# I need an Engine Whiz!



## ddearborn (Aug 24, 2009)

Ok I have a 455 block that has been bored .040. The block has a 400 crank 3.75 stroke and 1970 Ram air 3 heads. I am worried I will have to much compression to run pump fuel. I have been told by some that I could have anywhere from 11.5:1 to 12.5:1 compression. I dont want to put it all together to find out my compression ratio is too much. I bought this and a 1968 GTO in 2001 for $1500 and I am just now getting around to put it all togther. If anyone knows what kind of compression I am gonna get let me know.


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## crustysack (Oct 5, 2008)

you dont need an engine whiz- just go here and punch in all numbers Engine Size and Compression Calculator and that will give you your answer


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## 05GTO (Oct 6, 2004)

ddearborn said:


> Ok I have a 455 block that has been bored .040. The block has a 400 crank 3.75 stroke and 1970 Ram air 3 heads. I am worried I will have to much compression to run pump fuel. I have been told by some that I could have anywhere from 11.5:1 to 12.5:1 compression. I dont want to put it all together to find out my compression ratio is too much. I bought this and a 1968 GTO in 2001 for $1500 and I am just now getting around to put it all togther. If anyone knows what kind of compression I am gonna get let me know.


How did you get the 3.00" 400 crank to work with the 3.25" 455 journals?


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## 68greengoat (Sep 15, 2005)

It's my understanding that you'd need 87cc heads to get around 10:1 compression with your 455. Your heads are 72cc. I believe that will put your compression ratio too high. Crunch the numbers like Crusty said to be sure....


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## geeteeohguy (Feb 2, 2008)

I'm with O5 on this one. How on earth do you run a a 3 inch 400 crank in 3 1/4 inch 455 bearing journals? I wonder what parts you really have.


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## ddearborn (Aug 24, 2009)

sorry my mistake guys too wrapped up in too many #'s in my head. the crank is out of 428 with a 4 inch stroke. I will go to the web site and check it out. Thanks!!


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## ddearborn (Aug 24, 2009)

That web site is telling me that I have a 439 cu inch engine. The engine being bored out is a 468. So it is giving me the wrong calculations. Any other help is greatly appreciated. Here are the simple specs

455 block
Bore- 4.180 = 468 cu inch
Heads- ram air 3 72cc-2.11 intake 1.77 exh
crank # 9782769- 428- 4 inch stroke


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## AlaGreyGoat (Jul 6, 2006)

Actually, the calculator is correct for 4 in stroke at 439 ci.
You need 4.21 stroke of the 455 and it will be 462 ci.

Larry


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## 68greengoat (Sep 15, 2005)

ddearborn said:


> That web site is telling me that I have a 439 cu inch engine. The engine being bored out is a 468. So it is giving me the wrong calculations. Any other help is greatly appreciated. Here are the simple specs
> 
> 455 block
> Bore- 4.180 = 468 cu inch
> ...


If your block was bored out .040 as you originally stated, the bore would be 4.1910. Factory bore for a 455 was 4.1510 and a 4.21 stroke. At a 4" stroke you would have 441ci. That 4" stroke is killin' ya..... Calculations are right. I have a 455 bored .030(4.1810) with the standard 4.21 stroke which comes out to a 462ci. That's exactly what I thought I had b/4 using the above calculator.


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## geeteeohguy (Feb 2, 2008)

You need to trade that 428 crank for a 455 crank. Should be easy to do..428's are a lot more scarce than 455's.....In fact, I need one for an old 428 block I have laying around!


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