have a 350 now. was wondering is there anyway to know if i have a small journal or large journal motor?? i am doing my first bottom end and have alot to learn about it. I am wanting to stroke it to a 383, please correct me if i am wrong, but the stroker has more bottom end correct? thanks for the info. graemlins/clonk.gif

more than likely you have a 2.45 diameter crank if the motor hasnt been rebuilt..this is the standard size for a 350.the only small journal cranks i know of are in the old 327 motors.in 1968 when the 350 was introduced,blocks moved into the big-journal crankshaft era and the 327 was produced both in small and big-journal sizes.later 327s from 1968-1969,when the engine was dropped,had bigger main bearing journals than the earlier models.and yes,the 383 is an excellent motor to build from a 350 block.i'm building one myself and they have excellent torque and bottom-end over a 350.i'm going with a 040.overbore which will yield 385 cubic inches.one thing you need to remember is do not use a 400 smallblock piston rod because they will rob you of horsepower because of rod angularity.they are shorter than 350 rods and create too much friction trying to rub the outside cylinder walls. graemlins/thumbsup.gif go with a standard 5.7 rod or longer.

Some of the first 350's were small journal but they are few and far between now.

Originally posted by Dragn70:
Some of the first 350's were small journal but they are few and far between now. my guess is the '67 350's from Camaros right?

as has been said all 350s are large jurnalls .bowtie i dont want to start a argument but i dought if you would ever know if the 400 rods will rob any horse power .i have run 400s and 383s with both kinds of rods and seen very little track time differces. used to be the 383 piston for 5.7 rods were alot higher than 350 pistons but now days there are about the same. one advantage with 400 rods and 350 pistons is you dont have to clearance the rods or block. no matter what rod you use all ways use good after market rod bolts

its a 75 truck motor, 4bolt main, so this should be the large journal right? and anybody else got opinions on rods and pistons?

A '75 350 would be a medium journal - SBC 400's have large journals. The old 283's, 327's, and other old pre-68 engines typically have small journals.

The difference between the short 5.565" rod and the long 6.0" rod is not that huge for a street type combo. The 5.7" rod is good middle ground for the street IMO since 5.7" rods were used in just about every modern GM small block --- they are cheap and plentiful.

The shorter rod will provide higher piston aceleration rates which slightly improves volumetric efficiency and low-mid RPM torque. The greater rod angularity also helps improve low end torque by virtue of giving the piston more leverage on the crank.

The long rod has a few other advantages that can more than make up for the difference - especially in a high RPM motor. The 1st major advantage is lighter pistons. Since the pistons need to be shorter to accomodate a longer rod, the piston is shorter and much lighter. Also the slower piston acceleration rates can help ring stability at high RPM (like over 6500 RPM) which improves cylinder sealing and reduces blowby and lost HP. The longer rod having less angularity reduces side loading (and wear) on the cylinder walls which just plain helps durability at high RPM. I think the difference between the short and long rod is only about 4% though.

PS. Even the short 5.565" rods typically need some light clearancing work on the block. GM cast a small notch into the 400 blocks to provide the necessary clearance.

eric,
some awesome info there. I do not plan on running much over six, and maybe 6500 for giggles once in a while on the street. I am looking at making most of my torque and power down low, like peak horsepower around 6grand. but from what you stated i would rather run the longer rod and sacrifice a little low end. anybody else, feel free to voice opinions!!! graemlins/hurray.gif

Junk Yard, 67 was a small journal 290hp and so was the 302, both Camaro engines.

junkyard,no offense taken.i think the main mistake some people make when using the shorter 400 rod is they use a regular off-the-shelf flat-top piston and an open-chamber smog or low-compression cylinder head.this combination produces little or no more horsepower than a typical 350 built with a long rod and closed-chamber head.it does use more air and fuel,though,meaning it is an inefficient package.the debate over the shorter 400 rods losing horsepower due to friction against the cylinder walls(rod angularity) will probably still be around when we're all gone.i'm sure it is minimal if it really exists. ;)

ill agree bowtie and will add if im going to buy after market rods i would buy 5.7 or even better 6 inch rods to build a 383 for racing and the lightest pistons also but you want see me throw any 400 rod 5.56 away either.they make a good way to make a reel good steet or race motor using the cheaper 350 pistons even with 76 cc heads and a 292 solid cam you can run in the 12s easly .for marty the 302 used a 283 stroke small jurnal crank it was a great motor and loved rpms and i never knew that any 350s were built with small jurnals ,learn some thing new all the time on this board aint it great

