BBC help and ID

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prairiehotrodder
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BBC help and ID

Post by prairiehotrodder » Fri Nov 09, 2018 12:45 pm

A friend just purchased a complete BBC from racing junk. The whole combo seems kind of weird but in good condition. It will be going into an old IHC ratrod type truck that should be really light. He wants to street drive it lots and drag race it occasionally. He is around 22 years old and this is his first semi-serious motor. My main concern is trying to figure out the shortblock components and what flexplate and balancer it needs. It came with an old used junk stock 454 balancer and a stock 454 flexplate. The motor is a 489 as far as i can tell. He was told it was an 11-1 496.

Pistons are flat top with one valve relief SRP forged and only marking is a 73F on the bottom. Bore measures close to 4.280 with a caliper and looks like new.
H-beam rods with SCAT ARP 8740 rod bolts.
unknown weird looking crank, stroke neasures 4.25 with same caliper.
Edelbrock performer TBI heads with 100 cc chambers. Possibly been ported.
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had a brand new (unused) lunati solid flat tappet cam in it but we have replaced it with a comp XR294HR for ease of maintenance and reliability.
According to my guess/calculations compression should be near 9.7 CR.
To my logic the short block should be internally balanced ? Can anyone ID this crank ?
IMG_2591.JPG
IMG_2592.JPG
IMG_2593.JPG
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Dave Koehler
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Re: BBC help and ID

Post by Dave Koehler » Fri Nov 09, 2018 2:35 pm

Sounds like a new 454 H balancer and flexplate would be the ticket.
What makes you think otherwise?
Has it been run previously?
Granted, one might think it should be internal.
Any drill holes on the CWs?
Perhaps it is time to grill the seller.
Last edited by Dave Koehler on Fri Nov 09, 2018 2:47 pm, edited 1 time in total.
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prairiehotrodder
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Re: BBC help and ID

Post by prairiehotrodder » Fri Nov 09, 2018 2:41 pm

prev owner said it was balanced (whatever thats worth)
I thought all forged 4.25" cranks were internally balanced
According to DV's BBC book, the scallops cut off the rod throws of the crank indicate it should be internal balance.
who puts a junk stock balancer on a well built 489 ?
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Re: BBC help and ID

Post by SupStk » Fri Nov 09, 2018 2:42 pm

Can't say that I recognize the crank. With stock length rods it would most likely have to be externally balanced. It could be internal with + .250 rods.

9.7 seems low with 100 cc heads but I didn't run the numbers.
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Re: BBC help and ID

Post by Dave Koehler » Fri Nov 09, 2018 2:48 pm

prairiehotrodder wrote:
Fri Nov 09, 2018 2:41 pm
prev owner said it was balanced (whatever thats worth)
I thought all forged 4.25" cranks were internally balanced
According to DV's BBC book, the scallops cut off the rod throws of the crank indicate it should be internal balance.
who puts a junk stock balancer on a well built 489 ?
well, it is a 2 bolt block and the guy probably killed his budget.
If in doubt, pull it out and get it checked/balanced.
Racing junk stuff is always fun.
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Re: BBC help and ID

Post by prairiehotrodder » Sat Nov 10, 2018 6:23 pm

the previous owner says its externally balanced so we are gonna go with that. He seems like an honest guy. The weight on the flexplate has been sawed down to a smaller size and the counterweight on the very back end of the crank where the flexplate bolts on has been sawed away as well. I'm guessing is was used in some weird application then it had to be externally balanced to fix it. Not sure what to say. Old owner also says its a scat. Thanks for the help.
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Re: BBC help and ID

Post by racear2865 » Sat Nov 10, 2018 6:39 pm

Have done quite a few 489/496 BBC. First, I have never seen the rod throws cut like that and it be external. But per conversation above, if it has stock length rods, never seen a 4.250 be internal with stock length rods. lot of weight was scalloped from the throws. No way would I guess as to what it need. I would have to spin the crank to see. What will u do if you have a shaker. Tear back down and spin crank so why not do it now. My take.
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Re: BBC help and ID

Post by af2 » Sat Nov 10, 2018 6:39 pm

I am finishing a 489 tomorrow with Scat internals and will say the crank looks nothing like yours. It is smooth everywhere.
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Re: BBC help and ID

Post by prairiehotrodder » Sat Nov 10, 2018 6:59 pm

there is even some aluminum removed from some of the pistons just under the pin boss. Without taking it apart i can see that the oil ring is into the pin hole so that should mean that it has long rods ? I will let my friend decide what he wants to do. I agree that it should be all taken apart and balanced internally. The crank has rough ugly look to all the non-machined areas. And not a word or a number to be found besides whats in the picture above.
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Re: BBC help and ID

Post by ProPower engines » Sun Nov 11, 2018 1:45 am

By looking at the counter weight appearance it seem like it is an old 9000 series cast crank.
The old cranks were rough in appearance but decent. The forged cranks had a definitive wide parting line on the crank like a stock crank had. if it is a 4.250 stroke it is most likely a cast crank as well as externally balanced.
the 6.385 rod combo uses the oil ring spacer where the 6.135 rod did not.
I do at least 1 assembly like these a month for boats and they have been a very popular combo compared to the 502 engine.
They seem to make more power and have better fuel economy then the std deck 502,

I would still tear it down and completely check over all the clearances and other important details and thoroughly clean every where rather then just running it as dirt can hide and ruin your day later when you run it.
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Re: BBC help and ID

Post by Dave Koehler » Sun Nov 11, 2018 5:49 am

Aluminum removed from pistons.
Did not see any sanding marks on rods but maybe they got lucky.
H Balancer and Flexplate modified. Not particularly enamored with that idea but ya gotta do what ya gotta do sometimes.
Throws massively machined. Nicely done but if that was part of a "budget" balance I don't think they made wages.
Pretty good bet it has been balanced.
B..bu..bu But I would still do what Pro says and check everything.
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