Thread: unable to find casting numbers

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The block I have is a 96-00 454 bbc, the casting numbers are 12561359, yes I am positive those are the numbers, this is just a block on the bench they were easy to read. I was told it was a gmpp block however neither the gmpp website or a broad google search yealded any results for those numbers, please help im ready to take it to the machine shop but I would like to know what options I have with this engin.

I just picked up another 454 engine myself and the numbers wouldn't come up on Mortec or anywhere either. Evidently Chevy used some different casting numbers toward the end of the 454 production that aren't listed for some reason.

Closest I could find to your numbers is this one on Mortec:

12561357...454.......96-up...4-bolt, Gen.VI


Do you have a four bolt main, roller cam, plastic timing cover engine? If so, it is a gen VI. That is what both of the 454's I have are. Even the brand new crate 454 we ordered to replace the one I picked up had numbers that were no where close to anything anywhere that I could look up. I think since your number is only two numbers off of what Mortec shows either you are wrong on the last digit or it is just a later run than the one Mortec lists.

In either case, you and I own the good versions from everything I can read. If you want more info, here is a good site:

http://books.google.com/books?id=rUm...20main&f=false

Don

i do not worry about the casting numbers there is ways to tell what you have all 5and 6 blocks are 4 bolt mains they are one pc rear seals blocks the 5 is not set up for roller lifters this can be check by looking in the valley for the stands casted in the block if so it is a 6 block the older 5 block used a tin timming cover the 6 used a die cast cover both blocks use a open deck and would use a fel-pro 1037 head gasket up to a 4.370 bore the older mark 4 heads will not work .thing s that will not work from a older mark 4 engine are oil pan. timming cover ,a mark 4 cam can work in a 5 and 6 with some work but if roller solid roller you need tall body roller lifters . and would use a mark4 chain set .now i have made all the old mark 4 oil pan timming cover and mark 4 cam . i did this by putting steel billet caps from a mark 4 block drilling and tapping out the oil pan rail and drilling and tapping the block for the old timing cover you have to have the block line bored for the new main caps and you use one 1/2 of the two pc seal adapter in the block for the two pc rear main crank . there is no need to do this now they make every thing you would need for the 5/6 engines now .you can use a mark 4 crank in the 5/6 block with the two pc seal adapter works fine i done it a time or two. pistons will work rods with work head bolts will work older cam can be made to work if you have a 6 block they mill out the die cast cover for mark 4 chain set.they did make a tall deck blocks so you would want to check the deck height. i can tell this by looking at the top water pump bolt hole a 9.800 deck is about a 1/8 from top of bolt hole to the deck . and a tall deck 10.200 is about 500 there are things i do not care for on the gen 5/6 blocks some of it can be work out some can not

thanks both of you for your help... after inspection it is a gen VI for sure... any reccomendations for a roatation assembly? something in the forged varity...undecided about a blower anymore, going into a 67' cutlass occasional driver/track

i done the gen 6 in a turbo 540 and a 454 gen5 blown and a 489 blown and a hand full of the gen 5 and 6 with just carbs .i am doing a blower gen 5 right now forged is a good way to go i built many with the H beam rod and SRP piston i use the scat crank or the compstar crank

scats got a rotating kit on summit i've been looken at (PN:SCA-1-42454BE) for N/A or similar with dished pistons for power adder. thanks for the insite pat