1968 383 bore help

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Darren

Darren

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hey guys i pulled the heads off my 1968 383. The engine is a stock bore. my plan is to have the block honed and reuse the pistons with new rings. cylinders have a very slight ring ridge at the top of the cylinder walls. I was wondering what the specs are on keeping the stock bore so i can reuse the pistons and hone without boring? thanks
 
Darren said:
hey guys i pulled the heads off my 1968 383. The engine is a stock bore. my plan is to have the block honed and reuse the pistons with new rings. cylinders have a very slight ring ridge at the top of the cylinder walls. I was wondering what the specs are on keeping the stock bore so i can reuse the pistons and hone without boring? thanks
Click to expand...

You need to Mike the cylinder bores
 
Slight ridge means over bore! Otherwise you will have piston slap even with nerled pistons
 
Measuring it is the only way to know. There is a maximum tolerance for the bore.
 
There is also a tolerance for taper. According to the FSM if the cylinders show more than .005 out of round or a taper of more than .010 or the walls are scuffed or scored it should be bored.
 
Darren,

As a general rule, if the Engine is being used {for general performance}.

Mopar Big Block Cylinders should be 'Bored Out' if they are .006" 'Out-of-Round'.

The taper should not exceed .010".

cylinder-wall-measurements.gif
 
What is the best tool to measure with? And i take it is a must to have the pistons out? Thanks
 
It's called a "dial bore gauge". Can usually find ok ones on ebay. I have one. Works great to check out blocks before I buy them.
 
Dial Bore Gage

Best bet, is to ask your Machine Shop to check the Cylinder's for you.

I'm guessing that your Engine is either in your Garage, or still in the car.

Most Shop Guys will do a 'House Visit Check' for a 'nominal fee' of $20.00 or a 'Six-Pack' or a high-quality Coffee.

No reason to go out and purchase a Dial Bore Gage for $200 'plus'.



th
 
You should disassemble it and measure it yourself. Bad as I hate to say it, most shops will say it needs boring even if it may not. Besides, it's priceless buying the tool which doesn't cost much and learning to do something new yourself.
 
[ame="http://www.ebay.com/itm/2-to-6-Dial-Indicator-Bore-Gage-Set-0005-GRAD-Gauge-Engine-Cylinder-Hole-/360795250861?pt=LH_DefaultDomain_0&hash=item540112a0ad&vxp=mtr"]2 to 6 039 039 Dial Indicator Bore Gage Set 0005 Grad Gauge Engine Cylinder Hole | eBay[/ame]

This is the gauge I bought. Not a fan of the sweep on actual dial but had a standard one which fits as well. The unit is great for our occasional use. I was able to pickup a 400 block standard bore with only .002 taper & check all the bores myself. No more guessing & hoping.
 
To accurately check your bores, I would measure at TDC, BDC, and mid stroke. Parallel to the crank centerline and perpendicular to the crank centerline.


Maximum side load on the piston is when the crank is at 90° to the cylinder, meaning that the maximum side load on the piston is in middle of the stroke/cylinder piston travel. Measuring at the top and bottom of the stoke in the bore will not tell the maximum wear in the middle....
 
RustyRatRod said:
You should disassemble it and measure it yourself. Bad as I hate to say it, most shops will say it needs boring even if it may not. Besides, it's priceless buying the tool which doesn't cost much and learning to do something new yourself.
Click to expand...

Just as i was thinking. The car is a numbers matching car and i would llke to keep it standard bore if possible. Thanks
 
You bet. People are sometimes too quick to just say "bore it". If you've ever done machine work, you know right off the bat that Mopar blocks have a higher nickel content than most others and they do not wear as badly. Chances are you are still in spec for a STD bore.
 
my 1967 coronet manual says for a 383 max out of round before reconditioning. .005" for taper max .010"
 
I will be pulling the pistons this weekend. And looking for a bore gauge. Thanks guys
 
..............With it being #s matching even with it being near the max for taper and out of round it will still seal up good with cast rings, but remember u get what u pay 4 .......kim.........
 
Even if the bores measure "good", it means nothing until you bolt a head or torque plate on, and then you see why it makes a difference in ring seal.
.006" out of round and .010" taper?? that will be a piston knocking fog machine for sure.
I understand this is all relative to the budget and use, but you cant have sloppy bores and high expectations.
 
It simply depends on the application, and intended use of the Engine.

A} A weekend driver, for general 'show-and-go' driving.
B} Economy 're-fresh'
C} Budget Performance.
D} Medium Performance
E} Optimal Street/Strip Performance
F} Race-Ready
 
69 Cuda 440 said:
It simply depends on the application, and intended use of the Engine.

A} A weekend driver, for general 'show-and-go' driving.
B} Economy 're-fresh'
C} Budget Performance.
D} Medium Performance
E} Optimal Street/Strip Performance
F} Race-Ready
Click to expand...


Exactly. And good modern rings can make a world of difference with a "borderline" bore.
 
Darren said:
hey guys i pulled the heads off my 1968 383. The engine is a stock bore. my plan is to have the block honed and reuse the pistons with new rings. cylinders have a very slight ring ridge at the top of the cylinder walls. I was wondering what the specs are on keeping the stock bore so i can reuse the pistons and hone without boring? thanks
Click to expand...
Your maximum will be determined by the difference between the bore and the piston skirt and the total clearance. One means nothing without the other. The max wear is usually right where that ridge is, from the rings expanding under pressure of combustion. Yes, if the majority of the bore is in "good" shape you can hit it a good hone (not a 3 finger hone in your drill) and a fresh set of rings in and it will run and drive decent.

69 Cuda 440 said:
It simply depends on the application, and intended use of the Engine.

A} A weekend driver, for general 'show-and-go' driving.
B} Economy 're-fresh'
C} Budget Performance.
D} Medium Performance
E} Optimal Street/Strip Performance
F} Race-Ready
Click to expand...
Of course it depends on the application, but be realistic and honest here. If the bores are anywhere near .006" OOR it will smoke, use oil, be down on power, and have a short lived life.
A} nobody wants there weekend show car to smoke or be an oil burner.
B} the False economy of spending a little money to spend it twice later
C}Budget yes, performance no.
D,E,F not even close to being acceptable.
This is what most people dont understand,and then they claim the machine shop screwed them (and yes the often do) when the results are less than stellar. You cant have those conditions and expect it to not cause a problem.
This 413 had less than 500 miles on a refresh from a "Mopar Shop" no less and the owner could tell it was down on power, using oil, and not right.
Bores were only .0015-.0025" OOR and no, the rings werent sealing.
Piston%20ring%20wear%20413%20Chrysler.jpg


RustyRatRod said:
Exactly. And good modern rings can make a world of difference with a "borderline" bore.
Click to expand...

Modern rings -as I'm sure you know- are made very precise, and do not cover up bores that are out of shape. This isnt the '60's or '70's where it takes 1k miles to seat rings to "wear" them in. There is a good reason modern engines go the miles they do.
 
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