Steps for upgrading a 72 340?

[Tonker1]

After reading around about the differences between the years the 340 block was produced and available performance upgrades, I'm now trying to work out a logical order to building a streetable but aggresive 340 (not in that order)! To also note, my older brother has a 67 Camaro with a 350 replacement engine, approx 340hp, 420 ft lbs of tq andits completely unexceptible for the Chev to be faster. Its also approx 100lbs lighter than my Chall due to factory options. So in the nature of Detroit, help me restore the natural order of the muscle car eara and put the Challenger back on top!

To note, I'd rather not go down the path of forced induction or strocking and boring. Prefering to keep the concept of the 340 and work the engine as far as possible to a streetable rocket that'll last. ie, not a maintance monster.



How probable is it for the block to be a time bomb due to warp or cracking?
Because in Australia a full block inspection is high enough in price that it warants the purchase of a replacement 340 or R3 for summit racing.


Phase 1: Maximise Air flow
Cam
Push rods
Rockers
Cylinder heads
Later on port everything which air flows through


Phase 2: Increase compression ratio
Bore engine 5 thousandeths over to clean it up a bit
Compression ratio was dropped in 1972 by changing piston wrist pin location - reverse this by changing pistons
Compression ratio should be back to 10.5 to one?


Phase 3:
Tune the system so it all functions harmonisouly



Does this sound logical interms of order and changes?
Are their higher priorities/recomendations?
How probable is it for the block to be a time bomb due to warp or cracking?
Compression ratio should be back to 10.5 to one with piston change?


Cheers.

 

[Juan Veldez]

You don't build a new house on a crappy foundation, so it's important to verify the block is in good shape. Get a little help from someone that can verify that it is in good shape before starting any of the modifications. I now that's kind of a generic statement, but someone "in the know" will be able to analyze the situation and give you proper direction.

If you go to 10.5:1 pistons, I would recommend a set of aluminum heads so you don't have to worry as much about running pump gas/detonation.

Boring, if needed, should be just enough to make it round again. Not sure if 5 thousandths is standard, might need to go 10. Saves money on pistons if not custom. Balancing the assembly is important. Know what kind of crank you have!

Do at least a "gasket match" of the intake manifold, heads, and the exhaust manifold. This is cheap horsepower.

Get a cam/lifters that matches the power range of the intake and let the person you order it from know if you have an automatic or stick. And if he's good, he will ask you about the other components so the "system" all works in conjunction. I personally try to make horsepower from idle to 5,000 rpms so I don't need to wind it up and keep it there to stay in the maximum horsepower/torque power range. To each his own.

Don't stop at the motor, make sure the tranny is in good shape and don't go crazy if you change the rear end gears unless you have an automatic with an over-drive like a unit from Gear Venders. It can handle the horsepower and still make it a nice long distance cruising car.

I like that you included "tuning the system", that squeaks out lost horsepower without adding more parts! Good luck.

Well, that's my 2 cents. Anyone else want to add theirs?

 

[moparleo]

You ask " how probable is it for the block to be a timebomb due to warp or cracking?" Because in Australia inspection cost is high.... Really think about what you just asked. How could anybody answer a question like that without even looking at it or knowing the past history of the motor. Was it driven hard, had regular oil changes, over heated in the past ,prior valve job etc...
Every thing else you said was common sense. But doing anywork or spending money on something before you disassemble and inspect it makes no sense. Spend the money on the inspection. 340 blocks do not do well with overbores of .040 or bigger. The blocks' cylinder bores should be sonic tested for core shift which is very important if you need to bore to make the cylinders round again. It is the details that make the difference between good and best. Find a good machine shop to build your engine. The more attention paid to machine tolerences " blue printing " the more free horse power and reliability you will gain. If you want good advice on what parts to use, check with parts manufacturers whose parts you are planning to use. They all have tech departments who will help you put together a package to meet your needs and expectations.
Know what you want, and see if it is feasable. We all have to make compromises so decide what you are willing to give up to gain what you want.
If you have a track that you go to and know people running a similar type car.Get free info on their setups. The more information that you get before you spend any money, the more likely you are to be happy with your car.
Have fun!

 

[Tonker1]

Moparleo, don't get me wrong, I won't begin performance upgrades until I inspect the full drive train and the engine. It was more wondering, more like hoping there was a rule of thumb to the condition of these engines at 40years old. There are a few engine specialists I'll make contact with about an inspection once all current projects on the car are finished so I have a clear mind.

Thinking of cylinder heads and part selection, I'll predominantly use premium 98 octane fuel. Do higher than normal octane levels influence the sort of parts used/combinations of parts or am I beginning split hairs? Tuning will of coarse be affected fuel choice.

Cheers

 

[moparleo]

I didn't know what fuels are available in your country. Aluminum heads will cut weight, resist detonation, flow much better out of the box than stock heads that have been ported. Also cost less in the long run than rebuilding and porting an old set of stock heads. Pre 73 heads also do not have hardened valve seats necessary when using unleaded fuels. Like I said, make sure it has not been bored more than .040 . and check for core shift.

