Hot Rods Small Block Chevy Mystery Motor

we know it's cast iron, whether it's a 350 or 400.

Just for reference, here's the 350 crank that's laying in my yard.



And yours

 

Agreed on measuring the stroke with a tape measure...that's at least how I figured mine out. I'm just now learning about the possible confusion on the crankshaft flange.

 

It's not confusing to me. Because I check the pictures. And figure the odds of a dirty old truck engine having been stroked at some time in the past, and not having been decked.

 

I'm just gonna pour a coffee and wait knowing how a lotta guys did stuff when the whole "hot rod motor kit" shit hit the fan. And true enuff, GM wasn't opposed to using some castings for different uses like 350 or 400 when supply was short. I could go look at my 350 010 but what fun would that be? Like Willie Wonka, "The suspense is killing me, I hope it lasts..."

 

Have we measured the stroke yet? I am betting more on the side of it being a 3.48" stroke. I have pulled way more small blocks apart that were "hot rod" motors that were pretty much stock inside. The one I just pulled apart had a Hamburger oil pan, aluminum timing cover, etc. and I could see the pattern on the cam with the intake off to know it had a roller cam in it even though the lifters were gone. That cam happened to be a Howards grind with almost .700 lift. But, most I have pulled apart have something more like a 268 Comp cam and was a race motor...

 

More details...

Stamped steel rockers.

Single valvespring with damper.

Double roller timing chain.

No numbers or manufacturer stamped on the end of the cam.

Heads are 487's (not 487X) - good smog era open chamber heads with 76cc chambers, 1.94/1.50 valves, H141 date code - that's August (H), 14th, 1971. I believe these heads got hardened seats after 1971, but I'm not sure if that's model year or calendar year. Anyway, it appears that these heads are not original to the block, which appears to be a 1978 casting.

 

Like someone mentioned earlier, is the crank damper externally balanced?

 

Pull a sparkplug and scope the piston top to get an additional clue on compression. Measure the cam lift, maybe?

 

looks like a 400 by the end of the crank, in case someone already caught it.

 

OK, agreed, 350 crank.

 

@squirrel says the block is late 70's and the crank diagram is for pre'74 crankshafts. So, there is that. FWIW.

 

Has the rotators on the valve spring retainers, typical truck stuff. The timing chain set is the only hot rod part so far but the cam number would be at the other end. And usually hard to get any info out of...unless you get lucky.

 

So it's most likely a stock 350 with a double roller timing chain and maybe a cam, but who knows without measuring the lift. Looks like a rattle can "performance" rebuild on a 165hp 350. I have two of those engines. They're fine, they're just nothing exciting.

You might get lucky and it may have flat pistons instead of dished, but it doesn't look like you've lucked into anything exciting.

 

Heads are off. Doesn't look terrible inside, but definitely needs disassembled and cleaned before it's put back together and run.

Bore is 4.030" so it's been bored .030" at some point. Cylinders don't have a ridge, but not a lot of crosshatch evident.

I hit the pistons/rings with some Kroil then Marvel Mystery Oil and let it sit for a bit and then turned it over easily.

Oil pan coming off next.

 

I have a truck 350 that was only drilled for the large flywheel starter.

 

Cam is a flat tappet C1H290-S - pretty sure that's a General Kinetics hydraulic cam, 290/300 advertised, 112'ish LSA, around .450" lift.

 

Find a piston a bdc, you can check stroke.

 

350 truck engines had a fat torque curve down low which made them very flexible for cruising. A cam upgrade could wake them up a little more in the higher RPMs that this one seems to have. It can be a comfortable driver and still very sporty in a lightweight car.

 

Bottom end looks fine. Crank is a 3932442, confirmed as a 350 crank. Damn. Should have known better than to rely on shape of the crank flange.

Will remove a rod and piston next.

 

Bores look nice from what we can see, not a whole lot of miles. Looks like you got a good one.

The crank looks just like I figured. Rods...hmmm....restamped and funky nuts..but they seem to be holding together just fine.

 

I'd keep that cam. Seems a step up from what we used to call an "RV cam" so it should be a fun little 3 fiddy.

 

Rod journals have been ground .010" as noted on the backside of the rod bearings.

Pistons are cast Silvolite, 4.030, p/n 1436.

 

Ok, now I'm confused. Engine was said to have aftermarket rods (Manley?) but I'm not seeing any indication of who manufactured these. There are a few letters and numbers cast into the rods, including a GHK. The rod bolts also appear to be aftermarket.

Any ideas?

 

I think it's GMK, not GHK. Factory rods with aftermarket bolts.

 

Ok, I think I've culminated. Time to sell it and move on to the next project.

Thanks for all the input, I really appreciate it.

 

If the bore is good re ring it and replace the bearings and run it .
A 350 is not exactly a bad thing .

The non counterweight damper should have been the main clue it was not a 400 crank. If it's got a original 400 crank it's going to be externaly balanced on the flex plate /flywheel and dampner unless someone added a bunch of weight and that's not likely on a stock cast crank .

 

I'm fine with it being a 350, I just don't have anything to put it in. It came with a bunch of vintage Corvette stuff that I picked up as a package deal, and the plan all along has been to sell it.

It didn't have a flywheel or flexplate on it when I got it, but good point on the balancer.

Thanks

 

Well, now you know what it is and it appears it can make someone a good motor. We just never know what we will find when we pull some of this old stuff apart. And, you reminded me that I need to try to figure out what rods are in the one I mentioned.

 

Ok, looks like the engine is sold for $250 to a 16 y/o who is building a '78 Corvette with his dad. Good starter engine for someone on a budget.

 

That was quick....