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which KB pistons for a 451 #465714
09/11/09 04:30 PM 09/11/09 04:30 PM
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Lincoln Nebraska
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RapidRobert Offline OP
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400 blk 3.75". rb crank. What part # (kb hyper) do I need to look at? Closed chamber heads & I would mill the quench dome to get ~9.5-10.1. thank you for your time.

live every 24 hour block of time like it's your last day on earth
Re: which KB pistons for a 451 [Re: RapidRobert] #465715
09/11/09 05:09 PM 09/11/09 05:09 PM
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Seattle, WA
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rss Offline
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KB215s???

IIRC, you responded to an earlier post of mine on stroker buids and were planning to use 440 rods for your 451. I think the KB 215s use a 383/400 length connecting rod instead of the 440 rod. I don't recall seeing a KB piston for the 451 that used the 440 rod. I think others (440Source, Diamond, Ross) have forged pistons for the 451 that use the 440 rod. I'm just beginning to look into this myself, so it is very likely that I could be wrong.

Last edited by rss; 09/11/09 05:19 PM.
Re: which KB pistons for a 451 [Re: RapidRobert] #465716
09/11/09 05:27 PM 09/11/09 05:27 PM
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JohnRR Offline
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Closed chamber head , KB piston shouldn't even be an option , plus you don't need a quench dome with a closed chamber head

Re: which KB pistons for a 451 [Re: JohnRR] #465717
09/11/09 06:03 PM 09/11/09 06:03 PM
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Sunny So. Cal.
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mopar68 Offline
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For use with stock 440 rods web page

And for stock 383 400 rods KB215 and KB251

Last edited by mopar68; 09/11/09 06:06 PM.
Re: which KB pistons for a 451 [Re: RapidRobert] #465718
09/11/09 06:23 PM 09/11/09 06:23 PM
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VA
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Why not go with SRP pistons I did they are very nice.
http://www.flatlanderracing.com/
Re: which KB pistons for a 451 [Re: JohnRR] #465719
09/11/09 06:39 PM 09/11/09 06:39 PM
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West Plains, MO
DrCharles Offline
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KB280 with the 440 rod, but the quench pads *will* need to be milled.

Quote:

Closed chamber head , KB piston shouldn't even be an option , plus you don't need a quench dome with a closed chamber head



You do if you are using a thick head gasket and want to maintain quench and the right CR... also Eagle H-beams are something like .008 shorter than the stock 440 rod length, and the KB280 sits .010 down in the hole to allow for decking the block.

With the H-beams the piston flat should be .018 down the hole - and I did actually measure and confirm this. So I had my quench domes milled down to .030 high.

Using a .051 thick head gasket, that means the dome has a positive deck height (sticks out above the block) .012", resulting in a .039 quench distance.

CR calculated out to 10.4:1 after I cc'ed my chambers.

Measure twice, cut once!
-Charles
Re: which KB pistons for a 451 [Re: RapidRobert] #465720
09/11/09 06:43 PM 09/11/09 06:43 PM
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RapidRobert Offline OP
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Thanks guys. Charles I have some felpro blue SB ones that are .054". The .051" ones you mention is that the compressed thickness of the BB versions of the same felpro blue gasket?

Last edited by RapidRobert; 09/11/09 08:25 PM.
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Re: which KB pistons for a 451 [Re: RapidRobert] #465721
09/12/09 11:15 AM 09/12/09 11:15 AM
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JohnRR Offline
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Quote:

Thanks guys. Charles I have some felpro blue SB ones that are .054". The .051" ones you mention is that the compressed thickness of the BB versions of the same felpro blue gasket?



no , most of the felpro BB blue gaskets are .040 nominal ...
Re: which KB pistons for a 451 [Re: JohnRR] #465722
09/12/09 11:37 AM 09/12/09 11:37 AM
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West Plains, MO
DrCharles Offline
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It is a Felpro 1039 gasket and it is .051" thick. Believe it or not, sometimes I do know what I'm talking about


Re: which KB pistons for a 451 [Re: DrCharles] #465723
09/12/09 09:48 PM 09/12/09 09:48 PM
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JohnRR Offline
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Quote:

It is a Felpro 1039 gasket and it is .051" thick. Believe it or not, sometimes I do know what I'm talking about





Who said you didn't know what you were talking about, I said MOST

But like mr. rapidrobert I should not chime in on subjects I have little knowledge

Last edited by Johnahah; 09/13/09 01:03 AM.
Re: which KB pistons for a 451 [Re: JohnRR] #465724
09/12/09 11:36 PM 09/12/09 11:36 PM
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RapidRobert Offline OP
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alright I will order some KB 280's & mill the dome for quench distance. Any suggestions for a ballpark CR figure to shoot for (iron heads/stock cam/87 octane). Low rpm daily driver.

live every 24 hour block of time like it's your last day on earth
Re: which KB pistons for a 451 [Re: RapidRobert] #465725
09/13/09 01:50 AM 09/13/09 01:50 AM
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Quote:

alright I will order some KB 280's & mill the dome for quench distance. Any suggestions for a ballpark CR figure to shoot for (iron heads/stock cam/87 octane). Low rpm daily driver.



