I was reading that you can do this to make a 383. I was going to do a budget 355 (just pistons and balanced) but I"m thinking about doing a 383 w/ 400 rods cause I have some already. what is peoples opinion. a cheap 355 while I"m building the good 383, or a cheap 383 while I"m building a good 383?

thanks

Josh

 

NM

Misread the post...about to look like an ***!

 

That's the way it was originally done before all the trick parts became available. My old 383 was a short rod stroker and ran fine. It's a cheap way to make a 383.

350 block bored out .030"
400 crank machined to fit into the 350 block.
400 con rods (invest in good rod bolts)
350 pistons to whatever compression ratio you want. You could even cheap out and use cast pistons.

Since this is a factory component conversion, there's no requirement to clearance the block for anything. Get everything machined. Since you're using a mixture of parts, balanceing is always recommended even for a street engine.

Personally if you need to pull a 400 crank out of a 400 engine to make a 383, the 400 block had better be junk. No sense wasting a good 400 engine to make a 383.

 

k here is my part list then.


new scat cast crank for a 1pc rear seal
400 rods -new rod bolts
Forged pistons
all balanced

what I need to know is do I usea 400 or 350 Balancer/flywheel?

thanks

Josh

 

Stephen, I guess we're the older crowd, because that's how I built my first stroker.

The only thing I ran into was the block had to have a couple of notches removed for the rod bolts, and my pistons didn't work cause a couple of them, the skirts would hit the crank counter weights.
Oh and I used a junk yard 400 flexplate that didn't work, cause the bolts didn't line up with my converter.
If I remember right, I had the 400 crank machined 60 under, and used 10 over bearings. For the world of me, I don't know why they didn't go 50 under, and use std bearings. Maybe the machinery didn't have a 50 under setting

You can get it work, especially now with parts the way they are. You can get pistons with off set pin, or shorter skirt pistons.
I had my pistons machined, but that was back in the late eighties - early nineties or so.
I think I got 500 miles out of that engine I was a little crazy (er) back than ;D

Ron

 

You heavy line gurus can correct me if I am wrong, but I am inclined to think that if you are getting the rotating assembly balanced, you should be able to use whatever balancer you want - you just have to give it to the machine shop when they do the balancing (as always). Or (I *think*) you can get a neutral balanced balancer later (like for a late model one-piece rear main crank?) if they balance the rotating assembly entirely internally.

I think I am correct here.... I know handing over the balancer for rotating assembly balancing should eliminate any quess work, but I guess I am not all that certain on the latter part of my statement . Ya'll can straighten this out if I am not .

 

thats true, I guess I never thought of that.

thanks

 

Thats true but they will have to add tons of heavy, expensive mallory metal to the counterweights to get it balanced.

 

so if I"m getting this right when I have my rotating assembly balanced take in my L98 flywheel and flexplate, but a 400 dampner? once again I'm going ot be running a scat 3.75 stroke crank w/ stock 400 rods and some 350(.030 over) pistons. to make a 383. thanks

Josh

 

I thought about that before posting, but with him using an aftermarket crank I figured it would probably be on the heavy side and not need filling to get balanced out.... I was under the impression that the aftermarket cranks come on the heavy side expressly for this purpose (balancing). (Correct me if I am wrong again )

 

I would say definately bring in the L98 flexplate/flywheel from your application, but I guess I am still not 100% positive on the balancer... I am inclined to say (as I mentioned above) that you should be able to bring in the L98 balancer as well (a new one of course as you don't want to risk a new engine with an old balancer , but a stock replacement type).

I am actually building a 383 right now as well and my machine shop said to bring in the LT1 flywheel off my current 355 (I have a T56) and then I am going to purchase a streetdampr for internally balanced SBCs for my balancer. This is all going to work with a 4340 Eagle crank, 4340 6" H-beam Eagle rods, and Ross forged pistons.....

 

The L98 flex plate / balancer will not work with that combination. Leave it behind.

If you use the stock 400 short rods, there isn't enough room to internally balance the rotating assembly without using mallory metal. A stock crank isn't worth that.

You'll need to get your 400 crank turned down to 350 main journal size; if you have a set of rods out of one factory motor, not just eight rods from somewhere, and the crank they came with, then you don't have to have anything balanced. If your crank and rods came from different places, then you definitely should have them balanced. So with your replacement crank, you'll need balance work.

