400 vs. 403

[GoldOlds]

In my search for a motor to give a mild build-up and replace my original 350 (I want to race the car once in awhile and not worry about blowing up the original engine), I've come across two recent classified ads; one for a 400 BBO and the other for a 403 SBO. The details:

400 ---> • out of a '68 442. • rebuilt less than 6,000 miles ago. • mild cam. • making the "original" 365 hp. $750.

403 ---> • out of a '79 Trans Am. • runs excellent. • has aluminum intake. • $350.

Any opinions on the better selection? I know about the 403's windowed mains, paper-thin cylinder walls, etc., but I like the idea of a shorter stroke and a motor that'll drop right in the car while breathing alright through the 2.25" exhaust. What would the 403's compression be if I put my #5 heads on it?

- GoldOlds

[J-(Chicago)]

Get that 403.
$350 is a steal, for a fine runner, with an alum intake.

[Redog]

I vote for the 400.

Rebuilt, and not windowed

[J-(Chicago)]

If the 400 has all of the proper papers, get it too

[Redog]

^^ I could have bought a 400 without carb, mani, exhaust manifolds and valve covers with the orginal tranny for $300, but it was too much work. The one I got was running, but I updated it (carb wise)

I guess it depends on your plans for the car your putting it in, if's it's just a cruiser, I'd say got for the cheap one, but why is it so cheap

[captjim]

The 403 will work fine, and as you say it bolts right in. Cr with the #5 heads should be around 8.5, but there are a lot of determining factors. That is a "late" 400, long stroke engine. The "early" 400s were screamers, short stroke, big bore. I would not go to the trouble of going the big block 400 in this case.

[Olds64]

Why don't you want to use the 350 that is in your car right now? SBO engines are pretty stout, you could build a screamer with the 350 and not have to spend the money on another engine.

[captjim]

^^^^^^ Agreed. What is the application and how fast are you looking to go??

[Oldsguy]

I was thinking the same thing. For that matter, if you don't trust yourself to control the rpm's, you could always use an aftermarket ignition controler with a rev limiter.

[joe_padavano]

I'd go with the 403 as the long stroke, tiny bore 400 is not Oldsmobile's best design. I don't understand this comment however:

Originally Posted by GoldOlds

...but I like the idea of a shorter stroke and a motor that'll drop right in the car while breathing alright through the 2.25" exhaust....

- GoldOlds

Both engines will flow the same amount at the same RPM, so what difference does this make? If you're referring to the exhaust manifolds bolting up, the flanges on big blocks and small blocks are in the same position relative to the crank centerline (which is why W/Z manifolds won't fit a small block). Neither engine will breath adequately through 2.25" pipes.

[Olds64]

You won't have to worry about blowing up an Olds engine. Especially if you are just doing a mild streetable rebuild. If you start asking about hi compression pistons, solid lifter cam shafts, hi volume oil pumps, and double rolling timing chains then you should start worrying about blowing your engine. Not to say that double roller timing sets, and hi volume oil pumps aren't good additions to a streetable engine, even if they are overkill.

[GoldOlds]

Originally Posted by captjim

^^^^^^ Agreed. What is the application and how fast are you looking to go??

I'm looking for something in the 13.5 to 13.9 range (1/4 mile) that's very streetable at the same time. The car ('69 Cutlass) has a TH350 w/ shift kit and 3.73:1 limited slip Chevy 12 bolt rear end. It'll be mostly for crusing, but it'll do the 1/4 mile 4 or 5 times per summer - or at least that's the plan.

- GoldOlds

BTW, thanks everyone for your input!

[captjim]

I'm with Olds64, build the 350. It is extremely durable, you have the best 350 Olds made, and you already have it. I run high 13s in a mild 9 to 1 355 wagon with 3.42 gears. Driven daily. Bump the Cr up to 9.8 or so, a little more cam, you already have the gears, 13.5s should be easy. Here is a link to my combo if you want the specs.
http://72.22.90.30/phpBB2/viewtopic.php?t=28012

[GoldOlds]

Again, thanks for the input! I guess this could be one of those cases where the solution may be sitting right under my nose (or should I say "hood") all along. When a set of SBO heads are milled, do I . . . A) have the pushrods shortened the exact same amount B) install roller tip rockers or C) both A and B?
Does anyone have any experience/opinions on the Edelbrock "Power Packages" (cam, lifters, intake, carb etc.)? I faintly recall someone saying some aftermarket cams work better for the SBO than others . . . which are they?

- GoldOlds

[captjim]

I personally don't like the E-brock grinds, they are just copies of old generic ones. Slow lazy-*ss ramps. There are a lot of better ones out there, IMO. As for pushrods, again IMO, rocker geometry is often overlooked. The best thing to do is assemble the engine using whatever valve train you decide on, and then get an adjustable pushrod. Use it to determine the proper length, then measure it and order 16 of them. Of course, this assumes the valve stem heights are all the same. Check this, http://www.cranecams.com/?show=faq&id=6