I like the 6" rods in my 383. The other two we have are 5.7" rod and are by no means sub-par engines. But IMO the 6" must have some good qualities. I have a 3/4 Race cam from Crane in my engine, my dad has an Energizer 272/272. My engine will idle at 600rpm and pull 21" of vacuum. We can't get my dad's over 18" at 800rpm. I was told my engine would not idle well at all and the engine would yeild pretty poor results on the street. Oddly enough I get 20mpg without OD, and that is combined city/highway. It drives quite well and is very nicely mannered. We do have some major differences, but all of them in theory would have made his engine a better street type of motor, like, wider LSA, smaller intake runners, smaller header primary tubes. I think if you can get a good combo going the rods actually become quite important. But, as everyone always says-and they are totally correct- It is all about the parts as a whole. Long rods mean bubkiss if you have a 1050cfm Dominator on your stock cammed 283 small block. I would bet good money that the output capability of a given displacement(383 is possibly the most argued) has the same power potential with any rod length -if- everything else is matched. Now, longevity, that may be a different story. I think a shorter rod would wear the bores out faster and you might not get as much time out of the engine, but when it comes to output, I bet they would be pretty close.

i never heard of a small-journal 350 either,but i'll keep an open mind.hey junkyard,i'm a bama boy myself,not far from birmingham.is the dragstrip in steele,alabama a 1/4 mile? all we have locally are 1/8 mile.

I worked in a machine shop through high school. We rebuild a 350 from a '67 or '68 camaro that was small journal. They do exist.

PHR published an article in the early nineties wherein they dyno compared a 383 with 5.565" rods and 5.7" rods. The "short" rod motor made 3 or more ft-lbs down low and the "long" rod motor made 3 or 4 more hp up top.

Joe Sherman did a similar comparison a few years later, turning a SB 400 to 7,000 rpm with stock 5.565 and stock 5.7 rods and found the same thing.

If you calculate the rod angle, the difference in side loading, IMO, is insignificant with respect to cylinder wear.

I have a fresh 383 with 5.565" rods, flat tops, AFR's and it runs fine. I selected parts with a 6,000 rpm shift limit in mind. I don't think there would be any noticible difference with 5.7's. However, if I didn't have the stockers, I'd have purchased 5.7" aftermarkets.

For a street motor, stay away from the 6" rods and keep the wristpin out of the oil ring. If you want to routinely spin above 6K, the longer rods and lighter pistons may have merit.

bowtie the track is 1/4 mile track they run 1/4 on friday nights kid night.and on sunday for test an tune the rest of the time its 1/8 mile for sat night braket racing, this sunday it will be 1/8th mile though because they are having a benifit race for the boy that was killed at section track about a month ago when his dragster throtle hung open when his carb scoop cam off. all the profit of the race is going to his family .he also owned section track

I have several "History of the Camaro" type books and the story is Chevrolet had fears of releasing a new small block in a new model and having problems. They felt the extra displacement warranted larger journals. This has been discussed dozens of times here and on Team Camaro and (no disrespect intended) there has been no positive proof of a small journal 350.

Check out this site. http://www.mortec.com/journal.htm I've found their info very reliable.

Flame suit on!!

I am 99% positive that 1 did make it out of the factory because my dad had one in about 1974. A friend of his was the second owner of a 67 Camaro and he pulled the engine and put in a big block. There has been many conversations about that engine in our hot rod croud for years. The engine was sold in the late 70's and slung apart when the 8k tach pegged out in the water box at Riverside race track in Pearl, Ms. My dad spent 20 years as a dealership mechanic and has many stories about freak engine parts from the factory, mostly Mopar.