Mark71

Ok, so I know it is a little over my head now, but I plan on (re)building an engine for my Cutlass. It isn't that my current engine doesn't work right or anything - its actually running quite well - but I've always wanted to build one from the ground up. Plus, I'd like it to be an Oldsmobile engine, not an LS. I like LS motors (no offense to LS guys) - but I want to build my first one from a classic piece of cast iron.

So here's the first of a line of simple questions with difficult answers:
Should I go with a 350 or a 455?

Advantages of the 350:
More available around here, Cheaper (for the core), Everything else in my car is setup for a 350 because it has one now

Advantages of the 455:
More power , Easier to find used parts for, and let's face it, it's a big block!

Can anyone tell me - which has a better selection for aftermarket parts?
How hard will it be to get 1 HP per cubic inch out of an SBO 350?

Thanks!
-Mark

442Harv

If you what power and performance, just go with the 455. There is no replacement for displacement. Plus the 455 torque is just great for the street.

tru-blue 442

Big Block! Easy swap. Find a shorttail 400 bop. Don't forget the trans yolk.
If you can find some #5 heads from a 69 350, you can boost the power of
your current 350 by just bolting those on.

Allan R

Mark,
I went through this last year. Was going to go 455. Now I've decided to keep the original 350 and rebuild it. If yours is a runner now, you know what it's history is, how many miles on it, what kind of mtce it got etc. Plus, it runs. That big.

While I agree that a 455 will give you more power and loads more torque, you will have to change your trans. If you keep the 350 - when its done you just bolt it back up to the exhaust and TH350.

Really it comes down to what you are going to use the car for when it's done. There's lots of power in a Rocket 350. Maybe change your rear gears if you are looking for more pedal pounding burnouts. Personally I'd stay with the 350.

You probably can get 1 HP/Cu in out of a SBO. I'm not the guy to tell you how. But I would suggest that if you go that route, you're going to have to beef up your TH350 to take the new power/torque.

Good luck with your decision

Mark71

So it seems everyone is saying "go 455" except for Allan, so far at least. And Allan, I see your point, too!

I should make clear ahead of time that my existing 350 was rebuilt (before I got the car) and is the original block (not heads or trans) to the car. No matter what else happens, that motor stays in the car until I am done with the new one. I wanna drive my Cutlass while I build a new motor for it.

Here's another point that might tilt things one way or the other, and please don't laugh:In other words - is there a difference in difficulty between a 455 and a 350?

Allan R

Sounds like your power needs are pretty close to what I'm looking at too. I like that you're keeping the original engine; at least for now. I'd hang onto it even after, in case you decide you want to rebuild it and put it back.

Which is harder to build? Neither. They follow the same basic principles. Just follow the CSM for motor rebuilding and ask lots of questions here when you get stuck. Worked for me when I got stuck tearing down my 455. It turned out to be junk (#7) cylinder was split open by 2 cracks in the water jacket. Not repairable.

I really get your comment about being nervous. I was too. Still am about pulling the engine and redoing it. But as long as you take your time and do it right, there should be no issues. I have a buddy across the street who is a mechanic and can bail me out of tight spots when I need him. But he's also a police officer so he works bizarre shifts and I might see him only once a week.

I think you'll find there's just as many parts available for 350 as there is for 455's. Do you like gold or blue in your engine bay? If you decide on the 455? Make sure you get one that's pretty complete, including exhaust manifolds. I know guys will tell you that you can just swap parts across and that may be so. But the less you have to do that, the easier it is in the long run - my opinion anyway.

DeltaPace77

I went 455(actually 461 now). I basically started with a bare block, got together everything else, and had some expensive machine work done. I put it together myself, with custom polished/ported Dave Smith heads and TRW forged pistons, for 10.5 CR. I took my time, plastic gauging the bearings, and degreeing the cam. Keep in mind, you'll be needing some specialty tools, like ring compressor, balance puller, and degree kit. Also, the cost of machine work, will usually be a lot more than expected. The tranny you have now will bolt up just fine, but wouldn't use for drag racing on track rubber.

bigD

like allan said they are pretty much the same to build. a turbo 350 can be built to stand up to a 455 ...
i'm kinda at the same point as you with my '70, it has just over 100k miles on it and had sat in storage for 25yrs before i got it. it runs good but i'd just as soon pull the original motor and rebuild it as to run it to failure. it does run great but i have some sort of disorder, i can't drive anything bone stock! i know it's ridiculous but i can't help it... i have suffered with it ever since i learned to pull on a wrench...

Mark71

Yeah, I mean I know I can do it. I've just never done the whole thing before. My neighbors aren't mechanics, though. To be honest, I've read a LOT of books about engine building already. I have set a number of targets that I'd like to reach, but again - this won't be my last engine build up, so I don't want to go way overboard or anything. On my next one I'll go way overboard.

Tools! Yeah, I really enjoy buying tools. Also I already have ring compressors, balancer pullers, calipers, micrometers and some other fun stuff for the job. I'll need to get a degree kit at some point. And my micrometers are cheesy, so maybe I need to get some better ones.

