I ran across a guy who has took a 327 Small Journal and stroked it to a 383. What are your thoughts on this setup and what CAM and HEADS would I have to run.

It is a 327 block with the casting number of 3782870. It is bored to 4.030 over size with a new eagle crankshaft that has a 3.750 stroke and that was than ground so the mains fit the small journal block. It has 6 inch Scat I - beam connecting rods with ARP bolts and bushings in the small end for floating pins Keith black pistons part number KB 164 .030. It's a internally balanced 383 crankshaft so you can install the original harmonic balancer and flywheel.

Thanks, I'm in the 327 enging buildup process but never thought about this setup.

 

It'll work...but for a long term engine I could flog, I'd feel a lot better with that extra .200 on the mains. Hopefully they put some real generous filet's on those journals.

JIM

 

My 388sbc was built with small journals. From what I understand, the rotating assembly has less friction because of the less surface area with the smaller journals. I ordered my block (4.125 bore)was ordered with the small journals so I didn't have to use spacers

Here's a pic of my crank, you can see the radiuses:

 

The smaller journal crank has less bearing overlap, which can effect strength. The bearing size will have no influence over your selection of "CAM and HEADS".



And .100 larger rod journals. Both contribute to the greater overlap of the medium sized journal crank.



I'll bet those are the medium (intermittent) sized journals you are speaking of. Your bearings are larger than the 1967 and earlier SBCs that is the topic of this thread.

RACE ON!!!

 

Like 427 stated, it will work fine in street applications. However, if you are looking to beat the snot out of it, then you need to rethink this plan and perhaps consider having large journal main caps installed on your early block, line boring it and running a large journal crank. The journal overlap, the distance of material overlapping the main journals and the rod journals is what gives a crank its rigidity. There are plenty of these small journal stroker motors around with a lot of them being built from cast cranks like the SCAT 9000. (In addition there are small block 427 forged stroker kits out there that are only running .275" of journal overlap at 6,500 + RPMs). For peace of mind I would certainly go with a 4340 non-twist forging, have the counterweights cut back to the size of a 327 and have it nitrided when the machine work is finished. You want to have the rotating assembly balanced within one gram and the crankshaft end masses balanced to within one gram. I have an Eagle lightweight 4340 non-twist that has been machined this way. To maximize the journal overlap to .30", one should stick with the large journal rods combined with the small journal mains. Have the fillet radi ground to .125" which requires special bearings but this is done to help stiffness, minor, but we are looking for as much help as possible. Most of these motors don't see much above 5,700 RPM max due to the ability of the stock vintage heads and intakes to flow enough air which isn't great but a built in restriction so to speak so you don't over tax the bottom end. 383s like lots of air. Your stock heads with a good pocket porting job and multi angle valve job will be suffient. In addition, with a 383 your mean piston speed at 5,700 RPM will be About the same as a 327 spinning at 7K and will be putting out gobs of bottom end torque anyway. A nice dependable OEM hydraulic cam for a 383 with 10:1 compression is the L-82 cam. This will make for a great dependable driver.

 

The only problem with cutting the mains down that far is some times the oil holes get moved into the radius of the crank and in most cases the cranks are not renitrided after being turned.

 

There are lots of ways to find that last little HP...but when real race teams shrink this stuff, they are using the BEST available cranks. They commonly use Honda size rod bearings these days AND they narrow the main and rod bearings for less friction. BUT......they also tear this stuff down regularly to inspect and replace.

Yes there will be less bearing speed...that's where the slight help comes from....but this still doesn't seem like the prudent choice to me.

Look what GM did with the 350 and the 302's. in '68...they went to larger bearings. Then the 400's came out with another .200 on mains. We've been getting by for years with turning the 400 cranks down to the 2.45 range to make 383's,,,,,,but I still think it's asking for trouble without a real good forging in there and light rotating parts. And thats a LONG way from using KB pistons.

I think with the limited head flow, a 327 that could turn some RPM would spank the 383 in a race.


JIM