440 Piston Deck Height?
#1020220
06/25/11 02:21 PM
06/25/11 02:21 PM
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Joined: Jan 2003
Posts: 1,178
People's Republic of Kali
70runner
OP
super stock
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OP
super stock
Joined: Jan 2003
Posts: 1,178
People's Republic of Kali
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440-6 build: .030 over, SRP flattops (valve reliefs), SCAT rods, stealth heads, Lunati 60303, shooting for 10:1 CR. Going in 70RR, rebuilt 727, 3.23, stock manifolds, TTI 2.5 exhaust.
Engine shop machined block for calculated .005 piston deck (in the hole). With .039 compressed head gasket and approx 81cc chamber, -6cc on valve reliefs, comes to approx 10.3CR.
Doing my mockup used dial gauge to get TDC, then used a precision straight edge and feeler gauge to take piston deck height measurements (double checked with caliper depth gauge). Measurements were taken with rings in and at center of piston:
#1: .012-.013 (inches)
#3: .012-.013
#5: .013-.014
#7: .014-.015
#2: .011-.012
#4: .012-.013
#6: .012-.013
#8: .014-.015
These measurements don't change the calc CR much, just a couple of tenths lower. However, I'm a little concerned with the quench implications and also the increase from front to back. Wanted to get your opinions before I contact the engine shop. TIA.
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Re: 440 Piston Deck Height?
[Re: Twostick]
#1020222
06/25/11 05:18 PM
06/25/11 05:18 PM
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Joined: Apr 2006
Posts: 4,220
West Plains, MO
DrCharles
master
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master
Joined: Apr 2006
Posts: 4,220
West Plains, MO
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Quote:
If those #'s are correct, you need a new machinist.
Kevin
Not sure about SCAT rods, but IIRC, Eagle rods are .010" shorter than stock (down the hole), which I allowed for when selecting pistons and head gasket for my 451. Measure twice, cut once 
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Re: 440 Piston Deck Height?
[Re: 70runner]
#1020225
06/26/11 04:56 AM
06/26/11 04:56 AM
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Joined: Jan 2003
Posts: 27,421
Balt. Md
383man
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
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I take it the rods are new and not rebushed ? I only ask because I have seen rods rebushed cause the piston deck reading to vary a tad. I had my new 493 figured to zero deck so I could use the .039 head gasket but when I assembled it all the piston decks came in from .007 and .008 range down in the cyl. I figured the same as they were conservitive as we can always cut more. I went with the .039 gasket and it dropped my comp from 10.8 to 10.6 and I left the quench at .046 to .047. It is working great as it has been running for 3 weeks with no ping at all. And I rechecked the timing today which was right on 36 total all in by 1800 rpm. Let us know what the shop says when they measure it and give you their readings. Good luck , Ron
Last edited by 383man; 06/26/11 05:01 AM.
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Re: 440 Piston Deck Height?
[Re: 70runner]
#1020226
06/26/11 08:19 AM
06/26/11 08:19 AM
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Joined: Feb 2005
Posts: 4,333
Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,333
Prospect, PA
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Quote:
I'll take the block to them, with the pistons/rods in, and have them check it. Thx for gasket suggestion, but I'd prefer to get the deck height right and go from there.
This is no big deal. Just have them fix it. How they respond is what matters.
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Re: 440 Piston Deck Height?
[Re: 383man]
#1020227
06/26/11 10:30 AM
06/26/11 10:30 AM
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Joined: May 2003
Posts: 6,616
Downtown Roebuck Ont
Twostick
Still wishing...
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Still wishing...
Joined: May 2003
Posts: 6,616
Downtown Roebuck Ont
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Quote:
I take it the rods are new and not rebushed ? I only ask because I have seen rods rebushed cause the piston deck reading to vary a tad. I had my new 493 figured to zero deck so I could use the .039 head gasket but when I assembled it all the piston decks came in from .007 and .008 range down in the cyl. I figured the same as they were conservitive as we can always cut more. I went with the .039 gasket and it dropped my comp from 10.8 to 10.6 and I left the quench at .046 to .047. It is working great as it has been running for 3 weeks with no ping at all. And I rechecked the timing today which was right on 36 total all in by 1800 rpm. Let us know what the shop says when they measure it and give you their readings. Good luck , Ron
IMHO Ron, you too need a new machinist. Being conservative has nothing to do with it as far as you winding up with -.007 -.008.