I'd like to rebuild a turbo 350 for it, too, although I am still wondering if I can find an OD (TH2004R or 700R4/4L60). Regardless, TH 350's are common around here as cores and I was thinking of either rebuilding one or picking one up from Jegs / Summit / whoever. Supposedly they can handle up to 450 HP, not sure one the TQ numbers though.

Mark71

Forgot to mention that - I definitely don't want to wait until some major component fails in my current 350. Like I said, that's supposedly a numbers matching block and above all, it works fine. I don't want anything to happen to it.

stevengerard

Seeing that your car is a convertible it has more value than most other cutlii (except maybe a Rallye 350 or W31) so that could make you lean toward keeping it numbers matching.

I'm not an engine builder but I know its fun to have a 455 though as an example my neighbor has a 1970 Cutlass Convertible, I have a 70 W30 convertible - I'm just guessing if given the choice many folks would take my car for the same money as his. But on any given day they are the same car - used as a cruiser around town. He has a cool paint job, I have a cool paint job, his car is quick, mine might be a bit faster, in the end these are cruisers with torque. He has less problems with over-heating, car always starts, better MPG, doesn't worry about the "correctness" of the minutia I do, etc.

Just another perspective

DeltaPace77

You're probably not going to be using a standard 1" micrometer much, but if checking bearing clearance with telescopic T bore gauges, you'll be needing bigger ones. I generally use plastic gauge myself. The heads I got from Dave Smith Olds, have an adjustable valve train set up with poly lock nuts, so just like setting up a Chevy or Pontiac. Believe Mondello sells this too. Good idea picking up a couple books, with S-A Designs "Engine Blueprinting" Rick Voegelin beeing a good one. Also have Peterson's 1995 "Engines" that's really more of magazine, but has lot's of good stuff in it.

Mark71

Heh... Yeah, I considered that. Although, it is officially not numbers matching because only the block is original. The heads have been replaced, the engine rebuilt and the transmission swapped. The previous owner just told me it was rebuilt, gave me the receipts and I figured out that it is .30 over. He had just said "rebuild it to stock performance". Long story short, I'm keeping the original block either way. It is nice to have.

Yup... Just finished reading that one cover to cover. It seems to cover a lot of the more basic questions I would've had, but leads into some pretty advanced stuff (custom aluminum connecting rods, custom pistons with milled domes, race gas, strokers, etc.). I won't be getting into that on my first build, I guess.

I also went through Monroe's Engine Builder's Handbook (HP Books). Not bad and a little more "thorough". Assumes you know a little less.

DeltaPace77

For tranny, I actually went 700R4/4L60 brand new for an SUV application. Pretty sweet with a 3.73 posi rear, as thing really flies, getting decent highway milage. Works out similar to a 2.56 axle behind a TH-350, maybe better with the lock up converter. Had to use an adapter plate for the Chevy bolt pattern, move the crossmember back, and shorten the drive shaft, but no big deal. Can tell you, installing a Trans-Go kit in this thing is an all day affair though. If doing it again, would probably go "E" version, as computers are cheap now, and much easier setting up shift points, than messing with TV cables and governer springs/weights. This could be another project down the road, as should be fine with your current tranny for now.

Wraythe

The following is a win-win solution for you:

1. Purchase a big block engine (400, 425 or 455)
2. Rebuild big block engine
3. Install your freshly rebuilt big block
4. Archive your 350ci engine
5. Locate late model Corvette and smoke it to the weeks.

Personally I would locate low mileage LS2 engine with transmission attached, install then rock it

jag1886

What ever you do make certain you decide what exactly you are going to use the car for and weigh all your options.
I have converted a couple of cars to big blocks and found I drove them way less than I wanted to because they guzzled gas at a horrendous rate, my current build I stayed with a mildly built small block added an OD transmission and a 3:90 rear end, you get good acceleration and good gas mileage.
I would also consider your options as far as building the engine yourself, if you are going to do it totally hands on, find someone that can watch over every step of the build as you do it, book learning is great but there are things that can creep up that can just ruin your day.
Good luck with what ever you decide on!

DeltaPace77

That all sounds pretty cool, but in addition to a well set up 455 Olds, also have a C6 ZO6 Vette, with an LS7 under the hood. Only 3100 lbs, and not much gonna be smoking this thing.

Wraythe

Are you building your first engine such as Mark71? Your right about the performance of Z06 Corvette. Too bad late model Corvette are everywhere you go.

Speaking of Z06 Corvette, A complete powertrain is getting transplanted into my fathers '38 Chev 2door coupe which weighs less than your Z06

DeltaPace77

Now that's cool. Keep us informed of your dad's progress. As for the mention of engine building, built several myself. The 455 in mine, is done right with custom head work. The Vette's really for a different mission, as road track it with a group, on Hoosier R6's. The windshield G-Meter's showing 1.00-1.25 around turns quite often, and not exactly an every day experience.