Oversquare options

[MaineShark]

Well, clearly the standard 350 is an oversquare engine (1.149 bore/stroke ratio), but I was wondering what people think about going further.

Say, bore a 400-block .030 over, then toss in a 3.5" stroke crank, for a bore/stroke ratio of 1.187 and a displacement just a hair shy of 380 inches.

Just trying to find something amusing, for when I build an engine for the Shark. I was really thinking of a 406, but they're not exactly uncommon. Neither are 355's and 383's. I want something a little out of the ordinary.

Thoughts?

Joe

 

[Jack]

Well, clearly the standard 350 is an oversquare engine (1.149 bore/stroke ratio), but I was wondering what people think about going further.

Say, bore a 400-block .030 over, then toss in a 3.5" stroke crank, for a bore/stroke ratio of 1.187 and a displacement just a hair shy of 380 inches.

Just trying to find something amusing, for when I build an engine for the Shark. I was really thinking of a 406, but they're not exactly uncommon. Neither are 355's and 383's. I want something a little out of the ordinary.

Thoughts?

Joe

For many years the +30 400 block w/350 crank (makes a 377) has been and still is a popular combination with the circle track crowd in many parts of USA. Outside of that, not likely many know of it.

Friend of mine just dragged up an older asphalt circle track car from up north somewhere ... has a 377 ... cannot use in our region. He got the car & trailer both for about what the scrap is worth ... so he's golden.
JACK:gap
-edit- BTW Joe ... chevy Cup motors are based on a combo of 400's bore and 327's stroke ... makes a 352-360 depending on overbore & slight juggling of stroke (eg +0.035") ... Bowtie blocks & heads w/ remainder aftermarket ... I dunno but I'd guess that Cup ford & mopar quite similar.

Just a guess that a 377 C3 would be a bit unusual.

 

[MaineShark]

For many years the +30 400 block w/350 crank (makes a 377) has been and still is a popular combination with the circle track crowd in many parts of USA. Outside of that, not likely many know of it.

Well, if you go with a 3.5" stroke instead of a 3.48" stroke, you get 380 instead of 377. I was originally looking at the 377 option, until I tried to find cranks, and it looks like most of the cranks that are designed for this purpose are 3.5"

Joe

 

[G Winter]

Is it real expensive to have a crank cut for the stroke you want? With that I suppose you would need special pistons pin location to make it work,which might mean another special order. Just some food for thought.

Glenn

 

[Jack]

Well, if you go with a 3.5" stroke instead of a 3.48" stroke, you get 380 instead of 377. I was originally looking at the 377 option, until I tried to find cranks, and it looks like most of the cranks that are designed for this purpose are 3.5"Joe

Joe: Use a plain jane chevy 350 crank (3.48") and off-the-shelf "special" Clevite main bearing set P/N MS-1564P to fit 350 crank's smaller main journals to 400 block's larger main bearing bores ... that is SOP. If you find a used 400 block that still has standard-bore pistons in it ... you can be pretty darn sure it'll need AT LEAST +20 overbore ... probably +30 to clean up ... suggest you pass on any that need to go more than +40. FYI most hi-po 400 pistons are NOT available in +20 ... most are +30, +40, +60. The pistons for a 377 are readily available as of-the-shelf ... SpeedPro P/N H123CL are flat 2vr for use w/ 6" rods ... P/N L2467 are flat 2vr for use w/ 5.7" rods. Either make 10.3:1 CR w/64cc heads ... 9.1:1 w/ 76cc. All OE sbc employ 0.927" OD wrist pins.

OE 400: deck height 9.025", stroke 3.75", nominal main journal 2.65", nominal rod journal 2.1", cylinder bore 4.125", rod length 5.565".
OE 350: deck height 9.025", stroke 3.48", nominal main journal 2.45", nominal rod journal 2.1", cylinder bore 4.000", rod length 5.700".

Just my 2 cents ... I'm all for individuality ... but all those 406 folks can't be so far off the mark. If going to trouble of acquiring & prepping a good 400 block, why not build a 406 and take advantage of its high torque? There probably ain't THAT many vettes w/406 running around your domain.
JACK:gap