IIRC the procedure is deck, square and zero which are 3 different operations and require the use of a jig so the machine will cut square to the crank center line and as a reference to accurately measure the deck heights relative to the crank on the left and right side. Pistons are then installed in 4 corners and deck is measured again (SHOULD be the same +/- on 4 corners). If at this point they are .007/.008 in the hole the only nod to the conservative would be to cut .007" so your deck would be .000/-.001".
If you told the shop to/paid to have the decks zeroed (it does cost extra because of the extra labor involved and should show as such) I think you only got the first of the 3 operations and the shop either figured close enough or you wouldn't notice.
Again JMHO but if I paid for zero, zero means zero.
Kevin
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Re: 440 Piston Deck Height?
[Re: Twostick]
#1020228
06/26/11 10:59 AM
06/26/11 10:59 AM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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What they said, have a friendly sitdown w the guy/cover all bases & go from there. Holler how it turns out
live every 24 hour block of time like it's your last day on earth
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Re: 440 Piston Deck Height?
[Re: Twostick]
#1020229
06/26/11 11:52 AM
06/26/11 11:52 AM
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Joined: Feb 2005
Posts: 4,333
Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,333
Prospect, PA
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Quote:
Quote:
I take it the rods are new and not rebushed ? I only ask because I have seen rods rebushed cause the piston deck reading to vary a tad. I had my new 493 figured to zero deck so I could use the .039 head gasket but when I assembled it all the piston decks came in from .007 and .008 range down in the cyl. I figured the same as they were conservitive as we can always cut more. I went with the .039 gasket and it dropped my comp from 10.8 to 10.6 and I left the quench at .046 to .047. It is working great as it has been running for 3 weeks with no ping at all. And I rechecked the timing today which was right on 36 total all in by 1800 rpm. Let us know what the shop says when they measure it and give you their readings. Good luck , Ron
IMHO Ron, you too need a new machinist. Being conservative has nothing to do with it as far as you winding up with -.007 -.008.
IIRC the procedure is deck, square and zero which are 3 different operations and require the use of a jig so the machine will cut square to the crank center line and as a reference to accurately measure the deck heights relative to the crank on the left and right side. Pistons are then installed in 4 corners and deck is measured again (SHOULD be the same +/- on 4 corners). If at this point they are .007/.008 in the hole the only nod to the conservative would be to cut .007" so your deck would be .000/-.001".
If you told the shop to/paid to have the decks zeroed (it does cost extra because of the extra labor involved and should show as such) I think you only got the first of the 3 operations and the shop either figured close enough or you wouldn't notice.
Again JMHO but if I paid for zero, zero means zero.
Kevin
No disputing what you say here, it is all true. But I believe the lack of clear communication between customer and service provider regarding your very last sentence is exactly where the breakdown is. My experience is that the local reputable shops (i.e. not world-class) will do exactly what you describe above to achieve a nearly zero deck, if the customer is clear in the expectations, and is willing to pay for it. Usually (especially Mopar guys) are not willing to pay, or are not clear on what is an acceptable tolerance for the block machining portion of their desired "zero deck". When the machinist says that "we can get you close" without the additional expense, this is what the custom wants, and will get (whatever “close” is).
Every decent machine shop knows that most Mopar guys are cheap, and unfortunately, when a one comes through the door that is different, it might not be obvious to the service provider. It is not any different than anything else; you generally get what you pay for. Local reputable machine shops are not out trying to screw their customers.
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Re: 440 Piston Deck Height?
[Re: 70runner]
#1020232
06/27/11 12:02 PM
06/27/11 12:02 PM
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Joined: Jan 2003
Posts: 75,274
A gulag near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,274
A gulag near you.
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Quote:
Ron, yes the rods are brand new SCAT H beams. I haven't talked to SCAT yet, but I noticed their spec for rod length is 6.760". I've seen the 440 stock rod length variously listed at 6.766 or 6.768. If the machine shop surfaced the block based on stock rod length to .005 piston deck height and, if the SCATs are truly 6.760, then that may account for the measured deck heights. Anyway, I plan to address this with the shop next week.
Quote:
Most aftermarket rods have a 6.760" length. Why, I cannot say. But check the catalogs, you'll find 6.760 over and over.
R.
Yep there is your difference , the only aftermarket rod maker that got it close was Manley at 6.765 , all the chinese sourced H rods are at 6.760 , factory is 6.768 from everything I have read. What's more confusing is the GOOD aftermarket pistons makers spec their CH's with a 7.768 rod when there isn't one available  . I wouldn't be surprised if the other difference from front to back side to side is between the crank stroke and the rod lengths being a little different also.
