Hot Rod Forum banner

gm rocket block

29K views 53 replies 11 participants last post by  noslokcorb 
#1 ·
my friend had picked up an gm rocket block a few years ago

unfinshed bores and lifter bores
bbc cam bearings
400 mains
wet sump
tall deck block
max displacement is 455ci
i can purchase this block for 2,200 bucks , how stong are these gm blocks

reason im asking is i am building a 434ci twin turbo small block to run in x275
it will be 434ci 9.5-1 cr, with cnc afr 227 heads, solid roller cam , single plane efi intake with twin 66mm turbos

this combo is capable of 1000hp plus easy

with this block handle it or should i just buy a little m
 
#2 ·
If a true GM Performance "Rocket", it will be fine. That was Oldsmobile's "version" (thus the name "Rocket") of the 400SB, raising the cam and using the BBC timing set. The tall deck allows for longer connecting rods, a "must" for high RPM durability. Several years ago, we built an 1,800HP blown/alcohol 434 using the Rocket block and "splay valve" heads. 9,500 RPM, lived fine, went 6.60s in a LWD.

Jim
 
#9 ·
thanks guys i am not familiar with the rocket blocks at all
i know it needs a special oil pan since the oil pan rails are spread, now i just need to figure out the cost of assembling it versus getting a little m block and see how much cost difference there is
 
#12 ·
I already did something similar with a bare casting Bowtie 4.3 block.I can tell you unless you have a machine shop your never going to get a bare casting completed as cheaply as one that is already done. And my point of the link is those do come in various models and costs accordingly.
 
#13 ·
For those who don't remember, Oldsmobile heavily sponsored drag racers in the late 1980s. There were MANY Olds-bodied Super Stocker Cutlass Calais and Ciera cars with F.J. Smith RWD conversions using "corporate" motors. Olds designed the Rocket Block to fix many stock SBC shortcomings (as they did with the BBC in the DRCE motors). The "rocket block" nomenclature comes from the fact that there was an Olds rocket logo cast into the side of the block. It was never used for Pro Stock because the Pro Stock engines were 500 cu in by then, thus the use of the DRCE in that class.
 
#14 ·
There is no comparison between Rocket and Little M. Little M is a very good block, made as a "replacement" block for the 400, only "tough". Rocket is a RACE block. Yes, ProStock Truck is where it was most widely used, IIRC. Virtually everything for Rocket is either custom made or hard to find. That's the "price" of a true race engine. Even a Chevy. Many big block components "fit", as I recall. A custom crank is needed to use the BBC timing set. There's probably some sort of sleeve assembly to make it work if not a "blown" application.

So, if you're looking for the least expensive way to make "big" power and "live", Rocket is probably not for you. If you want the ULTIMATE in SBC technology and the most "bang", regardless of "buck", Rocket is the way to go.

Jim
 
#16 ·
There is no comparison between Rocket and Little M. Little M is a very good block, made as a "replacement" block for the 400, only "tough".
Might want to gert your facts straight the Little-m is not a replacement for the 400 block.

The Dart SHP block is more of a replacement for the 400 block.


Dart has there Iron Eagle block which is a replacement for the Rocket block with and can be bought with a STD. or BBC cam tunnel, 4.00 or 4.125 bore, 9.025 or 9.325 decks, 350 or 400 mains.
 
#18 ·
thanks for the info guys its really apreciated, i wasnt totally aware of how exspensive it would be to fill the rocket block, so im going to look into the iron eagle instead.
im thinking 4.125 bore 400 mains standard cam tunnel std deck as i can still make it a 434

ill prolly still buy the rocket block and let it sit like my friend has cause 2,200 seems like a really good price and im sure i could make my money back + some on it down the road
 
#19 ·
Sorry. From my point of view (engine builder), Little M IS a "replacement". That is, all the correct holes and flats and knooks and crannies to "fit" where a stock block "was", are there. Agreed, SHP blocks are less expensive and more "amed" at the street crowd. I certainly didn't intend for that to be a "blanket" statement excluding all others.

Jim
 
#28 ·
Yes that is the machine work costs,but how about the lifters and cam needed??.

We went through this with two separate aftermarket BBC's.I'm not saying for him not to do this,rather I am saying once you step into the world of aftermarket blocks and their options there is whole other pricing structure which he should be aware of in advance.Easy from here(the "cheap seats") to advise what to get,but he is the guy who has to pay for them. Just my two cents worth.
 
#32 ·
Need to add you have to have the tools and know how to correctly use them to check everything. Trust not one thing.We have on average around 120hrs in each race engine and we have been doing it for a very long time.Shop door is locked,no radio,total concentration on what is in front of you.Your eyes is the final decision.No do overs!!.
 
#33 ·
well heres is the whole deal im looking to put together

as i said 434 ci
and its been suggested i go with the afr 235 or 245 cc heads instead of the 227's
solid roller cam
single plane efi intake
twin 66 to 70 mm turbos

ideally i need to make around 1,200 hp to be competive really not a hard feat with the layout of the combo i know i want

the big thing is it must remain streetable and i dont mean the once a month 30 mile trip. this thing has to live on 400 mile round trips to and from the racetrack

so my main concern is really going to be in the roller lifters and valve train, i dont need a lifter leaving me on the side of the highway on the way to or from the track and i know on a bunch of forums there alot of discusiion about some of the solid roller lifters failing from different companys


im also not dead set on the 434ci as if this class comes to the local track there maybe a displacement restrictions so im keeping an eye on what happens before i order any rotating assembly
 
#37 ·
If your going to build a 434 use a tall deck Iron Eagle block. Using a 9.000 deck block you have to much pisotn hanging out of the bore at BDC which will be a problem down the road. A std. deck block to small of base circle cam rod ratio is not good, stroker pan which skips every other bolt hole which = leaks.

Now using a 3.875 X 4.185 which is a 427 is pretty common in our shops, Just saying.

Here is a quote from another shop on 4.0 strokes in 9.000 block.

We don't offer engine options in the 4.00 inch stroke version, (434/440) as well as the 4.125x4.00=427 It is because we feel them to be very short lived compared to the 4.155x3.875=421 stroke used in this short block. You may hear of those running the 4.00 inch stroke in competitive racing events but engine reliability and longevity are not the major concern. When it come to street rod use, it is in our opinion a somewhat short lived build. The 3.875 stroke is not like this, when using a high performance block such as the one used in our engines. You will not hear of engine failures on the 3.875 stroke builds as compared to the 4.00 inch. It would not cost us one dollar more for the parts and a very slight amount of labor to move up to the deeper stroke engine, but we are fairly certain it's the wrong route to take.
 
#35 ·
shouldnt be hard at all, what i was getting at is the roller lifters and related parts must be able to stand street use

we have a fellow board member thats making close to or just over 1000hp with a 406,afr heads,single plane and twin 66's with relativley low boost on pump gas. his is pretty much just a street car though he didnt build it to race in a class. so i have no doubts a 434 with the same heads will get me were i need to be
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top