building a 383

[raroZ28]

He came down in price to $225. It's a 4 bolt LT1 block with 25,000 miles on it. You can still see the cross hatches on the cylinder walls. It had spun the #3 main, but by looking at the pictures, I cant see any damage. I'm sure there is nothing wrong that a machinist cannot fix easily.

The block will need to be honed again. If the damage is too extensive, and you don't want to bore it, they can sleeve it for you. $$ Or, just pay about 110 bucks and get a bore n hone and go with a bigger piston. But since it was a main bearing I doubt the cylinder walls got damaged. 225 sounds like a steal for a 4 bolt, I'd jump all over that

[Jeff_in_Atl]

I'd like to use the stock flywheel and damper. What is my best route for balancing in this case?

"You need to tell your engine builder that you want to use a stock flywheel and the best thing you could do is give him the flywheel to use when balancing the crank."

Our stock dampers are not keyed, so I assume they are neutral?

yes

And my stock flywheel is couter wieghted, correct?

yes

Should I just have the machinist externally balance the 383 using counterweights on the flywheel?

yes because of your first statement "I'd like to use the stock flywheel and damper."

Or, would it be better to have it internally balanced and have a neutral flywheel?

doesn't matter

I would think that having it internally balanced would result in a smoother feeling engine,

doesn't matter

and it would be easier to replace the flywheel in the future?

yes

[TraceZ]

The block will need to be honed again. If the damage is too extensive, and you don't want to bore it, they can sleeve it for you. $$ Or, just pay about 110 bucks and get a bore n hone and go with a bigger piston. But since it was a main bearing I doubt the cylinder walls got damaged. 225 sounds like a steal for a 4 bolt, I'd jump all over that

I'm going to have it bored .30 over no matter what. What displacement does that make, .30 over with a 3.750 crank?

[Jeff_in_Atl]

I'm going to have it bored .30 over no matter what. What displacement does that make, .30 over with a 3.750 crank?

What is the standard bore of a 350?

[TraceZ]

Isnt a 350 a 4" bore with a 3.5" stroke?

[Jeff_in_Atl]

Isnt a 350 a 4" bore with a 3.5" stroke?

pieR²XstrokeX8
3.14 X (dia/2)^2 X stroke X 8

[raroZ28]

I think it would be...

5.7 x .030 = 0.171 + 5.7 = 5.871

5.8L then??

The actual displacement of the 5.7L might be like... 5666 cc, so that's the figure you would use to find the exact displacement. Been a while since I calculated this, am I off on anything?

[TraceZ]

Stock 350= 3.14 x 2.000^2 x 3.5 x 8 = 351.68 (5.7L)

stroked / bored= 3.14 x 2.015^2 x 3.75 x 8 = 382.47 (6.2L)

so, a 383 is actually a .030 over 350 with a 3.750 crank.


350 is to 5.7 as 382 is to X

350 382
--- = ---
5.7 X

350(X) = 382(5.7)

350X = 2177.4
---- ------
350 350

X= 6.2 Liters

[Injuneer]

Whoaaaaa......

Stock 350/5.7L is 4.000" bore x 3.48" stroke = 349.85 cubic inches.

One school of thought would be to limit the overbore to 20/1000ths, to leave you enough wall thickness for another cleanup bore in the future. I run 4.020 x 3.75" = 380.7 cubic inches. Also provides a little extra meat in the cylinder walls for a big shot of nitrous.

GM also makes a 3.800" stroke crank, to provide what they call a 383 cubic inches crate engine (actually 382.02) with a stock 4.000" bore. That crank and 20 over will give you 385.65 ci.

[TraceZ]

Great info, Fred. So, say I use a 3.800 crank. How would I know what length rod to use? Would it be a 5.7", or a 6"? Does it depend on the piston?

What are the specifics on the stock heads? What size are the combustion chambers?
If I have my stock heads P&P, what type of piston would work best to acheive the optimal compression ratio? What should that ratio be?

[Injuneer]

First you select the stroke. Then you select the rod length.... there is also a 5.85". Then you get a piston to match the rod + 1/2 stroke length, because the crank throw + rod length + piston compression height determines where the piston top sits, relative to the "deck height" (distance from the crank main centerline to the top) of the block. It might be a little harder to find an "off-the-shelf" piston to work with the 3.800" crank. Any good piston manufacturer can make you a set, but it adds a few $$$$.

[TraceZ]

Update:

The block is sitting in my garage on a stand now. The "spun" bearing never actually spun, so the block saw no harm. It doesnt even have any ridges at the tops of the cylinders.

I also got the front cover, oil pan, baffle, oil pump drive gear assembly, rear main ring, water pump drive and the oil pan rails.

This coming weekend I'll be getting the rest of the parts like the lifter retainer bracket, cam retainer and some odd nuts and bolts.

I'm still not sure if it is going to be a 383 or a 396.

[AmericanZ28]

Any pics?

[TraceZ]

Any pics?

Pictures? I never take pictures!! j/k.

Here are a few.

[TraceZ]

Check my math please...

proposed 383 (option A)
3.75" = crank stroke "400 crank"
9.025" = stock block deck height
5.7" = rod length
1.45" = piston compression height

The compression height of the pistons would need to be:
3.75/2 = 1.875 (half the stroke length)
9.025 - 1.875 = 7.15 - 5.7" rod = 1.45" compression height

proposed 383 (option B)
3.75" = crank stroke "400 crank"
9.025" = stock block deck height
6.0" = rod length
1.15" = piston compression height

The compression height of the pistons would need to be:
3.75/2 = 1.875 (half the stroke length)
9.025 - 1.875 = 7.15 - 6.0" rod = 1.15" compression height

So my question is... which would work better? Would one compression height provide better durability over the other?

Jegs sells pistons for both rod lengths to build a "383 with a 400 crank". What are the advantages / disadvantages? Is one way better?