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Help with possible 390 purchace |
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jl2556 
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Joined: Feb/16/2015 Location: tn Status: Offline Points: 98 |
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 Topic: Help with possible 390 purchacePosted: Oct/19/2017 at 7:00am |
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I found a 390 and the guy says it's 69 but has the 291 heads on it. Also, was set up for auto trans. Has balancer but no flywheel. It's got a big carb, torker, roller rockers & a 7 qt oil pan. He says it has the oil feed/lubrication fix done. Motor would be going in my 69 290 4 speed .
1. Did the 291 heads fit with no mods or are there modifications to make them fit? 2. Will the 7 qt oil pan have any clearance issues? 3. How hard will it be finding a stk 4 speed flywheel and harmonic balancer and is it expensive? 4. What else do I need to know/watch out for?  Here are some pics, the guy the seller got this from made a weird valve cover conversion to clear the roller rockers used cvevy valve covers I believe, though I did a little research on here and folks said the stk valve covers fit with no issues    |
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ramblinrev
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Joined: Dec/28/2008 Location: Wisconsin Status: Offline Points: 11543 |
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Posted: Oct/19/2017 at 7:47am |
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The 291 heads are a plus. They fit with dowels to the '69 block and allow use of the better flowing dogleg heads and exhaust. A flywheel shouldn't be too hard to find, $100-200 used, and aftermarket possibilities, BUT I think you'd need to disassemble and balance the rotating assembly with that flywheel and damper! (I'm not an engine builder, so the guys that are good at that can straighten me out if I'm wrong here.)
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74 Hornet Hatchback X twins (since 1977)
62 American Convertible (still worth the $50 I spent in 1973!) AMCRC #513, AMO #384 70 AMX 360 4-speed (since 1981) |
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mmaher94087
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Joined: Apr/01/2008 Location: Arizona Status: Offline Points: 1690 |
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Posted: Oct/19/2017 at 10:59am |
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Good luck stuffing that motor with a 7qt oil pan in an AMX or Javelin body.
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Mike
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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/19/2017 at 11:25am |
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It looks like someone got creative and made an adapter to use Chevy Valve Covers to gain rocker arm clearance. Without the flywheel, you have to commit to getting the rotating assy re-balanced with a 68-71 flywheel from 390 or 401, if you use a 290/343 flywheel as your basis, they will drill the crap out of the outer rim of the casting to make up for the large counter weight on the 390 engines. Are you sure it is not a 70 390, that would have 6291 heads, only way to tell is the block casting number...or even easier, what size are the head bolts....7/16 = 68/69, 1/2" = 70. Looks like an old build, so you are rolling dice, you have no idea of how far oversize it might be....another Forum member just got burned on a used 390 with .060 oversize bores. You know with the speed equipment, it was not a light footed driver....it is all about how much risk you are willing to take. Not sure why you say you need harmonic balancer??? There is one on the engine....does the engine pull through with a breaker bar on the front dampener bolt.....at least that would show if it is not locked up.
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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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Airdrie AMX
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Joined: Aug/08/2010 Location: Alberta, Canada Status: Offline Points: 329 |
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Posted: Oct/19/2017 at 12:05pm |
Looks like a Milodon 7qt pan, I have the same one. As far as fitting, it will just fine, hangs down below the crossmember an inch or so.
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72 amx javelin 401 4spd
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jl2556
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Joined: Feb/16/2015 Location: tn Status: Offline Points: 98 |
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Posted: Oct/19/2017 at 4:15pm |
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Thanks guys, I think I'm gonna walk away on this one.
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scott
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Joined: Jul/10/2007 Location: Wildwood Pa. Status: Offline Points: 3502 |
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Posted: Oct/19/2017 at 5:00pm |
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In one picture you can see a partial block casting number, it looks like 3190806, the 68-69 number.
One big question is how much does the seller want for it? Next big question is will the seller pull a head so you can see what the bore is? Will the seller drop the pan & pull a rod & main cap so you can see what the bearing size is? If you are looking for something to drop right in in place of your 290 with no work, this engine is not it. But, if the price is right, & it is not bored too far, the crank not cut too far, it may be a decent engine to build. If you don't like the 7 quart pan, take the pan off your 290 & install that. |
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jl2556
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Posted: Oct/19/2017 at 6:05pm |
What all would i need beside a complete motor if i wanted to do a 390 or 401? Maybe a stronger clutch. I assume my motor mounts and pwr steering pump will bolt up and work without any issues. |
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ramblinrev
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Posted: Oct/19/2017 at 9:40pm |
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You could do real well with a 360; which is much easier to find; which is less likely to have been over-bored than a 390/401; which would be a nice performance upgrade from your 290.
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74 Hornet Hatchback X twins (since 1977)
62 American Convertible (still worth the $50 I spent in 1973!) AMCRC #513, AMO #384 70 AMX 360 4-speed (since 1981) |
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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/20/2017 at 6:12am |
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Wise move Grasshopper to walk, unless it is cheap and have room for it. Any 68-70 390 and 71 401 will bolt in with no changes to any accessories, as long as you get the front dampener that was on it while running (aka: balanced factory or after wise). One small exception is 70 390 and 71 401, you need the log style 70 only exhaust manifolds...to make these "direct bolt in and not even have to change the exhaust.
Once you get past 1972 up, every few years in jumps can create some small challenges, if you are staying 4 speed, still okay.....again you must get the flywheel if the engine is not a virgin. You can buy a 72 up 401 flywheel in cast new, I have used several with virgin motors and no issues...they are made in China. The key can be to look at the front dampener to front pulley bolts, 3 bolt will allow all accessories to interchange, 4 bolt has a different spacing, there for the front accessories will change (water pump, water pump pulley, power steering (72 went to Saginaw Tear Drop Pump), A/C pump bracket is different. The difference is only about 1/4" or so, but the belts will not align well. There are many "work" arounds for this. If you don't care about looking exactly stock, you can pull all the front off a 73 up AMC of any model and swap everything, I did that on my sons daily driver 70 Javelin with 75 360 in it. I mainly did it since he drives to college everyday, I wanted the big front bearing on the water pump and the very reliable Saginaw Power Steering Pump. As Paul (ramblinrev)stated above a nice 360 is a great upgrade with minimal cost. Same reason I put a 360 in son's car, vs 390 or 401.
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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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mmaher94087 wrote: