[Skippy597]

Hey guys and happy New years.

Planning a build for my lemans and I'm solidly leaning towards the 428 just because it's cooler and less common to see. But have also considered the 455 but am unsure of the main differences. Is is just a displacement difference or is one better to build than the other. I'm not worried about the 27 extra cubes and both would be built the same Kauffman heads and stroker crank... Blah blah blah. Going for a low revving 550hp.

Would appreciate some input

Also because I'm sure someone is going to suggest it, I do not want to go with a 400. I know the smaller main journals is ideal but I'm not planning a 7000rpm screamer. And I'm honestly tired of seeing everyone having a 461 stroker based on the 400. Just my 2 cents.

[nas t eh]

Preference and availability. Motor mount holes.
What block do you already own or have access to?
If you put a stroker crank in your 428 is it still a 428?

[RocktimusPryme]

I gotta kinda echo the above, if you are using a stroker crank why worry yourself over it?

Im one of the dastardly stroked 400 crowd so Ive never done a bunch of research into the 455s, but I think I have read on here that there are some weaker blocks from the mid 70s. The 428 would likely all come from the years with no bad blocks. Someone else may correct me on that.


Honestly for cool I think I might try to replicate that 350 Pontiac build that was just posted. Hits the numbers you are after and would certainly save you some money in the up front cost of the block.

[Scarebird]

Originally Posted by Skippy597

Hey guys and happy New years.

Planning a build for my lemans and I'm solidly leaning towards the 428 just because it's cooler and less common to see. But have also considered the 455 but am unsure of the main differences. Is is just a displacement difference or is one better to build than the other. I'm not worried about the 27 extra cubes and both would be built the same Kauffman heads and stroker crank... Blah blah blah. Going for a low revving 550hp.

Would appreciate some input

Also because I'm sure someone is going to suggest it, I do not want to go with a 400. I know the smaller main journals is ideal but I'm not planning a 7000rpm screamer. And I'm honestly tired of seeing everyone having a 461 stroker based on the 400. Just my 2 cents.

I will be offering a 4" stroker 400 (giving 440 cubes with 0.065" overbore) soon with 85cc KRE heads soon. This of course has the 5 bolt motor mounts.

[johnta1]

I'd say the motor mount holes may be the only true 'difference'.
The 428 would be only for the 2 bolt engine mounts, while the 455 can use either 2 bolt or the newer 3 bolt mounts.
The 455 blocks from 1970 through 1974 would be the one to use for the 455's. (75 and up are questionable, but for your app probably OK)

Both will take the stroker cranks, but have to make sure the cranks are for the bigger mains. (not 400 strokers)

To me the extra cubes of the 455 block would make a difference and same price basically.
(no high rpm screamer there)

[steve25]

Either engine in a true street car built with good flowing aftermarket heads would be very hard to completely hook up , so to me it really boils down to how heavy your car is and it’s rear gearing in terms of what you build.

If your running a factory 4 speed then the added torque of a well built motor using just a 4.210” stroke no less a 4.250” stroke is going to eat up a factory 8.2” rear in no time!

I came up with a ratio for this in terms of added torque over a well built 400 and being able to beat on the car hard in terms of on the street usage.

Let me know what you folks think please.

The ratio goes like this , for every added 50 ft lbs of torque a given motor makes above a 3.750” stroke motor, you will spend a additional 3000 to 4000 Dollars to not bust up driveshaft, suspension and rear end parts when you beat on it over & over!

So in short the ratio is about 80 to 1.

[grandam1979]

Originally Posted by johnta1

I'd say the motor mount holes may be the only true 'difference'.
The 428 would be only for the 2 bolt engine mounts, while the 455 can use either 2 bolt or the newer 3 bolt mounts.
The 455 blocks from 1970 through 1974 would be the one to use for the 455's. (75 and up are questionable, but for your app probably OK)

Both will take the stroker cranks, but have to make sure the cranks are for the bigger mains. (not 400 strokers)

To me the extra cubes of the 455 block would make a difference and same price basically.
(no high rpm screamer

This is all good advice in my opinion ^^

[Skippy597]

Originally Posted by RocktimusPryme

I gotta kinda echo the above, if you are using a stroker crank why worry yourself over it?

Im one of the dastardly stroked 400 crowd so Ive never done a bunch of research into the 455s, but I think I have read on here that there are some weaker blocks from the mid 70s. The 428 would likely all come from the years with no bad blocks. Someone else may correct me on that.


Honestly for cool I think I might try to replicate that 350 Pontiac build that was just posted. Hits the numbers you are after and would certainly save you some money in the up front cost of the block.

That 350 build was super impressive for sure.

I get what your saying about the crank it's more of a back of my own mind thing that I think the 428 is cooler because you see less of them.

[Formulajones]

The key words I took from the OP post was "low revving and 550hp"

That right there is going to be a hell of a lot easier with more cubes. So I'd be looking at 455+ to get that done.

Really doesn't matter what block it's based off of. It really boils down to what's available to you. Most of the time, finding a good 455 block these days is getting a little more difficult, so most go for the 400 stroker builds simply because 400 blocks are more plentiful and generally a little cheaper.

[Skippy597]

Originally Posted by steve25

Either engine in a true street car built with good flowing aftermarket heads would be very hard to completely hook up , so to me it really boils down to how heavy your car is and it’s rear gearing in terms of what you build.

If your running a factory 4 speed then the added torque of a well built motor using just a 4.210” stroke no less a 4.250” stroke is going to eat up a factory 8.2” rear in no time!

I came up with a ratio for this in terms of added torque over a well built 400 and being able to beat on the car hard in terms of on the street usage.

