Turned down 428 crankshaft
 

Just wondering, does anybody still turn down 3.25” crankshafts to 3” to fit in a 400 block? Looking to build a 434-440” in a 400 block. Or does anybody have one for sale?

Turned down 428 crankshaft
 

Hi Adamo
I am no expert by any means but I think Butler sells a rotating assembly to accomplish what you are trying to do with your 400:

https://butlerperformance.com/i-2459...-4-000str.html


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Yes but I am looking at using a crank with Pontiac rod journals size

Where are you located? I'm in CA and have a 428 crankshaft I no longer need that needs to be cut undersized to use. Will let it go for cheap.

Thrust bearing widths are not the same you need crutch spacers and a olds main bearing set...

"...Looking to build a 434-440” in a 400 block...with Pontiac rod journals size. "

Not aware of a 3" main 4" stroke crank with a Pontiac rod journal size. I think it was member PONTIAC DUDE, down in Florida, that use to make & sell those spacer kits, for using the cut-down big main cranks in 3" main blocks. But after the cheap Chinese cranks came on the market, the demand went away. Doubt he still has any & doubt anybody else makes/sells em. Could be wrong.

But, forged cranks are available in the 4.210 stroke, 3.00" main / 2.249 rod bearing size.

They ain't cheap.

Here's a rotating assembly listed on the KRE site.

" Ohio forged 4.21 stroke crank with 3.00" main journals, Keith Black Forged Pistons, Eagle 6.625 H-beam rods, Total Seal file fit rings, FM rod and main bearings. $2,094.00 "

[url]http://www.krepower.com/Pontiac%20Rotating%20Kits.htm[/url

Just the crank is listed @ $800 plus shipping.

" 4340 forged 4.21 stroke with 3.00 main - Pontiac journal $ 800.00 "

http://www.krepower.com/Pontiac%20Cranks%20and%20Rods.htm

The cranks are listed @ $770 + shipping directly from Ohio Crank.

" 44004210P 4340 forged 400 4.210 stroke w/Pont journal $770.00 "

http://ohiocrank.com/crankshafts/#Pontiac

I have no idea if any of these prices are current, or if any of these places actually have any of these parts in stock.

I did this, I guess it's been about 22 years ago now. I didn't use a spacer for the rear main, simply had it welded up and re-machined. Still running fine to this day.

Any competent crank grinder can do this work, it's nothing special. The problem these days seems to be finding a shop that even has a crank grinding machine, and someone that knows how to operate it.

Most machine shops don't even have a crank machine, they are expensive and take up a lot of space, then they have to pay someone to run it all day, so they find it more productive to send the cranks out to someone else.

Not many here in Arizona that even do cranks. Depends on where you are located, there are only a couple that I even trust. A good one that Paul used got out of the business, not even sure where he's having crank work done now.

I use “marine crankshaft” in Santa Ana CA. Cranks are all they do. I would give ‘em a call see what they say.

Seems I remember reading that the problem is with the thrust bearing.

https://forums.maxperformanceinc.com...d.php?t=803915

http://forums.maxperformanceinc.com/...d.php?t=832920

Would somebody who knows please explain the EXACT problem.

I did a search but didn't find where PONTIAC DUDE advertised his product here.

If anybody can find a description of what he sold for this deal, please post it.

The width isn't the same, Also I had the rear main seal area welded up and reground too as that is not the same size either.

FYI,Marine Crankshaft will only work on forged cranks.They just welded my 400 crank to fit in a 301 block.Tom

Old school material on the subject from Bruce Fulper.


See 'HOW TO DO THE JOB'....

http://www.pontiacpower.com/FreeEngine3.htm


.

I remember Bruce talking about that decades ago. That and the fact that we had the parts just laying around prompted me to build one.

This was back before all these aftermarket cranks became available.

If I were to build one today, I'd just buy an aftermarket piece and do at least a 4.250 stroke.

4" stroke 455?
 

excerpt:

THE STROKER QUESTION

Another misconception that must be cleared up is what happens concerning the stroke when performing this mod. Cutting down the mains of the 421/428/455 crank has no effect on its original stroke, which remains the same as it was in the crank’s respective original block. When you install a larger stroke crank in a 400 block, you are not building a ‘stroker’ per se. (Although many guys just LOVE saying the word “stroker,) Rather, you are simply building the same engine on 3-inch mains. Let me explain.

A 400 has a standard bore of 4.120 inches. A 455 has a standard bore of 4.150 inches. By using a standard bore 455 piston in a .030-over 400 block, you end up with a standard bore 455 on 3-inch mains.

Similarly, a 421/428/455 share a 4.00 inch stroke. A 428 engine shares the 4.120-inch bore of a 400. You use a standard bore 428 piston when using a 421/428 crank in a 400 block, so you can end up with the proper deck height, just as you do when using the 455 piston on a 455 crank.

I haven’t singled out the 421 engine because most guys use the 1967 or later 14-degree valve angle cylinder head. If you’re going to use a 1966 or earlier set of heads with the 20-degree valve-angle heads, you must have custom pistons built. I can do that for you.

end quote

A 455 has a 4" stroke, as do the 421 and 428?

Did Pontiac ever make a block suitable for a 4.255" stroke, needed for a 455 if designed with a 4" stroke?

The 455 has a 4.210 crank factory. The aftermarket makes 4.250 cranks that drop right in to either a large main 455 or a small main 400. The 400 just needs some simple clearance surgery on the block itself to clear a couple of counter weights.
Larger stroke cranks are also available.

It's been a popular mod ever since the aftermarket has been making them. Especially since 400 blocks have always been more plentiful.

I did one years ago, dyno tested in Feb 1998....

1970 RA III 400 with 4 bolt mains.
455 crankshaft; machined for the block.

Our flow bench was a bit generous. I sold the heads to Paul Knippen and on his bench they were were 278-282 at .600" lift.

https://pontiacstreetperformance.com/psp/racerSC.html

P.S. ..... The Fulper info I posted above does not represent any endorsement. And unless specified it is not based on personal experience and is offered for general interest only :)

.

Ohio crank may cut the crank for you....and possibly do some spacers

That's cool Steve, I didn't remember you doing that with the crank. That's back around the same time I did mine.
I would have done a 455 crank instead but dad used that in the 428 block and left the 428 crank laying around.
Back then we were just using parts and pieces left over from other builds LOL

The first two 303 SCCA RA V engines I did used a 57-58 pontiac forged crank.We had to cut the mains too 2.5.Was no issue both engines still running fine after many years.At least with those there was not thrust issue like 3 1/4 main cranks.tom

As a retired ASE Master Engine Machinist( and crank grinder) I wholeheartedly agree. The most critical part of the process is welding the thrust flange and regrinding it to the correct width. IMO, a nodular factory 3.25” main crank that been correctly welded, re-cut to the proper width and nitrided is superior to a Chinese cast crank of dubious metallurgical origin