garagedweller2

I asked this question before and received 0 replies, so he we go again. Why weren't they installed stock, anyways?

ORVette

Scoggin-Dickey lists a GM 400 "Rocket Block" for $2299.00. It's the real deal! I think I've seen some GM Sportsman 400 blocks, but I can't remember where at the moment. Do you mean why didn't they just install them stock in Corvette's? I don't know either, would've been a nice option I think.

SmokedTires

You can get a 400 sbc block from Dart or World Products. I just got a Dart block with the 4.125 (400) bore & 350 mains for the destroke crank I'm installing for my future 388 sbc :D . FWIW, I seen a 377 sbc (same Dart block as mine) that is estimating 1400hp with the help of twin turbos ;) .

garagedweller2

Thanks! Who can answer the question on why they weren't installed by the factory? :confused: Also, what components are rocket block specific? I've heard that normal cams won't work? Is it preferable to use the 400 mains or 350 mains?

SmokedTires

I can't answer why GM never installed the 40 into the vette, but my guess is that they probably thought the BBC option was enough :( .

The mains depends upon wiether you plan on staying at or stroking to a larger displacement or destroking to a smaller higher revving displacement. I chose the 350 mains because my 3.625" stroke Bryant crank has 350 main journals. If you want a 377 which is a 350 crank in a 400, then you could choose either main (They have bearing spacers for installing a 350 into 400 main journals). I didn't want to use the spacers so I went with the 350 mains. With a stroker you could easily build a 427/ 434 sbc with either of the mentioned blocks. :)

Darkness

And you're still 14 :crazy: :crazy: :crazy: A 350 not enough? :smash: :smash: :smash:

Pete79L82

The rocket block is available in either standard deck height or tall deck height (.300 tall). They use big block cam bearings and a special large journal camshaft. They also have spread pan rails which require a special oil pan.

The standard deck height block comes with 2.45 main bearings. (350 size) The tall deck block comes with 2.65 main bearings. (400 size) Either one can be configured up to 468 cubic inch.

The 400 engine was never considered by GM to be a perfomance engine. They were never available from the factory with good heads/intake/crank/rods. Because of this Chevy never put them in anything other than full size cars(Caprice/Impala) and pick-up trucks. It was the circle track guys that realized their potential of big cubic inches without the weight disadvantage of the big block.

Paul L

Yes, they were very nice engines in station wagons where pulling trailors was a priority.

xrated

U can get a standard 400 block from VPW.
http://www.vpwmailorder.com/asp/prod...d=154&manu_id=

garagedweller2

Does any one make an internally balanced 3.75 stroke crank in 350 main size?

Monty

I am running a tall deck Dart Iron Eagle Rocket block. It is identical to a GM rocket Block, Dart actually casts and machines the blocks for GM. The only difference between and Iron Eagle and Rocket block is that the Iron Eagle is machined so that the same block can be equipped with either a wet or dry sump oiling system. The Rocket block is machined to be either wet or dry, available under individual part numbers.

As mentioned, they are availabe in either a 9.325" deck height, or in the aluminum version 9.500". Production block deck heights are 9.025". The pan rails are spread .400" on each side, .800" wider total to provide clearance for up to 4.125" stroke with out machining the rails. As a result, you will need a Rocket Block oil pan and aoil pan gasket. Almsot all the oil pan compnaies make a pan that will fit. Stef's makes a pretty nice sheetmetal aluminum pan starting at around $300, but Moroso offers a steel pan, including pump and pukcup, for about $50 less - it's in the Summit/Jeg's catalogs.

You can actually get either 350 or 400 mains in either the stock or tall deck blocks, and you can chose either SBC, BBC, or 50mm roller cam bearings in any deck height or main journal. If you chose a SBC cam bearing journal size, a standard SBC cam will work. If you use the BBC cam bearings like I do, you just specify the journal size when you order the cam. One thing to consider about the BBC cam bearinsg journal size in an SBC block: the cam manufacturers only offer it as a billet steel cam core, with a steel distributor gear, tehy do not offer the pressed on cast iron gear, so you will have to use either a bronze gear or the new, preferable composite distributor gear.

400 mains and BBC cam bearings are good for durability and strength since the cross section and overlap of the crank and cam core are larger. However, the larger bearing journals do create more friction and bearing speed, so compared to the smaller journals they eat a few more hp as friction. It's the same thing as running Honda rod journals, etc.

The cam location is .391" taller to clear a 4.125" stroke without a small base circle cam, and they all feature priority main oiling. With the raised cam location, you will need an appropriate timing chain, belt or gear set. Cloyes sells the right Tur-roller timing set for around $100, a belt drive is around $900 for this bloxk. A stock dimension btiming cover and gasket is used with timing chains.

Additionally, the blocks feature 4-bolt/stud steel main splayed caps. The rear main cap is secured with two 1/2" studs. The deck bolts/holes are blind tapped, so they do not protrude into the water jackets.

The cylinder walls are a minimum of .375 thick, so even if your bore the blcok out to 4.200", you still ahve laot of cylinder wall thcikness. The cylinder decks are .875" thcik, and the front and rear bulkheads are thicker as well.

Also, there is no oil filter provision for the Rocket blocks, so you must use a remote oil filter. The block is equiped with oil return ports at the front and rear of the block. Oil is fed to the lifter gallet through the front and rear of the block, so if you want to restrict oil to the lifters, you have to put plugs/restrictors in the front and rear of the lifter galleys.

You also have to drill some oil return holes for the lifter valley depending on whether you are using the block for circle track, or drag race use.


Any high-performance crank company can make an internally balance 3.75" crank, most are "off the shelf". Alternatively, any good machine shop can make an externally balanced crank, internally balanced with the removal and addition of material and mallory slugs.


[Modified by Monty, 12:26 PM 1/12/2003]

garagedweller2

Thanks! With the tall deck, you can use longer rods? Also, with longer rods, you need shorter pistons? And with the tall deck, do you need special intake manifolds?

Monty

Exactly, I run 6.125" rods, so even with a 4.00" stroke I ended up with a 1.53 Rod/Stroke ratio, identical to a 454BBC, and slightly better than a 5.7" rod 383 SBC. The decent r/s ratio, and lightweight pistons with higher pivot point amke for a very easy revving 4.0" stroke engine that is confortable at 7500rpm.

Dart, GM Perf Parts, Edlbrock etc makes cast intakes to fit, or you can add spacer to a regualr manifold. Although custom sheetmetal is an option...;)