 

[390racer]

Hi Tonker1 I don't know what part of Australia you are in nor do you say what "expensive" is because as far as I know most reputable shops will charge you between $150-$250 to hot tank your block, cracktest it and give it the once over, how can you deem that expensive???

 

[Tonker1]

There's a chance I've been mislead,
I spoke to some mechanics I met at work and they suggested a price range to me which included removing the engine (I don't have access to a hoist, could probably rent one though), dissembling, inspecting and reassembly. They may of coarse been trying to drasticly lighten my wallet!

Minor engine work is fine swapping through parts and so on, but I'm yet to do the full back to the bare bones block separation. This is not a fear of large or complex jobs, its more of an appreciation of mechanics and that the engine runs perfectly as is.

Dropping the engine and separating the block myself would save a lot of money which I've just spent replacing dilapidated drums with discs...

How hard is it and what needs to be done to separate the block from the rest of the engine?

390racer, do you have anyone in particular to recommend in Canberra for the inspection?

Cheers.

 

[Locomotion]

Tonker1,
When shopping around for a good engine shop, it will help if you find one that uses honing (deck) plates when boring & honing blocks. A shop having them would suggest that they pay attention to detail. These plates simulate the stress head bolts apply to the block while boring/honing it. It is worth some HP and extends ring life and seal because the bores will actually be rounder. Many places use a head gasket under them like you will use in the final assembly. Unfortunately it may cost a little more, if you can even find a place with a plate for a small block Mopar.

Minor bowl porting & polishing under the valves is an easy way to help airflow. Don't port too much without someone experienced with Mopar heads because mistakes can be made.

You may be able to hone a few 10-thousanths to clean things up, but you will likely need to go to the next oversize piston and bore/hone to the proper clearances. 5 thousandths is the average of what some piston manufacturers recommend to begin with. cast and hypereutectic tend to be run tighter and forged about that or a bit looser. You don't want too much because the pistons will be "sloppy" in the bore and reduce ring seal. If it's all original, it's probably worn enough to need an overbore anyway.

When shopping for cylinder heads, post what choices you end up with, OEM and/or aftermarket, before buying.

Cam and valve spring choice will be influenced by your converter and gear ratio the most. If you stay conservative with that, you'll need a cam with more torque to help accelleration. The major cam manufacturers can offer good suggestions as well as members here who have more experience with street/strip combos. You'll have to make sure you have enough retainer-to-guide clearance on the heads if you go with much more lift. Piston-to-valve clearance also, unless the aftermarket ones have deep pockets.

Use thinner (preferably good synthetic) oil - i.e.: 10w-30 instead of 20w-50 to free up a little HP. Same theory applies to rear end fluid. Bend open the "windows" more in your windage try, if it still has one, to help drainback and a deeper oil pan with baffles will help keep the oil away from the rotating assembly.

If you use headers, try not to use straight 1 5/8". 1 3/4" will help and consider an X-pipe in the exhaust system. I prefer TTI 1 5/8"-1 3/4" step headers, but they are pretty expensive.

Good luck!

 

[ramenth]

There's a chance I've been mislead,
I spoke to some mechanics I met at work and they suggested a price range to me which included removing the engine (I don't have access to a hoist, could probably rent one though), dissembling, inspecting and reassembly. They may of coarse been trying to drasticly lighten my wallet!

If you're forced to pay someone else to do the engine for you then you're going to pay.

When you say "some mechanics I met at work..." Who are these mechanics? Do they have a good reputation for building engines? Do they have a customer list for referral? I'm just asking so that we can have some clarification as to who these guys are.

As far as tearing the block down, let me say this: it sounds like you might have limited experience in the way of engines. Disassembly is as important as final assembly in how you inspect components you're taking out of the engine. Do you know what the bearings should look like for different wear that could indicate a problem with the crank or how it might have been driven in the past?

To me, it sounds like your a little confused on the point when you're getting quotes: someone with experience is charging for this kind of inspection and labor and reassembly (I'll assume that you'll be paying extra for machine work and parts) while comparing that to a replacement block.

Or are you talking about a crate engine? (Which defeats the purpose of buying another engine, as, if you're smart, you'll pay someone to tear down the crate motor and check the work that's already been done.)

As far as pulling the engine, you say you don't have a cherry picker. Here in the states we have places that will rent you equipment on a day by day basis, but I don't know much about Australia. That could save you some coin right there.

For the rest, you've been given a lot of good information here. If you're willing to tackle this project yourself then we're here to help. We've got some knowledgeable folks here who can help you step by step. Take your time, post a lot of pics, and I'm sure the guys here will get you through it.

 

[moper]

I agree with the guys who've responded. First - you need a goal. If to beat the Camaro is the goal, give us the ETs your car and his run now. Second - you need a budget. Third you need a plan. Notice at no time did I mention part numbers or suggestions... You need to nail down what you can spend, what you have, and where you want it to be, then we talk "stuff". Any real professional will start with these and work with you from there. If they are throwing numbers around without asking for these answers - move on.