Use a 400 damper, and a 400 flex plate if your can fit the large starter. Otherwise you'll need to use the small flex plate, and either have it "unbalanced" to the 400 spec, or use a "pork chop: weight.

Make sure the crank you use is intended for use with the short rods, because if it isn't, the counterweights will not fit under the pistons when they are at BDC. A typical "383 stroker" crank is set up for 5.7 rods, which do leave eough space for the counterweight, and so are typically internally balanced. a crank like that will not work with stock 5.565" 400 rods.

 

Since I just built an engine the way you are planning on doing, meaning the same parts, let me give you a little advice. First find out if the crank is internally or externally balanced. I ended up having to pull the motor fight back out of my car after being rebuilt due to the engine not being balanced along with machine shop guys ignorance as well as my own on the issue of balancing. I bought a cast Scat crank for use with the 1 pc. rear main, which is what you're planning on using. Secondly you can use the stock flexplate either if you have the entire rotating assembly balanced including the 400 damper or if you use a zero balanced damper along with an internally balanced crank. The part about the counterweights hitting the pistons when using shorty rods is true, but this won't matter if you're having the engine balanced and you don't mind spending fifteen minutes taking about thirty-thousandths of material off the outside of the piston skirts using a die grinder, or in other words grinding very little off the outside of the pistons. This is what I did and it worked out okay. You may need to have the rods resized as I did for the proper bearing clearances, and I would recommend having your rod journals on the crank chamfered, to help oil flow. But if you're unsure about your crank, balance your assembly anyway. My crank had about 300 ounces removed altogether, which makes me believe that my crank may have been internally balanced, in which maybe just taking off my 400 damper and putting a fluidapr on instead may have cured my balancing problem without pulling the engine. Either way, get the engine balanced and triple check all of its clearances.

 

thanks alot man that REALLY helped me out, just the info I needed
Josh

 

I also just got done building a 1 piece seal 383. I looked all over for a 1 piece 400 flexplate. I called several shops, ended up useing a l98 flexplate. The machinist had to add some weight to it, also used a 400 balancer. When I was looking for cranks, the internally balanced cranks were for 6" rods only. If you're going to all this expence, scat pro 6" I beam rods can be had for 270.00 more. 383 pistons don't cost anymore than 350 pistons. I Check out the 383 rotating assys, on ebay. Many scat rotating asemblys sell around 700.00, ready to go.

 

Eagle has cast and forged 383 cranks for 5.7" or 6.0" rods, 1-piece rear main seal, internally balanced. Just an FYI for others .

 

This is where the so called "bargain" stroker cranks get pricey...
Some of these need metal ADDED ( read $$$$ ) to balance 'em.

Also make sure you and the machine shop are on the same page. Alot of times, when they say "Balance" they mean they weight the rods, and take the lightest one and take material off the others to match, same w/ pistons.


Make sure they mean actually assembling the rotating assembly, w/ balancer and flywheel / flexplate and balancing them at speed.




HTH

 

When I had mine done all I did was bring in one of each. (piston, rings, etc.)
You should also get a sheet with bob weight, recip mass %, bla bla bla or least ask to get one.

If you have the option where you live, take it to a crankshaft shop.

Ron

 

Now maybe I'm missing something here......

But how did they balance it with one piston? They can multiply by 8 to get the "bob" weight, but it wouldn't be correct, because all of the pistons don't weigh the same, and they would have to add the weight of the rings.

When I have an engine balanced, they take all 8 rods, and they weight the big and little ends in a special vice looking rig......they. They take weight off the others to match the lightest one. Then they take all 8 pistons, with rings installed and weight them, again, they get matched to the lightest one.


I normally pay $300 for a FULL balance job, and it's worth it to me.....


HTH

 

The rods where already weight matched when I bought them.
The pistons & pins where right on, unless you consider .001 grams a discrepancy.
Had a fluid dampr, so that was out.

They basically took one set of rings, a piston, pin, rod, bearings, and flexplate. (I think that’s it.)

I think I paided right at 100 buck for the balance, and another hundred for the crank.
The crank was a 3.48" / .10 over...
Colorado CrankShafts.

Ron