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69 390 using 401 pistons? |
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iapexl8r
AMC Addicted Joined: Apr/13/2008 Location: north idaho Status: Offline Points: 639 |
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Posted: Apr/26/2008 at 11:45pm |
I am ready to send my block out to get hot tanked and bore/honed. looking for pistons, read this on keith blacks website "HYPER) High compression AMC piston. See Hot Rod Magazine, March 2004 issue, for 541 Hp engine build.
AMC 390 use AMC 401 pistons with 1968-69/9.175 deck block. Use 1970 and later AMC rods or aftermarket small block Chevy 5.85 rod. Chevy rod requires grinding crank journal to small block specifications. Stock rod use requires small end bushing to .9272. Compression ratios can be obtained by multiplying 401 compression ratios x's .975 to find approximate 390 compression ratios." does any one know what they mean small end bushing to .9272
Also does this effect cubic inches??
Chris
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5905 |
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Rods - '68-9 - 390 - 5.790" CL to CL - 1.0007 Press Pin Dia. - 1.553" Compression Height Piston
Rods - '70-0 - 390 - 5.858" CL to CL - 1.0007 Press Pin Dia. - 1.518" Compression Height Piston
Rods - '71-9 - 401 - 5.858" CL to CL - 1.0007 Press Pin Dia. - 1.508" Compression Height Piston
Crank stroke / throw, Con Rod, Piston Comp Ht, & Block Deck Height all work together
to determine Piston to Deck Clearance and effect CR.
Don't know the Compression Height or piston head dish volume of the KB pistons.
It must be such that the longer 401 Rods are needed to get good Deck Cearance and CR.
Understanding is the KB pistons are made for a readily available Chevy Size Piston Pin.
Believe the AMC stock size 1.0007" Piston Pins are harder to come by.
So to fit the KB pistons to the AMC Rods requires Bushing the small end of the Rods
to reduce the hole diameter to fit the Chevy Piston Pins
and believe changes them to Floating Pins instead of Pressed Pins like stock AMC.
which requires the use of retaining rings in the pistons to hold in the piston pin.
Stock AMC Piston Pins are Press Fit into the rods and float in the pistons.
Full Floating Piston Pins are "better" than Pressed in Piston Pins, free-er movement, less friction.
A source for CAST AMC 390 pistons is www.egge.com
They are listed under RAMBLER in the egge online catalog, not AMC.
Need to select a bore size on the egge catalog page in order for it to list a price.
Their pistons, like pretty much all aftermarket replacement pistons,
have an approx. .020" shorter compression height to allow for block and head milling
during the rebuild and yet maintain the stock Compression Ratio.
Which is convienent for reducing CR if building for "cheap" gas
if the Block deck height is left stock and the heads only skimmed for clean-up.
The stock 390 had 10.2:1 CR which may be a bit much for today's "cheap" pump gas,
or what's left of it that is, in the world today.
Saw your YouTube Video, looks like the "madness" has begun.
Did you see my '69 BSO AMX YouTube video(s) ?
Happy Hunting.
Edited by PHAT69AMX - Apr/27/2008 at 11:17am |
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bigbad69
Supporter of TheAMCForum Joined: Jul/02/2007 Location: Ottawa, Ont. Status: Offline Points: 6614 |
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Also does this effect cubic inches??
Displacement is determined by borexstroke. Changes to compression height of the piston or rod length do not change the stroke. Only altering the crank throw will change the stroke. Changes to bore diameter because of over-boring will change the displacement. a .030 over 390 is 395 IIRC. I looked at 401 pistons when I was building my 390. They have a lower compression height than the stock 69 piston and will lower your CR, especially if you use the dished 401 piston. I forget the actual numbers but, without a lot of machining, you're better off with proper 390 pistons. The cast Badgers are available as PHAT said, otherwise you're into custom forged or a lucky find on Ebay. |
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69 Javelin SST BBO 390 T10
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iapexl8r
AMC Addicted Joined: Apr/13/2008 Location: north idaho Status: Offline Points: 639 |
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please post link to your youtube. thanks for the tip on stock pistons will definatly check it out. I have decided to go ahead and pull the triger on the edelbrock heads the crank is going to need to get turned so I may just use the cough cough chevy 5.85 rods and the 401 pistons with the 17cc pistons. descissions decessions must do more research |
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WiSeNhEiMeR
AMC Apprentice Joined: Oct/29/2007 Location: Indiana - 47374 Status: Offline Points: 145 |
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The "small end" of your Connecting Rod ... needs to fit the piston's Wrist Pin ... in this case Keith Black is saying you will need a bronze bushing sized to just under an inch ie: .9272 pressed into the small end of your connecting rod to use their piston ...
