400 w/455 crank

[OrbitGTO]

I'm a 17 year exploring engine options to put in my 72 GTO. You hear Chevy guys rattling off all kinds of stuff about "stroker" motors, and I was just wondering this: is a .030 over 400 with a 455 crank a stroker motor, or (since the bore would then be the same), just a 455? Is this even possible? I don't know anything about pin height differences in the two motors, or con. rod legnths, so can anyone help me out here? Thanks

[OrbitGTO]

I'm a 17 year exploring engine options to put in my 72 GTO. You hear Chevy guys rattling off all kinds of stuff about "stroker" motors, and I was just wondering this: is a .030 over 400 with a 455 crank a stroker motor, or (since the bore would then be the same), just a 455? Is this even possible? I don't know anything about pin height differences in the two motors, or con. rod legnths, so can anyone help me out here? Thanks

[Pete D]

The first difference is in main journal size. The 389-400s have a 3" main journal and the 421-428-455s have a 3.25" main journal.

While the small journal motors have just a 3.75" stroke, the big journal motors have two different strokes, 4.00" for the 421-428 motors and 4.21" for the 455. Each stroke will require a different pin heigth in the piston because all Pontiac rods are the same length, 6.625".

You can not put a 455 crank in a 400 block without reducing the main journals from 3.25" to 3.00". Some folks have done this.

Since the 400 has a stock stroke of 3.75" I would say that a 4.21" stroke would qualify it as a "stroker".

As to the reasoning for putting a 455 crank into a 400 block by machining the journals to a smaller diameter I will defer to those more knowlegable on the list.

[PONTIAC DUDE]

OH NO, Flashbacks to the CL board. Don't get Gach wound up again or he'll start talking about wages again!!!!!!!! & another 100+ posting.

[Dick Duclow]

While everything Pete said is true, he forgot one important thing. The 455 crank uses a wider thrust bearing. To properly fit a 400 block (after being turned down) the thrust area of the crank must be made wider to compensate for the narrower bearing. This requires welding up the thrust area of the crank and cutting to 400 size.

[PONTIAC DUDE]

Olds bearing with a spacer behind the thrust. Have 5 sets of spacers made. Saves welding the crank up

[Gach]

OrbitGTO, Yeah if you have a 400 block, an a 455 or 421,428 crank" you can put into your 400 block, you'll need to use either 455 or 428 pistons, that's no big deal. You don't have to have the crank welded, as Pontiac Dude says, you can install and Olds thrust bearing, and shim it. The people to call to have this done are Crank Shaft Specialist. They get around 350.00 to do your crank. You'll end up with either a 455 or 428 depending on which crank you use. So yes you'll end up with a stroked 400 . Butler can supply you with the bearing you need ( can't believe I said that name ) or you can call Rock & Roll engineering, Bruce has probably done 100 of these cranks ( this will be fun
) of cause it's probably allot easier, and cheaper to find a good used 455, but if you already have the block, and crank" there's no problem in using them, and it will save you time and agervation looking around. Or if you got 4 grand laying around you can buy a from Indian Adventures, they take Green
Stamps too.

Now this guy Pontiac Dude likes pinkies, and on occasion has bend known to par take in chocolate lip eating contest, but he really knows his stuff, and has a kick @ss car ( hope your ready to get your butt whip Bruce ) He also believes in the "Witch Doctor" my poor writing, an grammar skills keep me from saying anymore, I'm sure others will jump in, who have less experience, but are better
writers ( Dude don't say it ) anyway looking forward to seeing another Poncho on the road.

[Maniac]

Why don't you drop a 455 in it? That's what I plan to do if I can ever find one!!

[Gach]

ooh don't use that word (drop) around Pontiac Dude

[OrbitGTO]

First of all, I'd like to thank everybody for the time spent trying to help me out. Then, I'd like to re-ask a question posed a few replys ago. What would be the point of spending all this money to make a basicly stock 455 block? I don't know about around y'alls areas, but in North Texas, they're still pretty readily available. I was only asking because I have a ready-to-go 400 only lacking the rebuild kit, and was wondering if there would be serious performance gains (such as the Chevy SB strokers), or if I would just be boosting cubes. Once again, thanks for all your imput.

[Old Man Taylor]

Orbit GTO - You make a strange statement, "would it be serious performance gains, or just boosting cubes". Boosting cubes is the key way to getting performance gains. That is why they say "you cannot beat cubic inches". All else equal, the engine with more cubes wins. With all of that said, it is interesting that I don't have a 455 yet. The street car has a 428 and the racer has a 400.

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Jim

[OrbitGTO]

What I was intending to get accross was that I really don't see a point in chopping a perfectly good 400 block when it isn't going to accomplish anything that a new 455 block wouldn't do. If I made myself sound ignorant or uneducated, I apologize.

[Gach]

OrbitGTO, it was a very good question, that is offen ask. There's an old saying you never know unless you ask. We some times get into diferences of opinions, but only you can decide according to your pocket book, what's best for you. There's allot more benedfits of making a 400 into a 455, but they are much more costly, then just going with a rebuild kit, the power that can be obtain is well worth the money if that's what your looking for. The reason I say this is because it's all dependent on how fast your looking to go, and what your can really afford. Gach

[WARPed]

Well here are my two cents

To put a 455 crank into a 400 block you will end up with a more expensive 455. Cost wise you are better off finding a 455 core to start with and you would be money ahead. Unless your plans include needing to use steel or aluminum rods, aluminum heads, four bolt mains, etc and will be turned well over 6000 rpm you would see no difference/ benefit between the two block/crank combos.


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10.949@122.54
6.982@99.75
brooksa@gte.net

[Todd]

You really won't see much difference between a 455 block/crank combo and a 400 block/455 crank combo until you get into the sub-10 sec 1/4 mile range. (or sub-9 sec depending on the weight of the car). Even then, the diff can be measured in just a few 1/10's, so it really depends on what you are doing with the car. Full-boogie race car: you need to explore this (and every other option) to go fast and remain competitive. Street car: you just wind up with a more expensive 455 (as noted above).

[Old Man Taylor]

OrbitGTO - My apologies, I think I misunderstood your point. I agree with WARPed and Todd. Unless you are really out to optimize power output, you would be better off with a standard 455 than converting a 400 to a 455. The benefits of the converted 400 are primarily in the upper RPM range.

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Jim

[Paul Spotts]

The latest cool news out is a new 3" main cast 455 style (for the389/400 motor)crank coming out. It is going to cost around $500 and best of all - it will be new. No more welding etc. Since 400 blocks are dirt cheap and 455's are not - this will be a great new item for the Pontiac world. I don't have a definite date when. I can't wait for this one. I never liked welding or spacers even though there has been a lot of sucess.