Looking for some advise.

I currently have a ‘71 S hardtop. I’m looking for more power. Trans has been built and can handle a lot more Torque/HP. Have 3:42 rear and no posi.

my engine is a 359 Rocket. 4bbl, cam and the heads were cleaned with new springs and valves put in about 1000kms. Basically the entire top end was rebuilt with a cam. Car sounds great. Runs well. It just doesn’t have enough power.

Should I, rebuild the bottom end, bore out the cylinders, put new pistons in?
Or should I look at putting in a 455? I have one lineup, but it could use a rebuild. Cylinder walls are in good shape. Heads are fine. This engine is from a 72/73 I believe.

I’m not looking for a race engine. I’m probably pushing 275hp in my car now. Looking to get around 350hp. I also don’t want to be putting in thousands and thousands of dollars into an engine.

Any insight on what you’ve done or suggestions is much appreciated.

 

That really is not going to gain much. What exactly are you looking for ? Off the line tire frying type performance or 120 mph wide open performance ?

 

You can easily get 350+ hp from a 350 SBO - CutlassEFI (Mark Remmel) from this board built mine and it peaked > 400 on the dyno. In the car currently it may be only slightly under that (I run shorty headers and 2-1/4" dual exhaust). Entirely streetable and decent idle quality - I run power brakes and a/c in my ragtop with no appreciable issues.

Roller cam setup appears to be what you'd need in addition to the right pistons and maybe some mild head porting - reaching out to Mark for his thoughts would be ideal place to start or search the board for past combinations which have been posted for SBO builds and their results.

 

Buncha questions:

1) Current trans, TH350 or 400? How was it "built"? What kind ot torque converter? A TH350 might not live long behind a 455 depending on what has or hasn't been done to it.
2) Current cam specs?
3) Compression?
4) Carburetor?
5) How much can you spend?
6) What do you want the car to do? 12 seconds through the quarter, or just a healthy rip from the back tires on the 1-2 shift?

For the street, horsepower numbers are pretty much meaningless -- you want to build for torque, and the easiest way to get that is with the 455.

Let us know.

 

Hmmm not true, see Scott’s (70’sgeek) post above.
9.5:1, small roller, made 420/430 on pump with full length headers.

 

Off the line.

 

1. 200R4 trans. It has a shift kitt in it. The guy who built it was a transmission guy. I don’t know much more about it.
2. Comp cam CL42-229-4 is the cam that’s in it
3.73 block with 71 heads. No idea what the actual compression is. 9-1?
4. Edelbrock 1406.
5. Depends. I’m in Canada 2k-5k.
6. Bit a of both. But more power off the line.

 

Thanks for that. I’ll reach out and or do some more research on this board.

 

1) You need to find out more about that transmission build, especially if you're going to put a 455 in front of it. A 200-4R won't survive for long unless carefully built. If you can't find out more about it, I'd rule out the 455. Do you know anything about the torque converter?
2) Not a bad choice for a mild SBO build. Single pattern, 218°/0.456/110 LSA, not a top-ender but should have some midrange punch without compromising low-end.
3) Do a compression test. This will not only tell you about the health of the engine but will also give you an idea whether you'll have enough cylinder pressure to support a bigger cam if you want to go there.
4) You might actually be better off with a Q-Jet. Edelbrock manifold as well or did you use an adapter?
5) If you're going to build an engine, you'll need more, especially if you're talking CAD(!)
6) That engine should be strong enough to run mid or even low14s as it sits, and give you a satifying kick in the butt when you romp it. I would look into making sure it's healthy and tuning is optimized before you give up on it and spend a whole bunch of money.

 

What is your rear gear ratio??? Likely 2.56- absolutely terrible for off line performance!!

 

Yes, but that is a totally different engine than what he is talking about. I bet the heads aren't stock. Etc.

 

On the motor Mark built for me, 7A heads with 2.00/1.62 valves valves (if I recall correctly), HS 1.6 roller rockers and possibly some mild port work. Roller cam, forged pistons and rods, Pertronix Ignitor II distributor, E-brock RPM intake and QuickFuel 780 carb are some of the other main highlights. If there were any rate-limiting steps to being a pump-gas street terror, it would be my 3.08 posi but even with that, it definitely ain't the 98-lb weakling of the group...

 

The biggest bang for the buck will be new rear gears, probably in the 3.73:1 range. Since you already have an OD trans, this will result in an effective 2.50:1 on the freeway, so driveability will not suffer. Your 71 came from the factory with a corporate 8.5" ten bolt axle, so parts for these pretty much grow on trees.

 

OP says it's 3.42, which isnt bad. I don't know that the improvement would be worth the effort to swap to 3.73.

 

3:42. One of the first things I had done. However I didn’t put a posi unit in which I’m really regretting now.

 

Why? Are you having traction issues?

 

You can't use the power you have now with a "One wheel wonder". Install a limited slip rear end and bigger tread width rear tires. And keep the front up. If you are sitting there spinning one tire, you ain't goin' no where, but the other guy is.

 

My understanding of OP's original complaint is that the power output of his engine is such that wheelspin is not a concern right now. Now if he does that 455 swap ...

 

You are probably at more like 8.5 to 1 for compression. Do a compression test and how is your oil pressure? The Mahle 10cc dish pistons will raise it 1 to 1, if zero decked. DSS also has 3cc and 12cc dish pistons. You would want W31 valves and some bowl blending on your current heads, also will need different springs if going to a roller cam. That cam should be about right but you could step up to roller cam. I have a complete hydraulic roller cam setup same duration numbers but about .080" more lift and Comp Evolution hydraulic roller lifters, all brand new and a new Cloyes billet timing set. I'm in Canada, PM me if interested. A 455 would easily get you there but a 2004R is not a strong transmission, killed multiple ones behind mild Olds 350's and 403's.

