340 Max Bore

[Newf]

Hi All,

I'm looking for a 340 motor for my 72' Demon. I am wondering what the max you can bore a 340 is? I've heard .040 and both these have been done to .060. Here is a description of the motors which would be the better if I can do a straight trade?

#1. asking price $3000

340 dodge motor, all rebuilt, rollerized, all of the good parts estimated 400-450HP good motor for your car or truck


1972 340 block, 1969 steel crank/rods, Kieth Black Hypereutectic Pistons 10.5-1, Moly Rings, Clevitte 77 Bearings, Melling High Volume Oil Pump, Mopar Bronze Oil Pump Gear, Comp Solid Roller Cam, Comp Solid Roller Lifters, Comp Pushrods, Crane Gold Roller Rockers, 340 X Heads Rebuilt with Porting/Polishing, Holley Aluminum Valve Covers, Mopar Electronic Distributor, Factory Balancer, Oil Pan,

Hone Block/Clean $80.00
Square Deck Block $180
Frost Plugs- PLC41B 10pcs $26
Crank Polish- $78
Oil Pump- M72HV- $95.00
Main Bearings- CLE-MS963P10- $69
Rod Bearings- CB481HN10- $88
Timing Chain- 91103-$77.32
Pushrods- 69690-13 $165
KB Pistons- UEM-KB243-060 $348.50
Rings- E286k60- $133.46
Distributer Bushing- PC780- $8.80
Cam Bearings- PD16- $41.20
Gasket set- QKS2114- $61
Valve Covers- Holley cast aluminium- $150
Cam- CCA-20-741-9 $332
Lifters- 828-16 $522.49
Rockers-http://www.hemiperformance.com.au/store2/p_2072_Small-Block-Crane-Cams-Gold-Race-Roller-Rocker-Kit $650
1969 340 X heads rebuilt ported polished- $1000
All off these parts add up too $4105.77. Some of the part numbers and prices are from receipts from the 340 and my stroker but are the same parts. The other part numbers and prices are from summit which would not include freight.

Valve Springs? not stock, don't know what they are #150?
Cam Plate- Diamond racing roller cam retainer $100?
Also included, Factory 1969 steel crank, Stock 340 Rods, 72 340 Block, Stock Electronic Distributer, Stock balancer, timing cover. All these parts are worth $1000 in my opinion, theres alot of expensive parts here that add up fast.

Looks like the intake and carb are missing in the first motor


Motor #2.




Asking Price $5,500


mopar forged crank ,new manley rods, arias pistons,total seal rings ,blue printed, new edelbrock alum heads .offy intake dual carters .set up for hot street pump gas or bracket est 475 -500 hp.will run on stand or dyno

Not much for parts list on #2 but apparently both are 10.5:1 compression and I am doing a straight swap for a car that was given to me. I'm not cracked about either one being .060 over but the other parts could be used with another 340 block in the future except for the pistons. Also I am wanting to build a daily driver so the dual carbs and tunnel ram would be used for trades most likely. I need to get specs on both cams and that might help with the decision but is relatively a cheap fix. Any advice is welcomed. Thanks in advance.

Joe

 

[72bluNblu]

It depends entirely on the block. Typically, max bore for all the small block mopars is .060". I've heard of some being bored to .080", and some that couldn't go .060".

I have a '68 340 block that was bored .060" over for me when I rebuilt it, no issues, plenty of wall thickness. I would suspect that the large majority of them would be just fine at .060" over. I'm also sure that there are probably 340 blocks out there that would be pretty thin at .060". It really depends on the individual block- ie, how much core shift it has, how rotted the water jackets are, etc.

For a street engine, I'd say there's a good chance that either block would be just fine. But, without sonic checking, there's really no way of knowing for sure.

 

[Newf]

It depends entirely on the block. Typically, max bore for all the small block mopars is .060". I've heard of some being bored to .080", and some that couldn't go .060".

I have a '68 340 block that was bored .060" over for me when I rebuilt it, no issues, plenty of wall thickness. I would suspect that the large majority of them would be just fine at .060" over. I'm also sure that there are probably 340 blocks out there that would be pretty thin at .060". It really depends on the individual block- ie, how much core shift it has, how rotted the water jackets are, etc.

For a street engine, I'd say there's a good chance that either block would be just fine. But, without sonic checking, there's really no way of knowing for sure.

Thanks for sharing, Seems like alot of lookers but few opinions on the matter.

Cheers

 

[2 Darts]

I'm kind of leery of a .060 overbore on a LA block, too. I think it depends more on the intended use of the car. I'm more inclined to say OK to which ever engine you prefer since you state the Demon is to be a daily driver. Unless you're racking up mileage a ¼ mile at a time.

My preference would be for the second engine. Either way you'll need an intake and a carb, possibly a cam, too. The second engine will give you the intake system as you pointed out to offset the cost. The first engine will need less cam to be suitable for a daily driver.

CCA-20-741-9 listing from Summit: Camshaft, Mechanical Roller Tappet, Advertised Duration 280/286, Lift .570/.576, Mopar, Small Block LA.

The stock 340 cam had these specs '68-'73 340 .430/.444 lift 268/276 duration; the '68 340 with manual trans. was .444/.453 lift .276/.284 duration if this helps you make comparisons with the cams available to you.

 

[moper]

If it's not being stroked then .060 over isnt usually a big deal. I've got several strokers running around at .060 over. So long as they pass a decent sonic test they're fine. If this was the 80s, blocks went from .030 to .060 all the time and while some did have overheating issues, most were fine.