Author Topic: 455 Bore question  (Read 408 times)

737driver

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455 Bore question
« on: May 25, 2019, 06:14:08 AM »
Last year I got a 455 motor as part of an estate sale I had purchased. Recently I took it to my engine builder/machine shop and found out that it had been bored out to .060 over and the crank was .040/.040. The builder suggested that the block could be bored .070 over (with new pistons) . He also mentioned the crank would have to be replaced as well. My question is, if the motor was bored to .070 over, would that cause any issues or be too much for the block. In all honesty I don't want to invest into a build if it isn't going to be a good idea to begin with.
thanks,
Jim
1979 Trans Am- Heritage Brown -W72 (Pontiac 400) -4Speed-WS6
1972 LeMans Convertible
1977 Trans Am
1972 Firebird
1971 Firebird
1970 Firebird
1977 MGB  Roadster Convertible

70_71_78

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Re: 455 Bore question
« Reply #1 on: May 25, 2019, 07:40:24 AM »
Considering that the newest block is over 40 years old, a sonic measurement of cylinder wall thickness is in order.  Rust in coolant passages and other factors may make those walls too thin to hold up.

hakitup

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Re: 455 Bore question
« Reply #2 on: May 25, 2019, 09:00:26 AM »
Another .010 really is that much more however I would ask the shop about sonic testing. When I bored mine to .060 I ask the shop and they told me it would be a waste of money, I have had no issues with my .060 (knock on wood).

From a machinist stand point .010 is really .005 removed from the wall and a sheet of paper is .003, I’m a visual person.

Tom H
"I don't know what you call it, I only know the sound it makes when it lies!!"

oldskool

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Re: 455 Bore question
« Reply #3 on: May 25, 2019, 04:23:35 PM »
If your cyl will clean up with just a hone, you might be able to get by with some forged 4.210 bore pistons, which are made with the 2618 material. This material expands more, therefore requires slightly more piston-to-cyl-wall clearance. The Icon IC888-060 pistons might work. ???

https://www.cnc-motorsports.com/pontiac-455-icon-forged-pistons-flat-top-5-5cc-4-210-bore-ic888-060.html

Shannon's Engineering is the cheapest source I've found for 2618 Race Tec customs.

https://shanonsengineering.com/products/auto-tec-small-block-pontiac-400-428-455-flat-top-pistons

But, you might come out cheaper buying a good 400 block(not a 557) that will safely bore .030 & going with a stroker assembly. 

Can't find any currently available .040 undersize 455 main bearings. So, you'll have to buy a good 455 crank core, or an aftermarket crank. 

Butler sells balanced stroker assemblies for most Pontiac V8's. They have both 4.21 & 4.25 stroke forged crank assemblies. A forged crank is $500 more. Can get Ross 2618 custom pistons any way you want 'em.

https://butlerperformance.com/i-24851151-butler-ross-468ci-4-211-balanced-rotating-assembly-stroker-kit-for-455-block-4-210str.html?ref=category:1459544

https://butlerperformance.com/i-24591348-butler-ross474ci-4-211-balanced-rotating-assembly-stroker-kit-for-455-block-4-250str.html?ref=category:1459544

These forged crank assemblies are also available for 400 blocks, in case your 455 block will not work.

   
« Last Edit: May 25, 2019, 04:26:00 PM by oldskool »

737driver

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Re: 455 Bore question
« Reply #4 on: May 25, 2019, 10:32:37 PM »
I got a good line on a crankshaft, but what I am seeing here is that the important thing would be to get a sonic check done . It makes sense that .070 bore is really not a major deal. I am not looking to build a race motor, just a good street motor to go in my 71Firebird.

Jim
1979 Trans Am- Heritage Brown -W72 (Pontiac 400) -4Speed-WS6
1972 LeMans Convertible
1977 Trans Am
1972 Firebird
1971 Firebird
1970 Firebird
1977 MGB  Roadster Convertible

Re: 455 Bore question
« Reply #4 on: May 25, 2019, 10:32:37 PM »

Aus78Formula

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Re: 455 Bore question
« Reply #5 on: May 26, 2019, 02:15:29 AM »
sleeve it

Re: 455 Bore question
« Reply #5 on: May 26, 2019, 02:15:29 AM »
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