360 swap into a 340 cuda

[don selleck]

Been working on a 70 340 cuda project for about a year had the non original 340 block in boxes with new edelbrock head air gap intake new pistons, Got a friend of mine that been assembling mopar engines for 30 plus years assemble the engine. had a few questionable areas with freeze plugs hole etc with the block. got it broke in and racked up 1250 miles on it using zinc add oil and 80lbs of oil pressure at cold idle, had a very slight antifreeze leak into exhaust would come out of exhaust very slightly on start up the disappear. Then wiped out wiped out the comp cam lifter on #1 or #3, or both havent disassembled it yet. kinda gun shy of messing with this again, so considering a 360 crate long block from blue print stroked to a 408 for more power any one installed one in a 70? and what issues i assume a oil pan swap would be in store and if I'm thinking correct should be same motor mount. thanks in advance.

 

[pschlosser]

no, I have not.

 

[rklein71]

My 408 based on a roller lifter 5.9 magnum with EQ heads feels more like a big block than the 340 I had back in the day. Lots of low end torque.

 

[Xcudame]

Balance is different unless the 408 has been internally balanced. If the 360/408 is externally balanced you'll need the correct harmonic balancer (if not included) and the correct flywheel/flex plate to prevent crazy vibrations.

On the wiped out cam lobes, I wonder if the rod bearings used had the notch to allow extra oil to the camshaft and lifters. I still think flat tappet camshafts benefit from that extra oil from the big end of the connecting rods. None of the new bearings have that notch anymore. I add it with a rat tail file and the bearing placed in an old rod bearings cap. (Am I the only one with miscellaneous one or two connecting rods from unknown motors - not sure where I picked them up over the years!)

 

[don selleck]

Balance is different unless the 408 has been internally balanced. If the 360/408 is externally balanced you'll need the correct harmonic balancer (if not included) and the correct flywheel/flex plate to prevent crazy vibrations.

On the wiped out cam lobes, I wonder if the rod bearings used had the notch to allow extra oil to the camshaft and lifters. I still think flat tappet camshafts benefit from that extra oil from the big end of the connecting rods. None of the new bearings have that notch anymore. I add it with a rat tail file and the bearing placed in an old rod bearings cap. (Am I the only one with miscellaneous one or two connecting rods from unknown motors - not sure where I picked them up over the years!)

was going to pic up possibly a blue print engine or pei. on the rod bearing notch, pretty interesting i removed the valve cover to see if any pushrod were lose or comprimised i started the engine and it did take about 10 seconds to get oil to come out of the push rod on #1. I just got everything disconnected. gonna hook up the cherry picker in the morning and pull it out and get it on a stand. heading out to the Ididit car car around 10 am a friend of a friend I havent met yet will be there with his dodge daytona he is the original owner pretty crazy. I would have been there park next to it if the 340 wouldn't have puked.

 

[Xcudame]

Mopar engines are tough! I'm always surprised when people have issues with them. Yes, Shivvy 350s are cheaper, but they don't last very long! I used to race a 70 Challenger in Street Stock and our engine lasted the whole year! Shivvies lasted about three or four races before they puked oil on the race track!

 

[don selleck]

Mopar engines are tough! I'm always surprised when people have issues with them. Yes, Shivvy 350s are cheaper, but they don't last very long! I used to race a 70 Challenger in Street Stock and our engine lasted the whole year! Shivvies lasted about three or four races before they puked oil on the race track!

ya comp cams aren't anymore, or the oil or something will find out the damage probably sunday.

 

[don selleck]

ya comp cams aren't anymore, or the oil or something will find out the damage probably sunday.

But anyway wondering the fitment of that 360 any oil pan issues or any clearance issues with anything? thanks again

 

[Chryco Psycho]

You will be fine with the 360 & different oil pan in a 70

 

[Challenger RTA]

Here's how the oil should be coming up evenly. There could also be a obstruction in the oil gallery.

 

[don selleck]

Well I take back what I said about comp cams, pulled the motor. looks pretty good no crazy wear, down to the lower end. didnt really sound like a rod knock, maybe a piston or wrist pin. Went to Ididit car show today pretty cool, off to my buddies poker game tonight, will continue with the disassembly tomorrow, and will get some pics from the car show and motor. thank you all for all your considerations.

 

[Adam]

I believe the drivers side motor mount on a 340 is the same as a 318. The drivers side mounting ears on a 360 block are closer together by 1/2, or 5/8, of an inch. The 318/340 bracket will leave a big gap at the rear mounting holes. You can get a 360 bracket, or make a spacer for the rear holes, or just stack some washers in there.

 

[Xcudame]

273/318 driver's side bracket is different from the 340/360. 340 and 360 are the same.

 

[don selleck]

Here's how the oil should be coming up evenly. There could also be a obstruction in the oil gallery.

View attachment 128363

Thats pretty interesting, mine is nothing like that i saw some air bubbles purging out of the rocker coming from the cylinder in question.

 

[don selleck]

after looking at the cylinder bores and overall machining on engine, very dissapointed. The block is a july 1969 340-6. so thats about as close I can get to the T/A motor that was in it, without spending a fortune on a real T/A and still not have a matching numbers. Probably would be best for the overall value of the car to go to square one and have the block tanked and magnafluxed, and go from there. Thanks for all your input.

 

[Challenger RTA]

Thats pretty interesting, mine is nothing like that i saw some air bubbles purging out of the rocker coming from the cylinder in question.

I would say, Drop the oil pan check all oil pump connections and gaskets. I would say it's sucking air from somewhere.

 

[Challenger RTA]

340 oil system

 

[don selleck]

found the fuk up missing copper gasket on pickup. had about 5lbs of torque to remove the bolts explains my air bubbles. so glad this was idleing at my home when this happened, could of been way worse. contacted another engine guy who is a friend of a friend who builds engines for a livin, Built a alcohol motor for another guy called time bandit.

 

[mrmopar340]

I forsee a rebuild sadly in the future. At least you were home and not on the road.

 

[don selleck]

yep, for sure. cam was small on it anyways it was pretty much a stock engine. so gonna tweak it up a little talking to a machinist/ builder wednesday. figured I'll get it in asap to avoid everyones elses winter projects