Bu Jian

So I have a 1977 Oldsmobile 350. I want to build some more power. Will all the things you can do to an earlier 350 work on this block? I do have # 5 heads that I'll have machined. I'm not sure how strong the window mains are but I plan on utilizing a halo for reassurance. Wisdom says look for an earlier block but I don't want to use that money for another block when I could use it on the motor I already have. Let me know what y'all think or if have any recipes for performance.

joe_padavano

You'll be spending money on the halo girdle, modified oil pan, and the machine work to install it, and you'll also have to machine the heads to accept the larger 1/2" head bolts on that late model block. Rethink the value of a different block (or even a DX if you really plan to get serious).

Bu Jian

I plan on getting serious. I will have to machine the heads, and I can add on enlarging the head bolts. I also plan on adding the girdle. What kind of horsepower and torque figures can I build this motor up to? I already, have Sanderson shorty headers, Edelbrock RPM intake, 3.42 gears out of an S-10 Blazer. I know I'll probably need a bigger carb but what can I do?

olds 307 and 403

Are you planning on taking it to the track? What HP are you expecting? How heavy of a car and what rpm do you plan on pushing the motor to? The windowed block isn't the only issue when going for higher power. The later light weight cranks are also weaker. Good luck, I would find a 76 or earlier block myself.

Bu Jian

I don't plan on taking it to the track. I do plan on the rare time to time stop light action. I want a bump in power. I'm expecting 350-400 horses. I thought changing out the pistons, doing some head work on the # 5 heads, girdle, carb, and I could be there. I'm not asking for a lot just the most out of what I already have

cutlassefi

So are you expecting 350 or 400? Harder to do the latter on a 350.

Bu Jian

I'm expecting the most out of this motor.

cutlassefi

My 350 Dyno mule made 405/418 with iron heads and a full roller Valvetrain. That can be duplicated fairly easily but it still takes a decent budget.

oddball

You're supposed to align hone the mains after changing to studs and a halo. Most halo installs require cutting down the top of the caps, which means you *really* need to align hone. And an align hone can introduce other problems. No oil pan mods are necessary though. Dipstick will take some work.
My windowed web 403 is putting out at least 450hp (2 cam changes since the dyno day) with a 5 main halo and has survived just fine on the street for .... 6 years? 7 years? The mains are very similar if not identical to the late 350, so that's something to go off of. I am using a 330 crank.

You also need to be precise with what kind of street manners you want. 400 hp + 350 cu inch displacement + vacuum brakes is a tough job.

Is your block already bored/honed on the cylinders for your final size and has a good flat deck at the height you want? If not, then it's basically a core and replacing it doesn't really add much cost.

Also, "most out of this motor" and "budget" seldom agree with each other. This is an Olds, not an LS.

joe_padavano

The only girdle that does anything structurally is one that ties the mains to the pan rails. That requires oil pan mods. I'm glad you've been lucky, but those flat halo girdles do nothing to make up for the lack of strength in the windowed mains. Like TSA, they provide the APPEARANCE of security.

olds 307 and 403

The cost of a pre 76 block costs less than a 5 main Halo, ARP studs and an align hone, let a lone a full girdles price. Get a 68 to 72 350. Better flowing heads untouched with smaller chambers, solid mains and the stronger "N" crank.

Bu Jian

Where would I find these 68 to 72 350's? Most of all that stuffed has been junked for Chevy or LS transplants here in Alabama. You pop the hood of a Cutlass and it is very unlikely to have an Oldsmobile motor.

cutlassefi

PM’d you.