428 or 455? (Do I Live Up To My Name?) - Pontiac GTO Forum
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post #1 of 32 (permalink) Old 05-29-2009, 04:50 PM Thread Starter
 
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428 or 455? (Do I Live Up To My Name?)

Ok, so I need this issue resolved unfortunately. I purchased what I thought was a 428 motor that had been stroked to 455. I have identified the block is indeed a 1970 428, now how can I tell if the engine has been stroked.


I do have a comp cams XE 262 in there, how would the car idle/perform with this cam in a 455 vs 428? This may be one way we can figure it out, right now the cam seems very mild with a very smooth idle. I am sure its pretty mild either way, but there should be a difference right?


Any help on this topic would be appreciated, and obviously easier methods are preferred.


Thanks again, and heres to hoping I didn't get ripped off. I am an honest guy and good money was paid to ensure I got a 455, I just hope I have it. Either way, both are great motors, but I hope its not an unnecessary trick, just so the builder could save some labor.
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post #2 of 32 (permalink) Old 05-29-2009, 06:00 PM
 
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i do not belevive there is anyway to tell if it is stroked while still being together. you would need to know rod length and crank stroke. also over bore but that is usally adds only 5cc total
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post #3 of 32 (permalink) Old 05-29-2009, 08:10 PM Thread Starter
 
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Well if there is no way to tell why do people get one over the other? Shouldn't there be some driving characteristics at certain RPMS with my cam that signify which motor it is?
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post #4 of 32 (permalink) Old 05-29-2009, 08:57 PM
 
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Originally Posted by Goatman455 View Post
Well if there is no way to tell why do people get one over the other? Shouldn't there be some driving characteristics at certain RPMS with my cam that signify which motor it is?
you MIGHT try dyno testing ... the 455 should put out significantly more torque. Other than that, I don't know of any way to tell without either some very sophisticated test equipment or a teardown of some sorts.

OR

Perhaps you could pull one spark plug and hand crank the motor till that piston is TDC, then measure the travel to bottom and see how that compares to a stock 428 or 455 stroke. You could use a straw or something like it that is stiff but won't scratch anything.
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post #5 of 32 (permalink) Old 05-30-2009, 07:11 AM
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Pull the pan and look at the casting #s on the crank is the only way I know to be sure.
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post #6 of 32 (permalink) Old 05-30-2009, 09:56 AM
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Teardown and measuring the crank pins, bore diameter, etc. will tell you the answer. If it were me, (and I've been at it a long time) I would leave it alone and drive it and enjoy it. Sounds like you have a good running engine. Cams will perform differently in different engines: a wild, lopey cam in a 350 or 400 will be much more mile in a 455. Stop worrying about it and drive!!!
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post #7 of 32 (permalink) Old 05-30-2009, 02:24 PM Thread Starter
 
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I know you are right, but I would like to know whether the motor I paid for is as advertised. Can anyone who has driven both in stock form tell me the difference in how they perform. At RPMS like 1000 how does a 428 pull vs a 455 (obviously the 455 should have more low end torque) How much low end does a stock 455 have? My engine makes nasty low end I can start it in 3rd gear from a stop, but I can hear the motor bog a bit.

Again I know we are working with perceptions and not facts, but anything that could help me is much appreciated.


What about sound?
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post #8 of 32 (permalink) Old 05-30-2009, 03:08 PM
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There's no way to tell by sound or how the car runs or drives weither it's a 428 or a 455. Casting #s on the crank or messuring the exact stoke is the only way to tell.
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post #9 of 32 (permalink) Old 05-30-2009, 04:39 PM
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Originally Posted by Rukee View Post
Pull the pan and look at the casting #s on the crank is the only way I know to be sure.
Goatman455, I know you're looking for an easy way to tell if it's been stroked, there isn't one. If you must know, I can relate I'm anal about this stuff myself, roll up your sleeves and do what Rukee recommends.

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Originally Posted by geeteeohguy View Post
Teardown and measuring the crank pins, bore diameter, etc. will tell you the answer. If it were me, (and I've been at it a long time) I would leave it alone and drive it and enjoy it. Sounds like you have a good running engine. Cams will perform differently in different engines: a wild, lopey cam in a 350 or 400 will be much more mile in a 455. Stop worrying about it and drive!!!
It's a done deal, you already paid for it. All you're going to do is get pissed off and rifle wrenches around the shop if you find out it wasn't stroked. Run it, enjoy it and tell yourself it IS a 455. You'll feel much better...
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post #10 of 32 (permalink) Old 05-30-2009, 06:53 PM
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My 389 starts out easily in 3rd gear with no problems. Maybe you actually have a 389.....
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