CS1972

I tried to search on here and the web with no luck at all. I have read in Bill Trovato's book where one could have the crank ground down (350) to accept 6 inch SBC rods, which is lighter than factory Olds rods? And use a custom piston to come up with 378 C.I. Have any of you guys tried this? I have a 76 350 in my 72 Supreme, no land speed record by no means......but those extra cubes could sure help in the torque department and fun factor.

cutlassefi

I've done a few of these, easy build.

Offset grind the crank to 3.500 stroke
SBC 6.00" Small Journal (2.00) Rod (Eagle, Scat)
350 SBC piston (you don't need a custom piston) 1.550 cd, 4.125 bore. (Speed Pro, Mahle, Icon, etc)

I just did one earlier this year, 323hp almost 400lbft of torque with a mild hyd roller.

Hope this helps.

380 Racer

As indicated by my handle on here, I raced a 380 for a few years then switched to a DX block. Here is almost anything you need to know:

DX block bored to 4.155
Program Engineering 4-bolt main caps, Main spacers from BTR
Main restrictors along with lifter restrictors
Mondello oil pump
Milodon windage tray

330 crank off-set ground .115 for a 2" rod pin and a 3.50 stroke
Manley 6.300" SBC Tour Lite rods with a .927 piston pin, 536 grams
JE custom pistons, .050 dome.....465 grams.....pins 116 grams
Clearences:
Rods.......0025
Side .......0027
Mains 1-4 .0030...#5 .0038
Piston to wall .005

#7 heads.....2.10/1.71 valves
milled .045 results in 12.75:1 compression (.010 deck hgt)
Flow 270 intake.....208 exhaust
1/2" head studs
Cometic head gaskets .040 thick......4.185 bore
HS rockers with 7/16 studs and guide plates
Jomar stud girdle
Comp springs.....160# seat 440# open pressures


.921 solid lifters (Crower I think)
UD cam specs:
.576/.593 lift
256/263 dur.@ .050
108 LS installed at 102
Hex-A-Just timing chain
ATI damper (external balance)

Modified Victor intake
950 HP carb 84 jets square, no PV
1" Super Sucker spacer
MSD ignition....33* timing locked in
Meziere water pump
Kooks Jet Hotted 1 7/8 headers

Produced 598 Hp at 7000 and 523 TQ at 5100

This is in my 70 Supreme. 3260# race ready
5400 Coan Converter, 350 Turbo w/trans brake
Narrowed 12 bolt Chev.....5.14 gears
14x32 slicks

The #7s sprinkler system was replaced by the Rocket Racing head/intake set up. Ran a best of 10.57.

If I were to build a street car, I would do a tamed down version of this engine.

CS1972

Now THATS what I'm talking bout! Thanks fellas, that helped a bunch!!!

61reoldsman

How Tame ? like a 400 hp and 400 ft lbs tq? motor,using the 7 iron heads ?and a smaller roller cam ?or a flat tappet cam ?How much compression would you use ?Just asking the question .Thanks

380 Racer

I'm not sure I would look for a certain HP. I would keep the compression below 10:1. Probably use Pro Comp heads and not mess with iron again. Would use the longest SB Chevy rod with a 2.0" crank pin and maybe some KB pistons. Might use an N crank if I found one with std rod throws. I'm not good with cam choosing so I would look for assistance from Mark, Comp or Engle. I would probably use a hyd flat tappet, of course a hyd roller would be considered. A RPM intake (I just plain like 'em) And I would run a Holley (again I just plain like 'em). I probably wasn't much help but I would adjust things as I went along. Oh ya, probably use a HEI, headers, Harlan Sharps and of course good clearances for bearings along with a HV oil pump.

Sheesh I hope I helped

61reoldsman

Well it's good to have people on here to reference when it comes to these kinds of builds as everybody has there opinions and thoughts and advice.I would like to keep a SBO in my car but the low rpm torque of a big inch motor would be nice too.So doing a stroker makes sense ,so kind of the best of both motors.Not sure if this would work but could a Pontiac 3.75" stroke 350 crank fit in an Olds ?Is it even possible with machine work ?They both have the same firing order but I'm not sure about the length of the motors front to back ,the 3.00" mains could technically be worked down to 2.5",any thoughts ?

cutlassefi

No each of GM's engine families are different.
Achieving more low end torque is not only done thru increased stroke, it can be done by increasing the bore as well. This discussion has been mulle dover many times.
You can do a 403 if you want to stay with a small block or bore and stroke yours to a 380 or so. Either way it'll make a noticeable difference.