WiSeNhEiMeR
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Don't Mind ME,
I'm Just a WiSeNhEiMeR from: Richmond INdiana N.A.M.D.R.A. #398 |
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5905 |
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Nothing spectacular. Had borrowed a friends camera. First experience with digital video.
It was a couple few year old camera, to download in .avi had to record to camera memory,
so video length was limited to 30 seconds. Uploaded (10) 30 sec videos.
Recently had a friend combine them all into 1 video, 5:25 long.
It was last autum and was unable to find a "camera man", so no burnout video, yet.
No premo resto car, but pretty solid.
Here's a link to the composite 5:25 video. Or can just search "BSO AMX" on YouTube.
I'm a smoker and the camera is right next to my face, so don't mind my breathing, sorry y'all.
Oh, and had a bit of a rough time opening my hood with only the left hand, not to smooth.
First videos I have ever taken and tried to deal with with an old PC and no DVD software.
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SS/AMX-MM
AMC Nut Joined: Aug/15/2007 Location: Nebraska Status: Offline Points: 117 |
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PHAT69AMX
One question....
Did you ever get the main job done? Ya know what i'm talking about or were you just breathing hard
Sr.
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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>>I looked at 401 pistons when I was building my 390. They have a lower compression height than the stock 69 piston and will lower your CR, especially if you use the dished 401 piston. I forget the actual numbers but, without a lot of machining, you're better off with proper 390 pistons.<<
To expand on that, if you drop the head of the piston in the hole, you lower quench, and you can cause issues. That's not a good way to lower compression. You want generally no more than .060 clearance.
I used KB pistons in my 70 and they have full-floating pins now, the shop bushed the rods.
But I also have proper height - 0 deck height and good quench design.
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iapexl8r
AMC Addicted Joined: Apr/13/2008 Location: north idaho Status: Offline Points: 639 |
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I think I will be breathing heavy just like that (probably worse) when my amx looks that good. nice vid. the car sounds really good(as well as looks really good), just the way I like them nice and snappy on the rev.
What cam are you running?
what heads?
what headers?
Will be waiting for burn out vid! If you were in so cal I would come shoot it for you. I have mini digital vid cam.
Thanks in advance Chris
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5905 |
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Fresh motor was dropped in last September,
343 block +.030 with 304/360 crank offset .010, 367 C.I., Cast Zollner dished top 360 pistons.
Heads are '70 ported, 2.02/1.68 StnStl 11/32 valves, milled ~.055, unshrouded, 48cc.
HS RR's 1.6 x 7/16, Crane Retainers & Dbl Springs, Torker, Holey 850 DP #0-4781.
Good ol' low cost Cyclone 1-5/8 x 3 collector headers, 2-1/2 pipes, FlowMaster 40's.
The cam, due to limited piston to valve clearance with pistons .007 above deck,
was limited to find one with about 64 degrees overlap.
It now has an Elgin / Clevite #E-1041-P cam and lifters, .488/.488 - 284/284 - 218/218.
It'is not what it used to be before with a stock cam reground by Chet Herbert in the 80's.
That cam was .513/.528 & 280/295 adv., have no cam card for that one, but it was much better.
Found a Lunati with specs like the Chet Herbert, but it has more overlap and not enough P to V clearance.
Tried advancing and retarding but couldn't get sufficient P to V with the Lunati.
Now has better idle vacuum and low end, but the old Chet Herbert wasn't that bad
and the Elgin cam as expected runs outta steam to soon, about 5000 rpm
and the 727 has a 3000 stall B&M 10" converter and gears are 3.73's with Moser Axles.
Menance, disappointed the ol' girl, just couldn't put the icing on the cake
Thanks for the comments
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