Maximum Taper on a 440...

[The Dartman]

What is the maximum allowable taper for a 440?

I am shooting for a standard bore rebuild on my '78 440 since there is very little ridge, and I can't afford new pistons. I will get the taper guage tonight, so I want to see if I'm in the right ballpark.

It looks like .003 to .005 is within the acceptable range, but I can't get any supporting documentation.

Thanks!
Dartman

[perfmachst]

hello, according to the chrysler service manual; .005 max for out of round,
.010 max taper in cylinder bores. max overbore is .040. just food for thought.

[lbk1956]

i saw the .010 value in a manual also. i rebuilt my 440 this summer, it had a small ridge, and the taper was .005 . i just had a shop hone it and i went back in with std pistons and it has turned out fine.

[duetz]

You can allways hone the cylynders out till they clean up and then have the machine shop knurl the pistons to take up the extra clearance.It,s cheap and very affective.

[Glen440]

I have a 440 in my car right now that is at max out of round, taper and has pitted cylinders. We proved almost anything can run and run good. It took a while for the cylinders to get decent compression but it did happen, I started at 130-150 and last check was 150-160. The only problem the engine has is it has alot of blow-by and was blowing the breather off on a 1/4 mile pass. I put a better breather on it and now it just sprays the hood a bit and drips on the header when it sits. Its a 77 block with standard 67 pistons.

It went 11.90@111.6 at 3750lbs. Just a mild setup with 516 heads, m1 intake and .528 MP cam. I figure there is 30-40hp hiding in a good shortblock.
I put it together cause I needed an engine and thats all I had.

I say you'll have no problems.

[Billydelrio]

I ran knurlled pistons in my .012" tapered 273 cylinders for eight years. It ran so good that I was in no hurry to build a replacement engine. Those same knurlled pistons are soon going into another freshly bored 273 block.

[MoparMarcIdaho]

Ever look at a top fuel motor going together at the track? They are loose as hell.The bad thing about taper is that every time the piston travels the rings flex.As long as they dont break and seat somewhat it will put out more power due to less friction.Dont get the end gap too tight because it will close up on the bottom of the cylinder.If you want to get 100.000 miles out of it bore.If you want a short lived high output drag mill cut the ridge and install.

[The Dartman]

You mention ridge, so I thought I would bring up another item:

My engine builder friend states that the since we are reusing the stock pistons, and the ridge is paper thin, that using a ridge reamer is not necessary. He even went a step further and said that it is very easy to ruin a stock bore, along with the block, for something that is not necessary for a straight rebuild. We thought a simple honing would be sufficient.

Any thoughts on this?
Dartman

[MoparMarcIdaho]

If you can catch it with your fingernail it needs to be dealt with.If you dont want to use a reamer a die grinder with a stone or carbide will do fine.You stand the chance of breaking a ring land if you dont do it.

[Billydelrio]

If the ridge is not removed and different pistons (same bore) are used, the top ring could be higher in the bore and pound against the ridge.

[The Dartman]

The same pistons, the same bore will be used so the idea is that the slight ridge and the rings landing in the same place will get by without a ridge ream. I guess the jury's still out on this one. There are only two cylinders that even catch my fingernail as I drag it accross, so the ridge is slight.

Here are the specs I came up with in taper and OOR:

Cylinder #1
Bore: 4.323
OOR: .002
Taper: .0005

Cylinder #2
Bore: 4.324
OOR: .001
Taper: .001

Cylinder #3
Bore: 4.324
OOR: .001
Taper: .001

Cylinder #4
Bore: 4.323
OOR: .001
Taper: .001

Cylinder #5
Bore: 4.324
OOR: .003
Taper: .0015

Cylinder #6
Bore: 4.324
OOR: .001
Taper: .0015

Cylinder #7
Bore: 4.324
OOR: .001
Taper: .001

Cylinder #8
Bore: 4.323
OOR: .001
Taper: .0015

This still looks like an excellent motor to do a standard bore rebuild on to me.

Dartman

[Billydelrio]

I don't see a taper problem. Re-ring it and go.

If a block/rod/piston combination is going to be ran at the same rpms that formed the ridge, then the ridge will not be a problem. If the same engine will see higher rpm than before, then rod/piston stretch at the higher rpms will cause the ring to be forced against the ridge.