383 Stroker

[The Sherriff]

Just bought an 86 K10 guy said it has a 383 Stroker in it, how can I confirm that’s what it is and what size transmission would be best for that motor? Any thoughts?

 

[75gmck25]

What transmission and rear end ratio does it have now?

You can buy or build a 700r4 that will survive, but it’s easier/cheaper to build a TH350 if you don’t need overdrive. TH400 will also work if you get one for a good price, but it’s probably overkill for a 383.

 

[Buck69]

Interesting.... I am not aware of a simple way if it does not have a fixed tag or build sheet supplied with it. They are a 5.7 bored .030 over with a slightly longer stroke. Originally a 400 crank was used with larger main journals, but aftermarket rotary groups are the more common way they are built now. Without removing the oil pan to identify the crankshaft or even a cylinder head, they just look like a 350 on the outside.
I suppose you could carefully try to measure the stroke through a plug hole, but thinking it will be tough as it isn't much more than 1/4" longer. Maybe you could figure out a way to measure the volume of air pumped on a compression stroke?

 

[Rickf]

Or with a scope, you might be able to read some info off the top of the piston.

 

[fast 99]

There are testers available that measure CI. Used for tech inspections on race cars. Likely not worth the expense for home use.

Does it have 3 soft plugs on the side of the block or an externally balanced crank? Either would be a sign of 400 sb parts. However, I believe that would make a 372 not a 383. Block casting number?

 

[idahovette]

Thot a 383 was .060 over???????

 

[Buck69]

Or with a scope, you might be able to read some info off the top of the piston.

Never thought of that, but you may be correct. Believe it depends on which con rod was used in the build though.

 

[mlsceo]

Thot a 383 was .060 over???????

.030 over with a 3.75 stroke.

 

[Rusty Nail]

If you stick the pedal about half way down doin about 20mph and the tires start roasting? You might have a 383.

Just kidding but not really.
Supposed to have a 400 crank innit . I'd start counting teeth on the flex plate and looking at the crank pulley for a key.
Prolly a two piece RMS block or it has a $1200 aftermarket crank innit.

If he said that and you can't tell by driving it? Outlook not good.

Hope this helps!

P. S.
A stock th350 won't last very long behind a well built 383.
I suggest th400.
If you had a 383, you'd know it. Looking at the piston tops won't tell you anything... I guess poor camshaft selection could wussify one though ?

You can tell by lookin if you have a 383.
Verify a two piece RMS 350 block with the casting number.
Keyed 400 crankshaft.
400 (153 tooth) flex plate.
Burning tires.

Not trying to be Debbie Downer but I'm a realist. Too much overlap turns lots of 350s into 383s with a for sale sign.

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[Bennyt]

400 is externally balanced. It should have an 8" dampener. If you feel behind it, you will feel a cut out half way around from 9-3 w/ the key at 12

Aftermarket damper will have a bolt in weight.

 

[Bennyt]

Does it have 3 soft plugs on the side of the block or an externally balanced crank? Either would be a sign of 400 sb parts. However, I believe that would make a 372 not a 383. Block casting number?

4 Bolt 400 block have 3 per side, 2 bolts have 2 with a large external rib for water jacket.

 

[SquareRoot]

400 is externally balanced. It should have an 8" dampener. If you feel behind it, you will feel a cut out half way around from 9-3 w/ the key at 12

Aftermarket damper will have a bolt in weight.

This. Pull the heads or confirm it is externally balanced. If it's done right, a turbo 400, 4l80 or nv4500 is in order for durability.

 

[The Sherriff]

Thanks for the info!

 

[Ricko1966]

If there's a round round track near you see if the you can get the tech guy to put the p&g on it for you. A 383 is a .030 over 350,327 or 302 block with a 3.75 crank,so you could run the block number to confirm the block. You can't tell what stroke it is without measuring the stroke. If you are lucky as others have mentioned they used an externally balanced 400 crank but they may not have. So to measure stroke you can pull the pan,or pull a head and measure the travel from tdc to bdc. Reading numbers off the pistons is an extremely unlikely even if they have a part number,due to the variables,it could have .030 350 flat tops on 400 rods,it could have purpose made pistons on 5.7 rods or 6 inch rods.

 

[Rusty Nail]

I wonder how much clearancing you'd have to do in order to stuff 6 inch rods in a 383. That would be so cool.
You have to clearance the web for 5.7s but it's only for two cylinders I think. (#2&5?)
The main journals of a 400 crank are bigger than the 350...they have to be enlarged. Whatever the word is..The machine work of the block is why they cost so much to build. Not providing a build sheet is very suspect...a guy would be wicked proud of it.

Now we're at the end of my 383 knowledge, (didn't take long) sorry I couldn't be more help. They are tire burning mothers though - ESPECIALLY in a pickup.
Gobs upon gobs of low end torque. That runs out of breath? Short rods?

Camshaft selection is critical.