Found a virginie 340 motor / now what to do with it?

[dodge freak 2]

So my engine shop is saying my Ebay 1972 340 from farm land southern Indiana had the stock pistons and crank bearings all looking in good shape. Cylinders are worn .006 to .008, one timing cover bolt even snap off since like the cover hasn't been off for a very long time


The J heads look to have had 3 or more valve jobs looking how thin the valve margins were. I told them at the time to just clean them up with the valves in place and I just store the heads since I have a good pair of MP 308 heads with the 2.02 intakes.

Now I am torn to stroking it to 3.58 or even 4 inches or the shop has a stock steel 340 crank .010 under. Eagle forged 4 inch stroke crank is $640 from Macinic Racing (which Summit should match). MP cast crank with a 3.58 stroke is $410....not sure what my shop wants for their steel 340 crank.

Yes $$$ will be playing a part...   

[dodge freak 2]

Yeah I know...


I could get a 7,500 rpm 340 which would sound killer at speed or a 416 that is rpm limited (can't afford a high rpm stroker




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[Tonefiend]

I am building mine with the stock steel crank.  My mopar buddies here tell me if I want a stroker to do up a 360. 

[Aussie Challenger]

I am building mine with the stock steel crank.  My mopar buddies here tell me if I want a stroker to do up a 360. 

Sounds like we have brainwashed you, now we have somebody else to work on.   

[Tonefiend]

Sounds like we have brainwashed you, now we have somebody else to work on.   

I don't know what I would do without you guys.   

[dodge freak 2]

Thinking more of a 340 stroke and rev it up high when needed. Means a nice 2,500 T.C. should be swap in the trans during the motor switch. Means more $

Guess the solid cam could go in later and I might reuse my 3 year old cam if the shop says it looks good and the lifter faces are not caved in. Would get new lifters.

All with all forged stuff and it balance the 340 should last  even up to 8,000 rpms . New main cap bolts-line hone, redo the rods-deck surface, and it be good to go.   

[Moparal]

8k on stock rods?    I wouldnt

[Topcat]

8k on stock rods?    I wouldnt

 

Eagle rods are significantly lighter also.

[dodge freak 2]

Yeah but all these $250 items add up! Those 340 rods should be in great shape being in a low compression  1972 340 that had stock bearings and cam. Today's pistons are lighter. With new rod bolts those rods they should be good to 7,500 

Now I thought about using like a Scat cast steel crank with a 3.58 stroke. Could use a .060 over 360 piston (which are a bit cheaper then 340 pistons)

Give me a 370 CI motor with no need to notch the bores out and it be bored out only .020.

But goodbye 7,500 rpms. I think 6,500 it last a long time.

Forged 3.58 strokes are too much cost.

[Aussie Challenger]

8k on stock rods?    I wouldnt

You say you may swap in a bigger cam later, get the bottom end right this time or a few hundred dollars now will be a few thousand later.   

[dodge freak 2]

This is how its shaping up.

A stock stroke 340  could even outperform a 4 inch stroke 340 IF it would rev up to 9,000+ rpms. That cost big bucks so it last and I would need a race 5,000 T.C. (maybe higher) Very un street able.

A 4 inch stroke 340 could last at 7,500+ rpms if H rods and all forged parts were used--again big bucks but more street able. Still it wear out -break sooner- at steady 8,000 rpms that the stock stroke 340 high rpm motor

A cheap cast 4 inch stroker crank and hyper pistons would be the cheapest stroker and might very well last if build right and not abused. Forged SRP pistons would be better. Still it be rpm limited but very street friendly. Could have a nice strong idle and make very good power for its limited rpms. 

Was told to think it over and call back Monday--well I thought it over but still     Price--shop opinion will decide it.

[Moparal]

A cast crank at 7,500 rpm    Not good for endurance either my friend.  I wouldn't recomend a fantacy rebuild.  I would just save up and buy 1 part at a time if need be.  Do you know where the oil goes when the engine gives up at 7,500 rpm's?  Once the rod goes through the oil pan, it gets to be quite tricky to be along with the ride.   

Yeah, think it through, since everything behind the engine has to do it's job when trying to make power.  And don't forget about SAFETY and SFI equipment.  I'd rather hear some great winner stories on your end of the post

[71chally416]

I used the Ohio crankshaft cast 4" crank. $295, and the machine work is top rate. > http://www.ohiocrank.com/mopar_cranks.html

The Eagle SIR rods are adequate as long as you keep the revs in the powerband of the motor with iron heads. It ain't gonna make a bunch of power over 6K anyway with 416 cubes. Mancini has the pressed pin version on sale for $99 a set.
http://chucker54.stores.yahoo.net/corodse.html

That's $400. Get a set of pistons and you're on your way.

[Aussie Challenger]

What are you going to use this motor for? 7 1/2 k, 9 k rpm, not too many race cars see this type of engine speed let alone road cars and you just don't skimp on $$ with that sort of rpm.   

[dodge freak 2]

Been finding more info on stroke motors. Seem they need lots of cam to turn the same rpms. Quote Mike Jones Cam "Only at the same RPM, but with a given cam duration, a big-bore/short-stroke engine will make peak power at a higher RPM then a small-bore/big-stroke engine of the same displacement. You also have to look at the fact that the slwer piston speeds of the shorter stroke  will make the engine more reliable.
If you look at any racing class where the displacement is limited, the evolution of the engine is an increase in bore, and a decrease in stroke"............ another quote from Mike "If you build two 402ci SB chevy's with the same heads to make peak HP at 7,500rpm, one with a 3.75"Stroke x 4.130"Bore, and the other one 4.00"Stroke  X 4.00"Bore, the one tith a 4.00" bore will need 10 degrees more seat duration.

Look at the Pro Stoke engines, Back when they ran big strokes, they ran cams in the 296@.050" range. Now with the shorter strokes, they turn a lot more RPM with cams in the 276@.050" range"........... end of quotes.

I was saying 7,500 and all forged parts--crank included.

Some poster from CNC blocks on Speedtalk was posting pictures today on a cast crank motor running 7,200. Was saying how the cast crank flexes and eats the bearings. Was also saying that Chevy 2 bolt main caps start dancing-walking-with stroke cranks in SBC--that is only 3.75 inches. 

So I am strongly leaning towards leaving the stock stroke 3.31 and getting nice forged pistons--a factory steel crank and a nice T.C. Maybe even a 10 inch boy--with a solid cam 7,500 rpms could be done.

Motor should last a long time using the short stroke.

To do a stroker motor right is too much $$$. Seems better to move up to a BBM if I want 400+ CI