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Piston Wall Clearance #110365
08/25/08 10:12 PM
08/25/08 10:12 PM
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Maracaibo,Venezuela
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What is the best piston wall clearance with Keith Black forged piston. I have .007”(according with KB instruction) and the engine turns with difficult when it’s hot.
I have a 360 .030” over bore, Mechanical Cam, 10.5 Compression Ratio, 185psi Static Compression.

Regards…. Jose Romero

Re: Piston Wall Clearance [Re: GTMaracucho] #110366
08/25/08 10:28 PM
08/25/08 10:28 PM
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Wichita Kansas
CH3NO2 Offline
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What is the ring gap set on the top ring?


Engine by DeTar http://www.kansasbadman.com
Re: Piston Wall Clearance [Re: CH3NO2] #110367
08/25/08 10:39 PM
08/25/08 10:39 PM
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Maracaibo,Venezuela
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.012".

Why??

Re: Piston Wall Clearance [Re: GTMaracucho] #110368
08/25/08 11:03 PM
08/25/08 11:03 PM
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Alabama
Mopar-Al Offline
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I believe minimum clearance in .0015

But if your ring gap is too tight, a kb hypo will expand more and can bust the rings

Re: Piston Wall Clearance [Re: GTMaracucho] #110369
08/25/08 11:03 PM
08/25/08 11:03 PM

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everything expands when hot. if the ring gap is to tight, it will bind up and lock the pistons in place.

The specs for kb pistons and ring gaps are on the kb site. just search it

Re: Piston Wall Clearance [Re: GTMaracucho] #110370
08/25/08 11:04 PM
08/25/08 11:04 PM
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Alabama
Mopar-Al Offline
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Quote:

.012".

Why??




I think thats around 4-6 thou too tight if not more.

Re: Piston Wall Clearance [Re: Mopar-Al] #110371
08/25/08 11:26 PM
08/25/08 11:26 PM
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Quote:

I believe minimum clearance in .0015

But if your ring gap is too tight, a kb hypo will expand more and can bust the rings




But what about Piston Wall to Cylinder??? .007" It's OK???

Re: Piston Wall Clearance [Re: Mopar-Al] #110372
08/25/08 11:26 PM
08/25/08 11:26 PM
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Lincoln Nebraska
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From KB site: "street normally aspirated" forged pistons top ring-.016" 2nd ring -.012"


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Re: Piston Wall Clearance [Re: RapidRobert] #110373
08/25/08 11:31 PM
08/25/08 11:31 PM
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Maracaibo,Venezuela
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Quote:

From KB site: "street normally aspirated" forged pistons top ring-.016" 2nd ring -.012"




Thanks....but I'm using total seal ring, is same??

Re: Piston Wall Clearance [Re: GTMaracucho] #110374
08/25/08 11:32 PM
08/25/08 11:32 PM
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Alabama
Mopar-Al Offline
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Quote:

Quote:

I believe minimum clearance in .0015

But if your ring gap is too tight, a kb hypo will expand more and can bust the rings




But what about Piston Wall to Cylinder???




.0015 thou

I do believe. This card says .0015

Re: Piston Wall Clearance [Re: Mopar-Al] #110375
08/25/08 11:34 PM
08/25/08 11:34 PM
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Alabama
Mopar-Al Offline
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Did you make sure you had good engine/body ground cables and the right size? This particular question can bite a lot of people in the but.

Re: Piston Wall Clearance [Re: GTMaracucho] #110376
08/25/08 11:42 PM
08/25/08 11:42 PM
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Lincoln Nebraska
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Quote:

Thanks....but I'm using total seal ring, is same??


I can't say Bro as I have never used them but I have wanted to even though a dyno operator told me once that they didn't make any more horsepower but I am not convinced but in your case at .007 it sure isn't the piston to wall clearance.


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Re: Piston Wall Clearance [Re: Mopar-Al] #110377
08/25/08 11:48 PM
08/25/08 11:48 PM
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Maracaibo,Venezuela
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Quote:

Did you make sure you had good engine/body ground cables and the right size? This particular question can bite a lot of people in the but.



