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1972 401 |
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amxdreamer 
AMC Addicted 
Joined: Jul/30/2008 Location: Vancouver, BC Status: Offline Points: 8509 |
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 Posted: Oct/25/2014 at 11:52am |
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I agree with others that if its not broke leave it! I would also figure out what rear you have before changing anything on the engine. My AMX came with the factory 2.87:1 rear ratio with the auto/AC etc. I have since switched to a 3.31:1 rear ratio and the car is a totally different animal!
I built my mild 360 (original to the car) to build power low in the RPM range to help get it out of the hole a little quicker. The car managed a 14.3 at 96mph in the 1/4 with the 2.87 rear. Looking to get it a little faster with the new gears and a better tune. Sooooo long story made short. Check the rear ratio and upgrade if highway gears, maybe change out the intake/carb and some decent exhaust. The petronix is another easy upgrade. In my opinion roller rockers aren't worth the expense for a stock engine that is staying at lower rpm's. |
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Tony
Vancouver, BC 1970 AMX 1972 Badassador AMO#10333 |
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BBKB
AMC Fan 
Joined: Jul/02/2013 Location: Illinois Status: Offline Points: 12 |
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Posted: Oct/25/2014 at 9:39pm |
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Man, lots of great info. My thought process on the porting was that I really wanted to keep everything as stock appearing as possible. But if the heads flow well enough, I'll leave them. The car was a daily driver of my Dad's for quite a few years. Like I said, he bought it new. While it's only got 57k on it, it leaks bad and can use a very good clean up and detail. That's the reason I had planned to tear it down and upgrade the cam, rockers and rebuild the heads. I'm afraid that the valve seals are leaking and they should be fitted with hardened valve seats. That was my thought process for the heads and valve job. The car runs just fine, a little rich, but runs and drives. I really appreciate the advice on everything. I think I'll stay away from the HEI. I just don't like the points so I want to switch to an electronic ignition. Please don't hesitate to reply, I certainly appreciate the advice and experience!
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Sonic Silver
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Joined: Nov/23/2011 Location: East Tennessee Status: Offline Points: 7949 |
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Posted: Oct/25/2014 at 9:56pm |
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401MATCOUPE
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Joined: May/20/2010 Location: Salisbury, MD Status: Offline Points: 5367 |
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Posted: Oct/26/2014 at 6:24am |
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Here is my two cents...on "lower" mileage 401, all original and just external leaker. If the engine is still running: 1. Do a compression check, if numbers look good and even...leave the engine long block alone.
2. Pull the engine, thoroughly clean the outside before you open it up. 3. No matter what pull the intake, front cover, valve covers and pan. 4. Examine anything (foreign oblects) in pan, look for parts of the cam bearings, etc. General condition of the internals...sludge, etc. The bits youfind will drive any other replacements.... 5. No matter what change the timing chain and gears, factory would have been plastic cam gear...it CAN NOT STAY. 6. Thoroughly clean the oil pan and pick-up, make sure you get up under baffle in pan, it is very sharp, so watch you hands. Even if you take to shop for hot tank this usually is NOT clean enough. 7. I usually pull one rod and one main to make sure nothing bad is going on there.....90% of the time theye are fine. 8. Either put air pressure in cylinders of rope in cylinder and rotate to TDC on each cylinder, use top end valve spring compressor and remove keeper, retainers and springs...replace all the valve stem umbrellas. Try and use the factory hard plastic ones, I personnal prefer those over rubber. Put in New Valve Springs, I like the Edelbrock ones for 1970 up engines...about $60. 9. Since you have rockers and such off, I clean all push rods, new lifters....(I am sure others will comment not to change lifters, but a very small piece of dirt can cause issues here...I replace). Clean everything before going back to gether and use assembly lube on a contact parts. 10. Remove the Hex Elbow on outside of block, it will be full of sludge....re-install after clean. 11. Pull all the freeze plugs,, make sure the block is clean inside on the water passages...stick your finger in there...then a 90 degree pick, use compressed air to get all the bits out, I do this with engine on the stand and freeze plug hole horizontal, gravity helps let the debris fall out. Put all new freeze plugs back in. 12. Clean the oil pump internals, resurface anything damaged, new seals, gaskets, put timing cover on before oil pan to make sure you get best oil pan seal... 13. I always install new water pump, new fuel pump, and typical tune up parts (plugs, wires, cap, rotor, PCV Valve, water temp transmitter, oil pressure switch, etc after paint) 14. Put all back together and paint. I am sure I forget some detail...but this is very close, I have had alot of sucess with this method in the past, the last 69 390 I did this to, the day after it went in, my wife and I drove the AMX to Florida and back with not one issue. Hope this helps...alos I totally agree, no porting needed and leave the 401 cam alone.
