[RallyBob]

I hauled up a complete 1975 long block from my shop basement today.

I wanted a 1975 block due to the large casting boss for the heater hose (where the block coolant drain is normally located). It’s not the lowest mile engine, but it had never been disassembled in its prior life as far as I knew.

I proceeded to pull the head and ancillaries from the block, and it did appear to be in good shape for a 47 year old engine. I still need to tear down the bottom end and measure/inspect all the components.

This block does have the infamous asterisk on the block stamping but has dished pistons. The block casting date is 1975, while the head appears to have been cast in November of 1974.

 

[terrylewisac]

Pretty clean Bob

 

[RallyBob]

Pretty clean Bob

I’m pretty happy with how clean it was.

Here’s hoping the bores are reasonably round and not tapered.

Ideally I’d just like to re-use the crank that’s in there, use the lightened forged 1.5 rods I’m currently working on, install new standard-bore dished pistons (notched for the big valves and ceramic coated), hone the bores, mill the block deck about .010”, and wash the block.

Guess we’ll see.

 

[RallyBob]

Mid-day break.
I still haven’t torn down the shortblock. My first job of the day was lifting the shortblock onto the engine stand. I really should get an overhead trolley for that. My back and legs will probably feel it in the morning….

Took a few pics of the block. Note the large water passage where a normal 1.9 drain plug would be. Since the 1975 thermostat housings have no fitting for a heater hose, this is where the heater core is fed from instead.

It looks like #3 cylinder ingested something at some point in this engine’s life. Small indentations were obvious on the piston.

In preparation for marking the valve relief locations on the low compression pistons, I set up my large degree wheel. I use a custom made crank arbor consisting of a piece of a stock crank pulley with a large hex nut welded to it. Then I bolt the degree wheel in place with a stock crank bolt. This allows the crank to be turned over without disturbing the relative location of the degree wheel.

 

[RallyBob]

Next step, I cleaned piston #1 really well, and applied Dykem blue to the relevant areas.

Following this, I prepped the cylinder head I’ll be using for marking valve relief locations. Some variables include larger valves, and a head that’s been milled .075”. This puts the valve locations deeper and further towards the edges of the cylinder bore. The camshaft will also have slightly more duration and overlap.

To further mimic a worst case scenario, I left the head gasket out completely. This brings the head lower (notches deeper) and the notch locations even further outward.

Using an old set of valves, I applied self-adhesive sandpaper to the valve faces, put the valves in the head, layed the head down, and spun each valve with a cordless drill while applying light pressure.

I did this at two different crank degree locations, at 20° BTDC, and again at 20° ATDC. The valves are barely open at TDC, but between 15-20° before and after the valves are chased by and chasing the pistons aggressively. This is where most interference occurs.

These pistons aren’t getting the notches, the new ones are. But I can measure off these marks and make a template to transfer the dimensions to the new pistons.

I’m sure there are those of you who think I did this long, drawn out process to get these results.

In truth, everything I did here took me under 10 minutes. it took about 25 minutes to photograph it and do this write-up on it.

 

[kwschumm]

Thanks for documenting your methods so well. Very educational and it is very much appreciated!

 

[RallyBob]

I still haven’t torn the entire shortblock down.
I think I will be using this shortblock for mock-up purposes on a two-piece dry sump oil pan for another project of mine.

Yea, it slows things down but my ADDHD kicked in hard today apparently….🤪

No wonder I never get anything done.

Anyhoo, I pulled the oil pan off and she’s pretty clean inside. Definitely exceptional for 47 years old. I’ve seen 5 year old cars that look a heck of a lot worse. Original oil pan gasket. Original rod bearings. Average bore size is 3.662-3.663”. A perfect ‘virgin’ bore would be 93 mm or 3.6614”.

#4 rod bearing and crank journal looks very good. So decent wear for the mileage and age.

The factory chrome plated top piston ring also looks very good. Zero chrome flaking. This engine led a pretty gentle life with frequent oil changes.

 

[rrossjr]

Thanks for documenting your methods so well. Very educational and it is very much appreciated!

I agree. Even though I am unlikely to ever go down this road (at least unassisted), I find the attention to detail really interesting. So, what exactly is the Dykem (blue stuff) for?

 

[RallyBob]

So, what exactly is the Dykem (blue stuff) for?

It’s machinist’s layout die. Just makes scribe marks easier to see.

 

[The Scifi Guy]

You're getting good at taking close ups! 🤩

 

[hrcollinsjr]

Flywheel been on a diet?

Harold

 

[RallyBob]

Flywheel been on a diet?

Harold

Good eye Harold. Yes, it has been. I weighed it at 18.6 lbs.

Kinda useless to me as I won’t use a stock Opel clutch any more. I’ve just had way too many of the pressure plates fail.

 

[RallyBob]

All torn down. Pistons and bores look quite good. Crankshaft looks very good. Main bearings have some wear.

 

[RallyBob]

Got an early Christmas gift in the mail today.
This officially doubles the cost of the cheap eBay turbo, but unfortunately it’s a necessary evil in order to use the turbo.

These are custom made waterjet-cut 1/2” thick steel flanges, based on my aluminum template I hand-cut. I got an extra flange cut in case I screwed up the first one, lol. I could also build a track-only large diameter down pipe with a side exit if I so desired.

I also had 4 copper gaskets cut out at the same time using the same pattern.

Thankfully, everything fits beautifully. I might have to enlarge the flange holes a few thousandths if I decide to use mounting studs instead of bolts. But the locations are spot-on.

 

[terrylewisac]

awesome awesome awesome, can't believe how clean the engine is but I'm looking at it and highly doubt you cleaned it for pics

 

[RallyBob]

awesome awesome awesome, can't believe how clean the engine is but I'm looking at it and highly doubt you cleaned it for pics

Nope, didn’t touch it. It’s very clean. The original owner of the Manta that this engine came from bought the car new. He was a car and gun collector, and kept meticulous care of all his stuff.

He apparently had a couple of 289 Cobras in addition to the Manta. He bought every rubber part for the Manta as spares between 1975-1980, including a NEW dashboard and bumper rubbers. I am still storing those rubber parts for the current Manta owner.

 

[terrylewisac]

I know you didn't I'm just amazed at what great shape it's in.

 

[RallyBob]

Picked up a few items at my powdercoaters today while shopping down in CT.

I had the MoreOpel sport springs that originally came from my Sportwagon coated just to have a clean set in inventory.

Then another race-oriented spring set that came out of my race Manta (which will be getting a coilover setup). I figured these springs will go into my Sportwagon when I want to do track days. 465 lb front springs and 200 lb rear springs. They will require a swap to different shocks with a shorter stroke and much firmer rebound damping.

Lastly my rear suspension trailing arms for the Sportwagon were done. I fitting the spherical rod ends to it, they are chromoly with Teflon liners and have a 5/8” shank and use a 1/2” mounting hole at the spring bucket.

 

[R-Tic]

Bob. Does your powder coat vender use plugs on threaded holes or do you tap them out after powder coating ? What I can see, it looks to be a very clean break between the coating the threads.
Thanks.

 

[RallyBob]

Bob. Does your powder coat vender use plugs on threaded holes or do you tap them out after powder coating ? What I can see, it looks to be a very clean break between the coating the threads.
Thanks.

It depends what I request. When rust prevention is paramount I tell him 100% coverage. Then I go back and chase threads and tap holes myself.

But other times I have him tape off threads (like external AN fittings) or use silicone plugs on internal passages that may not be easy for me to access after the fact.

They are very accommodating in that regard.