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Re: 440 Piston Deck Height?
[Re: Twostick]
#1020233
06/27/11 07:05 PM
06/27/11 07:05 PM
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Joined: Jan 2003
Posts: 27,421
Balt. Md
383man
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
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Quote:
Quote:
I take it the rods are new and not rebushed ? I only ask because I have seen rods rebushed cause the piston deck reading to vary a tad. I had my new 493 figured to zero deck so I could use the .039 head gasket but when I assembled it all the piston decks came in from .007 and .008 range down in the cyl. I figured the same as they were conservitive as we can always cut more. I went with the .039 gasket and it dropped my comp from 10.8 to 10.6 and I left the quench at .046 to .047. It is working great as it has been running for 3 weeks with no ping at all. And I rechecked the timing today which was right on 36 total all in by 1800 rpm. Let us know what the shop says when they measure it and give you their readings. Good luck , Ron
IMHO Ron, you too need a new machinist. Being conservative has nothing to do with it as far as you winding up with -.007 -.008.
IIRC the procedure is deck, square and zero which are 3 different operations and require the use of a jig so the machine will cut square to the crank center line and as a reference to accurately measure the deck heights relative to the crank on the left and right side. Pistons are then installed in 4 corners and deck is measured again (SHOULD be the same +/- on 4 corners). If at this point they are .007/.008 in the hole the only nod to the conservative would be to cut .007" so your deck would be .000/-.001".
If you told the shop to/paid to have the decks zeroed (it does cost extra because of the extra labor involved and should show as such) I think you only got the first of the 3 operations and the shop either figured close enough or you wouldn't notice.
Again JMHO but if I paid for zero, zero means zero.
Kevin
Its not the machine shops fault as I calculated it and I was off but I had them cut it on the high side as I did not want a positive deck. So I told them to cut .010 instead of .015 I was figuring. It was my choice to go with the .046 quench instead of cutting more off. It did not effect my comp much at all and so far it is working good as I ran a tank of 92 pump last week and no ping at all. Ron
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Re: 440 Piston Deck Height?
[Re: JohnRR]
#1020234
06/27/11 08:31 PM
06/27/11 08:31 PM
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Joined: Jan 2003
Posts: 1,178
People's Republic of Kali
70runner
OP
super stock
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OP
super stock
Joined: Jan 2003
Posts: 1,178
People's Republic of Kali
|
Quote:
Quote:
Most aftermarket rods have a 6.760" length. Why, I cannot say. But check the catalogs, you'll find 6.760 over and over.
R.
Yep there is your difference , the only aftermarket rod maker that got it close was Manley at 6.765 , all the chinese sourced H rods are at 6.760 , factory is 6.768 from everything I have read. What's more confusing is the GOOD aftermarket pistons makers spec their CH's with a 7.768 rod when there isn't one available . I wouldn't be surprised if the other difference from front to back side to side is between the crank stroke and the rod lengths being a little different also.
John, you hit it on the nose. The .006-.008 increased deck height is due to machining the block per original specs - even tho I seem to remember telling them to account for the slightly smaller rod length of the SCATs 
He said same thing as you..variation from front to back likely due to variations in stock crank, rods, etc. He said the "block is square" (they do a LOT of mopars) but they will recheck and remachine to .005. I suppose I'm gonna need to machine the intake manifold to fit the deck 
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Re: 440 Piston Deck Height?
[Re: 70runner]
#1020235
06/27/11 10:21 PM
06/27/11 10:21 PM
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Joined: Feb 2005
Posts: 4,333
Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,333
Prospect, PA
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Quote:
Quote:
Quote:
Most aftermarket rods have a 6.760" length. Why, I cannot say. But check the catalogs, you'll find 6.760 over and over.
R.
Yep there is your difference , the only aftermarket rod maker that got it close was Manley at 6.765 , all the chinese sourced H rods are at 6.760 , factory is 6.768 from everything I have read. What's more confusing is the GOOD aftermarket pistons makers spec their CH's with a 7.768 rod when there isn't one available . I wouldn't be surprised if the other difference from front to back side to side is between the crank stroke and the rod lengths being a little different also.
John, you hit it on the nose. The .006-.008 increased deck height is due to machining the block per original specs - even tho I seem to remember telling them to account for the slightly smaller rod length of the SCATs
He said same thing as you..variation from front to back likely due to variations in stock crank, rods, etc. He said the "block is square" (they do a LOT of mopars) but they will recheck and remachine to .005. I suppose I'm gonna need to machine the intake manifold to fit the deck
You can sometimes move rod/pistons assy around to figure out where the variances are: piston/rod assy, block machining, or crank. I would cut the intake side of the head if you think you'll need to do some cutting.
