Stock Piston Help!!!
Thread Starter
Intermediate
Joined: Apr 2005
Posts: 28
Likes: 0
From: Royal Oak MI
Stock Piston Help!!!
Well, I have ben lurking for sometime now, ad finally deceided to join. I hope someone here can give me a little insight.
I have a 68 427 (390HP) vert. The engine was running pretty bad and leaking around the freeze plugs so I pulled it too replace what was needed. Well I got carried away and broke it all down luckily because I found all kinds of issues. Most of it was fixable, but i have one last issue that bugs me. I called Comp cams to get a cam and lefter set that would give me a little more power but still be completely drivable. They set me up with a cam that is .532 intake and .532 exhaust that is supposed to have no problem working with the stock setup. Problem is now that the valves just touch the pistons when I turn it over by hand. after a little research, i am convinced that the pistons are no original like i had believed.
Does anyone have a picture of the stock 390 horse 427 pistons? If not, are they flat top, dished, domed??? Hopefully someone can clue me in.
I have a 68 427 (390HP) vert. The engine was running pretty bad and leaking around the freeze plugs so I pulled it too replace what was needed. Well I got carried away and broke it all down luckily because I found all kinds of issues. Most of it was fixable, but i have one last issue that bugs me. I called Comp cams to get a cam and lefter set that would give me a little more power but still be completely drivable. They set me up with a cam that is .532 intake and .532 exhaust that is supposed to have no problem working with the stock setup. Problem is now that the valves just touch the pistons when I turn it over by hand. after a little research, i am convinced that the pistons are no original like i had believed.
Does anyone have a picture of the stock 390 horse 427 pistons? If not, are they flat top, dished, domed??? Hopefully someone can clue me in.
Drifting
Joined: Sep 2003
Posts: 1,325
Likes: 6
From: FRANKLIN GA
Sorry can't help you out with any pics but 530's doesn't sound like much lift for a BB. Check to make sure you have the cam in right. The dots should line up on the cam gear and the crank gear. Are you checking with the head gasket in place? Something ain't right if your hitting at that low of a lift.
Thread Starter
Intermediate
Joined: Apr 2005
Posts: 28
Likes: 0
From: Royal Oak MI
The interference is with the engine assembled. Fel-pro head gasket, heads toqued down to 80 ft-lbs. The dome on the piston is 0.140 high. The only thing i hadn't thought of is if it is a 454 piston, would it cause a problem. I hear the pin location is lower for the 454 and it might cause the piston to go up higher in the cylinder. Right now the piston comes flush with the bore on the block, and the dome sticks into the chamber.
Advanced
Joined: Jun 2004
Posts: 96
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From: portland TN
Are you sure you got the pistons back in correctly. If it has a dome there is a certain way they go into the engine. Most people get them in upside down and or do not pay attention that there are left and right pistons and they left and rights alternate from side to side. If they are installed upside down you will have to tear everything back apart and start over.
Remember Rod Tangs to rail. And the open side of the Piston valve reliefs (^) should not face the outside of the block.
Remember Rod Tangs to rail. And the open side of the Piston valve reliefs (^) should not face the outside of the block.
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From: Corsicana, Tx
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I agree...that type piston should clear easily with that cam. I've run .620 lift cams on stock pistons with no issue in a 427. Actually the lift has little to do with it, the duration and I/C and LSA will cause more issues, but likely that cam is small enough.
I have to agree to verify the cam is installed correctly and that pistons are correct. Usually they would hit head if they are upside down..but I've seen it done. They turn fairly well on stand but when you hit starter they crack a cylinder wall.
What heads are you using? There are Open chamber and closed chamber pistons.
The 454 piston is actually shorter. It has to be to allow for the longer stroke in the same height block.
Original 390 Hp pistons are closed chamber (the dome does not come all the way to the edge of piston on spark plug side) with a dome as you describe.
Did you by any chance install bigger 2.19 valves in the heads for more power? They are often an issue with stock type pistons. The "depth" of the valve relief is OK, but the 'radial" clearance of the valve around edge of pocket is insufficient and the touch in the corners.
