed pistons
- Thread starter pittsburghracer
- Start date
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Closed chamber heads or open? I like going with flat tops with a closed chambered head and then go with a tighter quench. Depending on the type of rod you're using and how long the rods are, .025 piston to head clearance isn't unheard of. Right now I have a 440 with .070 (hate that!) and it produces 10.3-1 but the piston were on the shelf and the only stock bore slugs I had and didn't want to buy more. It's not a race engine anyways. Years ago a helper didn't check clearance and I thought he did and the engine ended up with .019! It ran a 10.0 right off the trailer but the owner wanted to use a small shot of the happy gas. The engine did fine for 3 passes until the button was hit and it split a cylinder right off the line.
Damn that's a sexy looking piston!
I like to smooth out the sharp edges a little on the valve reliefs.....
And that’s the first point I was going to bring up. My last 408 had 340 style open chamber head, flat top pistons, and a Felpro 1008 (or is it 1009) gasket. Not anywhere what that combo should be but it still ran 9.70 at 2800 pounds and 10.0’s at 3200 pounds. And I never had the block squared or cut so they were in the hole some.
Time to put the laundry on the back.
yellow rose
Overnight Sensation
I've tested it. Even at 15.5:1 on a 3.313 stroke with W2 heads I've never had an issue with flame travel. Never had to run more that 36 total on gas and I ran 40-42 on alcohol, which is well within normal timing.
And that was a big dome. I had a couple of used Pistons with those domes on them...but I used them up doing some development work when I went to the W5 stuff or I'd take a picture of the domes. They was big.
If you think about it, the small block Chrylser has about the best plug location you can get in a wedge head.
If you look real close, you can see the plus is almost in the top of the chamber, almost like a Hemi. That's why a big dome isn't a killer like most thin it would be. Even on the SBC stuff with a big dome I only had to run 2, maybe 3 degrees more total with a big dome over a flat top.
If you look at that super sexy domed piston you have and imagine where the plug would be...it's almost on top of the dome.
If that same dome were used on a SBC head (not talking about really cool 18 degree or SB2 stuff, just regular 23 degree heads) instead of the plug pointing down on the top of the dome, it would be pointing right at the side of the dome.
That's a big difference in plug location.
Run the gas ported, domed sexy Pistons. You won't regret it.
And that was a big dome. I had a couple of used Pistons with those domes on them...but I used them up doing some development work when I went to the W5 stuff or I'd take a picture of the domes. They was big.
If you think about it, the small block Chrylser has about the best plug location you can get in a wedge head.
If you look real close, you can see the plus is almost in the top of the chamber, almost like a Hemi. That's why a big dome isn't a killer like most thin it would be. Even on the SBC stuff with a big dome I only had to run 2, maybe 3 degrees more total with a big dome over a flat top.
If you look at that super sexy domed piston you have and imagine where the plug would be...it's almost on top of the dome.
If that same dome were used on a SBC head (not talking about really cool 18 degree or SB2 stuff, just regular 23 degree heads) instead of the plug pointing down on the top of the dome, it would be pointing right at the side of the dome.
That's a big difference in plug location.
Run the gas ported, domed sexy Pistons. You won't regret it.
yellow rose
Overnight Sensation
All the better. Easier to get Rod bearings and pin selection is far better. So a double bonus.
A real nice pin came with the pistons and the .043 rings are sitting here. I didn’t touch the crank yet to mic it. I may go ahead and finish this build for early season testing. I would like to sell the 4 inch eagle crank and rods out of my 422 and switch over to Molar stuff but my racing fund account needs rebuilding first. Lol
Do the rounded edges on the valve relief give you anything worth mentioning?
gzig5
Well-Known Member
I'm going to guess that sharp corners don't do you any favors when it comes to detonation inception.
SwedishViking
Well-Known Member
Would those pistons work well on a closed chamber head like the W2/W5?
Wyrmrider
Well-Known Member
good- no 340 style
flame travel bad on BBM on SBM not so much
still small dome or FT or dish and small chamber better if you do not block your flow
it's all about head flow first
and tight quench on non trailer queens
flame travel bad on BBM on SBM not so much
still small dome or FT or dish and small chamber better if you do not block your flow
it's all about head flow first
and tight quench on non trailer queens
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