1969 plymouth valiant engine upgrade

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I recently bought a 1969 Plymouth valiant with a 318. The motor has a dead cylinder and I bought the car to put some horsepower in it.

My first question is what size rear end did it come with. It came with a 318 so I'm hoping its not to wimpy and doesn't need to be upgraded.

Second I don't feel like screwing around with the 318. I'm considering a 360 or 408. Or big block 383/400. I'm leaning towards the small block.

Can't find any magnum engines from wrecking yards around where I live. Some 360 LA style come up once in a while. Seems tons of 440's come up. Almost bought a 400 but it was sold already.

I'm a over the road truck driver. So the car will only get driven a few days a month. My time is limited but I have access to people whom I can hire to put the engine in and rebuild if necessary. And a shop for it to be at in the process.

Blueprint engines short block 408 stroker shortblock is on my mind. Finishing it off with a set of decent heads and etc.

The deal is this as far as goals. Able to be driven on the street. A mid to low 12 second car. Dragstrip in Bakersfield ca isn't far from me. Would like to take it there.

Gears I can change to accommodate the engine. Just don't want a high revving engine at highway speeds.

Its got the 904 3 speed auto.

Gas mileage isn't a huge concern. Don't mind adjusting lifters if I wind up going solid can.

Give me your thoughts. I'm open to all suggestions. Thanks in advance!

If for some reason I go big block 383/400 stroker I got a weiand tunnel ram for it. Lol. Yeah I know they aren't good on the street. But it would look cool! Lol
 
Cool, car. You can build your existing 318. Stroke it into a 390. Would be good for 400HP. The 360 would get you a little more cubes and torque. I the 904 is already a good trans. look at your rear does it have any bolts facing on the back cover or is it smooth. Better yet post some pictures if you can.
 
The 340 was the performance engine. Don't recall that they were an option in 1969. The 340 TA was the primo small block, a few years only (72-73?). Although the 360 is more of a "truck engine", there are many fairly cheap parts to make one hot today. I would lean more toward a Magnum since you get roller rockers, MPFI, and crank triggered ignition included. Wait and you will find. If you want to keep a Magnum tranny, you need to cut and reform the trans tunnel in the car. Some even install a modern Hemi, and there is a forum for that. Big blocks give a front heavy car, unless you get aluminum heads and water pump housing. There is a forum and even a website (bigblockdart.com).
 
Welcome to FABO Running! Thanks for "running" the roads and getting all of us our goods. It's a tougher job then most realize.

As far as the Valiant.....99.9% chance that a teen/auto has a 7.25" rear from the factory. Could it have been changed over the years...maybe, but I doubt it.

As far as going 12's in that car, I think a LA360 is your best option. You're in Cali, so I'd give a call to Brian at IMM Engines in Indio. He and his Dad are some of the best Mopar engine builders on the west coast, and members here.

It won't take a ton of power to run those numbers in a "fairly" light A body, and a good rebuild on your original 904 trans will surely handle that.

As far as the rearend.....the best case scenario would be to go with a 8.75 originally out of a A body. The next best would be a 8.25 from a later model with a good "sure grip" or aftermarket carrier.

If you decide to go 360, a gear around 3.91 would get you in the ballpark. If you go with a "stroker", meaning a 4" crank, you may be able to pull off consistent 12's with a 3.55 gear, or even 3.23's depending on how stout the engine is along with the converter choice.

Congrats on going with a nice Valiant build.....I only wish I was in a good situation to build one myself...
 
OldmanRick said:
Welcome to FABO Running! Thanks for "running" the roads and getting all of us our goods. It's a tougher job then most realize.

As far as the Valiant.....99.9% chance that a teen/auto has a 7.25" rear from the factory. Could it have been changed over the years...maybe, but I doubt it.

As far as going 12's in that car, I think a LA360 is your best option. You're in Cali, so I'd give a call to Brian at IMM Engines in Indio. He and his Dad are some of the best Mopar engine builders on the west coast, and members here.

It won't take a ton of power to run those numbers in a "fairly" light A body, and a good rebuild on your original 904 trans will surely handle that.

As far as the rearend.....the best case scenario would be to go with a 8.75 originally out of a A body. The next best would be a 8.25 from a later model with a good "sure grip" or aftermarket carrier.

If you decide to go 360, a gear around 3.91 would get you in the ballpark. If you go with a "stroker", meaning a 4" crank, you may be able to pull off consistent 12's with a 3.55 gear, or even 3.23's depending on how stout the engine is along with the converter choice.

Congrats on going with a nice Valiant build.....I only wish I was in a good situation to build one myself...
Click to expand...

Ricky's post,great info.The one missing factor,exhaust & headers. (The biggest pain,here). I.M.M. good honest people,can't go wrong.Chassis & brakes, will need some fore thought.
With some careful choices,a 360 with 3:55's should be a 12 second runner, done right.
 
R4Sedan said:
Cool, car. You can build your existing 318. Stroke it into a 390. Would be good for 400HP. The 360 would get you a little more cubes and torque. I the 904 is already a good trans. look at your rear does it have any bolts facing on the back cover or is it smooth. Better yet post some pictures if you can.
Click to expand...


I have thought about doing something with the 318. But cores for 360 seem cheap enough. There are bolts in the back of the rear. I think ten.
 
