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Compression Height - AMC Pistons

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PHAT69AMX View Drop Down
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    Posted: Mar/03/2008 at 6:16am
for reference
 
AMC Piston Compression Heights per 1999 Badger Piston Catalog
 
..................... Badger .. ( Stock )
C.I. ... Part # ... C.H. ...... C.H. ....... CR ........ Year ....... Piston Head Shape

290 ... P834 ... 1.588 ... ( 1.601 ) ..... 9.00:1 ... 1966-69 ... .040 RECESSED HEAD

304 ... P890 ... 1.588 ... ( 1.601 ) ..... 8.40:1 ... 1970-79 ... .140 RECESSED HEAD

343 ... P886 ... 1.588 ... ( 1.601 ) ... 10.20:1 ... 1967-69 ... VALVE RELIEFS - NO DISH

360 ... P891 ... 1.588 ... ( 1.601 ) ..... 9.00:1 ... 1970-78 ... .190 RECESSED HEAD

390 ... P888 ... 1.548 ... ( 1.553 ) ... 10.20:1 ... 1968-69 ... VALVE RELIEFS - NO DISH

390 ... P892 ... 1.548 ... ( 1.551*) ... 10.00:1 ... 1970 ....... .135 RECESSED HEAD

401 ... P894 ... 1.495 ... ( 1.508 ) ..... 8.50:1 ... 1971-74 ... .300 RECESSED HEAD

( *Assume .012 deck clearance for '70 390 same as '70 304 and 360 where PAS shows .045 same as '68-9 )

Stock Compression Heights calculated from other engine specs as listed in Performance American Style.
 
9.175 Deck Height 1969 and earlier
9.208 Deck Height 1970 and up
 
5.875 Connecting Rods - all 290-304-343-360
5.790 Connecting Rods - 1968-69 390
5.858 Connecting Rods - 1970 390
5.858 Connecting Rods - 1971-up 401
 
.060 Deck Clearance - 1966-69 - 343-290
.045 Deck Clearance - 1968-69 - 390
.012 Deck Clearance - 1970-up - 390-360-304
.002 Deck Clearance - 1971-up - 401
 
Any additional information, corrections, or information sources welcomed.
Imortant information to have when calculating Compression Ratio
and Quench distance, or for ordering or buying new pistons of any type.
 
Cool
 
( edit - additional reference specs added below )
 
Stroke ... Throw
3.280 ..... 1.640 ... all - 343-290
3.440 ..... 1.720 ... all - 360-304
3.574 ..... 1.787 ... all - 390
3.680 ..... 1.840 ... all - 401
 
Bore
3.750 ..... all - 304-290
4.080 ..... all - 360-343
4.165 ..... all - 401-390
 
Head Gaskets
0.022 Stock Thickness - 1966-69 - 290
0.028 Stock Thickness - 1970-up - 304
0.048 Stock Thickness - all 401-390-360-343
0.0?? Stock Thickness - ??? year 360 low CR ( one year is odd-ball )
 
Bearings
2.7472 ..... Crank Main Journal - all 401-390-360-343-304-290
2.0944 ..... Crank Rod Journal -- all 360-343-304-290
2.2481 ..... Crank Rod Journal -- all 401-390
 
Wrist Pins
0.9309 ..... all - 360-343-304-290
1.0007 ..... all - 401-390
 
Pushrods
7.767 ..... 1966-69 - 390-343-290
7.800 ..... 1970-71 - 401-390-360-304
7.820 ..... 1972-up - 401-360-304
 
end of document


Edited by PHAT69AMX - Mar/03/2008 at 10:25am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6PakBee Quote  Post ReplyReply Direct Link To This Post Posted: Mar/03/2008 at 9:29am
Phat, you are the man.  Thanks for taking the time to type this all in.  Great info for a novice like me.  Thumbs%20Up

Edited by 6PakBee - Mar/03/2008 at 9:29am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Cj-360 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2008 at 10:52am

Hi Phat69AMX,

The figure you've provided are very interesting as AMC figures are RARE!

I know, cause I've been searching for them all over.

I have a 360 with .30 over, and I've ordere a pair of Edelbrock RPM Heads with 54 cc chamber but not installed yet.

I already have Badger P891 pistons, can you tell me what the new CR will be with the new heads? And what gaskets should I get? Shall I get the SCE Copper gaskets from Summit or just the normal ROL gasket will do?(Those copper gaskets are really expensive)Embarrassed

And one thing that I noticed is that CompCams suggest the use of +.150" longer push rods with their cams, which should be: 7.820+.150= 7.97
And Edelbrock suggest 8.095" push rods with their heads, which way should I go?ConfusedDead
I already have small block chevy push rods on the engine!!!
 
I highly appreciate your comments/assistance as I'm long far away from U.S. and making a mistake when ordering parts, costs me big $$$! loss.Cry

BTW, if you are interested to know my engine specs are:

- Harland Sharp Pedestal Mount Roller Rockers ( with stock head) and I've also purchased Crane Gold Racers Roller rockers for the Edelbrock head

- CompCams XE256H Cam kit (.477/.484") lift & 212/218 duration @.050"

- Edelbrock Performer Intake

- Holley 470 truck avenger Carb.

- DUI Distributor

- Badger p891 +0.30 pistons

- K&N filter + Flowmaster Dual Exhaust + Edelbrock Shorty Headers

My car is '77 Cj-7 with TH-400 tranny & TCI Saturday Night 1800 stall converter which is just too much for the cam, I'll have to change it to stock I think.

