GM Block Part # 10051106 Availability??

[John L.]

Greetings all..
I was thinking of building up a replacement LS-5 engine for my 71. One of my older parts books shows this # to be a Mark IV Block and I was considering using a new block instead of finding a good clean used one. I would like a few opinions on this idea. I also have a frest set of 3904390(Closed chamber heads) I would like to use also with this engine but will need some help with the correct piston selection for these heads & block combination. My correct LS-5 engine is in very good shape and I don't want to tear into it and start changing cams and heads and pistons ect.,ect.,ect.
I would like a CR of about 9.5 to 10, I will also run headers and a stronger cam than stock. I also have Intake 3919849 off a 69-390 car I would like to use also.
Yeah I know, another Red Neck from N.C.; Hey what do you expect, I used to hang around with John Woods in the late 60's. I could tell you guys some good stories about Woods; another day another time.
Any help is appreciated. John Liner

[Clem Z.]

all mark IV stuff has been discontinued by GM

so i do not think you will find a new one in stock. there are aftermarket blocks that are the mark IV type

[Clem Z.]

the aluminum block # 12370850

is a mark IV type and you could paint it orange to fool the people.

[John L.]

Re: the aluminum block # 12370850

Clem...I need more green to do that; you and Joe are the only ones I know that could afford to do that. Thanks for the reply.

[John L.]

What about another 454 block Clem

Clem, what would you use for a replacement block? Would you try to find one from another 70-74 corvette? How about one from a Impalla or a Chevelle from 70-74 years? Are there better ones than another? Do you have any ideas regarding the heads and piston combination I was talking about? Thanks!!

[Mark #28455]

Re: What about another 454 block Clem

You can get a late model Mark 4 block from the 1980's for $200 to $400 in perfect shape from a 1 ton truck. The 4 bolt main ones are usually spotted because the original engines had the oil pan reinforcements (long strips under the bolts) and the valve springs had some wierd sheet metal cylinders surrounding them - those engines usually seemed to have the 4 bolt mains and were from 88 or 89 I think.
Mark

[John L.]

Re: What about another 454 block Clem

Good idea Mark, but isn't there some differences in a trucks block deck height?
Not sure if there the same as a passenger cars block are they? I don't know enough to know; thats why I am here asking. Do you have any ideas with regard to my questions about the pistons I would need to use my closed chamber heads?
The heads (#3904390)are off a 66 427/390 car; they have been totally reworked & cleaned, new springs, new guides & valves, pressure checked, new hardened seats; ready to bolt on and go. If I use a truck block will the crank be good enough or will I need a better one? Many questions, many answers, many ways to go, just trying to sort it out before I start turning wrenches. Thanks!

[Robert Willis]

Re: What about another 454 block Clem

The tall truck blocks were in the heavier trucks (5 ton). The 3/4 and 1 ton trucks used the short block.

[Clem Z.]

Re: What about another 454 block Clem

the trucks would have a cast iron crank but i should hold up. with your heads #390 at 98 cc and with a .040 deck,.039 head gasket,-2cc dome volume the CR would be close to 9:1 using the pistons discribed above.you should have the crank and rods magnafluxed to be on the safe side. the rods should also be reconditioned with new bolts. remember the 454 is external balance so you will need the correct damper and flywheel. do not forget to check into crate engines because they are a good value if you have to buy a lot of parts and need machine work

[John L.]

Re: Thanks Clem & All

Clem & All who responded....Thanks.
I have thought about a Crate engine, but the Old Hot Rodder in me keeps trying to come out. I like taking something like a 80 truck engine adding a set of 390 heads a 3919849 intake and misc. parts and breathing new life into a bunch of old parts. Clem could you be a bit more specific with regards to what pistons (part #'s or applications the pistons I should use) with this setup?
Thanks again guys.
John

[Clem Z.]

Re: Thanks Clem & All

federal mogul part# H625P 30

[John L.]

Re: Thanks Clem *NM*

[Joe L.]

Re: Thanks Clem & All

John-----

I'd would have liked to recommend to you one of the greatest deals in connecting rods ever. That's GM #12496661. This is a set of 8 brand new GM #10198922 rods which are 7/16" rod bolt, LS-6/LS-7 rods. This is the second best big block rod that GM ever offered for Mark IV engines. It's also used in Mark V and Mark VI engines. The 12496661 kit used to be available for about $300 FOR ALL 8 RODS.

Alas, it's been discontinued. You can still buy the 10198922 rods but only by "per each". The "per each" cost is about 120 bucks, GM list. Even at a discount price, these rods are now on a per-set basis, not competitive with available aftermarket rods.

[John L.]

Re: Thanks Joe

Joe that is sad, you could buy 8 for $300.00 and now 8 will cost $960.00. WOW thats incredible. What do you think the chances I could find a 12496661 Kit at some GM Dealer using a Parts search? Slim to none I bet. What do you think I could find a competitive set for? Also with regard to the crank, what would you recommend to use that wouldn't break the bank, aftermarket or GM?
Thanks for the response, I was hoping you would chime in also.
Best Regards, John Liner

[Joe L.]

Re: Thanks Joe

John-----

I doubt that many dealers ever stocked this set, so finding it in stock might be tough. Some of the performance dealerships might have a set, though. At this point, they could break up their sets and sell them individually---pure profit here. The rods were individually boxed and labeled within the larger, set box.

454 steel cranks are expensive. The cast variety are no longer available from GM, either. I think that a GM crank would be your best bet in a NEW crank. I'd say about $600, or so, discount. I think that you'd probably pay about the same for a Scat or Eagle. I'd go with the GM piece.