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1978 lincoln 460 broken rods

3K views 10 replies 5 participants last post by  markaria 
#1 ·
I am new to these forums and am hoping to learn a lot from some of the resident gurus on here! Ive been lurking for a little while reading up on these engines as i recently acquired a 1978 lincoln continental town car with 88k miles with the lovely smog era 460 from a close friends father in law.
He stated that the last time the car ran he let his friend drive it it and it backfired and was running very rough after it backfired. He tried to see if the timing was off but it didnt make a difference. He also told me the backfire blew the exhaust clamp off the muffler. So the car sat for a year or so before i got it... My initial thought was ignition issue/timing chain jumped/possible carb issue etc.
Anyways i got the car into my shop and decide to get her running...got her to run but it was running very rough/shaking definitely not running on all 8. So i decided to do a quick ignition tune up (cap/rotor/plugs) pull plugs and found one plug in cylinder 5 destroyed (!). I then decided to do a compression check and found some eye opening numbers:
cyl 1 and 5 (front cylinders on both banks) both had zero
the rest were all close to 150 with one other being a bit low at 120ish
(was a cold test)
So I figured maybe stuck valves from sitting? Pulled valve covers and all appeared ok...one valve in cyl 5 seemed a little sticky but i worked it loose with some oil...and i found a slightly bent pushrod on same valve...replaced pushrod and still came up with zero compression on those two cylinders. So I decided to pull the passenger side head to see what was going on. I have taken apart a lot of motorcycle/import motors...not a lot off old school stuff so was definitely looking forward to it lol...other than the weight of the manifold/heads (holy crap!!! glad I have a cherry picker).
Once the head was off at first glance nothing looked bad...valves looked ok...piston looked ok...but the piston in #1 sure looked like it was high up in the bore for one of these low compression engines that should have the pistons "in the hole a bit" below the deck...i lightly pushed on that piston and it pretty easily moved all the way down the bore...without any of the other pistons moving!:surprise: I can turn the crank and that piston isnt moving so obviously it has a broken rod on cylinder 1 and most likely 5 as well though i havent yet verified that. After I found this craziness upon further inspection I noticed the oil pan up front by where the crank throw for cyl 1 and 5 would be had some small dimples in it that were made from the inside out (obviously from part of rod that must have made some very slight contact). I am amazed that this engine even started as from my experience with newer engines most end up with holes in block as there is no real clearance if a rod breaks.
My question to all of you 460 gurus out there... what would cause a rod to break like that? Are the stock 460 rods pretty weak or was the engine overrevved? Though I cant imagine it...can a big enough backfire break a stock rod? My experience with hydrolocking is it usually bend rods and motor locks up...this one turns freely. Just a bit baffled on the cause.
Also I am actively searching for another 460... will a mid 80's 460 engine(pre efi) bolt up the same way to all accessories that are in car now? Also wondering about hp ratings....seems all the 73-78 460s are rated at around 210hp but the 83-86 carbed 460s are rated around 20 more...is there a difference in parts/pistons/rods/cranks and what is the interchangeability between the 1970's and the pre efi 1980s blocks?
Sorry about the long post but figured its important to note all what happened...
thanks in advance to any and all insight you may have!
 
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#2 ·
With dimples in the pan , I'd say it spun a bearing . No sense in wondering, pull the engine and tear it the rest of the way down. The problem should be obvious as to what failed.
 
#4 ·
I'm definitely pulling it...not really wondering...obvious rod (s) broke... I was just giving yall a rundown of chasing an interesting no compression issue. Anyone know if the accessories (ps /ac/act brackets etc from a 78 lincoln 460 will transfer to any 460 that's pre fuel injected?
Thanks
Also....perhaps I'll do a mild build on the next motor before tossing it in...would be fun to have a little more fun with that huge land yacht!>:)
 
#3 ·
I snapped a rod in #5 and was only going about 45 mph, it snapped about an inch below the wrist pin and sure did make a mess. I had holes in the pan and a bent valve but got lucky and didn't hurt my aluminum heads. Also the bottom rail of the block got nicked badly so I just put together another engine, never could figure out what happened to the rod but it looked more shiny on one end of the crack so I figured it was cracked for a while before it let go.
Good Luck,
John
 
#5 ·
Everything should interchange. Just make sure the timing cover has a fuel pump provision.
 
#11 ·
Small update...Well I picked up another 460 inexpensively that I will go thru before putting it in the lincoln...interestingly the block is a d1ve...heads d3ve just like the broken rod engine I have...and the valve cover sticker even says conforms to 1978 emmisions....pretty cool me thinks....possibly even cooler is that the intake manifold looks to be replaced as it has a different shade of blue on it and a dove 9425 casting # on it...which means no emmisions and regular 4 barrel (not spreadbore) carb will fit :)
 
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