Take good care,

HoumanSmile

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Alliups Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2008 at 11:02am
Awesome!


Steve
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2008 at 12:38pm
Using:
4.110 Bore
3.440 Stroke
9.208 Deck Ht
5.872 Re-Con Con Rod - 0.003 shorter
1.588 Comp Ht
0.028 Deck Clearance
27.5cc Dish Volume
54cc Comb Cham
0.045 x 4.265 FelPro Head Gasket
 
Result:
8.62:1 Static CR
 
All values used are Nominal, have manufacturing variations,
and should be confirmed from actual parts for actual values.
 
Recommend determining correct Pushrod Length at time of assy
using a pair of solid lifters and adjustable length pushrods.
Many variables affect correct pushrod length, deck mill, cam base circle, etc.
 
Options to increase Static CR:
Mill Block Deck 0.028 for 9.180 Deck Ht to reduced Deck Clearance to 0.000
results in a calculated 9.13:1 Static CR using above nominal values.
Piston to valve clearance must be clayed to confirm 0.100 minimun.
Another option is to offset grid the crank in combination with deck milling
to achieve 0.000 deck clerance and also slightly increases displacement.
 
Using:
4.110 Bore
3.460 Stroke - crank offset ground .010
9.190 Deck Ht - deck milled .018
5.872 Re-Con Con Rod - 0.003 shorter
1.588 Comp Ht
0.000 Deck Clearance
27.5cc Dish Volume
54cc Comb Cham
0.045 x 4.265 FelPro Head Gasket
 
Result:
9.17:1 Static CR
 
What is the CompCams suggested Static CR for the XE256H camshaft ?
 
In all cases dynamically balance the rotating assembly.
 
Have always used the FelPro head gaskets.
Have heard good things about the other gaskets, but have not used the ROL or SCE gaskets.
Gasket thickness and hole diameter affects static CR.
 
Many parts are best sized and purchased as machine work is done and as engine is being assembled.
 
Assume the carb is a 670 cfm Truck Avenger rather than a 470 cfm.
Would think the 1800 stall converter would be ok.
Re-working the advance curve in any distributor can offer significant gains.
 
( corrected typo error of bore size - thanks for pointing it out )


Edited by PHAT69AMX - Oct/20/2008 at 8:57pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote whizkidder Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2008 at 2:09pm
4.08 plus .030 = 4.11 on my calculator....
Ron Frost
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BassBoat Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2008 at 5:45pm

the compression calculation is correct, its the bore diameter in the post that is the typo.

phat's the man....

:)

BB

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Cj-360 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/21/2008 at 4:33am
Thanks very much for all the advices.
Actually the carb is a 470 cfm truck avenger, not a 670.
 
But in the information Phat69AMX posted the P891 has a 9:1 cr.
I was also told earlier that Badger p891 is same as Keith Black 2225 piston and if you check Kb-slivolite webpage, they also say that this piston will produce 9:1 cr with original 58 cc heads. It doesn't mention in ths webpage the word " 58cc" but I have in writing from them that the 9:1 cr was procudece using the 58cc heads. I asked their tech. dpt. before I but the Badger pistons here in Iran.
 
So, how come now with  54 cc heads the c/r is being so low? Could it be that the piston dish volume is less than 27.5cc?
 
I think I'll get the Edelbrock gaskets as they are probabely matched with the heads.
Isn't there any kind of flat top/domes pistons for the 360 engine???
 
Do you guys have any idea of dropping a 401 crank in my engine? I heard special pistons are required, which I definitly cannot find here in Iran. Isn't possible to use the 401 crank with 360 pistons & connecting rods?
 
All you kind comments are highly appreciated.
 
Thanks,
Houman
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Oct/21/2008 at 6:32am
Understanding is the listed Badger catalog 9:1 CR figure assumes both the block and heads to be milled .020 reducing deck height to 9.188, combustion chamber volume from 58cc to about 55cc nominal.  Using a deck clearance of .005 assuming a stock 5.875 Con Rod rather than a .003 shorter re-conditioned 5.872 Con Rod, working backwards from 9:1 CR, it comes out to be about 27.0cc to 27.5cc piston dish volume.  Some assumptions must be made when making calculations without having actual parts in hand.  Catalog only lists depth of dish and does not list an actual dish volume.  All values are nominal and have dimensional tolerances that can affect static CR.  Catalog information is not always 100%.  Badger Catalog also says 9:1 CR for 1970-78 when the 1970 AMC 360 had smaller 50.60cc heads.  To know for sure one must measure in-hand parts and compensate.  Other than custom forged pistons, the only known source for smaller dished 360 pistons is www.egge.com who offers 343 4 barrel flat top w/reliefs 4cc ? and 2 barrel small dish 14cc ? cast pistons which are the same bore as a 360 and listed under Rambler on the Egge web page on-line catalog, but information provided by Egge says they have a shorter 1.570 compression height, and Egge would not quote a dish volume.  Would need to use .003 shortened re-conditioned 1968-69 390 5.787 Con Rods with the 401 crank, and 1.580 comp ht pistons for .001 deck clearance, all values being nominal, in a 9.208 deck height 360 block, as well as block modification for counterweight clearance afaik.   It's rather interesting that a 4.110 bore .030 over 360 block with a 3.68 stroke 401 crank yields 390 cubic inches.
I'd say that about does it for the "free sample".   Wink
 
 


Edited by PHAT69AMX - Oct/21/2008 at 6:35am
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Hey, Thanks
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