Don't forget to consider your operating altitude. Approximate 10% static compression loss per 2500 ft.

Or not...

Re: which KB pistons for a 451 [Re: RapidRobert] #465726
09/13/09 03:31 AM 09/13/09 03:31 AM
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Puyallup, WA
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StealthWedge67 Offline
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Quote:

400 blk 3.75". rb crank. What part # (kb hyper) do I need to look at? Closed chamber heads & I would mill the quench dome to get ~9.5-10.1. thank you for your time.



Why bother with Hypers? I'm using KB823's (forged), with Stealth heads @ 84cc, I had the block decked to 0, provides about 10.4:1 with quench.

LemonWedge - Street heavy / Strip ready - 11.07 @ 120
Re: which KB pistons for a 451 [Re: StealthWedge67] #465727
09/13/09 11:13 AM 09/13/09 11:13 AM
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Nanaimo, B.C.
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The hassle is trying to find pistons for this combo in a .030 over. They are all 33 or 35.
Re: which KB pistons for a 451 [Re: GwaiiEagle] #465728
09/13/09 12:08 PM 09/13/09 12:08 PM
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Puyallup, WA
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Quote:

The hassle is trying to find pistons for this combo in a .030 over. They are all 33 or 35.


Well, if he hasn't bought pistons yet, I doubt he's had the block bored & honed. So, what difference does it make whether it's .030 over or .033 over?

LemonWedge - Street heavy / Strip ready - 11.07 @ 120
Re: which KB pistons for a 451 [Re: GwaiiEagle] #465729
09/13/09 12:40 PM 09/13/09 12:40 PM
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JohnRR Offline
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Quote:

The hassle is trying to find pistons for this combo in a .030 over. They are all 33 or 35.



4.375(.033 over) is a VERY POPULAR ring size AND it's what most GOOD off the shelf 400 based stroker pistons are sized at .
Re: which KB pistons for a 451 [Re: JohnRR] #465730
09/13/09 12:51 PM 09/13/09 12:51 PM
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West Plains, MO
DrCharles Offline
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And he could always get file-to-fit rings and set the proper (large) top ring gap for the hypers

Re: which KB pistons for a 451 [Re: DrCharles] #465731
09/13/09 01:07 PM 09/13/09 01:07 PM
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JohnRR Offline
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Quote:

And he could always get file-to-fit rings and set the proper (large) top ring gap for the hypers



With hypers you don't need to go thru the hassle of getting a file fit ring , the std ring size for the give bore is your file fit ring , getting a .005 oversize is just making more work for oneself .
Re: which KB pistons for a 451 [Re: JohnRR] #465732
09/13/09 01:33 PM 09/13/09 01:33 PM
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Lincoln Nebraska
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RapidRobert Offline OP
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Quote:

With hypers you don't need to go thru the hassle of getting a file fit ring , the std ring size for the give bore is your file fit ring ,

Thank you double R, I had forgotton about that. Certainly no need to spring for file fit. They rough bored it as it had some rust to see what it would clean up at & they called & said 30 over. Any suggestions for CR and piston clearance?

live every 24 hour block of time like it's your last day on earth
Re: which KB pistons for a 451 [Re: RapidRobert] #465733
09/13/09 04:58 PM 09/13/09 04:58 PM
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JohnRR Offline
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compression I assume you want it pump gas friendly ? 9.5 steel heads , with good quench , 10 - 10.5 alum with good quench , piston clearance is set by the piston you choose , don't hone till you have the pistons in hand .
Re: which KB pistons for a 451 [Re: JohnRR] #465734
09/13/09 08:32 PM 09/13/09 08:32 PM
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West Plains, MO
DrCharles Offline
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RapidRobert, how big a cam are you planning to run... a small cam will not allow as much compression (higher cranking pressure) as a bigger one, for a given octane gas...

Re: which KB pistons for a 451 [Re: DrCharles] #465735
09/14/09 12:39 PM 09/14/09 12:39 PM
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Nebraska
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The pistons I chose for my 451 build were the KB823. Yes they are forged but I had a notion to throw some NOS at it in the future. Basic 400 block, 440 forge crank, Scat 6.760 rods and mild cam.

1973 Dodge Charger SE 400 Magnum
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