# 428 or 455? (Do I Live Up To My Name?)



## Goatman455 (May 29, 2009)

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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## auburnconsulting (Nov 3, 2008)

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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## Goatman455 (May 29, 2009)

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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## BobG (Dec 20, 2006)

Goatman455 said:


> 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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## Rukee (Feb 8, 2007)

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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## geeteeohguy (Feb 2, 2008)

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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## Goatman455 (May 29, 2009)

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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## Rukee (Feb 8, 2007)

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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## 68greengoat (Sep 15, 2005)

Rukee said:


> 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.



geeteeohguy said:


> 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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## geeteeohguy (Feb 2, 2008)

My 389 starts out easily in 3rd gear with no problems. Maybe you actually have a 389.....


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## Goatman455 (May 29, 2009)

I appreciate all the help, I want to let this go, but I gotta hone in a bit more, I have this cam:


COMP Cams: Xtreme Energy™, XE262H: Cam & Lifters


My question is, how would this cam idle a 428 vs a 455? How rough would the idle be in a 428 vs how much more mild in the 455? 

Thanks again.


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## geeteeohguy (Feb 2, 2008)

Goatman, you will NEVER BE ABLE TO TELL BY THE IDLE QUALITY BETWEEN THE TWO. They're just TOO CLOSE in displacement. You're picking flyspecks out of pepper here. It looks to me like you're going to have to pull the motor, pull the heads, and pull the crankshaft to verify if the crank has been worked or changed, and what your actual stroke is. Figure on about 20 hours of hard labor and about $300 in gaskets and materials. But you just gotta do it.....if you don't, you'll never sleep again!!!


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## auburnconsulting (Nov 3, 2008)

did you see if the block says 455? what is the casting number of the block? our little 389 makes 425hp. we can start in 4th gear. had too when detent plate in trans was stuck on the gear fork. it pulls harder than any 455 i ever had. they were all stock 455's though. i have had alot of 400 as well and this is the best running pontiac engine i ever had. it does have 670 heads on it, balanced and blueprinted, edelbrock intake and holley.


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## jetstang (Nov 5, 2008)

If Pontiac is like Chevy, 427/454, bore is the same, 427 just has shorter stroke. Shorter stroke motors rev quicker and can go to higher RPMs. Depending on your application, light car, bigger gear, a short stroke motor will be faster. If you a pulling stumps with a truck or hauling heavy loads, then you want the big torque of a stroker motor. Cam, compression and head combination will dictate if you have a lot of torque. Big cams, high flow heads and big compression will not be 800 RPM torque motors, as they don't make power until 3,000 RPMs or so, that is why you run a high stall converter.


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## geeteeohguy (Feb 2, 2008)

Bore is not the same on a Pontiac. The Bore on a 428 is 4.12", and the stroke is 4", same as a 421's stroke. (The 421 had a 4.09" bore). The 455 has a 4.15 bore and a 4.21" stroke.....so it's the only Big-Journal Pontiac with more than a 4" stroke stock. You MIGHT be able to pull a sparkplug, stick a brass rod down the cyl with the piston at the bottom of its stroke, and very carefully turn the engine by hand and measure with a dial indicator guage the amount of travel of the rod from bottom of stroke to TDC (Top of stroke). I would use a piece of plastic or a brass rod or tube....something that won't get stuck in the engine or mar the cylinder wall.... You'll be looking for less than a quarter of an inch of difference between a 4 inch and a 4.21" inch stroke, so look sharp.


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## Goatman455 (May 29, 2009)

Well the block is a 428, but it is supposed to be. I was told it was a 428 stroked to 455. I bought it from a professional, I double checked everything, but I haven't pulled the motor apart to see.

It feels strong, I dropped my drive shaft and shattered the yoke (that's a lot of torque!). It doesn't seem to like to rev very well and has a lot of torque off idle but of course the cam as I showed you is very stock (xe 262).


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## Rukee (Feb 8, 2007)

The 428 crank is worth a bit more then a stock 455 crank, I bet the builder had no problem stroking it to a 455.


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## geeteeohguy (Feb 2, 2008)

I agree, Rukee. I have a '69 428 block in search of a crank....I pulled it out of my '65 in 1987 after I "upgraded" it to a Blue Journal crank!!! (Didn't like 7000 RPM on a Saturday morning long distance commute). 455 cranks are waaaay more common. Me, I'd rather have the 428 with the stock crank.


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## Goatman455 (May 29, 2009)

Rukee said:


> The 428 crank is worth a bit more then a stock 455 crank, I bet the builder had no problem stroking it to a 455.



Well this is certainly good news.


What happens if you just put the 455 crank in the 428? What about the bore? Can you just put the crank in but not bore it?


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## Ranger01 (Nov 14, 2008)

Its possible to do, but your engine would run like complete crap. You have 2 options, either live with the engine (if it aint broke, dont fix it), or have someone tear it apart to check if its what the guy says it is.

I for one am kinda getting tired of this thread. I shall repeat in massive letters in red type what you can do.


THE ONLY WAY TO FIND OUT WHAT BORE YOU HAVE IS TO TEAR IT APART AND MEASURE IT.

Hope that helps! :cheers

(Disclaimer: Im not tryin to be an ass here, but we've said many times that that is what you've got to do.)

Oh, and if you need any help with anything else feel free to ask!


