340 Engine rebuild kit

[1 Wild R/T]

Yup, looking at your bearing pictures that engines been run pretty hard to be showing copper & the pocking of the mains which looks like a fatigue failure....  I would be using a bore gauge to see what kind of roundness & taper your dealing with..... I might throw a set or rings & bearings at it if I had zero budget but I sure as hell wouldn't put a stroker kit in without at least measuring the bores... Be clear with the machinist you'd like to keep the stock bore but if it's to far outta spec it's gotta be bored....

As far as just dropping a stroker kit in place, some folks get away with that to a point, there may be grinding for clearance of the rods/bolts & crank ... Most of us also double & triple check clearances, file fit rings, sometimes bearings need scraping to clear a chamfer....  As you assemble keep a close eye on rotating torque as each piece is added... If it goes up significantly you need to go back & find out why....  If there's issue I like to assemble once without rings so I know whether it's just ring drag or a tight bearing...

[tdwnilla1]

Accidentally had this all in the post 1 Wild R / T shared.

Thank you Chryco that is correct, 1 Wild R/T thank you for thinking of me but like Chryco said I don't want to bore if I can help it. Honestly, with only 40,000 original miles on it I am quite disgusted that I have to do any of this to it but unfortunately replacing my main bearings and rod bearings did not make my lower end rattle go away it only quieted it down a little and bought me some time so I can still go to the Syracuse Nationals. Is there a specific stroker kit I should be looking for ? I would like to do as much of this myself as I can. I have means of honing the cylinders even though they don't look like they need it but it cant hurt to polish them as long as it is already apart. I live near Syracuse and we have a local place that turns cranks (Syracuse Crank and Machine) if I had to but by the sounds of things I can go with the stroker and it comes with a crank I believe. With all of that said, all I would need to do is have my block acid dipped and magnafluxed and put the stroker kit in and that would be it for my lower end and then all I need to do is get my heads done to oe specs correct ?

[tdwnilla1]

In the other post you state you have replaced the bearings already and have bottom end noise. Did you check clearances? I'm just curious if you have wrist pin noise or cylinder to wall noise. Just because the engine hasn't been bored doesn't mean the cylinder walls are straight all the way down either.
I do believe in leaving the cylinder walls as thick as possible but sometimes a bore is required for proper results.

I did not remove the engine to replace them so I could only mic half of the main journals as the crank was still in the motor and they all were within specs. The rod journals were also within spec so I went with the standard bearings. I had 2 excellent local mechanics tell me that it was my mains so I figured I would do the rod bearings while I was right there. My first thought was mains as well because of past experience. It only makes the rattle at a certain RPM (no tac yet) I'm guessing around 2500. I seriously hope I am wrong but fear I am not. If I get a chance later I will fire it up and post a video with the sound it is making and perhaps one of you can shed more light.

[RUNCHARGER]

Hmm: Okay, If it was mine I would take it easy on it until winter and then pull it out and have a pro measure everything. Crank journals, piston diameters, cylinder walls, wrist pin clearance etc. before doing anything. I wouldn't spend a nickel on parts until finding the root cause of the noise. Unfortunately, 60,000 miles is enough to have lots of wear with an old carbureted engine that has probably had a ton of cold starts.

[Rich G.]

It all comes down to what are your goals. If you're just having it rebuilt and keeping it stock ( which I'm in the process now) I wouldn't buy a kit. Have the machine shop check the block to see if the bore is still good and you might get away with a hone and new rings. Of course cam bearings and freeze out plugs. I put in an Edelbrock performer cam in my other 340 and it runs great. Basically stock and trouble free. Now if you're looking for high performance then that's a whole different ballgame.

[1 Wild R/T]

It all comes down to what are your goals. If you're just having it rebuilt and keeping it stock ( which I'm in the process now) I wouldn't buy a kit. Have the machine shop check the block to see if the bore is still good and you might get away with a hone and new rings. Of course cam bearings and freeze out plugs. I put in an Edelbrock performer cam in my other 340 and it runs great. Basically stock and trouble free. Now if you're looking for high performance then that's a whole different ballgame.

Thing is he's got a 73 340 so low compression which really hurts it.....   But clearly not ours to make choices so he's gotta decide.....

To the OP you say you've built engines, my question is how long ago?  Cause there have been lots of problems with parts quality in recent years that in the past weren't much of an issue, cams going flat which in the past was some horror story you heard but virtually never experienced have become common & expensive to fix....  I'd rather warn you up front rather than hear you crying the blues later....

[tdwnilla1]

Probably about 20 years since I built a motor......... Chevy 350 so pretty common. I am no professional but dont want to spend a small fortune either. I know I have some decisions to make so I am trying to get the most and best possible guidance I can. To my original question and like @Rich G. stated can I use the 71 340 rebuild kit if everything is within spec to do so ?

[1 Wild R/T]

Yup...

[tdwnilla1]

Thank you. Out of curiosity why in the hell is the kit only available for 68 - 71 ?

[1 Wild R/T]

Thank you. Out of curiosity why in the hell is the kit only available for 68 - 71 ?

Because no one who's building a 340 wants to build a low compression dog.....  The pistons you get in this kit are the early style high compression piston....  The block don't care what you put in it....   Back in the 80's all you could find easily were 72-73 low compression pistons....

[tdwnilla1]

Thank you.

[tdwnilla1]

Sorry if I keep asking the same questions but I have so many suggestions and responses it is difficult to keep track. No matter what I decide stroker like Chryco said, or what Rich G. Said about keeping it stock like I would like to with the exception that I have to at least have the crank turned I should be fine using my stock heads. Sorry to beat this all up but I don't want to screw anything up, these 340's are not very common and all Mopars are expensive to play with ...............not to mention it is an all original numbers matching car.

[RUNCHARGER]

Your stock heads can work with a stroker. You should at least put 2.02 intake valves in them no matter which way you go. If you were to use the stock heads on a stroker with no port work and no headers the tendency of the engine would be to perform stronger in the low RPM ranges than a stock 340.  Performance would drop off in the higher RPM ranges because of lack of airflow.

[tdwnilla1]

Thank you..........all of you for the great responses !! I have some homework to do

[Topcat]

The factory 340 air cleaner on a stroker would also cut down some on power.

...Change one thing and you have to change others.

That is the way of the World once you go after market.