Let me know what you folks think please.

The ratio goes like this , for every added 50 ft lbs of torque a given motor makes above a 3.750” stroke motor, you will spend a additional 3000 to 4000 Dollars to not bust up driveshaft, suspension and rear end parts when you beat on it over & over!

So in short the ratio is about 80 to 1.

That's a solid way to think of it. Maybe I shouldn't even bother with a stroker and just do a stock stroke 428 build. I do plan on upgrading to a 9" down the road but currently have an 8.2 with 3.26 and limited slip. Also yes I have a m20 Muncie that I will be running.

[hurryinhoosier62]

IMO, it’s a case of six of one; half a dozen of the other. You could get into rod ratios, bore to stroke ratios, etc., but outside of all out racing these mean little in a street engine. There are conversion engine mounts to use five bolt mounts with two bolt blocks or vice versa. It’s going to boil down to what is your preference and how large is your budget. IMO, putting a 4.00 or 4.21 3” main stroker crank in a 400 block is actually a bit better since you ARE reducing your main bearing speeds(3.00 verse 3.25).

[Stan Weiss]

Originally Posted by Skippy597

Hey guys and happy New years.

Planning a build for my lemans and I'm solidly leaning towards the 428 just because it's cooler and less common to see. But have also considered the 455 but am unsure of the main differences. Is is just a displacement difference or is one better to build than the other. I'm not worried about the 27 extra cubes and both would be built the same Kauffman heads and stroker crank... Blah blah blah. Going for a low revving 550hp.

Would appreciate some input

Also because I'm sure someone is going to suggest it, I do not want to go with a 400. I know the smaller main journals is ideal but I'm not planning a 7000rpm screamer. And I'm honestly tired of seeing everyone having a 461 stroker based on the 400. Just my 2 cents.

If both the 428 and 455 blocks get the same stroker crank and are standard bore. There is about 7 ci difference.

Stan

[Steve C.]

" Going for a low revving 550hp."

Using KRE aluminum d-port heads ? And ported for your goal ?

Example here, un-ported KRE d-port heads and 60919 cam.
4.185 x 4.25"/ 467 cubic inches

502 hp at 5200 RPM

Nice low revving truck motor combo.

https://pontiacstreetperformance.com...d455MikeG.html

And another example, same cam and un-ported heads:

https://www.motortrend.com/how-to/05...-dyno-results/


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[68WarDog]

In stock form how far in the hole is a 428? I like the op goal of an uncommon 428 build. I recently scored one myself, but considering a 440 build with it.

[Skippy597]

Originally Posted by Steve C.

" Going for a low revving 550hp."

Using KRE aluminum d-port heads ? And ported for your goal ?

Example here, un-ported KRE d-port heads and 60919 cam.
4.185 x 4.25"/ 467 cubic inches

502 hp at 5200 RPM

Nice low revving truck motor combo.

https://pontiacstreetperformance.com...d455MikeG.html

And another example, same cam and un-ported heads:

https://www.motortrend.com/how-to/05...-dyno-results/


.





.

That's perfect, I don't really care about having to get 550, just thought it was a good goal to shoot for.

[Skippy597]

So I'm planning an old school cool build. For example I'm planning on running a offy intake and dual Carter afbs, Mickey Thompson valve covers, wood/phenolic carb spacers, solid flat tappet cam/lifters, scrubbing the heads of any markings and painting them with the block. And just think it would be cool to say I have a 428 under the hood. I'm willing to pay the premium as long as there isnt any reason to avoid them.

Also not trying to throw shade at the 400 crowd. There is a definite reason why they are so desirable but I just want to be different.

[Half-Inch Stud]

" Yea, i run a bored and stroked 428 "

No mystery here for the 455 vs 428; bore up as the block allows.
455 for street duty, and 428 stroke for a wee higher RPM, for race duty, for highe HP.

Yet, realistically, i tink the valvetrain limits HP-acquired RPM, so a 455 Stroke with the good valvetrain is....for the ET and MPH Win. Just not my game. Street 455 to 5500 RPM is plenty of excitement. Really.

[tom s]

Weird,I have 3 cars right now,ALL with 428s?I have a 389 and a 455 sitting in my garage holding the slab down.Tom

[Skippy597]

Originally Posted by tom s

Weird,I have 3 cars right now,ALL with 428s?I have a 389 and a 455 sitting in my garage holding the slab down.Tom

Well you're a legend so I would expect nothing less. Actually the fact the you run them tells me all I need to know. So I'm sold on the 428.

Really appreciate all the feedback guys, I love this forum.

[326HO-Lemans]

I have a 69 360hp 428 I've been hoarding for many years. Wanted to run it in my 74 firebird at around 500hp but after reading the following by Cliff R I'm not so sure....

"I would tread softly toward the 1969 4.00" crankshaft. I've seen just enough of those crack and fail to avoid them. Not trying to put a big black cloud over anyone's 428 build but over the years I've encountered several of those cranks that were either cracked or broken. One was in an engine I bought and put it in the Ventura. The crank ended up being cracked and took out the thrust bearing.

During my search for a replacement I found several others cracked or not serviceable and my crank grinder told me to go another direction. I ended up getting an earlier crank with a different casting number and it was fine and survived may years of abuse until I replaced that engine with a 455 back in 2000.

That was quite a few years ago but during my research I found different casting numbers for 421/428 cranks. Some early were Arma-Steel, then they used a casting from 67-69, then another casting in 1969 with a different part number. I'm pretty sure all of the bad ones came from 1960 360hp engines, but they may have used that casting in other. Anyhow, it was the later one that we found issues with.........FWIW........Cliff"