Crankshaft prep

[Mb125]

BME rods and factory pontiac rod journal and I spin my 462 to 7000 rpm. Oil pressure still reads 60 psi at 7000 rpm after 5 years im using melling select oil pump and no fancy mods to crankshaft or block and .0032 rod bearing clearance.

[keith]

Thanks Gach .. I have 2 sets .. 6.66 and 6.64 c-c, BBC width, .990 pin, and sbc big end diameter. Not working first motor they will be used in yet but Bruce's schitzoid NR100 cam may team with my victor and some good heads to make that little Astre see some air like your GTO in a stock block 400/? conversion with them in it . Just talking cranks today.

Really I need to focus on Kool-Aid 444 and get-r-done. Am ordering 2 dual quad linkage setups Friday, the Mr Gasket plain jane and Edelbrock progressive to get my intake setup to the point I like so I can try on my mule motor in enduro car while Paul balances/cryo's my new Scat crank. Would like to find 2 older small pattern afb's to rebuild and try, to avoid having to use adaptors on my low-rise DQ if you have any hanging around tho.

[keith]

Wow that's useful info to me Mb125. Thanks!! Longevity there with the BME's and factory crank. You are talking about a factory cast crank not forged right? Didn't know they had Pontiac journal BME's but assumed they might as mine appear to be custom sized as well. Guess your .032 rod bearing clearance is specified by him as "Minimum main and rod bearing vertical clearance .003" ... wasn't absolutely sure it meant oil clearance. You probably observed the other clearances .016 min side clearance, .0006 min pin clearance and .060 piston-head, rod-block,cam too.
Is the 462 a stock block and crank turning 7000RPM routinely? You must have some big heads to make power that high? Would lead me to believe reduction in bob weight enhances rpm capability significantly and more a factor in rod journals not going away. For me to use any of my straight Pontiac factory cranks and my BME rods I would have to reduce rod journals to sbc big end size so would go with larger than factory radius, offset or not, but its good to know a factory crank has lived long in a situation like yours so I might get away not going to that trouble.

[Mb125]

Kieth
I'm running a .030 over 1973 455 block
Factory cast 455 crank
20 cc dished pistons
Factory #16 D port heads
Compression ratio is 9.4:1
Solid flat tappet camshaft
The rod side clearance was within BME specifications

[keith]

Thanks MB for that good info.

My crankshaft odyssey continues ... Scat has had 800 of the 1136.00 quote for a forged custom rod journal 4400P42010 they were supposedly grinding from a raw forging on hand to -.020 stroking to 4.040 since 09/06/2017. Creating my long-rod zero-deck 444 with lightened/strengthened r/a. I was hesitant on spec'ing custom thrust grind and did not provide them with a completed crankshaft order form till 3/27/2018. So we are both are to blame to that point anyways.
They then said they had only finished cranks they could not add the .040 stroke to, they said they could add .020. I asked what happened to the crank I put 800.00 on they had no answer. When I finally said ok to grinding a finished crank they said they could only get .005 or .010 unless I ground the crank to -.030 which is the last undersize BBC H-bearing available. I would not do that but am now having 2cnd thoughts as they said if journals get damaged they can be hard-chromed back to an available bearing size. I would still like to have 1 bearing set to go to if the crank needs a regrind without having to hard chrome the crank back up to size. I asked about waiting for raw forging again and Brian McCullough said "Can do, .040 stroke @ 2.179, 8 weeks for raw forging" ... that was 6/14. So here I am.
I have relied on verbal communications with Scat and have only a credit card slip for the deposit, I do like that they do some operations in the US and appear to be a very competitive as well as accomplished American business. I think they make quality stuff I can use and would like to do business with them. I was ripped off completely by Doug Rowe however and hope something similar isnt happening here. I do have a buddy who lives close to their Redondo Beach facility who is a machinist and may send him over there to see whats up. I am going to try talking to Tom Lieb soon, to see if he can expedite this crank as well as possibly grind a 400N crank to my BME's for my extended wait time. I see from their you-tube video they sometimes grind factory cranks for evaluation etc.

[blykins]

Originally Posted by Mr. PBody

A good radius in the fillets is mandatory. The BBC rod mod is a good thing. Using Icon 428 pistons and shortening the stroke up about .050, the 6.8 rod is just right. Be sure the grinder understands "radii" AND offset-grinding.

The oil chamfer is also a good place to "help". A leading trough on the main and a trailing one on the rod does the trick. No sharp edges.

Jim

I'll have to do a +1 to all of this. I usually do BBC journals on all of my Pontiac crankshafts. The 6.7, 6.860, or even a 7-7.1" rod works really well on short stroke engines. A fat radius on the journal is paramount, followed up by a quick bearing width clearance check.

[Zedo]

Originally Posted by TA63

Hello, you guys have any tips and tricks for improving the durability of our stock cast cranks in performance motors? I'd like to put together a 400 that will live happily seeing 6k or slightly more on occasion.

shot peen, mag, check for straightness.
check journals, polish
cut undersize and polish if needed.
make sure filets are enlarged if cutting journals to maintain strength
chamfer oil holes
balance entire assembly with rods, pistons, balancer, flexplate or flywheel being used.
you can have the counterweights cut down and lightened too, most of the really high HP builds have a lightened crank, then it definitely must be balanced. but it's not something needed for a street motor.