I have the battery in trunk, and have only one ground cable, because the motor mount are metal without rubber.

Re: Piston Wall Clearance [Re: GTMaracucho] #110378
08/25/08 11:54 PM
08/25/08 11:54 PM
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Lincoln Nebraska
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could you hook up a batt up front so that when it is warmed up & acting up & dragging you can see if it's a voltage drop issue or an engine friction problem.


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Re: Piston Wall Clearance [Re: RapidRobert] #110379
08/26/08 12:03 AM
08/26/08 12:03 AM
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Maracaibo,Venezuela
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In resume:
Piston Wall to Cylinder: .015"
Rings Gap: First: .016"/Second: .012".
Is That correct??

Re: Piston Wall Clearance [Re: GTMaracucho] #110380
08/26/08 12:15 AM
08/26/08 12:15 AM
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Lincoln Nebraska
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In your 1st post you have .007" ptw with forged pistons. What do you mean "in resume"?


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Re: Piston Wall Clearance [Re: RapidRobert] #110381
08/26/08 12:20 AM
08/26/08 12:20 AM
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Maracaibo,Venezuela
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Quote:

In your 1st post you have .007" ptw with forged pistons. What do you mean "in resume"?



I'm confuse, .007" PTW is goood?? or .015" is the correct clearance??

Re: Piston Wall Clearance [Re: GTMaracucho] #110382
08/26/08 12:30 AM
08/26/08 12:30 AM
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Lincoln Nebraska
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in your 1st post you have .007 piston to wall clearance with your forged pistons, & in the next post you have .012 top ring end gap clearance, correct so far?


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Re: Piston Wall Clearance [Re: RapidRobert] #110383
08/26/08 12:33 AM
08/26/08 12:33 AM
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Maracaibo,Venezuela
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Quote:

in your 1st post you have .007 piston to wall clearance with your forged pistons, & in the next post you have .012 top ring end gap clearance, correct so far?




Yes sir

Re: Piston Wall Clearance [Re: GTMaracucho] #110384
08/26/08 12:58 AM
08/26/08 12:58 AM
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Lincoln Nebraska
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on their(KB) site they want .004 piston to wall clearance on the top ring for each inch of bore with forged(not hypereutectic) pistons(If I am reading their site correctly,it was a little confusing) which would put you at .016" for a street normally aspirated application(the top ring). At .012 you are tighter than they recommend but I dont know if your rings are butting & causing the problem or not but the more I think about it I would be inclined to think the rear mounted battery & long cables are the culprit. When its warmed up it cranks too slow & this is the issue right? At that point in time could you pull the plugs & see how it cranks & also with the plugs out put a socket & breaker bar(or torque wrench) on the front harmonic dampener bolt & see how hard it is to turn ? or easier yet at that point in time get a jump directly to your starter & dont use your trunk battery & see what it does. It is midnight here & I am going to have to sign off. I will get back to you tomorrow. Post what you find out.


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Re: Piston Wall Clearance [Re: RapidRobert] #110385
08/26/08 01:32 AM
08/26/08 01:32 AM
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Maracaibo,Venezuela
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Quote:

on their(KB) site they want .004 piston to wall clearance on the top ring for each inch of bore with forged(not hypereutectic) pistons(If I am reading their site correctly,it was a little confusing) which would put you at .016" for a street normally aspirated application(the top ring). At .012 you are tighter than they recommend but I dont know if your rings are butting & causing the problem or not but the more I think about it I would be inclined to think the rear mounted battery & long cables are the culprit. When its warmed up it cranks too slow & this is the issue right? At that point in time could you pull the plugs & see how it cranks & also with the plugs out put a socket & breaker bar(or torque wrench) on the front harmonic dampener bolt & see how hard it is to turn ? or easier yet at that point in time get a jump directly to your starter & dont use your trunk battery & see what it does. It is midnight here & I am going to have to sign off. I will get back to you tomorrow. Post what you find out.




