Hot Rod Forum : Hotrodders Bulletin Board - Reply to Topic
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine> Piston /wall clearence
User Name
Password
lost password?   |   register now

Thread: Piston /wall clearence Reply to Thread
Title:
  
Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Additional Options
Miscellaneous Options

Topic Review (Newest First)
10-29-2002 06:53 AM
slider in wa It sounds like you have put some money and thought into this motor. The guys are correct on checking the clearance. Your .020 is to big a gap. In my opinion,most clearances are checked at or near the center of the cylinder.See what the manufactures of the pistons say about where to check clearance.You are right to question this. Track it down, and be sure.
Good luck, and let us know how it turns out. will ya?
Slider in Wa.
10-29-2002 06:15 AM
engineguy Dittos to all the messages above. The ring land area will generally be somewhat smaller diameter than the skirt area. Also, the piston manufacturers instructions as to WHERE to measure the skirt must be followed exactly. .020" is way too much, if this is what it turns out to be. Many aftermarket replacement pistons do have the clearance built in, but I am not sure about JE. Anyway, the machinist should have measured each piston individually and bored each cylinder accordingly. Used to be that you would find several thousanths difference between the diameters in a set of forged pistons, however newer pistons and good performance brands such as JE are usually right on the money.
10-29-2002 03:27 AM
engineczar Most Pistons (possibly all)come through with the clearance built into them for the bore size ordered. If you order a +.030 piston for a 350 Chevy than the bore size should be exactly 4.030 and the piston will be smaller by whatever the piston maker determines is the correct clearance. JE pistons come with a sheet that shows where the piston is measured just so the machinist can confirm the size. Take a set of verniers, dial calipers, or dial bore gage and measure the bore.
10-28-2002 06:34 PM
Quepas00 .0065 would be tight .0085 will be loose.

Go to this site and check out dyno results on the 350 with 420 HP. It has all the specs they used on this motor.
http://edelbrock.com/automotive/index.html
10-28-2002 06:18 PM
TurboS10 I am currently have a set of JE pistons that are at the machine shop with the block for boring. I found that the top of the piston in the ring land area is much smaller than the skirt(what little there is). I measured, but cant remember the exact number. I believe there was at least .020 difference from top to bottom. I would check the clearance at the skirt. If it is .020 there you are screwed, but I am betting it will be around .003 if your machinist did his job. You will hear that forged pistons need .005-.01, but new alloys used in pistons today are much different than those of yesteryear. Todays forged piston dont require the clearance that old ones did. My sbc 400 TRW forged pistons were fit at .003 wall clearance and there is no rattle when it is cold. Hope this helps.

Chris
10-28-2002 05:29 PM
warlock I can fit a .020 feeler in between the lower piston skirt and the cylinder wall and its a loose .020! I think the machinest messed up the bore and is just trying to pass it off to me. Anyway, i will contact JE pistons by phone to confirm this. Thanks for the help.

[ October 28, 2002: Message edited by: warlock ]</p>
10-28-2002 04:08 PM
BOBCRMAN@aol.com are you sure its twenty thousants, that is wwwwway to much clearance. try .002 or two thousants. which is not enough for forged pistons. the actual piston to wall clearance depends on the design of the piston, the material its made of, cast or forged or hypereutectic cast. the bore size and what its going to be used for. consult the pistons manufacturer for correct wall clearance.. i'm always seeing keith black pistons with the top ring lands pulled off and the owner cussing the piston manufacturer as bad pistons, but they didn't read the basic instructions included in the set that says hyper pistons have to have different clearances and way more ring end gap, the top ring butts from the heat transfer and away goes the top of the piston. most forgings in a 4" bore are .0035 + due to the way the piston expands. way back in the old days we ran them at .008+ and thought nothing of it but materials are different now and ring tech is better.
10-28-2002 03:39 PM
warlock
Piston /wall clearence

I am building a 383 stroker with a completely forged bottom end. I am using JE flattop pistons, Oliver rods and crank and am planing on using 250,300hp shots of NOS.The compression ratio should be around 11.0 to 1. My piston to wall clearence is about 20 thousants with a ring gap of about 18. Is this to much clearence??. The machinest that bored the block swears it needs the clearence for the pistons to expand. does this sound right to you guys?? I am new to this and dont want to put together my EXPENSIVE toy only to have it puffing smoke time i fire it off. Any advise would be Helpful. Thanks in advance.

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


All times are GMT -6. The time now is 07:39 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.