Project Blown 305

[Cuttyman9]

And I know the feeling, I'm at 9 vehicles... all projects (either because I turned them into a project or they started that way) at 28 so I def understand the thought there haha.

[turbobill]

The block is a bit different on the Toro-Flow as it has a balance shaft on the left side just above the oil pan rail and the assorted gear train to turn it.

I believe the rod/main bearings are the same size between both and the cylinder head bolt pattern is also the same. The bellhousing and rear of the engine looks the same.

Some gaskets are the same and I wouldn't be surprised to find the rods and some of the valve train may be the same too.

[Cuttyman9]

Interesting, I wonder why they have a balance shaft if it's the same everywhere else?

I wonder if the block was reinforced further than the gas variants?

Would be neat to investigate.

[turbobill]

I doubt I'll have both of mine apart at the same time so I won't be able to help lol. I wouldn't dare pull the heads of the Toro-Flow as I have yet to see any available anywhere.

[bigblockv6]

Originally Posted by Cuttyman9

Interesting, I wonder why they have a balance shaft if it's the same everywhere else?

I wonder if the block was reinforced further than the gas variants?

Would be neat to investigate.

The ToroFlow engines did use crossbolt mains, so they were a 4 bolt main vs 2 bolt main for gas engines. In 1973 GMC had redesigned the bottom end of the block only on 478M gas engines with much larger main journals as well as more beef in the main saddle area and much larger main caps & bolts but still a 2 bolt main. When I get a chance I'll take some pics of the newer main caps vs the older main caps and post it.

[Cuttyman9]

That would be awesome, the mains in these aren't too terribly large from what I've seen.

I almost think a big diesel block would be a good foundation if not better than the rest since it's setup for 4 bolt mains although I don't plan to rev this hard, just make the blower work early and stop at 4K.
The hard part will be making the truck work on the freeway unless I adapt an nv4500.

[bigblockv6]

I think you'll be fine up to 4000 rpms, sounds like a fun project and you're doing something that nobody has attempted, pay no attention to the nay sayers

[Cuttyman9]

Thank you! I'm very excited about it.
I'm hoping I can come up with a way to grab the 478's and toss one in for the time being and sell the 305 to build the other.

I'll have a bunch more coming very soon when the blower shows up with the adapter plate and front cover!

[bigblockv6]

If you toss in a 478 just know you have to have the correct 8 bolt flywheel that has offset weight on it since these are externally balanced engines. A 401 may be a better choice, most 401's will accept the 305 flywheel as long as they don't have the 8 bolt crank flange.

[Cuttyman9]

Didn't know that, maybe I'll start with the 401 then and build on both of the 478's haha.

Weird they would go internal and external balance on the different sized engines of the same family