I was asked the other day about small journal and large journal engines (Chevies)..and if you know me...there's no short story..always the long one..but I thought I might try to cover just some of the differences you may encounter on Chev engines...Now..stick with me here...I will tend to jump around a bit as my feeble brain tries to remember this info..
the best way to check is by the block casting number..and plenty of web sites show all these..like this one..generally speaking, small journal engines were up to about 1967, and large journals took over from there..
looks like a typical early 283..or early 265...or SJ 327...they all have little differences to work out what they are..
this pic is an early small journal motor..as you can tell by the big canister oil filter...but it's a 283, as you can tell by the small balancer that doesn't use a damper ring...also, real early 265s didn't have side engine mount location...so..it's a 283...
the other give-away on small journal engines, is they all have an 1 1/4" hole next to the distributor..this had the road draft tube in it...and real late ones had a plug so a PCV valve could be used...if you want to use late valve covers, with PCV..just fit a welch plug in the hole..
SJ 327..note the larger balancer with a damper riveted to the rear..later versions went to the conventional damper with outer ring, and generally around 6 1/4" dia....most, but not all 327s had 4 barrel carbs, where most 283s had 2bbrl...but they did use visa-versa
looks like a late 327...as it has non breather valve covers, breather is in the tube in the intake
typical of what a 350 would look like, as there is no hole next to the distributor...but differences crop up...most orange painted 350s were from late 1968 until about late 70s...then they were blue for a while...and then black
large journal motor..as it has bolt pattern heads...screw on oil filter, and typical 350 large counterweight on the crank flange....but....early 305s were orange...and use 350 style cranks as well...you have to go always by block casting number..
late blue motor..most were 305s...350s weren't used in too many vehicles..mostly pickups in the 80s..
Here's why 305s are good as far as cooling...3.736 bore more room between each cylinder..like the 283s, 3 7?8", the extra water in that gap seems to make them run cooler
three welch plugs on the side means this is a 400...although, don't be fooled..early 400s still had two plugs...look for the counterweighted balancer and flexplate, that 400s had
400s ran hot, as the bores were siamesed...hence, small steam vent holes drilled into the deck helped this problem..350s are 4" bore, 400s are 4 1/8"
not all 350s are 4 bolts, as a lot of people think...probably more 2b than 4 were produced
this is what most people use these days..a new crate 350..note that just about all late black 350 blocks had short pads for the engine # stamping..early are much longer..
typical black engines also had a wider balancer, that extended rearwards...most of these had the timing mark moved way around, so timing light check was done in behind the water pump...could be 305 or 350...but only 350s were 4 bolt optioned..305s were 2b, and..although technically the cranks were the same with the 3.48 stroke, the counterweight was different for the smaller pistons, so you can't swap easily without rebalancing
from around 1988, GM sort of solved the rear main seal leak problems by using a crank with one piece round seal
late on the left, early on the right
this is how people normally identify a block..by writing the casting number this means a 307.
and..this is where you find it
350 crank on the left has a pretty well straight line from the crank to rod journal, where as a 307/327 crank on the right has a 'dip" in that area.
on the left is a 350 steel crank, as shown by what looks like a 1/4" wide area that's been ground away....the cast cranks just have the small parting line.
small counterweight on the left one means a 307/327 crank..right is typical 350
here they all are..well, except for the 305s..and the rare 262s,,265s, 267s..but I have only ever seen one of each in my life
350 8" balancer on left,................................ 400 8" balancer on right..note the counterweight made by removing material from one side
400 on the left,.................. but the smaller 7" 350 style on the right
starters and flywheels..they made two, and most, but not all blocks have the pattern for both starters
factory small bellhousing vs large..notice how the large housing has a bulge to accept the wider mounted starter
standard trans flywheels in large 168 tooth style...350 on the left, but 400 on the right, as it has a built in counterweight.
groan...late 350s with the round flange need the counterweight..so they put them on the flexplate like so...but you can't mix 'em with earlys, as the bolt patteren is smaller..phew!.(but you can get them to suit small or large diameters)
typical early small starter on the left, with the straight pattern, and late staggered on the right
small and large flywheels, sometimes known as 153T vs 168T, ...or 12 7/8" vs 14 1/8"
typical early flexplate has no counterweights..but this one does have, so would be a 400 (or a 454..they look similar, but 454 counterweights are slightly bigger..hope that didn't confuse you )..anyway, .but large or small is need to go with the starter
luckily, just about every new gear reduction starter has 4 holes, so you can use it as small or large configaration
really late starters went to these small body diameter..handy if space is a problem...and less weight..
here's the firing order for all of the chevs...1-8-4-3-6-5-7-2
well..I hope this helped...I didn't get into things like right and left dipsticks..mixing and matching cylinder heads..
.how you can bore a 307 to 4" if your lucky, and use a 350 crank to make it a 350.but then it fools you with the block #...
same can be done to some 283s, bore them 4" and make a 302, or put in a 327 crank and make it a 327.
.how to build a 383, using a 350 block and a 400 crank...
a 377 using 400 block and 350 crank...so many things you can do...
.I needed to build a small cube supercharged motor for a CC/G class 30 years ago..I used a genuine extremely rare 302 steel crank , put it in a 305 block, with custom pistons to suit the small bore and short stroke...and it made 266 cubes..smashed the existing record on the first dragmeet..............but that's another story..
Note ...always try clicking on the photos, as some of them load in larger format...
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