Is this 455 junk? Bore runout.
 

I pretended to be a machinist today, and measure the bore of my .060 over 455 that had really bad blow by. I pulled the motor in 2017. Did other jobs on the car and now have turned my attention to the engine. Compression and lookdown test were done before hand.

From what I measured I think the block is junk. Just looking for a second opinion.

i purchased a 4-5" inside micrometer and a bore gauge. The micrometer was calibrated then set to exactly 4.211 and verified with a dial indicator. The bore gauge was zero'd to the micrometer. Pistons are still in. Measurement were taking 1" down, Midway down and right at the piston about 4" down.

I don't know what the acceptable run out is.

Cyl Thrust / NonThrust
1
.0006 .0001 top
.0000 -.0006 mid
.0000 .0003 bottom

3
.0011 .0007
.0009 .0008
.0009 .0015

5
.0017 .0003
.0009 -.0002
.0009 .0014

7
.0005 .0005
.0005 .0000
.0005 .0010

2
-.0008 -.0010
-.0002 -.0013
-.0013 .0006

4
.0010 -.0001
.0002 -.0010
.0010 .0006

6
.0015 .0000
.0004 -.0004
.0010 .0013

8
.0009 .0002
.0000 -.0004
.0008 .0005

You didn't talk about what you want to do with it? Also didn't mention if it's a valuable block, like an SD-455. The numbers you report are a workable situation, especially if the block was .030" over. At .060, your options are much more limited. If your desire is to really pursue this, I would do 2 things. First install a torque plate and re-measure the cylinders. You will find substantial change in all directions, especially on a +60 455. Second, have the block sonic tested to see if you have enough cylinder thickness left to have a set of custom oversize pistons made. They can be made any size. If the taper isn't too bad and the sonic test is favorable, you could probably have a usable block at .070 over. Most likely the cost of custom pistons will be more than just buying a STD bore 455 core block. I bought 2 STD bore 455 blocks recently for $1000.00. A set of custom forged pistons will be around a grand. If it were an SD block I would try to save it. A particular numbers matching block for a 71-72 TA or a 71 Judge, you get the idea. Run of the mill 455's are still affordable. Good luck with it.

If you don't have a torque plate, you can torque a head with a gasket in place and measure from the oil pan side.

As long as the bores will clean up at .010” then the first to do would be to hard block it with the heads on or a deck plate up to darn close to the bottom of the water pump passages.

You should also really have a Sonic test done because a good shop when they do the overbore can shift the cutting work to make the best of the wall thickness you do have.

On the cylinders this is done on during mock assembly you will need to confirm that you still have enough rod side clearance.

You should also confirm the valve to valve notch clearance front to rear after this work, not only the normally depth checking.

A whole lot of SBM racers run big hp numbers with only .060” of bore thickness between cylinders once they do the hard block routine!

Naw. ring will ride that conical so toss the thought!

Redo: Make roundness reading at High-noon and 9:15, to attain blowby propensity.

THIS >>> https://m.youtube.com/watch?v=9GPstH1lUYY

So your saying that the measurements are worthless without a torq plate?

This sounds like more effort and expense then what its worth.

I was more trying to make sense of the numbers. Maybe i cant without a torq plate? I didnt know what is acceptable tolerance. Wasn't sure if a simple rehone and new rings is all it needed.

I didn't want to give up on the block unless it made sense. It didn't overheat and had good oil pressure. I just couldn't live with the massive blow-by spitting oil all over the block.

There are many other reasons for very bad blow by besides that some of the bores being off by .0015” or so!

What is / was the two compression rings side clearance in its groove?
More then .004” is not good if your looking for good sealing.

If you still have a few of the old rings and you square them up in a few of the bores what is the gap averaging at ?

The skirts on cast pistons can collapse without cracking which will make for the pistons rocking and loosing ring seal .
How do the piston skirts mic up.

If you do not want to go thru the expense of sonic testing then just hard block it and bore it for custom pistons and it will be fine.

If I am not mistaken NHRA Super Stock classes allow a .070” over bore and that’s what they all run!

What Paul is saying is that by measuring the bores with a torque plate installed you will be getting an actual view of how much out of round the bores actually are while under stress. Bores can distort as much as .0015 when the heads are installed and properly torqued. What I am seeing right now tells me that a simple torque plate hone to .070 and the use of a custom .070 over piston ( as Mike suggested) will allow to use this block IF an ultrasonic inspection reveals there is enough material left in the primary thrust surfaces of the bores ( around .125-.135 minimum). Less that that means you have a rather interesting beer can holder. 455s are notorious for core shift.

No not at all, and I have no idea how you would draw that conclusion from my post. I offered advice for you, so you can measure your bores if you dont have a torque plate to use, as someone else suggested you should do.

However, if your block has been honed with a torque plate you won't get accurate readings measuring the bores with nothing attached to the deck. One should also have the main caps torqued when measuring.

I appreciate all the responses.


Pistons are forged TRWs and still in the engine. Thus skirt collapse doesn't seem likely (Also first time I have ever heard that was a thing). I have not tried to mic the pistons or measure the ring gaps at this point.




That is good information. Thank you.

The motor is still mostly assembled at this point. I pulled 3 455 out of junkyard in the late 80s to make 1 complete 455 back in High School. It was rebuilt in 92 I believe. No Idea if a torq plate was used back then. It has NOT seen many miles in its long life. It jumped from my 77 GP that I still have to my 68 bird. It also went form a flat tappet Ultra-dyn to a roller stump puller. It was at that time the blow by issue really started to show up. blew out the oil pan gasket. Blew out oil from the valley pan gasket and valve covers when hitting higher RPMs. I would end up with a huge oil spills by the distributor with it dripping down the side and a trail of white smoke and burnt oil in it wake.

When I finally figured out it was a blow-by issue (2017) the responses I got back were , either the cylinders were out of round or the rings were bad. Both seamed likely since it is a 60 over bore and at one point I had a carb that was likely washing down the cylinders.

I thought the responses would be more cut and dry. I was expecting either people telling me the block was done or saying that a hone and new rings would do it.

Just running through the cost at the machine shop. I would expect I need to
1. strip out the crank and pistons.
2. Sonic check
3. remeasure the bores with a torq plate
4. Hard block it
5. Full rebuild to .70 over if it passes

I have a spare running 455 that I was debating on using. As well as other 455 engines that need rebuilt. At this point it seems more logical to move my cam and heads over to the other 455 I have. Not sure if that running 455 I have has forged pistons or not. That is my only concern with using it.

Don't scrap the block, Paul can sell you a lightly larger pistons/rings. Of course the sonic check will tell you for sure. Surely someone in CR can do this!!@