Thanks for your help..... Now I have in my hands somethink to do tomorrow

Re: Piston Wall Clearance [Re: GTMaracucho] #110386
08/26/08 02:38 AM
08/26/08 02:38 AM
Joined: Feb 2007
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MOPAR HEADQUARTERS IN ALDEN NY
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here are the real specs take your bore size and times it by .0065 to get your end ring gap, witch would be around 25,28 thou is were i set up small blocks.


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Re: Piston Wall Clearance [Re: GTMaracucho] #110387
08/26/08 02:48 AM
08/26/08 02:48 AM
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ptw on kbs is 2-4 thou there designed to be tighter than forged i set up at 4-6 thou ptw, its where the top ringland in piston is machined that it comands twice the end gap for expansion if you dont follow that piston top will break off when under load and up to temp


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Re: Piston Wall Clearance [Re: hemigod426] #110388
08/26/08 08:54 AM
08/26/08 08:54 AM
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You didn't read the original post. He says the pistons are KB FORGED. He says he has 0.007" piston-to-wall clearance, I think that's too much, but it's the maximum in the KB chart for drag racing, 4" piston. He says he has ring gap of 0.012". The chart says 0.004" per inch of bore diameter, that would be 0.016" so the ring gaps are too tight.

R.

Last edited by dogdays; 08/26/08 08:58 AM.
Re: Piston Wall Clearance [Re: dogdays] #110389
08/26/08 10:18 AM
08/26/08 10:18 AM
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Marysville, O-H-I-O
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he also said hard turning when hot...could it be a timing issue instead of a clearance issue?


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Re: Piston Wall Clearance [Re: 70Cuda383] #110390
08/26/08 10:39 AM
08/26/08 10:39 AM
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Lincoln Nebraska
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Quote:

he also said hard turning when hot...could it be a timing issue instead of a clearance issue?


excellent idea! Could it actually be something thatsimple as overadvanced timing On our stock car we had to engage the starter THEN switch on the ign to get it to crank when things were hot. If he grounds the coil wire & then cranks we'll have the ans to that.


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Re: Piston Wall Clearance [Re: RapidRobert] #110391
08/26/08 11:13 AM
08/26/08 11:13 AM
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Columbia, CT
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.007 on the pistons is ok, loose and mabye noisey when started cold, but ok. .012 on the top ring is bad, and technically, leaving the 2nd ring a little bigger than the top will help ring seal. So with a 360 (4.03 when bored .030 over) I'd be setting the top ring at .017 and the 2nd ring at .020. Also, always round up when you get a "point something" (4.03x.004= .01612, or .017). You want to err to the large side on any performance engine.


Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
Re: Piston Wall Clearance [Re: RapidRobert] #110392
08/26/08 01:03 PM
08/26/08 01:03 PM
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Maracaibo,Venezuela
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Quote:

Quote:

he also said hard turning when hot...could it be a timing issue instead of a clearance issue?


excellent idea! Could it actually be something thatsimple as overadvanced timing On our stock car we had to engage the starter THEN switch on the ign to get it to crank when things were hot. If he grounds the coil wire & then cranks we'll have the ans to that.




I have 34° and MSD 6 Digital Plus with retard option

Re: Piston Wall Clearance [Re: GTMaracucho] #110393
08/26/08 01:18 PM
08/26/08 01:18 PM
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Clearance for piston to wall clearance is made
at the shirt not the top ring. Ring end gap is based on bore diameter as well. Forged pistons
are clearanced at .004 to 5 thousands.
The measurement of .0015 is 1 1/2 thousands.
.005 has been the sweet spot for forged pistons.
The piston materials used today are of much better
quality and grow less than materials used in yester year.

logan426

Re: Piston Wall Clearance [Re: GTMaracucho] #110394
08/26/08 02:46 PM
08/26/08 02:46 PM
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Lincoln Nebraska
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Quote:

I have 34° and MSD 6 Digital Plus with retard option


That answeres that Q without even having to do anything.


