Building a 340

[68FishNate]

Hey guys, first I want say ANY help is greatly appreciated. I don't see life in my Barracuda with the 318 powering it to pull it out and do the machine work or make it have more power than it does. Currently, it's driving, but probably need to replace piston rings, probably have head work needing to be done and leak out of the rear main seal. Still able to enjoy, but the time and money, I'd rather put in to what I want the car have in it.

In short, I want to build it right, I know it costs some money and time to do it right.

I purchased a long block 340, disassembled it and put it in the machine shop today to get checked, cleaned, etc. Taking it apart, the motor looked better than my 318 did when I refreshed it, just trying to get it back on the road. Big plus.
This block is currently .030, steel crank, turned and previously balanced. Heads are J heads and valves and springs have been upgraded, currently unkown. As I was told, previous work didn't look old or abused and probably could use cleaning, new bearings, rings, and rebuild it, slap an intake carb and water pump and go.

However, I want more. Lol. How do I get more. Machine shop asked me to find a cam, recommending roller. So, I'm asking for some wisdom and advice.
I found this one.
Howard's Cams Retrofit Hydraulic Roller Camshaft Part # HRS-713175-10
Camshaft, Hydraulic Roller Tappet, Advertised Duration 272/278, Lift .525/.525, Chrysler, Small Block, Each

I gotta start somewhere and making the first decision will help guide how far down the rabbit hole of spending.

Goals: Enjoy it on the road, city, back roads and highways as well send it down the track. This is not a drag car build. 395-425 hp before later upgrading heads to Trick flows. Very fun cruiser that I take to the track.

I will also be looking for an 8_3/4 rear-end 3:55? Or Dana 60 3:54

Car is a 4 speed manual.
Any thoughts towards cam, build, what am I getting myself into, etc. What's next, intake, carb, I'll take it and it's greatly appreciated. Thank you

 

[crackedback]

Looks like an XE268H cam in it. Whatever bigger cam you choose will likely require different and dual springs.

I hope your rod caps are marked with the rod itself. Shouldn't do what you did. Take one rod out, put the cap on it with the nuts. No chance of mismatching them.

That one cylinder is really clean, popped a head gasket?

Might do a quick hone/fresh rings and put it back together.

All depends on how fat the wallet is on where you go with the process.

 

[68FishNate]

Looks like an XE268H cam in it. Whatever bigger cam you choose will likely require different and dual springs.

I hope your rod caps are marked with the rod itself. Shouldn't do what you did. Take one rod out, put the cap on it with the nuts. No chance of mismatching them.

That one cylinder is really clean, popped a head gasket?

Might do a quick hone/fresh rings and put it back together.

All depends on how fat the wallet is on where you go with the process.

It had a flat Tappet cam in it that I already thought I wanted to go bigger than what it was.
The caps were all numbered, looking back, I agree, better practice for rebuilding.
The motor had been sitting for a while, not sure last run, but there was a piston rusted down in the piston with no flex as the ring should.
Happy to be going through the steps

 

[mygasser]

re the rear axle, you should consider an exploder 8.8 too. 31 spline shafts, lsd, disc brakes, 3.73 gears and same pcd as mopar bbp. cut the case long side down by 2 7/8" to fit a second short shaft and it's almost exactly A body 8 3/4 width too. what's not to like?
neil.

 

[Plymouth 65]

I'm not sure how much bigger cam you should use. That XE268H should work well with those stock 10 5:1 pistons. To much cam and your low end torque will be disappointing. 65

 

[RustyRatRod]

I wouldn't use a hydraulic lifter in any clean slate fresh build. Solids make more power everywhere. And with all of the great adjustable valve train choices there are, if you need to adjust once a year, it'd be a miracle.

 

[Scott_ 69HemiDart]

You will get a ton of great information here. I'm looking forward to seeing where this project goes and how the 340 comes together.

 

[Newbomb Turk]

You need to be at least 10.5:1. At least.

To do it with those pistons you have to measure the recess in the head, add in gasket thickness and then do the math and see where you are.

The last 340 I did to get an actual 10.48:1 with those pistons I was .045 out of the hole and an .039 gasket. And that was .045 quench.

If the shop doesnt comprehend that the deck of the piston has to come out of the hole just like Chrysler says, find a better shop.

I’m a firm believer in doing a half inch down fill and doing the math to know the compression ratio because it matters. You can’t guess.

 

[9secRR]

I’m a firm believer in doing a half inch down fill and doing the math to know the compression ratio because it matters. You can’t guess.

that's what I do, half inch down fill. only way to do it

 

[Dartswinger70]

you could build that thing close to stock tune it and get 300 -325 horse.

 

[68FishNate]

you could build that thing close to stock tune it and get 300 -325 horse.

Is that currently what it is looking like it would make with the .030 over, j heads 2.02 and previous cam xtreme comp cams 20-223-3 268/280 .477/.480.
Currently pondering goal on timeline for the 340. Weather is perfect to be driving and enjoying.

 

[marksmopars]

I have two running 340’s and both run 9.25 compression to operate on pump premium gas. I have solid lifters and a healthy cam with results of 400 hp at 6200 rpm, 385 at 7000. More than enough for what I want, fyi.

 

[ValiantRacing]

You need to be at least 10.5:1. At least.

To do it with those pistons you have to measure the recess in the head, add in gasket thickness and then do the math and see where you are.

The last 340 I did to get an actual 10.48:1 with those pistons I was .045 out of the hole and an .039 gasket. And that was .045 quench.

If the shop doesnt comprehend that the deck of the piston has to come out of the hole just like Chrysler says, find a better shop.

I’m a firm believer in doing a half inch down fill and doing the math to know the compression ratio because it matters. You can’t guess.

Just curious how many CC's were the heads?

 

[68FishNate]

Just curious how many CC's were the heads?

Hoping to get that information soon from the machine shop.

 

[Newbomb Turk]

Just curious how many CC's were the heads?

lol I just had to pour them on Monday and I have forgotten. I have it written down in the shop.

My memory says 65. When I go back out I’ll verify that.

If you hadn’t asked I would have remembered it for sure.

 

[Dartswinger70]

Is that currently what it is looking like it would make with the .030 over, j heads 2.02 and previous cam xtreme comp cams 20-223-3 268/280 .477/.480.
Currently pondering goal on timeline for the 340. Weather is perfect to be driving and enjoying.

take measurements if it doesnt need machine work assemble and drive. All builds are a tear down and inspect now everyone here will spend your money but remember its 3 choices Overhaul, rebuild, or balance and blue print. balancing and blueprinting is expensive and should be considered for an all out race application. Overhaul is new parts and gaskets not much machine work, rebuild is the machine work etc. you have to measure and inspect decide which one you are doing. each one goes up in price naturally.

 

[Dartswinger70]

Just curious how many CC's were the heads?

J heads were all over the place according to legend sometimes up to 71 cc as I have read somewhere. Tis is why its good to measure if you want to be absolutely sure the cc kits are cheap at summit and use windshield washer fluid