JIM
I have to agree to verify the cam is installed correctly and that pistons are correct. Usually they would hit head if they are upside down..but I've seen it done. They turn fairly well on stand but when you hit starter they crack a cylinder wall.
What heads are you using? There are Open chamber and closed chamber pistons.
The 454 piston is actually shorter. It has to be to allow for the longer stroke in the same height block.
Original 390 Hp pistons are closed chamber (the dome does not come all the way to the edge of piston on spark plug side) with a dome as you describe.
Did you by any chance install bigger 2.19 valves in the heads for more power? They are often an issue with stock type pistons. The "depth" of the valve relief is OK, but the 'radial" clearance of the valve around edge of pocket is insufficient and the touch in the corners.
JIM
Last edited by 427Hotrod; Apr 27, 2005 at 08:25 PM.
Thread Starter
Intermediate
Joined: Apr 2005
Posts: 28
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From: Royal Oak MI
I will measure the valves to make sure they are 2.02, but I beleive them to be stock. The heads are original closed chamber oval port.
the cam I put in is a comp cams 11-675-4.
Intake Exhaust
Valve Adjustment 0.016 0.016
Gross Valve Lift 0.532 0.532
Duration At 0.015 Tappet Lift 262 268
Lobe angle is 110 degrees. Comp said it would work with the stock setup, but I talked to a guy who thought I needed 114 degrees for this engine.
the cam I put in is a comp cams 11-675-4.
Intake Exhaust
Valve Adjustment 0.016 0.016
Gross Valve Lift 0.532 0.532
Duration At 0.015 Tappet Lift 262 268
Lobe angle is 110 degrees. Comp said it would work with the stock setup, but I talked to a guy who thought I needed 114 degrees for this engine.
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
Originally Posted by no_rice_burners
I will measure the valves to make sure they are 2.02, but I beleive them to be stock. The heads are original closed chamber oval port.
the cam I put in is a comp cams 11-675-4.
Intake Exhaust
Valve Adjustment 0.016 0.016
Gross Valve Lift 0.532 0.532
Duration At 0.015 Tappet Lift 262 268
Lobe angle is 110 degrees. Comp said it would work with the stock setup, but I talked to a guy who thought I needed 114 degrees for this engine.
the cam I put in is a comp cams 11-675-4.
Intake Exhaust
Valve Adjustment 0.016 0.016
Gross Valve Lift 0.532 0.532
Duration At 0.015 Tappet Lift 262 268
Lobe angle is 110 degrees. Comp said it would work with the stock setup, but I talked to a guy who thought I needed 114 degrees for this engine.
BigBlockk
Later.....
Melting Slicks
Joined: May 2001
Posts: 2,131
Likes: 4
From: May help you? You can sure as hell try!
I used Kieth Black Hypereutectic pistons in my rebuild. They were very close in dome configuration to my originals. There may be a picture of the dome on the KB website.
Piston to valve clearance in my build was an easy 0.2". My cam is 0.5" intake 221' duration and 0.510" exhaust 232' duration @ 0.050". I wouldn't expect your cam to be that different. Are you sure the duration numbers you're quoting aren't at 0.050"? Normally duration is quoted at 0.006" (advertised) and 0.050" (SAE). If those duration numbers are at 0.050", that is a big cam! This would probably be the cause of your problem in that case.
LSA difference between 110' and 114' won't make much difference in piston to valve clearance but the 114' LSA will make the engine idle a bit smoother and give more vacuum at idle.
Piston to valve clearance in my build was an easy 0.2". My cam is 0.5" intake 221' duration and 0.510" exhaust 232' duration @ 0.050". I wouldn't expect your cam to be that different. Are you sure the duration numbers you're quoting aren't at 0.050"? Normally duration is quoted at 0.006" (advertised) and 0.050" (SAE). If those duration numbers are at 0.050", that is a big cam! This would probably be the cause of your problem in that case.
LSA difference between 110' and 114' won't make much difference in piston to valve clearance but the 114' LSA will make the engine idle a bit smoother and give more vacuum at idle.
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