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Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar) 68X,GoPac,390,4sp,52A 69X,GoPac,390,4sp,64A 70X,GoPac,390,4sp,87A,8 70X,GoPac,390,4sp,BBO,8 70 Jav SST,390,AT,BSO 74MatX,401,AT,Prototype 74MatX,401,AT |
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nda racer
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Joined: Nov/28/2009 Location: Ohio Status: Offline Points: 2591 |
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Posted: Oct/26/2014 at 1:51pm |
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As for the timing set, inspect the new one. Some the oil passages are machined wrong and you'll eat s^!t up.
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401MATCOUPE
AMC Addicted
Joined: May/20/2010 Location: Salisbury, MD Status: Offline Points: 5367 |
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Posted: Oct/26/2014 at 3:17pm |
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One more thing I thought of in your OP....For a car that is not driven hard and often, save your money on the hard seats if you do have to pull the heads, unkless there is major seat issues. I have 100K on a set of 3220502 heads with no issue after simple valve and seat touch up...the original AMC built went 158K until it had a oil pressure issue, which was a bad 4 and 5 cam bearing..lost the babbit.
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Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar) 68X,GoPac,390,4sp,52A 69X,GoPac,390,4sp,64A 70X,GoPac,390,4sp,87A,8 70X,GoPac,390,4sp,BBO,8 70 Jav SST,390,AT,BSO 74MatX,401,AT,Prototype 74MatX,401,AT |
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dbomb
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Joined: Jul/22/2012 Location: new jersey Status: Offline Points: 705 |
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Posted: Oct/27/2014 at 5:15pm |
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Block work and Boring cyls and replacing pistons is where things get moderately expensive . If it were mine id get an engine module rering kit from somewhere and definitely put new bearings in it and put new cam bearings in it as they like to delaminate . Mike the bores and number the pistons and take pictures if its your first rodeo. Pick out a nice cam and have at it. When ya think about it a 150 dollar valve spring kit is cheap while its apart much more expensive when she drops a valve down the road . Ya gotta think its 40 years old now how long do ya want it to run for in future.And im sure you have better things to do than pull the mill again down the road. If yuoure gonna ebay or craigslist it then regasket and spray bomb it. Oh even if youre just resealing it Id replace headgaskets as well as they have a way of rotting out.
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rebuiling 73 amx need parts
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73jav
AMC Apprentice 
Joined: Sep/29/2009 Location: Owosso Michigan Status: Offline Points: 108 |
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Posted: Oct/28/2014 at 5:25am |
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If you're going to change the dist and cam make sure you keep the original matched gears to put back in. and don't change the timing cover to one of the new junk ones.
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captscot
AMC Apprentice
Joined: Feb/05/2013 Location: N Brunswick, NJ Status: Offline Points: 241 |
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Posted: Oct/31/2014 at 4:54pm |
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With the very low mileage on your engine keep the stock 401 AMC cam, it is a medium competition cam. I just began restoring my 1972 AMX that I'd purchased new. It has a 401 and 727 auto trans. Rebuilding the engine I want everything to remain stock and original, therefore I wanted a new cam with the same stock specs. Recently checking all 401 cams available, most are reproductions that DO NOT have the same factory specs or others are listed as "stock" replacement for "AMC V8s 304, 360, 401." When compared, those specs are the camshafts AMC made of the 304 & 360. AMC wanted different performance for the 401 and so made a camshaft specifically for that engine. Today I just located and purchased a NOS AMC camshaft for the 1972 401 which has the AMC part number 812-1156. Specs are Lobe lift .286, Int Dur 296.32, Exh Dur 303.55. The 304 & 360 AMC cam number is 448-6476. Lobe lift .266, Int Dur 263.5. Exh 263.5.
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Sonic Silver
Supporter of TheAMCForum
Joined: Nov/23/2011 Location: East Tennessee Status: Offline Points: 7949 |
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Posted: Oct/31/2014 at 6:37pm |
The stock 304-360 cam has about 11-12 degrees less duration , and 5 degrees less overlap than the 401. Also, it has .032 less lift. The thing that helps the 401 cam make some top end power is the retarded intake timing. The intake valve closes much later than the 304-360 cam, and the Edelbrock Perf cam. and nearly the same as the Comp 268. It would be a good cam if you had some compression, and need to bleed off some cylinder pressure. Where it is slightly worse is low end power, which the 401 has plenty of anyway.
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BBKB wrote: