GM big block question- what is this?

Brett_Murphy said:

Curtis said:

you spend the money on an aftermarket TCM, or you spend the money on a TH400 with a GV Overdrive behind it and have a 6 speed auto with OD that will take more abuse than you can imagine.

I'd no idea they had an overdrive for a TH400.


 

Gear Vendors Overdrive

I had one behind a TH400, but they make them for almost any trans you can imagine.  Its the same unit, just a different adapter tube and coupler.  Goes on behind your tailshaft and has a .74:1 OD planetary set.

Nice thing is you can engage/disengage manually or let it do it's thing automatically.  Flipping the switch lets you split gears and get a 6 speed auto.  Nice for towing, not necessary in your application.  The only electronics are a little box under the dash that counts speedo clicks to know when you hit a certain speed, and a three way toggle switch.

But, as we discussed before, a BBC will make a broad enough torque curve that 3 speeds is more than enough.  Do an axle ratio that suits the highway RPMs you want and pick a good stall speed for the cam.

The TH400 never came with a lockup TC, so the hot ticket that a lot of people do is find a switch-pitch converter from an early TH400.  They have variable vanes that stall higher until second gear, then pitch up for efficiency.

This thread speaks directly to the latest addition to the stable: '88 Chevy 3500 2wd, single cab, long bed dually with a 350 TBI and about 45k on the clock. I inherited it, literally, from a friend who reached the end of regulation last year. His passing was not a tragedy in the moment but a long running drama that ended when it ended.

At any rate, I've got this truck and it runs pretty well with the 350 but I've got a newly rebuilt '86 454 that's in an RV with 23k on the clock. I got the RV with a frozen engine years ago; it got that way by a failed intake manifold gasket that leaked coolant into the #3 cylinder and rusted it solid. I yanked it, rebuilt it and reinstalled it. Probably ran 1500 bucks for parts and machine work. It's .040" over with new pistons. Forged crank/4 bolt main. Unfortunately, it's sat for another coupla years and now we have invited guests that have rendered the rest of the RV garbage.

The question is: Is it worth the time to yank the 454 and swap it into the 3500? I would imagine the 454 would be superior for towing and truly heavy duty work. I don't think the gas mileage is going to be much worse since the 350 has to work pretty hard to get the thing down the road; it gets about ten right now dragging the brick around. I'm guessing the TH400 in the RV is probably the tip for the swap. Are headers, intake manifold, carb and mild cam worth the expense here? I don't remember what the RV has in it but '86 wasn't exactly the Acme of internal combustion development...

 Suggestions please...

That is pretty amazing, but not exactly budget friendly on a project that's just for giggles.

rdcyclist said:

This thread speaks directly to the latest addition to the stable: '88 Chevy 3500 2wd, single cab, long bed dually with a 350 TBI and about 45k on the clock. I inherited it, literally, from a friend who reached the end of regulation last year. His passing was not a tragedy in the moment but a long running drama that ended when it ended.

At any rate, I've got this truck and it runs pretty well with the 350 but I've got a newly rebuilt '86 454 that's in an RV with 23k on the clock. I got the RV with a frozen engine years ago; it got that way by a failed intake manifold gasket that leaked coolant into the #3 cylinder and rusted it solid. I yanked it, rebuilt it and reinstalled it. Probably ran 1500 bucks for parts and machine work. It's .040" over with new pistons. Forged crank/4 bolt main. Unfortunately, it's sat for another coupla years and now we have invited guests that have rendered the rest of the RV garbage.

The question is: Is it worth the time to yank the 454 and swap it into the 3500? I would imagine the 454 would be superior for towing and truly heavy duty work. I don't think the gas mileage is going to be much worse since the 350 has to work pretty hard to get the thing down the road; it gets about ten right now dragging the brick around. I'm guessing the TH400 in the RV is probably the tip for the swap. Are headers, intake manifold, carb and mild cam worth the expense here? I don't remember what the RV has in it but '86 wasn't exactly the Acme of internal combustion development...

 Suggestions please...

Yes.  If the motor home is trashed by all means.

I have no idea what happened here. Did they try to heat it up and succeed beyond what they were expecting?

It came right off, though.

The cam is spinning freely, but I couldn't get it to slide out. Maybe tomorrow we'll see what kind of shape that is in.

I am betting I couldn't get the cam out because I didn't move the retainer.

HOLY CRAP, Well If It Slid off after THAT, I would say they were trying to Pin the Key, That was Loose in The Key way , Maybe it  was Too Small or What?, Look At The Crank Nose Close see if the Key way is Buggerd up , If the Chain is Tight and you want I have some crank Gears, You May want New though ,Single row are not Expensive

There was no chain, just the interlocking gears.



 

I wonder if that is a reverse rotation marine engine?

A gear drive with no idler gear reverses the cam rotation.

Well, the plot thickens, then, and the original question comes into play:

What is this thing?

In reply to bentwrench :

Will also have a funky distributor gear so the distributor and therefore oil pump spin in the right direction, if it is a normal rotation engine with a cam designed for a 2 gear cam drive.

