SB 3.79" or 4.00" crank?

Getting ready to start my pump gas street/strip R1 build. I have a .010/.010 3.79" crank but I'm considering buying a Scat lightweight 4" crank. The pistons are going to be customs so the price will be the same.

Experiences, thoughts or opinions?

What bore?

40+ years of 3.xxx stroke cranks otta be enough for us...4.00 for max effort and 4.250 max effort street. Jmo

"Small Block Rated to 600 Max HP"..... what I read in one of the descriptions. Guess the price reflects that.

4.09"

I'm biased but I like a short stroke combo personally.

I have been pleased so far with my 3.79 stroke crank in a stock 340 block. Ran a new best last weekend even though I have lost over a 1/2 tenth in the 60 ft. for some reason and it is sputtering around the mph lights.

I'm 3260# with a 4.10 gear and figured the 4" stroke might be a little help.

I've got both and I am big on revs but my junk is light
and in my street rod its a 4" for the added torque.. that
torque is nice and it still revs decent... I take it to
7500 rpm... the 3.79 goes way higher but if you stay with
4.10 gears you will never reach the high revs... I use 4.56
gears in the smaller engine and 4.10 on the 416 engine

3.79" can make as much or more power by trading RPM for torque, great for lighter combos and/or tigher gears. The problem with the 4" is only on the top because it's tough/expensive to get enough Head flow. A 4" (generally) will ET an automatic car quicker all else being equal though, plus it's so well proven and sorted out, it's tough to make a rational argument against just going for cubes. 3.79" even with a longer 6.200 or so rod still winds up with a fairly heavy piston due the tall 9.58-ish deck height. 9.200 deck blocks are a natural for the 3.79 though

I like the 3.79" stroke if you have limited deck height, but there is little substitute for cid on a naturally aspirated engine. If it is a tall deck application I would go 4" crank all day long.

Thanks Brian. The deck is 9.58".

If you're buying a crank, may I suggest BPE's 4.25" crank? He's a board member and posters here rave.

Bigger cubic inches moves the torque and horsepower curves to the left. It'll make the same power but at a lower more usable rpm. Plus you may be able to save money on valvegear due to lower redline.

R.

More CID = more low end torque. Means less rpm, less gear, less valve train strain, less cam required, etc... All good things. 4"+ is a no brainer on a tall deck.

That being said... If you already have the 3.79“ your not going to build a worthless combo by using it. It all comes down to budget at that point.

You could save some bucks vs a 4" crank by offset grinding the rod Journals to the popular 2" "327 SBC" size and find anywhere from a 6.125" to 6.3" .927 pin SBC rod and get to about 3.90" stroke PLUS get a lighter bobweight. If I already had the crank I'd probably look at doing that...or sell it to offset the cost of the 4" to 4.25"

I have a 4.25" BPE in my 440" W2, it's a BEAST but very docile

another Pic

Thanks guys for the input, 4" is probably max I'll go as already I have 2.125"/6.123" and 2.100"/6.125" rods. An entire 4.125" kit is around $2800 and I can buy a 4" crank for less then $1000. The 3.79" will either go in my 340 block sometime or be sold.

I bought a K1 crank 4" 360 mains and chevy rods for $500 to the door last year and a set of k1 chevy h beem rods (645grams) for $226 I think. Was checking out some of the new SRP pro pistons for around $650 with rings and pin (422grams plus pin 106grams). I think that the 4" stroke is a better alternative for what I am going to use it for which is mostly street use. You can see that with balancing will be around $2000. For a couple of hundred more in gaskets, bearings and machining it is a good start on a short shortblock

Where did you find the crank and pistons that cheap?

I found a couple of options on ebay for the pistons that I was wanting. T believe it is around MSRP for them considering they are an off the shelf chevy size. The crank I got from a company in texas. I believe it was part of the k1 clearance last year like the rods. I would give them a call and see if they still have them it is possible because they were not advertising the crank.