Im really getting sick of my 305, it nothing against overall 305's mines pretty quick but mine is just a trouble prone engine. As soon as I fix somehitng something else goes wrong. So I was looking to put something new in it.

I can get ahold of a 350 block easily and all the aftermarket parts on my 305 like my cam I can transfer over.

With a stock 350 block what do I need to make a 383? How much does the block have to be bored, what length rods do I need etc.....?

 

typical 350-383 uses a 4.03 "bore so .03 over bore and a 3.75" crank. Depending on the deck height, usually around 9", you can get anywhere from 5.7 to 6" rods for it. You'll need some different pistons with the correct compression height so the piston comes up to TDC around level with the block, you can have it recessed or sticking out slightly if you want I guess. Also you may need to notch the block for clearance on the rod bolts.

 

Dont most stock 350's come with 5.7 rods? So your mostly just going to .030 over and putting the 3.75 crank in?

Would you get more HP by going with the 6.0 inch rods?

 

The 6.0 rod is the way to go. with the increase in stroke the side loading on the piston will decrease with the 6.0. Also it is alot easyer on the crank down stroke with the longer rod because the rod angle is different at the end (bottom) of the stroke. It will rev smother and quiker. Oh yea all 350's came with 5.7 rods from the factory.

Good Luck
Steve

 

Yeah I meant you could use anything from 5.7 inches to 6 inches. 5.85 or 6 inches is a better choice though for the reasons stated above. But depending on what your going to do to the engine you may want to go with 5.85 like if your using heavy amounts of nitrous or boost.

 

There are simple and cheap ways to make a 383. Racers have been doing it since the 70's.

Start with a 4" bore block. The most popular is the 010 casting. Get a 400 crank and con rods (5.56"). Bore the block out .030". Have the mains on the 400 crank turned down to fit into the 350 block. Use +.030" 350 pistons. You'll also need a 400's balancer and flexplate/flywheel. It's a simple conversion. This can only be done as a 2 piece rear main.

It gets complicated when you start using custom parts. Going to 5.7" or 6" rods means the wrist pin is moved up higher in the piston. The higher it's moved up, the more it's moved into the oil control rings. Using a longer rod also requires clearancing the block so that the rods or rod bolts don't hit. This may also mean using a small base circle camshaft. Using the longer rods means you also need special stroker pistons. All SBC rods except those from a 400 are 5.7". They're not all the same though. Because of the different engine sizes, rods have different weights. Whenever building an engine with mismatched parts you should always have it balanced.

There isn't very much you can reuse from the 305 for the 383. The heads probably won't flow enough to be worth while, the cam will be mild compared to being in the 305, the 305's TPI won't be enough to feed the bigger engine. What size are the tubes on those headers. 1 1/2" will be too small.

It's better to build an engine with the longest rod possible but it's not always required. I ran a short rod 383 for 2 years in my race car. It ran high 11's at 117 mph. It blew up when the "stock" bottom end finally let go. Before I raced it, the engine had a LOT of street miles.

 

Hows this for a stroke of luck....My Dad calls me today because I told him i was getting tired of the 305 and he told me he just bought me a 4 bolt Main 350. There was something else rare or special about the block too something about Nickel I guess for stregthining.

Anyway, I understand pretty much everything you guys have said save for what exaclty I have to do about clerancing with the crank and the deck. Especially If I go with the 6.0 rods. I was looking at 6.0 H-Beam rods with full float pins. I think thats what Im gonna go with.

 

Here's a couple pictures of my 383 clearanceing, and a comparison of a 6" stroker rod with a stock 5.7 rod. With those 6" rods, the rod bolts stick out of the back of the rod less, and therefore less clearancing is required. I didnt need a small base circle cam. But with the 3.75 stroke and 6" rod, the wrist pin hole is way up in the oil ring land. You can see in the picture of the block how the pan rails and bottoms of the cylinders have been clearanced for the rods. Also, keep in mind that if your rod bolts come that close to the oil pan rails, they may very well hit the oil pan. Nobody told me about that one, and I didnt discover the problem till the motor was already in the car, and i was turning it by hand to adjust the rockers. Heh, good thing I discovered it before trying to start the thing. Anyway, some people use the 350 oil pan without a problem, but mine was hitting pretty bad. I clearanced my pan with the BFH. Although they do make oil pans specifically clearanced for stroker motors.

http://www.fbody.com/members/ViciousZ/383clearance.jpg
http://www.fbody.com/members/ViciousZ/rods.jpg

You may have to cut and paste the URL, as fbody.com seems to be a bit pissy lately about hotlinking.