4:00” or 4.21?
 

Looking at a new build same block, 2 cranks., a 69 428 crank in a 1975 455 2 bolt block or a 4.21 crank in your 75 455 block. at .030 bore, .010 rod/mains. Your plans for the engine are serious street/ strip action. You want to build a strong lower end end strong enough to handle a hyd roller cam with duration somewhere around 245/255 duration at .050 and around ~.580” lift Your plans include either Ross forged pistons or ?. I will be using a quality 6.7 rod. Rear gears will be around 3.73 , appropriate 10”converter chosen as well. Exhaust will be 3" with Doug's headers. The heads will be aluminum round port 290-305cfm, Intake will be a RPM OR Torker II
So
1 ) Use the 4" crank in 455 block + .030. 440
2 ) Go for cubes and build a 2 bolt 462 .+.030
Car a 68 Firebird. Is there a difference of these 2 motors or not so much and why you chose either!

OEM heads or aftermarket?
The longer stroke crank would be my choice with either type of head.
Aftermarket head allow better breathing for either stroke.
Build one short block of each!

Torker 2 would be my choice either way.


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Aftermarket aluminum heads and again 1 block 2 cranks! Always liked the 4.00 strokes 428 fan. Just want some discussion on build.

My choice would be 4.21 crank, Less convertor needed and 3,73 gear be perfect. I like cam spec’s to easy 11.50 maybe 11.20 nice street driver. Pump gas.

I like the 4.00 crank. Like the way they rev. easy to use with your old iron heads and a dish piston to get some easy power. if going aftermarket then more cubes always helps.
Just my 2c

If your willing to dump at some point the 3.73 gears then I would build the 4.210" stroke motor since it will complement the port volume of the heads better, IF we are talking about Round port heads.

If these are D port aftermarket heads then even concidering the weight of your car I would go with the 440 build.

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

Cliff,

Thanks for the warning on the later shafts I went back and looked and this one is a 1967 Armasteel crankshaft is 9788787 if it makes a difference in your selection. Magged and turned 10/10. as is the 4.21 just thinking the 4.00 would not be as explosive on the lower end torque and more on the mid-upper range.

I've built 455's just like you described. I like the combo. One of the 455's dad used in his car for years. Edelbrock round port 330 cfm heads from Kauffman, and his custom ground hydraulic roller with 254/262 @ .050 and a little over .600" lift. Had an RPM intake on that one and was 10:1 compression. Ran great on pump gas and ran easy mid 11's in a 4,000 lbs. car in the heat of the day with a 400 turbo and 3.73 gears through a full exhaust system and DOT tires.
I liked it, torque everywhere. Made a very nice street engine, he drove it all over the place.

The lone 428 I built was a mild version that I did 25 years ago, with a turned down 428 crank to fit a 400 block, flat top forged TRW pistons that I machined a dish in to use with the #13 iron heads, had 9.7:1 compression, mild hydraulic cam 218 @ .050 and stock iron intake. It made a nice engine for a long time and ran great, but I just don't see those builds anymore. Seems most people when needing to buy a crank would just rather spend the same money on a 4.21" or 4.25" and go that direction, since the build cost is about the same it makes the decision pretty easy for most to go with cubes.

The 1967 Arma-Steel cranks are fine....

If this was a stick car I'd say 4". I love mine. TQ everywhere and likes to spin

The 4.21” crank is free horsepower.

I know our engine building friend Mick would wholeheartedly agree.

He thought it was a shame I didn’t put my 455 crank into the mix when I built my 421, but I was wanting to get most of the factory feel of a restored ‘64 421 HO so I didn’t add the 455 crank.

Of course if traction might be an issue the 4.00” crank might be a plus, but realistically either way you go you’re going to struggle to keep from going sideways. :3gears:

built a 455 with factory 4.210 stroke crank eheads 10.50 to 1 compression 234 238@.050 duration hyd roller cam 3.42 gears street car went 11.68@114 proven combination in a 1962 catalina

I'm with Nick that it depends on the transmission choice. I have had a 463 and a 433 in this car with no other changes. Both make plenty of power but I felt the 463's powerband was not well suited for my car or the way I drive it.

I would go with the 4.21 with good rods. It will make more power at any RPM vs the 4.00. I have never bought into the smaller is better theory. :p

Lol, sounds like a Jim Hand build!

In reply to post number 16 and a Apples to Aplles test, I guess you have never seen dyno reports where with stock heads the 455 peaks in hp at no more then 5200 while a 421 will hit peak hp at a 7% higher rpm and a 400 cid motor streches that to 13% higher rpm.
If you use aftermarket heads in such a controled test the same thing would take place, but at higher rpms, so buy into it!

So, if Round ports use the 4.21 stroke crank for the compliment of the ports, As, I only have the round port aftermarket heads...SO,
I was thinking the longer stroke builds a ton of low-end torque and with the lighter 68 Firebird then say a Lemans, GTO, GP, the 4.00 crank may be easier to hook. what compression and cam would you use?

Hmmm, 301 might be the hot ticket then!!:D