I plan to build either a 406 or 434 SBC this winter. Yesterday, I called Shafiroff and they suggested that I build the 434 with the World block. Both the World block and the Dart Little M have a 9.025" deck height. So I see two negatives with using one of these blocks to build a 4" stroke 434:

1) 1.5:1 Rod-to-stroke ratio. With a 9.025" deck height, I don't think I can run more than a 6" rod;
2) I would have to run a small-based circle cam.

Now, if I were to use the Dart Iron Eagle--which has a 9.325" deck height--I can run at least a 6.2" rod and a normal base circle cam. However, the Iron Eagle block costs $500 more that the World (and $250 more than the Little M)and has additional costs and complications on top of that:

1) Wider pan rails means I have to buy a custom oil pan--that's an extra $300+ (I think);
2) Remote oil filter;
3) Slip collar distributor;
4) Possible starter clearance issues;
5) 6.20-6.25" Eagle H-Beam costs an extra $80 versus the 6".

I figure I have to spend at least an extra $880 to go with the higher deck. So should I fork it out for the taller deck, or should I not worry about the shorter deck's negatives and go with that? All opinions will be appreciated.

 

What is your application?

My thoughts are enough power can be made on the standard deck heights to
rule out the extra costs unless this is purely a strip motor.

You'll also have to consider pushrod length. Extra weight and length in rotating
and reciprocating assembly is going to limit your RPM.

Will this engine be naturally aspirated?

 

Application: street mostly, with autocross and open track days, as well. With the 434, I was thinking of a 6500 RPM peak. I'm planning to install a T56 with 4.1 gears.

Zeroto69: The additional weight of the valvetrain and the rotating kit required by the tall deck is another question mark. Thanks for reminding me.

 

I thought this thread was a typo... I pictured a BBC question like ""to 10.2 or not to 10.2"

0.300 is enough that the R/S starts looking favorable... I'd imagine any headers you have now would even fit that small change.

Yeah the rods will be 20 to 50 grams more... but they'll need to be heavy anyway if you're looking for serious power like this in a street-driver.

Maybe a 427 standard-height with good heads is all you really need... I dunno. hopefully some experienced engine builders will chime in on this one.

 

The plusses aren't that big a deal. Use either the Rocket or Eagle blocks in standard deck height and you can use a large cam core with big block cam journals (the cam is raised). But is this really a priority in a street build turning ~6500 rpm? The large cam core is going to be stronger than a comparable material small-core cam but how much spring pressures are we looking to use??

Believe me, the plusses are very attractive when looking to build a race engine but the extra costs that come with them aren't groovy for a street build.

You mention r/s ratio. I crunched the numbers for a 9.325 deck block with a 6.25 rod and compared them to a 9.025 with 6.0" rod combination. Here's what I came up with....

6.0/9.025
Max piston velocity
7174 fpm
Max piston acceleration
102,939 ft/sec²
Compression @ BDC
1600 g's
Tension @ TDC
3200 g's
% of estimated critical load
74%

6.250/9.325
Max piston velocity
7147 fpm
Max piston acceleration
101,910 ft/sec²
Compression at BDC
1632 g's
Tension at TDC
3268 g's
% of estimated critical load
73%

So you lower max acceleration ~1,000 ft/sec² by going to the 6.25" rod. About the same rate of change in going to a 6.0" rod in your 350. Spin a 350/5.7" rod combination to 7,000rpm and you have very similar maximum piston acceleration at 101,678 ft/sec². Just trying to create a bit of perspective here. The r/s ratio just doesn't enter the picture for me.

One negative to the high deck is the pushrod length. Longer pushrods = more flexing. So you will want a really beefy, preferably tapered, pushrod if you want to keep accurate valve timing. And they'll never be as stiff as a pushrod of the same construction in shorter length.

That and all the other costs of a tall deck IMO don't make it worth the extra dough. The spread pan rails I see as a big plus if you want to go to a 4.125 stroke. That crank will almost drop right in on a spread rail block.

My 2 centavos.

-Mindgame

 

I'm not completely familiar with autocross, but from what I've seen of it I'd consider the time & $$$ for the 434 to be some serious overkill in the engine compartment. Seeing what a 406 can do on a short track and the relative low cost I'd go that route. Then the $$$ you save can be put into the suspension setup of the vehicle which is just as critical when handling is the other half of the game.
JMO.
Steve...

 

Amen!

$800 buys you a full set of road race rubber plus perhaps even a set of used wheels.

It also could buy you an eight-point roll bar, a five-point race harness, and a race helmet.

Or, most of a good braking system.

 

As long as you stay under 4800fpm on piston speed you will be OK,as MG related to.
The big cost issue IMO is going to be a set of heads and intake to feed it.An engine like that should make 800+FWHP and that is going to take a lot of air.A Good set of 15-18* heads to feed that monster(to make it perform like it should)will set you back 4-5000 dollars and an intake will be another 35-4000 dollars.
It would be serious healthy,but is it worth the extra,when you can make 650-700 with a 383 or a 396 in a factory 4 bolt block and a good set of heads that cost 1/2 as much.

 

Please forget I said that.... don't know what I was thinking. The tall deck blocks all make use of raised cam location (.391 higher). So the pushrods are actually a tad shorter.

I'd just leave it at that.

And I agree with Larry... you can do the 383/396 and make the power but it won't be near the streetability of the 427+ builds. But if you want to build the bigger engines to the same extremity, there's that much more power waiting.

-Mindgame

 

Do keep in mind that with a small base circle cam, a 4" stroke can be pulled off with a production GM 400 block.

 

I have called Both Shafiroff and Hard core on there 427-454 SBC Engines as well as Dyno-Flo.

As long as you use the 4in crank it is a drop in and no problems from what they told me. They said to check cam clearance but it should be fine as long as i use the right rods(this suprised me)

I am going to probably have Shafiroff build my short block. It looks like I will be using a GM Sportsman block So I may keep it to 427 to start with. I have recieved a few names for people who can port my 18* heads for what I need. It SHOULD be mellow with a HUGE bite when I get done

 

For future reference, here's an engine built by Hot Rod using a Dart Iron Eagle block. The article discusses the benefits and considerations of using the raised deck height and cam locations of the Iron Eagle versus the standard deck height and cam locations of the standard SBC.

http://www.hotrod.com/techarticles/engine/113_0312_454/