BillGrissom said:
The 340 was the performance engine. Don't recall that they were an option in 1969. The 340 TA was the primo small block, a few years only (72-73?). Although the 360 is more of a "truck engine", there are many fairly cheap parts to make one hot today. I would lean more toward a Magnum since you get roller rockers, MPFI, and crank triggered ignition included. Wait and you will find. If you want to keep a Magnum tranny, you need to cut and reform the trans tunnel in the car. Some even install a modern Hemi, and there is a forum for that. Big blocks give a front heavy car, unless you get aluminum heads and water pump housing. There is a forum and even a website (bigblockdart.com).
Click to expand...


Thanks for the info. Leaning towards a small block since that's what it has in it. A hemi Iwould be cool but harder to make work from what I have read.
 
OldmanRick said:
Welcome to FABO Running! Thanks for "running" the roads and getting all of us our goods. It's a tougher job then most realize.

As far as the Valiant.....99.9% chance that a teen/auto has a 7.25" rear from the factory. Could it have been changed over the years...maybe, but I doubt it.

As far as going 12's in that car, I think a LA360 is your best option. You're in Cali, so I'd give a call to Brian at IMM Engines in Indio. He and his Dad are some of the best Mopar engine builders on the west coast, and members here.

It won't take a ton of power to run those numbers in a "fairly" light A body, and a good rebuild on your original 904 trans will surely handle that.

As far as the rearend.....the best case scenario would be to go with a 8.75 originally out of a A body. The next best would be a 8.25 from a later model with a good "sure grip" or aftermarket carrier.

If you decide to go 360, a gear around 3.91 would get you in the ballpark. If you go with a "stroker", meaning a 4" crank, you may be able to pull off consistent 12's with a 3.55 gear, or even 3.23's depending on how stout the engine is along with the converter choice.

Congrats on going with a nice Valiant build.....I only wish I was in a good situation to build one myself...
Click to expand...

Thanks for the information. So I will more than likely be searching for a rear for it. 3.90 gears seem low to me. I used to drive a 68 camaro 396 with 373 in the rear. On the freeway that thing was buzzing. Lol. Back then I drove fast so that could be why though. Lol.

I am really excited about this valiant and having a Mopar. Nothing against chevys. It just seems where ever I look there they are. Lol.
 
Abodybomber said:
Ricky's post,great info.The one missing factor,exhaust & headers. (The biggest pain,here). I.M.M. good honest people,can't go wrong.Chassis & brakes, will need some fore thought.
With some careful choices,a 360 with 3:55's should be a 12 second runner, done right.
Click to expand...

I have seen I'm engines website. I am considering the rhs heads he offers. Thanks for the info.
 
Yeah, it's probably a 7 1/4. That's what was in mine too. Their is a thread on here showing pictures of the different Mopar rears, show you can decipher them. Check craigslist 8 3/4 pop up. Check that for engines too. Mines was originally a 273 and I found a 318 and w 360 heads machined and ready for assembly for $400 the guy needed money. So be patient and things will come along.
 
This is about the best shot of a 83/4 I have this is the front of the unit.
 

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He said he thinks ten bolts on the rear, I'm thinking 8 1/4.

Although a 7 1/4 would have been more common.
 
R4Sedan said:
Yeah, it's probably a 7 1/4. That's what was in mine too. Their is a thread on here showing pictures of the different Mopar rears, show you can decipher them. Check craigslist 8 3/4 pop up. Check that for engines too. Mines was originally a 273 and I found a 318 and w 360 heads machined and ready for assembly for $400 the guy needed money. So be patient and things will come along.
Click to expand...

I looked at your thread on your car. Mines the same gold. Lol.

Great build, and the red looks great!
 
Been checking Craig's list for the past month or so and the wrecking yards. Well today the wrecking yard near by has a magnum engine. If I get back in town before its gone I'm going to look at it.

The magnum engine is top on my list cause of the roller camshaft and lifters. If I could find one good enough to just replace pistons, rings and bearings, etc. Minor rebuild. That would be ideal. Then I would be able to spend more money on some heads. And go roller cam.

I guess if the heads were good I could just reuse them. But honestly I don't want to. I would really rather spend the money on a good set of heads for it.
 
Just picked up a magnum 360 out of a wrecked truck with 120,000 miles. Making a little headway. Now time to figure out what to do with it. Heads, cam, intake?

The rear end is the weak one. So another rear end is in order.

The car will get driven about two days a month. Looking to take it to Bakersfield to drag race it. Drive on the street to. I will be getting a weighted torque converter. Stall unknown tell engines figured out.

Hoping to get into the twelves preferably low 12's. I'm open to suggestions with what to do with the engine. Hoping to leave the short block alone. Hoping to spend under three grand on the engine from here.
 
One of two ways to go,here. I recommend a Edelbrock RPM Air Gap ,here.E.Q's ,or RHS will get you there.Was more impressed by the E.Q.'s ,out of the box. Either way,have the valve guides cut down for more valve lift. We now have a Magnum section here,also check out LXguy's "Magnum swap.com". How fast ,do you want?.Low 12 he's ,a slam dunk. What do you want it,to do?.
 
Abodybomber said:
One of two ways to go,here. I recommend a Edelbrock RPM Air Gap ,here.E.Q's ,or RHS will get you there.Was more impressed by the E.Q.'s ,out of the box. Either way,have the valve guides cut down for more valve lift. We now have a Magnum section here,also check out LXguy's "Magnum swap.com". How fast ,do you want?.Low 12 he's ,a slam dunk. What do you want it,to do?.
Click to expand...

Thanks for the info! And about the magnum section. Didn't even realize. Lol
 
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