Bernhard

I have bean having second thoughts about my 403 build and am only $2000 into it with parts and a low km engine.
I have thought about going Big block as well and have made inquaries about that possibility.
The car that the eventual build will be going in is a street car that will see the track.
2dr olds G body with no hood scoop so intake is limited in height
Car has to have good street manners and be reliable.
8.5 diff with 3:73 geras 2004r.
Goal to be running mid 12's through the mufflers and on dot tires.
I know this can be done with a 403,455,400,425 and a 350.
I want the engine to be as mild as possible and still reach my goal
I have bean flip floping like a polition on my build.
I have read old posts on diesel builds
positive big inch small block that is strong
You can use the stock diesel crank and stroke it True or False?
You can use the stock roller lifters in a mild build True or False?
The major cost of a diesel build is the 425 crank and custom pistons?
Other costs in a diesel build ?
cheeper rods with a dx build true or false.
403
Big bore positive
weak block negative
With my 403 build you have the added cost of a halo or full girdle
330 crank
455 positive
big cubes has good hp and tq
455 cheep pistons and crank .
negative block sits higher and is wider
likes to spin rod bearings needs large bearing clearances
does not like rpm with out small chevy rod journals
week rods
headers that exit through the wheel well or $800 un coated headers

What are your thoughts?

380 Racer

This is all just my opinion. You don't need a DX to accomplish what you are doing. Personally I would do a 380 in an early gas block. You would have the bottom end strength, lifters a non issue (by the way you don't need roller lifters, never had them till this version of my SBOs). Do an offset 330 crank, some good SBC rods and some custom pistons to get the CR you want with some E-brocks. Up until the second cam in my 380 were hyd flat tappets.
I had a couple BB in my car over the years and didn't like them. The 403......heard way too many bad stories.
There, you now have my $.02.

PS. According to my calculator in a 3700# car, you only need 380 HP to run a 12.50 ET.

gearheads78

Mid 12's in a G-body is a cake walk. If thats as fast as you want to go I would just stick with what you have. I would not dive in to a DX unless you want to go 10's or faster.

cutlassefi

Doing both right now, a 380 and a DX. Pros and cons to both.
But I agree with Nick, a well built 380 is good way to go and should get you to your goals.

Bernhard

Thanks for the replys I appreciate it.

Intragration

What did you not like about big blocks, 380? It's all I run, I love them. More cubes equals more power and milder characteristics, everything else being equal. (not saying that a small block can't get the job done, you're the one with the wheels in the air, not me ) A 455 with a Performer and a drop base air cleaner will easily fit under the hood of a G-body. Hooker 3203s have a primary that goes over the frame rail and meets back up with the collector, but it's not a problem for me. Dick Millers require a mini-starter but don't go over the frame rail. My car doesn't have a lot of power options and I removed the AC, it weighs about 3,300 pounds.

Having said this though, if you've already invested $2k into your 403, why not just finish it? It's not like it's going to explode when you start it. 12.5 is moving, but I don't think it's asking too much of a 403. JMO.

jims2000lt

If you go 455 I have a bit of advise.
I'm running 9.8 to 1 comp, 530ish lift Hyd cam, 3.42 gears, 3500LBs
and turning 11.50 - 11.60.
Not totally mild but I drive it about 35 - 4o miles to the track, run it, and drive home.
Its not the fastest but in my area it fast for a street car.

I'd do a 455 or early 350 and save the DX for the Hardcore guys. My .02.

Redog

If you worried about the block of a 403 not being strong enough, just go with a 350 and use a 395558 "2" block

You'll turn 12's pretty easy with that set-up

380 Racer

#1 is oil pressure, or lack-there-of.

Intragration

I've never heard of oil pressure problems specific to BBO. Do you have more information on this? I've heard about the drainback issue, but it's my impression this isn't unique to BBO. I can say that I've never had problems with oil pressure on mine, it's generally 50 PSI with 10W30 and a standard volume pump on cold start and cruise. The lowest it dips is into the low 20s at idle after a long highway cruise.

380 Racer

If you have HP clearances to live, you most likely not see 50 psi. Both BBs I used had the 15# pro light come on going thru the traps. Scared the crap outa me. Where have you been? It is a common problem.

Intragration

I'm relatively new to high-performance Oldsmobile, but I've done quite a bit of reading. I've really never heard about this, although again I'm not saying it doesn't exist, it's just news to me. What is it that causes this to be a problem with BBO but not SBO? Larger bearings?

380 Racer

That is why my DX has 2.5" mains and 2.0" rod journals.

captjim

No expert by any means but my take it that it is a combination of large journals on both main and rod, big stroke, heavy components, along with a less-that strout block. You can minimize by going to light pistons and excellent machine work, but by the time you go .004 on everything to make up for the above, there just isn't much pressure to be had. This really isn't an issue on a street rod, but more of a race thing.

cutlassefi

Imo it's more of a block integrity, component and/or oil drainback issue.
A 351W Ford has 3.00" mains, ever hear of any issues with them? I don't.

But done right they'll live with little to no issues.

captjim

I did not say the 3" main was the problem, just an overall factor. Again, fair block, heavy parts, long arm, big journals.