The "Little M" cylinder block by Dart will be used....400 with steel mains.
What is the biggest stroke I can get without doing any cutting on the new block? Do not want to take any metal out for clearances, or bore it out.
Can I then tell what my CID will be?
If I have 74cc head, can I then tell what rod length I will need? I want to stay with a 5.7 or 6.0 rod for $$$$ reasons, so that may also figure in to what the stroke of the crank should be.
Also, I want to be between 11-11.5 compression. So then I will need to figure out which forged piston will need to be used. Again for $$$ reasons I want to get something off the shelf, i.e. a piston with a part#, so I don't have to wait 6 weeks or more for special pistons.
I have seen on the Lunati web sight that they have 15 different rotating assemblies, all 4340 with forged pistons, but I don't know enough to read into what I would need.
Any help appreciated.

 

The biggest stroke you can get in a 400 block without cutting is...you got it, a 400 crank, which is 3.76". If you're willing to do some machine work, you can pretty easily fit a 3.835 (I think) crank which will give you 421 cubes or 427 cubes on an overbore. The most you can machine for is a 4" crank for most 400 blocks, which will give you a 429 or a 434 with 0.030" overbore.
For any of the cranks, especially stroker cranks, it is recommended that you use a small base circle cam.

Use of the 5.7" or 6" rods is recommended, since the stock 400 rods were so short that they caused a side-loading problem in the cylinder bores, which could crack them between the siamesed bores. Use the biggest rod you can get pistons for. Of course, any rod longer than stock will require some minor clearancing, so you won't totally get away from that.

Your pistons will have to be a high pin-location piston, sometimes going into the oil ring land. But it will result in less piston rock and better stability. These high pin 400 pistons are expensive. So be prepared.

One aspect of longer rods is higher compression. I suggest you call the supplier of your choice, Lunati, Speedomotive, etc., and they'll be glad to build you a bench engine, tell you what you'll need, and estimate the compression ratio. Then they'll tell you the price. Lunati's very expensive, but their stuff is good quality. Speedomotive has good bargains, but you have to be careful with them, which is the general consensus.

A 434 will probably run you the most money, perhaps as much as 10 grand to build one all forged, with roller cam and everything. A 421 will probably almost cost you as much. A really well built 406 will cost you about 6 or 7 grand.

Actually the cheapest 400 combo you could build is probably the best-running and makes a very popular race engine because of it's totally happy rod to stroke ratio, and that would be the long rod 377. It's a destroked 400 using a 350 crank, 6 inch rods, and a 0.030" overbore. That gets you 377 cubes with a spectacular 1.73 rod/stroke ratio. Think of it like a 327 with *****.


[Modified by MoMo, 10:34 PM 2/13/2002]

 

The World Motown block says it will take a 3.875 stroke without machining, and I know they use 4.00 with some work (check the 427 short blocks). The Dart block says it will take 4.00 max stroke, but isn't clear is that is with or without additional machining. SRP makes pistons for most of the long stroke setups with 5.7, 5.85, or 6.0 rods at around $500 per set.

The Flatlander racing site is a good place to check for representative prices, they also have rotating sets and complete motors (at their sister site crateengine.net). A complete 434 short block is $5400, so $7-8k for a complete motor does seem like where you will end up.

-Greg

 

You also have the choice on those blocks of main bearing size. Go with the smaller 350 journal size. The rotating assembly is best bought as a kit. Good internally balanced crank/pistons/rings/rods/bearings is @ $1500 for good forgings.

3.875 X 4.125 = 415 ci
4.00 X 4.125 = 427.6

The price is the same. So your better off with the longer stroke IMO. If you don't have heads yet your better off with less cc heads and dished pistons.


[Modified by gkull, 9:34 AM 2/14/2002]

 

I agree with George, go for as much stroke as will reasonably fit in the block and maintain a rod/stroke ratio over 1.5. If this is a street car, you want torque. Even with a 4.0" stroke, you can easily rev it up to 7500+ rpms if that's what you want - but you'll hardly ever get it up there on the street.

I've got the Dart Iron Eagle/Rocket Block and I went with a 4.0" stroke. VERY little machining necessary, all we had to do was put a small 1/4" diameter notch at the bottom of each cylinder to fit the 4.0" stroke. However, the Little M has standard width pan rails, so they may have to be notched slightly, but it's not a big deal. A 3.875" stroke as already suggested would be a good choice for your block through. You can bore thsoe blocks out to 4.200" and still ahve at least a .300" thick cylinder wall all the way around, which is more than alot of stock production blocks have with standard bores. The problem with going past 4.200" is piston selection, but you can get anything custom.

A 3.875" stroke, 6.00" rods and a 4.155" bore would probably be your best bet.

