318 crankshaft specs

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mopardude318

mopardude318

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What is the measurement supposed to read when I measure the crank snout where the harmonic balancer slides on? What is within usable tolerance?

This is probably the ugliest crank snout yall have ever seen...

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If the balancer fits................ tight.........

Soooo, how did you get the balancer off that thing? Heat and beat? You could also get another crank, 318 cranks are everywhere. but if it is standard, and the journals are in spec, run it!
 
No...he pulled the balancer off by hand!

which is why he needs to know specs to know if his crank has to small of a snout or if the balancer has to large of an inside diameter
 
what year is your engine???????
By the way your 318 takes the same damper as a forged crank 273/318/340.(neutral balance)
If you go to mancini racing, this is how they list there dampers.
 
T67POWER said:
what year is your engine???????
By the way your 318 takes the same damper as a forged crank 273/318/340.(neutral balance)
If you go to mancini racing, this is how they list there dampers.
Click to expand...

I don't think the year matters now because it isn't original to my 68 cuda, which kinda pisses me off but oh-well, I'm over it....

FWIW, the block is a 77 318. Has the stamping 3/11/77...

If it's bad, I'll look for a forged 318 crank and just have it turned 10/10...There's a couple on craigslist for 50 bucks...lol
 
The year of the engine does matter.
The engine book i suggested you get, and you replied that you have not only one but two mopar small block engine books,they are what you need to look at.:read2:

The pistons weight is what matters per year.
A crank out of a 273 has a piston weight of 530grams.
A crank out of the same year 318 has a piston weight of 592grams.
If you go to use a 273 crank ,you will have to have it balanced to the 318 pistons USING MALORY HEAVY METAL$$$$$$$$$

You need to have the crank balance.SO....
If you find a 340 crank, you will have to balance it, BUT i believe you will only have to have weight taken out of the crank, due to the 340 pistons weight being .720 grams.
The shop should only drill the crank and not have to add malory heavy metal ,and that get's very expensive.
Look at the list and find out the weight of your pistons to know what way to go to say your self a buck possibly.
It also matters what the cost of the crank is so weigh it out.GET IT.:tongue3: :sad3:


LOOK IN THE BACK OF YOUR LARRY SHEPARD BOOK.
HOW TO HOT ROD SMALL BLOCK MOPARS.
 
Why go 273,or 340 crank and spend money getting it balanced instead of going with another 318 crank and have a basic plug and play set up? (that is if it comes down to him needing a crank of course)

Plus not to mention he has .060 over after market pistons.....which pretty much eliminates the hole piston weight aspect of everything...pretty much if you have to swap out the crank,you will have to have your rotating assembly balanced going off of what you say correct?
 
Ok then.
Was the engine balanced when built????
If the answer is yes????
If the answer is no??????
It does not make a difference.

The pistons and crank where not made together as an assembly.
Using a new crank means a RE-balance.

His new crank would have been balanced to a stock piston weight from the factory.
The assembly has to be rebalanced for sure,and knowing what the factory balanced each years 273\318\340\engines to helps if you have a choice.
All cranks are not balanced the same, even 318 cranks.

Just because you have a modern .060 over piston,how does that eliminate a balance job :scratch:
Any good motor is balanced.
This motor was possibly never balanced in the first place.
 
I think you missed the part where I said "pretty much if you have to swap out the crank,you will have to have your rotating assembly balanced going off of what you say correct?"

I did not say that it would not need balanced...what I meant by "eliminates" is that since he has punch over pistons...it eliminates the numbers you tossed out in grams for factory piston weights seems how his are not factory.

anyhow, I get what your saying and I agree.

but before he starts thinking about cranks and balancing and all that mumbo jumbo,he needs to find someone with a 318 crank to compare snout diameters to so he knows if his is within spec and to know if he has a wrong balancer or wrong crank or worn part or whatever the case may be.

Because he balancer should not have came off the crank by hand.
 
also, I have seen engines used with pre balanced cranks and the piston balancing was done by shaving metal off of the ends of the rod caps.

If this was the case with his engines balancing that was done when whoever did the machine work and installed .060 pistons and in the event he had to get another crank....As long as he reinstalls a pre balanced crank ....his assembly would be no different than it was before and should not require balancing.

just my .02
 
I will measure a 273 forged crank i have, since he wants the info.
He should buy a new damper and also get a new crank drift key.
I don't think the crank is bad ,even though it looks a little beat.
 
There is know such thing as a pre- balanced crank.
Any engine is balanced as an assembly.
Each part is balanced to the other.
 
T67POWER,

okay...I looked at my crank and compared the numbers in the book.

My crank has a casting of: 3751841, Which the book lists it as a 1974-1991 318 cast crank, and approx. 54 Lbs.

All my rods have this casting: 2406782, Which the book tells me they are from 1964-1971 273/318 rods and approx. 726 grams

I agree that cast 318 pistons weigh 592 grams, add a little more for the .060 oversize which mine are. (don't know what brand, very limited markings, and they are cast)

So as we can see, my rotating assembly is from all different years, but shouldn't matter, as long as it was balanced together. I'm guessing that MAYBE it was balanced by the last rebuild because there are holes drilled in 3 different counter weights.

I am aware that I will need a rebalance if I get a new crank, and yes, I am getting a new harmonic dampener, and will put a new crank drift key....
 
If the engine was never balanced then i would do so, and give them the new harmonic balancer and flex plate your running on the motor so they can make it right.
You have gone this far and this is such an important part of a performance engine.
Telling the shop all the information about the engines parts will help them, and it's good to know what was installed in your engine.
After they balance it,you will know how far off it was also.
The holes are drilled on factory cranks.
This does not mean that your engine was balanced when rebuilt.
 
T67POWER said:
I will measure a 273 forged crank i have, since he wants the info.
He should buy a new damper and also get a new crank drift key.
I don't think the crank is bad ,even though it looks a little beat.
Click to expand...

Any news on the measurement buddy?
 
Well, I measured with digital calipers and I got 1.531" evenly all the way around where the dampener slides on the crank...And where the timing gear presses on, the measurement was 1.565" evenly all the way around. So to me, I think the dampener was worn out, or the wrong one, not the crank...But we will see....
 
You should measure the O.D of the crank snout and the I.D of the dampner and see if someone here on fabo has another crank and dampner you can compare measurements with.

I find it VERY hard to believe that someone here on fabo does not have a 318 crank and balancer laying around....come on guys,help James out and run out to your pile of parts and run off a couple quick measurements for the man.

If it was a little more than a month ago i would have gladly helped you out bud but I already assembled my engine and I turned in my old crank as a core so I am not of much help lol.

I would assume the the snout would have to be pretty beat up for it to not be within spec unless for some reason it was turned or something.....I have no clue.

But odds are your crank is good
 
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