Posted By: RapidRobert
which KB pistons for a 451 - 09/11/09 08:30 PM
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.
which KB pistons for a 451
Posted By: rss
Re: which KB pistons for a 451 - 09/11/09 09:09 PM
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.
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.
Posted By: JohnRR
Re: which KB pistons for a 451 - 09/11/09 09:27 PM
Closed chamber head , KB piston shouldn't even be an option , plus you don't need a quench dome with a closed chamber head 
Posted By: mopar68
Re: which KB pistons for a 451 - 09/11/09 10:03 PM
Posted By: DAMOPARS
Re: which KB pistons for a 451 - 09/11/09 10:23 PM
Why not go with SRP pistons I did they are very nice.
http://www.flatlanderracing.com/
http://www.flatlanderracing.com/
Posted By: DrCharles
Re: which KB pistons for a 451 - 09/11/09 10:39 PM
KB280 with the 440 rod, but the quench pads *will* need to be milled.
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
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
Posted By: RapidRobert
Re: which KB pistons for a 451 - 09/11/09 10:43 PM
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?
Posted By: JohnRR
Re: which KB pistons for a 451 - 09/12/09 03:15 PM
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 ...
Posted By: DrCharles
Re: which KB pistons for a 451 - 09/12/09 03:37 PM
It is a Felpro 1039 gasket and it is .051" thick. Believe it or not, sometimes I do know what I'm talking about 
Posted By: JohnRR
Re: which KB pistons for a 451 - 09/13/09 01:48 AM
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
Posted By: RapidRobert
Re: which KB pistons for a 451 - 09/13/09 03:36 AM
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.
Posted By: 64Post
Re: which KB pistons for a 451 - 09/13/09 05:50 AM
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...
Posted By: StealthWedge67
Re: which KB pistons for a 451 - 09/13/09 07:31 AM
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.
Posted By: GwaiiEagle
Re: which KB pistons for a 451 - 09/13/09 03:13 PM
The hassle is trying to find pistons for this combo in a .030 over. They are all 33 or 35.
Posted By: StealthWedge67
Re: which KB pistons for a 451 - 09/13/09 04:08 PM
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?
Posted By: JohnRR
Re: which KB pistons for a 451 - 09/13/09 04:40 PM
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 .
Posted By: DrCharles
Re: which KB pistons for a 451 - 09/13/09 04:51 PM
And he could always get file-to-fit rings and set the proper (large) top ring gap for the hypers
Posted By: JohnRR
Re: which KB pistons for a 451 - 09/13/09 05:07 PM
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 .
Posted By: RapidRobert
Re: which KB pistons for a 451 - 09/13/09 05:33 PM
Quote: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?
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 ,
Posted By: JohnRR
Re: which KB pistons for a 451 - 09/13/09 08:58 PM
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 .
Posted By: DrCharles
Re: which KB pistons for a 451 - 09/14/09 12:32 AM
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... 
Posted By: 73Charger
Re: which KB pistons for a 451 - 09/14/09 04:39 PM
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.