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## Rukee (Feb 8, 2007)

Goatman455 said:


> Well this is certainly good news.
> 
> 
> What happens if you just put the 455 crank in the 428? What about the bore? Can you just put the crank in but not bore it?


Yes you can just swap the cranks and that's exactly how you 'stroke' it. And you do not need to bore the cyls to make a stroke job run right.


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## geeteeohguy (Feb 2, 2008)

Rukee is dead riight. 455 cranks are dropped into 421's and 428's fairly regularly. The only thing that changes is that the stroke goes from an even 4.00 inches, to 4.21 inches. It has nothing to do with bore diameter, and it is totally acceptable. I DO agree with Ranger01, though...;if you're that anal, and keep wondering, then you have no choice but to tear it down. If you do, let us know how much you want to sell the pieces for, after you loose interest and motivation to put it back together and re-install it in the car.


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## Goatman455 (May 29, 2009)

So if you just stroke a 428 with a 455 crank what does the displacement end up being? Bearing in mind that a 455 is a 457.6 cubic inches. Am I goatman448 or something perhaps? Edit: I guess it could be goatman450.


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## jetstang (Nov 5, 2008)

When stroking to 455, you have to bore .060 over. But, you have to change the entire rotating assembly, crank, pistons and rods, not just install a crank. If you just put the crank in the pistons would be out the top of the cylinder at TDC, correct. Unless you got rods and pistons to compensate for the new stroke. So, a stroker 428 is a 455, unless stock bore, then it would be a 441 CID.


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## geeteeohguy (Feb 2, 2008)

Jetstang, I don't agree. All the Pontiac rods are the same length. The bore is smaller (slightly) on a 428, and the stroke is .21" longer. That's it. If you have a .030 overbored 428, it's the same diameter as a standard 455, so with a stock 455 crank, you'd be at 455 cid. I don't have time to refer to the charts, this is off the top of my head, but check it out.....it's true!
Jeff


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## jetstang (Nov 5, 2008)

.21 stroke has to go somewhere, so thats assuming the 428 piston is a quarter inch below TDC so the new crank will go to a zero deck. I am sure they didn't leave 1/4" up top for stroke.


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## Rukee (Feb 8, 2007)

jetstang said:


> .21 stroke has to go somewhere, so thats assuming the 428 piston is a quarter inch below TDC so the new crank will go to a zero deck. I am sure they didn't leave 1/4" up top for stroke.


It's not going to raise the piston a quarter inch, it's going to raise it HALF of the 0.21 difference in stroke, or 0.105".


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## Goatman455 (May 29, 2009)

The car will idle without stalling with the idle adjustment screw backed all the way out. Is this unusual?


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## Rukee (Feb 8, 2007)

No, it's not. Prolly just the throttle shaft bushings are worn and it's leaking air causing the increased idle rpm's. As long as it runs good, run it!


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## Goatman455 (May 29, 2009)

Nothings leaking air and the RPMs were not increased, it was idling at like 400rpm.


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## Rukee (Feb 8, 2007)

You can't tell the throttle shafts are leaking air unless you test for it, and 400 rpm's is too low, 800-900 is were it should be at an idle.


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## Goatman455 (May 29, 2009)

Yeah, the screw kept backing itself off for some reason, at least the car wasn't stalling at that idle.


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## mf464p (Nov 4, 2021)

Hey, I have a 69 428 in my custom s. It is a 455 now I bored. 030 and installed a 4.210 crank. Very easy


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## BearGFR (Aug 25, 2008)

Like everyone has been trying to tell you, the only way to know for certain is to measure the bore size and stroke length, and to do that you'll have to pull the engine, tear it down, and measure. It's just not possible to infer by ANY aspect of how it runs/performs, no matter which cam it has, which intake it has, which carb, which exhaust system, or anything else.

I think perhaps NASCAR tech inspectors do have a device that's capable of measuring displacement without a teardown, so if you happen to know a friendly one that's probably your only option to tearing it down and measuring.

A factory 428 has a 4.120 bore, a 455 is 4.150 --- that's a mere 30 thousandths of an inch difference. You can't "eyeball" that, even with the heads off. You have to measure it with a precision measuring tool.
Likewise, a 428 has a 4.000" stroke, a 455 has 4.210" - that's less than 1/4 of an inch difference. Even if you do manage to insert something into a cylinder through a spark plug hole and manage to turn the engine over without your tool hanging a valve and bending it, good luck on measuring that small of a difference.

Wanna know something else? A strong running 428 that's cammed right, and fed right, will eat a 455 alive. That extra .210 stroke length imposes a pretty hefty penalty in terms of how high the engine is able to rev safely. A 428 will stay together at an RPM where a 455 is unlikely to, and if the engine is cammed to make peak torque up in that RPM range, it will make more power than the 455 can unless one spends mountains of cubic dollars to enable the 455 to rev that high also. It ain't cheap, and it's not guaranteed.

So, like others have been saying - if it runs strong and it's fun to drive, just enjoy it and don't sweat the details.

Bear


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## BearGFR (Aug 25, 2008)

jetstang said:


> .21 stroke has to go somewhere, so thats assuming the 428 piston is a quarter inch below TDC so the new crank will go to a zero deck. I am sure they didn't leave 1/4" up top for stroke.


 Yep, the difference is in the pistons. 455 pistons have a different pin height than 428 pistons. All stock Pontiacs use the same rod length. 

Bear


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