I found this listing and see there are specific block and head types. What kind of power would this engine put out? If I recall the mid seventies 455's were still strong.

https://www.jegs.com/i/ATK+Engines/0...iABEgIPSPD_BwE

 

The only thing I see from the description and pictures is it is a 455 with J heads. No mention of compression ratio, piston design, camshaft profile, or anything else that is relevant to the rebuild.
There is no way to even guess at the power output with the severe lack of information in the description.
I would contact them and ask a LOT of questions before purchasing one.

 

"Not for motor home applications"

Tells me they have no confidence in the thing under extended heavy load. (In other words, it's not built as well as when a long-block came out of the Olds engine factory.)

 

The GMC motorhomes used Toro engines.
I'm sure your aware of the differences between a Toro engine and others.

 

The ATK long-block isn't pictured with motor mounts, exhaust manifolds, an oil pan, or an intake manifold. That'd affect fitment, but you'd just transfer those parts from your existing engine along with a suitable oil pickup tube on the pump.

What else would a '70s Toro engine get, that would make a difference in durability? They got the same iron crank, the same non-heat-treated mild-steel connecting rods, cast-aluminum pistons, etc.

At best, you might have larger-diameter valves and a different camshaft--although I think that was more '60s than '70s.

I think that ATK just doesn't want the engine run hard.

 

Toro engines get high compression pistons and not the low compression version. A different cam,large valves,oil pan with an extra quart,crank scraper,windage tray.
And we won't even get into the fact Oldsmobile generically blueprinted their engines by comparing parts and grouping like parts together. My guess would be that they kept the best groupings of parts for the higher end engines.

 

I predict it will make less power than it should and not as much as you want.

 

On one hand, it'll definitely not be a National Record Holder but should be a decent stock driver engine. They all have decent torque. Call them for more info/guarantee etc. Says free shipping but they want a core engine. To build one yourself, you'd have that much into it and possibly a lot more, depending on your goals. Jmo.

 

The GMC Motor home was made from '73--'77. Did the Toro get high-compression pistons in those years? I'm guessing "no". Same with the cam and the valves--I bet the Toro got the same thing as every other 455 by '73.

As said, the oil pan, scraper, etc. all gets swapped-over from the previous engine.

So what you're saying is that ATK takes less care and uses less precision than Olds did when building thousands and thousands of Toro engines.

THAT IS EXACTLY MY POINT. Thanks for agreeing.

 

Your welcome and thank you for sharing your assuming opinion that you work so hard to present as fact.

 

Aren't you assuming that the Toro long-blocks, as built by GM, are significantly different from 455 long-blocks intended for other applications during the years the GM Motorhomes were being built?

I know all about how the manifolds and oil pans and mounts and any number of other accessories are different from Toro to standard passenger car. None of that is part of a long-block.
I know about Toros getting different blocks, cams, larger valve sizes...in the 1960s. Probably 1970, and maybe 1971. Show me how the Toro or motorhome 455 long blocks from '73 to 77 were different from "ordinary" long blocks, 'cause I don't know of any differences, certainly none that affect durability.

I don't see anything that says ATK doesn't permit use of this in a Toronado. Just that they don't want it stuffed into a motorhome. The only thing that makes sense is that ATK knows a motorhome engine is going to run HARD lugging tons of weight and pushing huge frontal area, and they don't want the liability for engines that spend extended time at heavy throttle. In other words, they're concerned that they aren't building them as well as GM did.

I would be asking ATK about piston compression height before I put down any money. If they're using ordinary "rebuilder" pistons, the compression height is likely to be ten or twenty thousandths too low--reducing compression even if the "dish" is the proper size.

 

If I was in the market for a long block, and knew who supplied the engines, I would go straight to the source. Don’t buy the engine thru JEGS, contact ATK. I think they do custom engine work, maybe they would be willing to build it to your specifications. Assuming it’s quality machine work, with quality parts, and assembled correctly with the proper clearances, it should be every bit as good as a factory long block.