[Dave Schiffers]

I'm not sure where to post this...... if it needs to go elsewhere, I'll move it.

I just got back my block from the machine shop and now have 3 cracks in the the main saddles. 1 crack on the #2 main saddle, and 2 cracks on the #4 saddle.

My machine shop says they are repairable for a stock rebuild, perhaps for a #'s matching deal.

The details on the block are: 1970 455 4-Bolt, code XF, casting # 9799140(.030 over) have matching heads #64 (milled .050) and crank.

First..... What the opinion......

Junk...... or, stock rebuild, maybe #'s matching deal ?

Does anyone have any interest?

Thanks, Dave.

[cnc]

My thinkin once its cracked who knows how far the crack really goes I know things can be welded BUT.....would u chance it....who's Shop Dave...

[Dave Schiffers]

Hey there Chris, it was...

Atchison Machine Service
London Ontario

Dennis said that they would drill below the crack and peen in something and that that is supposed to stop the crack.

I'm just checking to see if there is any interest.

[BVR421]

If it were mine Id probably use it for a low compression stock rebuild used in light service like a Sunday cruiser, nothing more. Probably last many years.

[pontorquer]

What's the history on this engine ? Was it beaten on before or overheated ... ?

[Cliff R]

BAD place for cracks. Consider the block two 4 cylinder blocks attached together. Look at the amount of actual material holding the two halves together, isn't really that much there as the lifter galleries are open on the non Super Duty blocks.

I'd skip on any sort of repairs in that area. Sucks not being able to repair/use the OEM block, but a 400 block from the same period would be a viable replacment with one of the new 4.21" forged crankshafts in it. Unless, of course you could find another numbers matching 455 block, which are pretty scarce these days........Cliff

[Mr. P-Body]

Ditto Cliff. Get a 400 block and "stroke" it. Much stronger. This is the "Achillie's (sp?) heel" of 455s.

Jim

[PONTIAC DUDE]

X 3

They will eventually take off towards the cam journal. With the thin main webbing area of a Pontiac block and stress cracks that bad now.

I doubt they will put that in writing that you won't see any further damage after their repair.

No interest here.

[Dave Schiffers]

pontorquer.... I've had this engine I my '68 Firebird for the last 15 years. Likely less than 5000 miles since rebuild. To my knowledge, it wasn't mag'ed before the rebuild. So it could have been already cracked. I never had any issues with it, till the head gasket let the coolant/oil mix. I caught it right away, and thus the tear down for inspection before next build.

From comments above, its looking like junk???

Dave.

[pontorquer]

That's too bad, It's such a rare 455 4 bolt main, I wonder if deadly detonation caused the cracks ???

[Cliff R]

The signs of detonation would be noticed on the upper rod bearing shells, and on the piston tops if it was really severe. I've seen a few Pontiac engines cracked in the saddles, but it is not all that common.

If placed in service, as Ken mentions, the cracks will head towards the cam bores, and the block will eventually fail. I would imagine you would have main bearing issues way before the block actually split, as the cracks would open up under heavy load, or so one would think?.....Cliff

[Dave Schiffers]

Allright, scrap it is !!!

Thanks folks.
Dave.

[rascal455ho]

I have same setup sittin in garage.Standard bore good.had to turn crank.

[1971WARBIRD]

pull the 4 bolt caps and send it to pontiac heaven,it lived a long hard life time to rest.

[DiamondJim]

I also have a running 1970 XF 455/370hp with original heads/intake/carb etc sitting at my shop. If your block is trash you can still get some significant cash from the numbers matching crowd for the 64 heads, original carb etc. Goodluck -Jim

[Tom Vaught]

Junk

I knew a guy who cracked a 63 Split Window Coupe block from water in the block and a cold snap. It cracked on the outside of the block water jacket. Yes, with that kind of crack you can drill the holes on each end of the crack and then fill the crack with epoxy, braze, etc.

The main webs being structural members in the block will typically not survive with cracks forever.

Detonation does cause cracks typically at the #4 Cap first followed by the #2 cap. These cracks occur at the block mating surface and travel upward towards the bolt head on the center bolt bore.

I would say that your block saw another stress. Did you have a solid motor mount on the block?

Tom Vaught

[Dave Schiffers]

Your right Tom. It did have solid engine mounts, and also a solid tranny mount for maybe a 100 miles, then switched to poly tranny mount. There was also detonation that I couldn't hear when the engine was running.

I saw the evidence once I tore down the engine.
- Top ring was broken into 3 pieces?
- Detonation slowly ate down toward the first ring land on about an 1/8 - 1/4 of one piston?

Dave.

[Evil Stu]

Dave,

Is it EUN 0080088 by any chance?

Stu

[Dave Schiffers]

Evil Stu

???

[Evil Stu]

You have a PM