That is seriously old school though, more likely to be marine engine.

The lower keyway is fine. The slag from the melted gear came off with a few taps, but the crank has some damage- I'm not sure it is usable any longer. 

I can't get the upper gear off. I've tapped it and hit the junction with a bit of penetrating oil. I'll try again tomorrow.

From the way this is shaping up, I may just need to get all new things for the block, if I decide to use it. The price tag on this is going up pretty quickly.

In reply to Brett_Murphy :

I can’t imagine that a welded crank wouldn’t be warped- or have micro fractures. 

The crank  had slag on it- it doesn't look like they welded the crank itself. I'm not going to be making huge power with this engine, but I'm thinking using a different crank is a good idea.

 

Scat makes a good cast crankshaft for a BBC, reasonably priced.  Most likely that was a reverse rotation marine engine, so the cam, distributor and oil pump are standard items, as the cam was still turning clockwise. Just use a timing chain set and no problems then.

Did it come with a starter?  Reverse rotation engines mounted the starter backwards (pointing toward the rear) so they could use an off-the-shelf starter mounted to the bellhousing to spin the motor backwards.

If it is a reverse rotation, I highly doubt it was marine; more likely genset or industrial.  Since the mid 70s, no one really made a reverse rotation marine engine because all of the outdrives were updated.  Reverse rotation was used in double engine boats and inboards for a bit, but it was cheaper to engineer the outdrives in-house for the required rotation instead of altering the engines, so outdrives were reconfigured.  A few velvet-drive ski boats hung on to reverse motors until about 82 (ski nautique for example) but they were almost all Ford 351s.

Odd engine for sure.

I forget (and too lazy to search the thread) did you post the stamping number on the block?  That won't tell us much, since whoever was the end-user likely bought an off-the-shelf crate engine and modified it for their use, but it might point a finger in a direction.

Double check the crank.  If it is a genset or industrial motor, it likely has a forged crank.  Marine motors used to get forgings, but advancements in metallurgy meant that cast cranks were more than adequate for marine use starting in the early 80s.  Either way, I wouldn't hesitate to use that crank again.

The thing to do would be to post a picture of the distributor gear on the camshaft. 

Something is jangling in my memory that says medium duty trucks got a two gear cam drive as well.  So it may still be a forward rotation engine with a reverse rotation CAM... which will have a reverse beveled gear on it and corresponding reverse beveled gear for the distributor.

The bevel on the cam/crank gears supports this.  If it was a normal rotation engine, the cam would be thrust rearward in the block, which is the way GM does it (cam gear bears on the cam plate)

It didn't come with a starter. Once I get the camshaft out of the engine, I'll certainly post a picture of it up.

Thanks everybody who is helping with this. I'm way out of my comfort zone with this thing, and I keep convincing myself I bought a boat anchor somehow. I have to keep telling myself that as long as the block is good, every new discovery just moves the starting line back a little.

I've taken to calling this thing the Big Block Bamboozled, even though I didn't pay much for it.

Just to refresh things, the casting number on the block was 14015445

The camshaft gear set appears to be reverse rotation for a marine engine.

The cam wasn't rusty at all, and the engine spins, but the cylinders have a bit of a mark where the rings were sitting for however long they were sitting.

The only clear mark on the cam was the number "342"  I've not gotten the gear off yet, so maybe there is a mark under there.

This may be the part number, but I have to clean it up a bit before I can read it (tomorrow).

Yep, that cam does look like it is a forwards direction cam, meaning reverse direction crank.  Mind is blown that the timing gear would pull the cam forward instead of thrusting back.

Also that lobe next to the distributor gear looks destroyed, so it's not like you'd be using that camshaft anyway.

Relevent numbers on a Camshaft will be on the Face or End of camshaft and ectched in, I have seen an Ink Stamp But Not Ever Stamped into a cam , Those on the shaft are meaning less to Design of lobes.

The engine only spun correctly one way, and I thought it was locked up before I spun it that way, so I think it was counter clockwise. It was late when I was doing all of that. If it is a reverse rotation crankshaft, that pretty much means the good parts I got were the block, the intake and maybe the heads- but I won't know about those until I start messing with those.

I'll get a better picture of the cam- I wasn't planning on using it.

What are camshafts made out of? Is this an alloy that can be used to make knives? I know a guy that might want it.

Cast iron, with a layer of hardening.  You could probably snap it in half by whacking it against a table.

If you look closely at the worn-down lobes, you can see the color change between the hardened layer and the soft core beneath.

It is All Good Except The Cam and Drive Gear, An Engine will turn any Direction the CAM is cut for,  So You Need a Cam and Gear that uses a Chain,or Idler gears, normal, But right now i am Confused about your Dist. Drive Gear. You might download a Mercrusier PDF on the BB chevy for reverse rotation, there was a time they used a Different Pin location on pistons in a reverse engines but stopped that. The Flywheel cover that came on Mine could use a Starter on Either Side.