I have a spare 348 truck block complete-going to have it rebuilt. I have heard that the truck blocks were lower compression, how much I don't know. I read once where some had rev limiters on the distributer, don't know how true that is. On a Jalopy forum I'd read 10/1 pistons would give you 8/1 compression. What differences one needs to be aware of I'd appreciate as I begin to disassemble it.
348 "x" Truck Block
- Thread starter july2849
- Start date
Look for notches in the cylinder combustion area. Some so called truck blocks had only one notch the same as passenger car blocks. A true 348 "truck" block will have two notches in the same area. Ordering pistons for the passenger car block you get what you order, if you order 10.0:1 piston your compression will be 10.0:1.
First off,what is the casting number on that block? If it's either 962 or 655,which is where the X on the block is usually found,then Ray is right about the pistons.The 962 and 655 blocks were heavy duty car blocks with slightly thicker main webs and armisteel caps.These blocks started in the 62 production.A truck block with the earlier 5011 casting had two notches in the combustion chamber area,one under each valve.
No worries, block comes back from casting codes as a 1961 passenger car. Half your problems are put to rest. This block has only one notch. All 348 engines had at least one notch. Your question was why the notch. It was used to lower compression for truck build engines. Truck engines see a boat load of idling time and are notoriously loaded heavy and owners expected to use regulat low octane fuel for obvious reasons. GM used the single notch block double duty for trucks and cars to reduce costs. Good news for you pistons of almost any compression ratio are available.
Is there any was to fill one of those notches? I suppose welding would introduce stress???
Probably lots of fixes have been tried.
Probably lots of fixes have been tried.
My end use for the block is undetermined. I bought it as a slave block in to have in the shop, and have used it as such. It helped me determine that the engine build shop on my current 348 used a short oil pump shaft, naughty boys.
I was thinking about a mild build, something to drive around the city-block was said to have 40K miles on. I'll get the dates.
Next question I read that "X" blocks had wider spacing for water pump and holes were a different configuration-I will check that.
I was thinking about a mild build, something to drive around the city-block was said to have 40K miles on. I'll get the dates.
Next question I read that "X" blocks had wider spacing for water pump and holes were a different configuration-I will check that.
Water pump bolt spacing on all W blocks are the same. As much as I know.
Some of the truck W engines had different water PUMPS,but they all bolted on in the same place.
That 962 block is from a truck or industrial application since it has 333 heads, truck intake and and a truck oil pan. Check suffix code on the right front.
PS. Not all 962 blocks are the same. The early version had no X and had a normal alpha numeric date cast. The bearing webs were not as thick as the later versions with the X and Julian casting date. I don't recall if those had 2 notches or just one. I seem to recall they also only had a single notch and used an intermediate truck head until the 333 came out.
PS. Not all 962 blocks are the same. The early version had no X and had a normal alpha numeric date cast. The bearing webs were not as thick as the later versions with the X and Julian casting date. I don't recall if those had 2 notches or just one. I seem to recall they also only had a single notch and used an intermediate truck head until the 333 came out.
So many things could have been swapped out over the years also. Back in the day if you damaged a block you got one wherever you could. There was nothing special about the 348 block, nothing. Matter of fact you could say the same thing about the 409 block as far as contractors were concerned if a dump truck or car needed a 409 block you sourced it wherever. In my case I bought a 409 out of a milk truck. It had a "New Idea" four speed behind it. I pealed it down to find a 1962 passenger car block, 690 heads, solid lifters and a 348 crank rods and cast pistons. Being that the notches were machined in I suppose if your wrench was anal enough you could end up with two notches in a car block pulled from grannies 59 Parkwood. I defer to Cecil.
I imagine that welding up a notch would be easy for companies that do it well. Midwest cylinder Head in Nevada Iowa is known for fixing Cast metal motor parts in anyway you can dream.
Get bigger valves and do some simple hand porting and you would get there quick. Hydro flat tappet will get you there. Anyone have Dyno results to share with this combo and some specs of the motor for a better understanding?
That's kinda what I was thinking. I'm surprised someone hasn't tried it.
400-425 real hp would be easy with a 10-10.5 compression if the short block is slightly stroked[409 crank],a hyd.flat tappet or hyd.roller cam in the 230 in,236 exhaust @.050 range.As to pictures for the heads,look up Yellow Wagon's posts from his build for his stock stroke ,10.25-1, solid flat tappet,476 hp 409 engine.
July while getting 400+ out of a 348 is definitely doable it gets much easier if you go with 1 of the stroker combos a 3.5 crank nets you ~380 ci,the 3.76 gets you ~402,and a 4.00 gives ~427 ci. each step up makes it easier to achieve your goal power at lower rpm which makes it easier on parts to boot,just something to keep in mind as you plan your build.As far as the 333 heads I believe there is a guy on here who has made well over 500 with them of course that is with larger valves and some port work.Oops my bad Yellow wagon was the guy I was referring to and for some reason I thought he made over 500.
The day that his engine was dyno'd,the air temp was in the mid 90's,with humidity to match! Cooler,denser air,and a roller cam would have easily have pushed that engine into the 500 plus range.John's right about the stroke.The stock stroke 348 can reach 400 ,but the torque peak would be so high that you'd need deep gears,and a loose converter for a street car.
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