340 crankshaft stroke

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1969340dart

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I have a quesion for the engine builders,on a stock 340 Crankshaft the stroke is 3.31,at what point on the other stroke cranks do you have to go to different pistons.Or better what is the most stroke you can still use a stock piston.
 
ANY time you change the stroke, you need custom pistons. EVERYTIME.
I guess that if you have say pistons that are .100 down in the hole you could concievably offset grind the crank .100 to get the piston to zero deck. But it would cost a lot more than just buying a correct piston in the first place. You'd have to go to a chevy type rod and then your pistons wouldn't work with those rods. afu.

don
 
I was watching a car TV show, forgot whcih one, and they went to Egge for a tour. There custom pistom makers for old engines. Like Old HEMI's, early V-8 Fords, flat top Fords, etc....

They use a calulator to figure out custom piston diamentions for any given stroke.
Use of a stock piston is possible if you have a understanding of how to shorten piston skirts and crowns for clearance.
Otherwise, at best, a stock piston will only take a modest increase in stroke and work. But work how well is the question not to mention how long.
 
Well, truthfully, if a piston fits the bore, has the pin size you need for the rods you're using, and doesnt pop out of the deck far enough to hurt the top ring, it "fits". I wouldnt run it any further up then down about .040" from the top edge to keep it clear of the chamfer of the bores. You can use a low compression stock piston in some big block builds to get a "0" or close to "0" deck height with a longer stroke crank. I dont think any 360 pistons or low compression 340 pistons will work in a 340 block with a 3.58" (360) or 4" stroke. You can take a factory crank, and offset grind it undersize and increase the stroke as much as .060 if the crank is good to start with. The thing is, you are left with a piston with no valve reliefs, that's heavy, and that isnt very strong, and, the max you can get is only 10" more. Not really worth the cost, as offset grinding will cost more than std crank work.
 
The reason I am asking was because I already have stock crank and 3 sets of pistons I can use but was thing if going to either a 3.55 or 3.58 stroke and was wondering if the pistons I have will work.Thanks for the answers you guys are very helpful.Nice to find a site where people will try to help others out.

Thanks :salute:

Bobby Dodson
 
Hi, guys

I know that this is my first post and I really don't want to start
out on the wrong foot but, I thought that Tom Hoover built a 372
using stock 72, 73 340 pistons and a 360 crank. He took material off the
top of the piston and maybe off of the skirt, it's been awhile since I read it.

It was in the old Mopar books and a mag. had the details with
what he did. I still have the mag. somewhere. If a person had
the pistons already and had access to the machines or a friend
it can be done.

Danny
 
That may be correct.
Would you do it that way? If so, your braver than me.
 
See that line I put in about not having any valve releifs? You cant run a cam bigger than about .520 lift and 300°ish duration that way. Like I said, it could be done, but unless you have the machine shop in your basement, it's really not that cost effective.
 
Rumblefish360,
Would I do it? If I had the parts and was doing a mild street engine, yes.
I would not go out and buy parts to do it this way or tear my 340 apart
to do it.

Moper,
The largest cam I've ever owned was that hemi grind for my big block at
the time. I think it was 280° and .474 lift. I know some want that big stuff.
 
The thing is I only want to have to do this one time! I do not want to have t pull the engine out if at all possible! I prefer to go ALL NEW! I do nt like taking chances and although I am pretty good at engineering things I am no engineer!LOL Only thing that will be used is the block and maybe the crank but I am pretty sure there will be an early Christmas present in form of a new crank. I know how to sweet talk my Sweetie into letting me do things for my cars that most women would frown on there husbands doing! I really don't catch too much flak for spending a little extra especially when I can justify it! A good salesman can just about justify anything!LOL

Bobby Dodson
 
Dan0954 said:
Rumblefish360,
Would I do it? If I had the parts and was doing a mild street engine, yes.
I would not go out and buy parts to do it this way or tear my 340 apart
to do it.

Moper,
The largest cam I've ever owned was that hemi grind for my big block at
the time. I think it was 280° and .474 lift. I know some want that big stuff.
Click to expand...
Well God bless ya. I'm not sure I'd want to spend the time, not that I have any real time besides the mornings when I come home from work, to try that out. Perhaps when the kids get older and not need my attention that much.

Smart move on cam size. Your right. Most people want the bigger is better thing.
 
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