As for pistons, you can get custom JE's for about the same price as off the shelf pistons, and I've never wiated longer than 2 weeks. I just got a set of custom JE's for my turbo engine and I recieved them 10 days after I ordered them. You can also get their SRP line for about 2/3's the coast, pretty much the same piston, just not as much lightweight machining done.


[Modified by Monty, 9:44 AM 2/14/2002]

 

Gkull,
Why do u think I shoud go with the 350 mains instead of the 400 mains?
What formula did u use to come up with the CID figures?
Thanks for your help.
I did talk to Dart and they said that anything over a 3.75 stroke crank would require some cutting on the Little M. But if I went with the Iron Eagle, I could go bigger like Monty pointed out.
I did see where worlds Motown block does have stroker clearance for the 3.875 crank without cutting. Thanks Greg.
I've heard nothing but good things on the Dart blocks, not too familiar with the World block.
I will be maxing out at 6500 as that is what the Superram is good up to.
Now, if I go with a 4.0 stroke, do I need to go with a 5.7 or 6.0 rod?
Will the rod length affect compression ratio? Or will that be determined by the piston selection?
How can I learn which rod will work for me?
The heads that will be used are AFR 190's. 74cc. I would like to trade up, but cannot presently.
Thanks for the info.
Thanks guys for your help.

 

It's a trade-off when selecting between 350 and 400 main journal diameters. The 350 journals are obviously smaller than the 400's, thus there is less friction and the bearing speed is slower. The 350 mains MAY give you a slight power advantage, but I'd guess it would be in the single digits on a 500+hp engine. The 400 mains, being larger, means the crank has a larger cross section and is stronger, but the bearin speed is slightly higher and thus slightly more friction. I chose the 400 mains for the extra strength, but as with the power difference, it is very small. Either way is acceptable, you might catch a price break with the 350 mains, but it would be minimal.

I prefer the Dart blocks over the Motown blocks, but the Motown blocks are good blocks form the one's I've helped otyher guys with. They intially came out with 1/2" main bolts/studs and had some main web cracking issues in high-horsepower racing situations, but I think they've since gone back to the stanfard 7/16" diamter main bolts/studs and I haven't heard of anymore problems. Even the one's I know about where in 1400+hp 'street legal' racing engines.

Still, I prefer the options available on the Dart blocks, like the spread pan rails and raised cam. When you get to a 4.0" stroke or more, these features really help out alot, and go a long way towars making it work. I also like the fact they offer tall deck blocks. I went with the 9.325" deck block, which allows me to run a 6.125" rod with the 4.0" crank, maintaining an acceptable r/s ratio of 1.53. A 5.7" rod, 383 has a 1.52 stroke, so it's comparable.

Rod lenghs do not affect compression ratio, that is determined by your piston design (dish, valve reliefs, dome, etc), combustion chamber volume, head gasket thickness and stroke( plus any crevice volume).

To find the longest rod you can run, call your piston manufacturer of choice. Tell them what your deck height is, you stroke, and what your application is (rpm range, desired compression ratio, forced induction or N2O) and they will tell you what their minimum recommended compression height is. They can also tell you what the longest rod would be, but if they don't, all you do is subtract :

deck height - (1/2 of your stroke + piston compression height) = longest rod length

In most cases the result will not be a standard rod lenght, so you can just chose a standard rod legnth that is shorter than what the result was. You would then add the difference to the pistons compression height.

i.e.
9.025 - (2 + 1.20) = 5.825 or 5.7 (some companies make 5.80" rods).

 

http://www.smokemup.com/utilities/calc/displacement.cfm

This is a nice site for all kinds of calcs

The block grinding is not a big deal. Call a couple of shops and say that you want to put a 3.75 stroker crank in your 350 and you bought the 350 journal size internally balanced crank. Just price it out. I would imagine your going to hear 2-300 dollars.

Weight is the all important factor. Your slinging more mass. Monty mentioned bearing speed also.

I'm not a superram expert. But logic tells me that they have a max cfm rating per tube. So the higher you go with C.I's the lower the max rpm is. So if a 383 guy tells me the max rpm flow is 6500. Your 427 is only going to have enough air for 6000

 

Yeah, if your choking this thing down with a Superram, it doesn't really many how many cubes you have over 400 inches, it'll just be that much more unusable low end torque and even less rpms on the top end.

 

We must also consider that he is trying to do this with 190 heads as well. Peak HP will probably occur well under 6000 rpm with the heads and intake.

If he now considers that machining the block is acceptable, then the longer strokes may be used, but now he should step up the rest of the components. Spread rails are advantageous on the 3.875" stroke and larger, unless you are going to step up to serious rod selection (i.e. Oliver strokers, etc).

What are the goals? This must be decided before proceeding with the plan.

Just my thoughts on the subject.

Aaron