Last edited by BSB67; 06/28/11 12:00 AM.
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Re: 440 Piston Deck Height?
[Re: BSB67]
#1020236
06/28/11 09:24 AM
06/28/11 09:24 AM
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Joined: Jan 2003
Posts: 75,274
A gulag near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,274
A gulag near you.
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Quote:
Quote:
Quote:
Quote:
Most aftermarket rods have a 6.760" length. Why, I cannot say. But check the catalogs, you'll find 6.760 over and over.
R.
Yep there is your difference , the only aftermarket rod maker that got it close was Manley at 6.765 , all the chinese sourced H rods are at 6.760 , factory is 6.768 from everything I have read. What's more confusing is the GOOD aftermarket pistons makers spec their CH's with a 7.768 rod when there isn't one available . I wouldn't be surprised if the other difference from front to back side to side is between the crank stroke and the rod lengths being a little different also.
John, you hit it on the nose. The .006-.008 increased deck height is due to machining the block per original specs - even tho I seem to remember telling them to account for the slightly smaller rod length of the SCATs
He said same thing as you..variation from front to back likely due to variations in stock crank, rods, etc. He said the "block is square" (they do a LOT of mopars) but they will recheck and remachine to .005. I suppose I'm gonna need to machine the intake manifold to fit the deck
You can sometimes move rod/pistons assy around to figure out where the variances are: piston/rod assy, block machining, or crank. I would cut the intake side of the head if you think you'll need to do some cutting.
Best way to eliminate one set of variables, rod length and piston CH is to take one rod and piston combo and move it from corner to corner, that will tell you if the deck is off and/or the stroke is different from front to back, could put that same piston/rod combo on all rod journals to check stroke variance on the crank.
Cutting the deck is like cutting the head , you need to account for that somewhere , be it the head or the intake something needs to be cut. since this will be a small amount I would take it off the intake , easiest thing to clean up if the heads are already assembled and ready to go , you can make up for that little difference if it goes on another engine with the thin fiber intake gaskets.
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Re: 440 Piston Deck Height?
[Re: JohnRR]
#1020237
06/28/11 12:50 PM
06/28/11 12:50 PM
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Joined: Jan 2003
Posts: 27,421
Balt. Md
383man
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
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Quote:
Quote:
Quote:
Quote:
Quote:
Most aftermarket rods have a 6.760" length. Why, I cannot say. But check the catalogs, you'll find 6.760 over and over.
R.
Yep there is your difference , the only aftermarket rod maker that got it close was Manley at 6.765 , all the chinese sourced H rods are at 6.760 , factory is 6.768 from everything I have read. What's more confusing is the GOOD aftermarket pistons makers spec their CH's with a 7.768 rod when there isn't one available . I wouldn't be surprised if the other difference from front to back side to side is between the crank stroke and the rod lengths being a little different also.
John, you hit it on the nose. The .006-.008 increased deck height is due to machining the block per original specs - even tho I seem to remember telling them to account for the slightly smaller rod length of the SCATs
He said same thing as you..variation from front to back likely due to variations in stock crank, rods, etc. He said the "block is square" (they do a LOT of mopars) but they will recheck and remachine to .005. I suppose I'm gonna need to machine the intake manifold to fit the deck
You can sometimes move rod/pistons assy around to figure out where the variances are: piston/rod assy, block machining, or crank. I would cut the intake side of the head if you think you'll need to do some cutting.
Best way to eliminate one set of variables, rod length and piston CH is to take one rod and piston combo and move it from corner to corner, that will tell you if the deck is off and/or the stroke is different from front to back, could put that same piston/rod combo on all rod journals to check stroke variance on the crank.
Cutting the deck is like cutting the head , you need to account for that somewhere , be it the head or the intake something needs to be cut. since this will be a small amount I would take it off the intake , easiest thing to clean up if the heads are already assembled and ready to go , you can make up for that little difference if it goes on another engine with the thin fiber intake gaskets.
Because of the few parts that can make the deck off a few thousands I always am conservitive and then I install a piston and rod without the rings in all 4 corners and take my readings. That way if I need to cut more I dont worry about damaging rings when I pull it back apart if I cut the deck more. But I decided to go with what I had on this last eng since it was still close enough for good quench and the decks were even. Ron
Last edited by 383man; 06/28/11 12:52 PM.
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