Stock SBC block w/ 4" stroke?
 

Guys I am trying to "HIDE" as much displacement as possible in a SBC motor. I know you can put a 3.75" and a 3.875" crank in a stock 350 block. I know aftermarket blocks can easily swallow a big crank, but they are also easily recognizable too. So, can you stuff a 4" crank in a stock block?
The cam is not a concern, I have a solution for that if I go this route. What I want to know is what size rods to use between 5" & 6"? And is a low compression dished piston out of the question because of pin / ring clearance? And are the oil pan rails too thin to clearance for the stroke? What is the affect on cylinder walls of all this extra stroke?

Thanks for the engine building lesson,

Mal

4" in a stock block... gonna be real hard... you have the pan rails to worry about.

You want cid in a small package ?? Go 4.125+ bore with a shorter stroke. HP rules afterall...

It's not uncommon to see stock block 434 and 440 SBC's in dirt racing, but the blocks are partially filled with Hard BloK or something similar. As Tom said, you really get into the rails, lots of clearancing.

Are you trying to hide it, or simply make it fit?

It depends on the application, too. Is it a low rpm street deal, or a high rpm endurance deal?

Is the vehicle heavy or light?

A bunch of stroke will help low-end torque but will take longer to get to a higher rpm level. A big-displacement small-block will require sufficient port size to feed it at the target rpm level, which means you could be getting into offset rockers etc to make it work as well as possible.

Share more info, and more specific details can be researched. Is there a budget for this?

~Scott Parkhurst~

i doubt that you can do the whole engine for what a nice big cube crate SBC costs... a 595 hp 434 from schafiroff costs 9K, less carb and ignition... and it works and comes with a warranty... i sincerely doubt you can develop a big cupe stock block SBC with matched heads and cam.. that just performs at that level with same durabillity.. for that amount of money.. so i guess you have to decice how badly you want to hide displacement

i mean i installed a set of OLDSMOBILE ROCKET valve covers, welded to sbc rails on a friend of mines 31 ford.. and 1 out of 200 spoted that it was a chevy engine...

if you grind the obvious "Dart" casting off a crate engine, paint it orange and install plain jane tin and perhaps even an aircleaner with a 327 sticker.. no one will notice...

and if yoy cheat at the track.. they will catch you no matter which block you use!

That makes sense with the short rod length to stroke ratio; alot of pressure on the cylinder walls. Hard blok is not a route I want to go since I will drive this thing on the street.

Ok but I am confused on the clearancing issue. Dart, World, and others stuff 4" cranks in their blocks. They make thier blocks w/ raised cams and thicker pan rails OK given, but they still use stock deck height am I right? I would think rod ratio and piston pin clearance would be an issue for them.

How are they or their customers getting around that?


Mal

The application is for a street driven car that will see time on road courses. So the rev range will vary. No endurance stuff, maybe 5 laps at the most. The vehicle will be heavy about 3500lbs.

The heads are a whole different story that will require another thread, so for now assume they are big enough and exotic enough to feed the need. My focus is the ability to stuff a large crank in a small block and how long it will stay in there. Basicly doing it because I can (if I can :_paranoid ).


Mal

The only track I plan to "sneek" in at is the local friday night test and tune. There is always someone willing to donate money to help me break my automotive customizing addiction.

Mal

I had a Dart Iron Eagle tall deck (9.325"). The rails were spread and the cam raised. With a 4" stroke, 6.200" rods, the CH was 1.125". The drawback of the block was that it required a special pan, intake manifold, and adjustable slip collar distributor.

I get it. While I appreciate your angle, the capabilities of the big-inch small-block crate engines out there serve the need. Otherwise, if you really want to build this within the confines of a stock small-block, there's plenty of potential in a 406 to make the kind of power you're looking at.

The thing is...once you decide to go after that other 40-50ci, you really want the raised cam/taller deck to make it work for you. You need to give that crank room to swing and you want to run good connecting rods, and they need clearance too! You don't want to be grinding the rod bolts down or notching the bottom of the cylinder bores if you don't have to. To get a bunch of stroke into a stock block would require these kind of clearancing techniques and while they've been done before, they are also the reason the aftermarket tall-deck/raised cam blocks were engineered in the first place!

So, I'd have to recommend either a very serious 406 or an aftermarket block-based 450-ish inch setup. Based on what I know, which ain't as much as lots of other guys, but is a little more than most, building torque will not be your challenge here. Putting it to the ground will be. I think if you've got 500-550 ft-lbs being put down without tire spin, you will be a happy guy. You can make that kind of power with a very serious 383 or a very good 406. A mild aftermarket block-based 450-plus inch SBC can do even better at lower rpm.

~SP~