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Re: Piston Wall Clearance [Re: RapidRobert] #110395
08/26/08 05:58 PM
08/26/08 05:58 PM
Joined: Jan 2003
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Oklahoma City OK
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That 34degees is total advance, what is the initial advance, most engines with more than 10 degrees will be hard to start hot when fresh. (Hadn't heard someone talk about grounding the coil, spinning the engine, and tuning it on in years. Not a good idea with an electroic ignition though )

Re: Piston Wall Clearance [Re: Cudajon] #110396
08/26/08 06:24 PM
08/26/08 06:24 PM
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ky.
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I think you need a mini starter. I run 16 degree base timing on all my smallblocks and have never had one of them grunt when starting hot.

Re: Piston Wall Clearance [Re: kenworth_goose] #110397
08/26/08 06:39 PM
08/26/08 06:39 PM
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Columbia, CT
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But did your rings butt?


Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
Re: Piston Wall Clearance [Re: moper] #110398
08/26/08 07:30 PM
08/26/08 07:30 PM
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Lincoln Nebraska
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Quote:

But did your rings butt?


YES lets get a breaker bar on there & find out. I assumed that the retard he has is for starting rather than on the other end. I would think hard cranking at a particular initial would depend on the CR. You can ground the coil wire on an electronic ign, its cranking it with the wire open that can fry them.


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Re: Piston Wall Clearance [Re: RapidRobert] #110399
08/26/08 09:55 PM
08/26/08 09:55 PM
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Balt. Md
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When its hot and cranking slow unhook the MSD box and then crank it to verify if it is an over advanced ign. You have forged pistons and not hypertech pistons so then I agree the top ring gap should be .016 to .017 and the .007 Piston to wall clearence is a bit on the loose side at .007 but it will work. Will most likely be a bit noisey when cold like was said but it will be ok as it's not to tight. If you find the eng is tight and its not the ign then I would think about that .012 top ring gap you have in it. Good luck , Ron

Last edited by 383man; 08/26/08 09:56 PM.
Re: Piston Wall Clearance [Re: 383man] #110400
08/27/08 07:18 PM
08/27/08 07:18 PM
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Maracaibo,Venezuela
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OK Gents....
Today I talked with my mechanic and he said that the first ring is .017" & second is .022".
I started and warm up the engine, then I pull out all spark plugs and turn manually and the engine is very..very hard to turn.
Maybe on this week end we pull out the engine and check everything again.
I'm thinking go to more clearance on Piston to wall, what about .010"??

Re: Piston Wall Clearance [Re: GTMaracucho] #110401
08/27/08 09:34 PM
08/27/08 09:34 PM
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Maracaibo,Venezuela
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Re: Piston Wall Clearance [Re: GTMaracucho] #110402
08/28/08 12:06 AM
08/28/08 12:06 AM
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Maracaibo,Venezuela
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Any Coments???

Re: Piston Wall Clearance [Re: GTMaracucho] #110403
08/28/08 12:14 AM
08/28/08 12:14 AM
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Lincoln Nebraska
RapidRobert Offline
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Quote:

Any Coments???


no mas until he gets in there & mikes everything.


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Re: Piston Wall Clearance [Re: GTMaracucho] #110404
08/28/08 12:15 AM
08/28/08 12:15 AM
Joined: Feb 2007
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MOPAR HEADQUARTERS IN ALDEN NY
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.010 is way to much it will rock at tdc. first i would pull pan in car to see if crank is bent or rods are binding, just a though before you pull motor and tear down


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Re: Piston Wall Clearance [Re: hemigod426] #110405
09/10/08 09:56 PM
09/10/08 09:56 PM
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Maracaibo,Venezuela
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Hi,
I made new electric system (new cables, relays, etc) and BINGO the car can start OK.
Thanks a lot for the support, and this weekend I will test the car in the race way.

Regards....Jose


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