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 Are remanufactured/rebuilt cranks bad
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CRM318
Tribal Scout

USA
30 Posts

Posted - 14 May 2014 :  5:56:05 PM  Show Profile  Reply with Quote
I just took the crank out of my 400 and there is some light scoring on the mains and especially the rod journals. The crank measures 2.99 and the rod journals measure 2.24. On the chance that I cant turn them down, are remanufactured or rebuild cranks from and autoparts stores bad? The reason that I ask is that I cant find a 3.75 crank on the market, they are all stroker cranks or kits and I am using #16 heads so I cant go that big.

1970 Pontiac GTO, Atoll Blue, 400, TH400, 3.73 Safe T Track

bigD
Indian Spirit

USA
643 Posts

Posted - 14 May 2014 :  6:45:39 PM  Show Profile  Reply with Quote
That strictly depends on what the specs are on the particular crank you get. The only way to know the exact specs is to measure or have someone to measure each journal.

Now, I had a real bad experience with a non-Pontiac machine shop way back yonder. So I started building my own motors. I tried to do everything I could, to not use local machine shops. So, for my 455's, I bought reground crank kits from my local wholesale parts warehouse. They all worked just fine. I built lots of 'em and they all ran 12's on the track, with never a single failure.

Now I'm quite sure that this would make most Pontiac engine builders today gag, and shout "don't do it", but that's the way I did it and it worked for me. Today, if I did not have a machine shop I could trust, I would contact one of the big Pontiac shops and find one that would grind a crank correctly for me and also supply the correct bearings. In other words it would be a crank kit, but done by a competent Pontiac shop. I have never seen any prices for this service. But I assume a phone call could get that info.

I'd call Len 1st, since his engine prices seem to be a bit more reasonable than some of the bigger name shops. Any of the Pontiac shops should have plenty of 400 cranks because of so many stroker builds using the blocks but not the cranks.

http://lenwilliamsautomachine.com/Home.html

Mr. P Body, who posts on this site, could give you a price from his shop, and would know if they even sell crank kits, separately.

Actually you can buy a new 3.75 crank, but it's forged and it ain't cheap.

Here's one for $645 + freight from Ohio Crank.

http://www.ohiocrank.com/pont_cranks.html

You can probably get a Pontiac crank ground, plus the bearings and freight for much less.

Edited by - bigD on 14 May 2014 6:54:39 PM
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CRM318
Tribal Scout

USA
30 Posts

Posted - 14 May 2014 :  8:22:19 PM  Show Profile  Reply with Quote
What goes into grinding a Pontiac crank that differs from others? How far down can you turn a Pontiac crank? I ask because, if my measurements are correct, they have already been turned down a bit. I have found a crank from Crankshaft Rebuilders Inc. Part# 21160 Its $244.00 after core charge and it comes with corresponding rod and main bearings. Seeing as the rod and main bearings would be about 200 dollars for a set, it seems like a good deal. Are all 400 cranks interchangeable?

1970 Pontiac GTO, Atoll Blue, 400, TH400, 3.73 Safe T Track
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bigD
Indian Spirit

USA
643 Posts

Posted - 15 May 2014 :  04:30:37 AM  Show Profile  Reply with Quote
quote:
Originally posted by CRM318

What goes into grinding a Pontiac crank that differs from others? How far down can you turn a Pontiac crank? I ask because, if my measurements are correct, they have already been turned down a bit. I have found a crank from Crankshaft Rebuilders Inc. Part# 21160 Its $244.00 after core charge and it comes with corresponding rod and main bearings. Seeing as the rod and main bearings would be about 200 dollars for a set, it seems like a good deal. Are all 400 cranks interchangeable?



(1) it's not so much that the Pontiac crank is that much different to grind. But it's the attention to detail that a particular crank grinder may or may not provide. Finishing each journal to within acceptable specs is not a haphazard sort of a deal. The grinder must know what he is doing and take accurate measurements of each journal, and continue grinding/polishing til each journal is exactly the correct size. Some grinders will take this challenge more seriously than others, and will produce a more accurate product. Some will just try to do a good enuff job to keep their job.

(2) You can turn a Pontiac crank down .060 or more. BBC cranks have rod journals that are .050 smaller than Pontiacs and they can be turned down at least .030 or more. So there is plenty of meat to turn the Pontiac crank down a LOT. However, you are limited by the size bearings that are available. Most brands for Pontiacs are available in .010, .020, & .030. undersizes. So, you can safely turn 'em that far. And for the rods, King brand even makes a .050 & a .060 undersize.

(3) Rod and main brgs $200 per set ? No they are not quite that high online. Here is just one set of Clevite 77 rods and mains I found on Ebay for $135.

http://www.ebay.com/itm/Pontiac-400-Clevite-Race-Main-Rod-Bearings-Set-/350078654634?pt=Motors_Car_Truck_Parts_Accessories&hash=item51825058aa&vxp=mtr

(4) All 400 cranks will bolt in, but there are some differences. Some of the cranks from the late '70's had a smaller flywheel centering ring. They were 2 1/2". All the earlier cranks were 2 3/4". It is also said that the earlier cranks were made out of better material. So I'd stay with one of the older 2 3/4" cranks. With these you must use a flywheel or flexplate with a 2 3/4" center hole. Also, if you run a manual tranny, some of the Pontiac cranks were not machined for a pilot bearing. So you'll need to make sure that the crank you get will accept a pilot bearing.


Edited by - bigD on 15 May 2014 5:44:12 PM
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CRM318
Tribal Scout

USA
30 Posts

Posted - 15 May 2014 :  10:53:38 AM  Show Profile  Reply with Quote
Thanks for the info!

1970 Pontiac GTO, Atoll Blue, 400, TH400, 3.73 Safe T Track
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Mr. P-Body
Running Bear

USA
2258 Posts

Posted - 19 May 2014 :  8:51:52 PM  Show Profile  Visit Mr. P-Body's Homepage  Reply with Quote

You get what you pay for...


NEVER buy a "reman" crankshaft if you don't HAVE to. That is, if your crank is salvageable, do it. Crank companies will weld a cast crank without thinking twice. A recipe for failure. You never know what comes in the box.

Clevite "77" bearings are antiques. They (Clevite) sold the name to Michigan Bearing in the late '80s. Now defunct. The "77" alloy was popular with the steel crank crowd for many years. Bearings are vastly improved over those days.

The Clevite "P" series (CB758) is the stock-replacement type. Simlar to Federal Mogul 1555CPA. The "H" series are the performance bearings. Better for steel cranks and large radii ("narrowed"). FM makes a performance bearing as well. 7020CH. We use King for most but "stock" applications.

Federal Mogul 4040M (3/4 groove) is the main bearing of choice for the 3" journal, "non-race". We use them and 113M ("race") in most, with the King 5511AM when we can find them. We don't use Clevite mains. Avoid full-groove mains in all but high-RPM applications. They oil the rods better, but will wear the crank out much more quickly.


There is nothing "special" about grinding a Pontiac crankshaft. Any crank shop that does high performance and/or diesel cranks can handle it. Tell them "low limit".

FWIW

Jim

Edited by - Mr. P-Body on 19 May 2014 8:52:59 PM
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bnorris_74
Crazy Horse

USA
1442 Posts

Posted - 06 Jul 2014 :  07:11:39 AM  Show Profile  Reply with Quote
TTT
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