Difference between '70 and '71 & up pistons

I'm buying a borescope to take a look at the inside of the cylinders of the '71 455 motor in my '70 GS455. I can't find out who rebuilt it but, it runs very strong and I want to see the pistons and valves to know if it was rebuilt with higher compression and bigger valves.

So, can someone post pics of 1) Top of a 1970 455 piston and 2) a 1971 or later piston top.

 

I have 70 stock pistons and stock 72 pistons if no one else does. I will have to go tm my storage unit and look for them.

Nelson

 

Ray,
I found a couple of my pictures.

Top picture : My 72 stage-1 455 before I rebuilt it
Second picture : My 70 GSX 455 before I rebuilt it.

Both are stock, I hope this helps.
Nelson


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I think you will have a hard time with a scope to see the difference in dish between a 70 and 71......its hard to tell on the bench sometimes without being able to physically measure the depth of dish

 

If nothing else, you’ll be able to see if they went with stockish dished pistons, or flat-tops.

Which borescope did you get? I bought the Vividia with an articulating head about 2 years ago for $200 and the video & pics are pretty good.

 

I haven't bought the scope yet and still shopping for one on ebay. Were you able to look up at the valves with your scope?

 

This seems like it's going to be a tricky "look" without the right scope. Imo

 

After looking at some pics, I think you're right. What about compression numbers? The compression on my 455 motor with Wiseco Pistons and 10.5 to 1 was about 190 psi per cylinder. But, that was with a mild cam with more overlap than a stockish motor. Would the static compression numbers on a 70 motor be that much higher than a 71 & up motor?

 

Hell, maybe I'll just run it through the quarter mile once or twice. An 8.5 motor should run at least 5 MPH slower than a 10 to 1 motor.

 

Stock pistons, low or high compression, will be hard to tell in the motor but you will be able to see the valves and see if they are closer or have a gap.

 

Ray,

You might want to find someone in your area that has this machine:

https://store.katechengines.com/whistler-compression-ratio-tester-p174.aspx

Maybe call the company and see if they will tell you if any business in your area purchased one.

It would be the most accurate way to test the compression in your engine, without taking it apart.

JW

 

In order to see the valves with the bore scope, you will need to make sure that piston is at BDC, then take the scope and tie some string or fishing line around the end.... insert the scope all the way to the piston and then pull the string so the camera points up at the valves. I’ve done this before and it works.

 

Absolutely. It has a head that can turn 180 degrees. Here is a link to the one I bought. Looks like the price went up to $250. Well worth it for what I use it for.

https://www.oasisscientific.com/viv...g-borescope-videoscope-inspection-camera.html

I use it mostly to inspect exhaust valves in aviation engines, but also look at cylinder walls, piston tops, and even a few cam lobes.

 

Most of the ones now have a 45° mirror attachment that avoids this. Just poke it in a sparkplug hole and turn it until it faces the valves.

 

Ok, the pistons on the right are labeled 73 and 76,
Any idea what year the pistons on the left are?
JIM

 

They all look to be low compression