400 to 463 stroker with 455 crank
 

I have a 400 I am planning on putting a 455 crank in it. I already have the crank and a shop that will turn it down to fit. What I’m wondering is what have you used for the thrust bearing? That seems to be the main worry I’ve heard. Also I have a set of 16 heads and 6x heads which would you recommend for the 463

It’s really not worth dumping all that money into getting work done to a factory 455 crank to fit 3” mains.

Just get a new 4.210” stroke crank with the needed 3” mains.
You can get pistons to work compression wise with either of those casting number heads.

The 6X heads have a better intake port then the 16 heads and even though they only have a 1.66” exh valve it’s been shown ( at least in a 455 ) make more power up to 5400 rpm , which is fine for general street and street strip usage.

Either way you do go head wise be sure to get new valves.

I’d rather not spend that much on the stroker kit when I already have the crank and can get it turned for $200 and my machine shop can weld the block and hone it to spec. I just want to know where to source the bearing or shim. I’ve heard there’s an Oldsmobile one people use?

Yes, a Old’s thrust bearing needs to be used.

Nothing personal, but your nuts to get a iron block welded.

The Olds bearing with special shims designed to fit between the back of the bearing and the block. Each assembly has to be custom fitted for tolerance.

You don't hear about many doing the factory 455 crank into a 3-inch main these days.


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I have a 400 60 over with a factory 455 crank built by Pontiac Dude 18 or so yrs ago. Do you or anyone remember what method Ken used back in the day to make the 400 block and 455 crank work? I seem to remember him, for a lack of a better term, inventing/developing a block modification to make the combo work. Do you think it involved welding? My knowledge is weak in this area. Wondering if what ken did might help the OP with his project? Thanks

Yrs ago 1970 era. That friend of mine Jim built a 3 main block with a moldex crank about 463-7 ci.Then used the RAV heads in a stock car. Thst car was very fast the BB chevies couldnt keep up. I saw it run. Just saying. I'd use a stroker crank not a factory cut down. Think about the time and money then what if you a have problem? Not trying to rain on your ideas. Welding a block I wouldn't unless it was for numbers matching restoration for show. Sorry my 2 cts.

I built a 428 crank in a 400 block 26+ years ago it's basically the same deal. I ended up welding the crank thrust and rear seal area and then machining it to tolerance.

Not a cheap process even 26 years ago. Had to find a competent crank grinder that knew how to weld and repair cranks to make that all work. These days those guys are even harder to find.

Personally, I agree with Steve, I wouldn't bother with it these days, to me it's a waste of time and expense. Just buy the appropriate crank and run it. If you want to use your 455 crank, find a 455 block to put it in. Or I'm sure someone out there needs an OEM 455 crank for their 455, you could sell it to offset the cost of the new crank

"...welding the crank thrust and rear seal area and then machining it to tolerance".

X2

A 455 crank in a 400 block. I did the same to my numbers matching 400 block 28 years ago. The combo ended up making over 600 hp at 6400 rpm.

It lasted for quit awhile. The block is now sitting in a shed with cracks on the thrust, a cracked rod journal and with cracked mains.
This dispite competent crank grinder that knew how to weld and repair cranks to make that all work ! !

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We've done a handful of these and never had an issue welding the thrust. Some made a lot of power. If done properly I wouldn't worry much about welding as long as you have a good crank guy and it's used in a mild application. Be sure to let the guy know both the front and rear surfaces need weld. However the aftermarket offers cast crankshafts that cost about the same as prepping a factory crank properly.

When I have done them I just used an Olds thrust bearing then took a Pontiac thrust bearing, installed it into a pair of thrust main caps that are bolted together. Then chucked that up into the lathe and cut the shims out of the original thrust surfaces. Very easy to make.

Here's a page I had made from the info here on PY.

PY Thread on 455 conversion


:)

And that was my whole point. 26+ years ago that wasnt as much of an option. Today it's just a no brainer to buy a new crank done.

You don’t have to weld the crank or the block; you use spacers to locate the Olds thrust bearing. If memory serves me the total thickness of shims needed is .060. Tom S sent me one he and a friend of his fabricated. It is aluminum and very well made. I’ll be using it in the 3” main 421 I will be building for my Cat.

Yes, I know you do not have to weld the block, but the op stated in post 3 that the shop he was using would weld the block.

The spacers are the way to go.Im old enough to have known one of the great crank Masters,Joe Reath.He would not weld cast iron.He was one of the original welded stroke crank sellers.I had a 61-62 forged factory 389 crank that was a 1/2 in stroker.also had full counter weights that his shop had done.It was in one of the RA V engines I sold years ago.FWIW,Tom

The new stroker cast cranks are all 4.25” stroke with BBC RJ’s, the new cast 4.21” cranks with Pontiac RJ’s have been discontinued. The 4.21” stroker and a cut down N crank doesn’t have much advantage on a mild build over a new cast crank since the budget friendly factory forged 455 SpeedPro pistons have been discontinued, and only cast versions are available. The cost for new forged pistons and rods end up being a wash between a 4.21 and a 4.25 stroke, but the BBC RJ has more bearing and connecting rod options. If anything, the advantage for most things goes to the 4.25” crank.

On our cars we have 6x-4 heads with a 4.25” stroke Molnar crank 77 TA, 16s on a 68 GTO and a cut down N 4.21 crank with shims, and 96 heads on a 71 T37 with a 455. Of those heads, for a mild street combo I prefer the flat tops and the 6x heads over the 96 heads, or the 16 heads with dish pistons.

Agree, and with all that said I prefer the 4.25 cranks with bbc rod journals. Drop in deal and done with no home made spacers, no welding, no fuss. No real reason to make it any harder than it has to be.

If you are so set on using that 455 crank, get a 455 block for it.
No one is turning down 3.25 cranks to 3" these days. Its a VERY old school thing to do.
I would be suspect of any grinder doing such a grinding job for only 200$ anyway.
I do have a turned down/welded 3" main 4.25 stroke crank that I have had forever. I was told it was steel when I bought it, but it has the square cheeks like a cast crank. Sent it to Crankshaft Specialist back in the day and had them turn it and weld it. You can not see where they welded it, looks perfect but its one of those things where I am not totally sure if its steel or cast. leaning towards cast . Shiniest "cast" crank I have ever seen though.

Take a 1/8” drill bit to the flywheel flange if chips fall out it’s cast.