 

No. I should have had posi put in while I was having the gears replaced.

 

1. My mechanic passed away last summer. Trusted him. He was a transmission mechanic. When he built it, he said it would be able to handle a big block if I decided to go that route.
2. Good to know.
3. Okay I will do that. Do I still need to do that if I decide to bore out the cylinders?
4. I have an Edelbrock intake currently on the car.
5. Good to know.
6.I assume you are talking about the 350?

Thanks again for your insight/suggestions.

 

Yes, this. I can spin them. But off the hop it's still pretty slow. At lest to me it is.

I had an '86 Mustang GT years ago with a stock 302 and a 5 speed. Quick car that was great off the line. Stock rearend as well.

 

1) Sorry to hear that. If you're comfortable with the transmission, use it.
3) No, but I would use it as a diagnostic for your 350 prior to ruling that engine out. Regardless, at this point, boring out the 350 is getting a bit out over your skis. If it has internal problems, I would be inclined to proceed directly to the 455.
4) Then stick with the 1406, I guess, although you could probably go a little bigger.
​guess.
6) Yes, the 350. If it's running right, it really should outclass a Mustang GT.

 

Thanks again.

One more question. A side from rebuilding the engine or putting in a 455, is there anything I can do to add horsepower? I have 2.5” duel exhaust. But what about a better coil, ignition system? Anything bolt on I could add?

 

Thanks. I’m in Ontario.

 

Headers, and that's it, really. Might as well make use of those big 2.5-inch pipes. Assuming you have the original points ignition, electronic upgrades are more effective for convenience and reliability than performance gains. As discussed, the cam is a pretty good choice and you probably won't have the compression to handle much more anyway. The only other area I can see for improvement while remaining under the heading of "mild street SBO" is the carb could be a little bigger. Gains would probably be minimal, though.

How about this, though? Before throwing crazy money at it, why not see if you can get with a good performance shop to optimize what you have? Timing and carburetor tweaking can often yield better gains than adding parts. You don't sound like you're too much of a DIY guy but there are also lots of resources available if you want to go that route or have difficulty finding a shop in your area. They're getting harder to find, especially ones that are familiar with Oldsmobiles.

One thing I'm trying to get you to avoid is spending a whole bunch of money on the 350 and then deciding you're still not satisfied and wishing you did the 455.

 

Thanks for that. I do have headers on it. My mechanics brother in law is also a mechanic and is an Olds guy. He’s got three of them. Him and I do chat from time to time. He’s a really good mechanic as well but not too sure if he’s a guy who you go to for more power. I should see him Thursday and talk to him. He said I could always buy a 403 and use my heads, intake and cam and in it. But I do hear the cylinder walls are thinner.

I did have metering rods but in my current carb. My buddy has a Holley 700 (I believe) that I’m sure he would let me try out.

I’ve helped build a few engines in my time. Can do the bolt on stuff. Carbs is something I k own very little about.

I’ll talk to my brother in laws mechanic this week and do as you suggested and talk to shop and see what they suggest. Thank again for your response.

 

Oh thats a quick car from birth, a mildly built 1974 350 even in a 71 body is going to have a hard time feeling like it.

First issue the 71 weighs 500 lbs more.
You need a stock stick W31 just to be able to pull on it.

You would need to have CutlassEfi or the like complete the build to all out performance.

I guess you may be figuring the peak GT and Cutlass engines for their respective years are both rated 200 hp net stock to stock. So it should be closer with the slight build, but no way. The 302 was designed to rip. You would need a nice healthy 455 just to feel like that GT because of the weight disadvantage. Or a fully built 350.

1971 Cutlass S 350 200hp G92 (3.42) stick = 8 second 0-60
1986 Mustang GT 5.0 200hp 2.73 stick = 6 second 0-60

 

I'd think you're ripe for a 403 as a rebuilt shortblock and re-use the 350 heads, cam, headers, and intake. This would save costs over rebuilding a 455.
Torque comes from cubic inches and compression, and is utilized/felt best with lower rear gears and less weight. You are limited somewhat in all of these areas.

 

Absolutely !

Once you take into account every facet of this thread, this is a brilliant deduction.

The best of all worlds, big block torque while being able to reuse existing components. And no additional weight.

And that will be covered as well if you come across a healthy stock ready to drop in 403... just headers and true dual exhaust and it will likely feel more impressive than your current.... The extra 50 lb ft from the long tube header'd 403, and she will start feeling nimble like the Stang...

 

Yeah, I had stock 403 bottom end with these #6 heads 2.07/1.56 valves 9 to 1 compression, 150 to 160 psi compression with a 204/214 Edelbrock cam and full length headers with a 2000 stall TH350 and 2.78 gears. Stronger than the 9.5 to 1 Olds 358 with the same cam. Easy one wheel burn outs. I would have kept it in the car but the rod bearings were down to copper and starting to knock. Replaced them, knock gone but still low oil pressure.

 

Thanks for all this information. I know where there is a 403 block. I’ve got all the tools end parts ready to go. Maybe I will go in that direction.

Just to be clear I can get my one tire to spin off the line. I can actually get it to squawk going into third. It’s just not as powerful as I want. With the setup I have in the 350, I’m probably pushing 260 maybe 270 hp tops.

 

👍 I bet.

Ahh then you may have to rethink this again. The thing with modern mild cams they have a tendency of killing torque while maximizing hp. And excessive torque is what makes these cars fun on the street when stockish. It takes extra effort ($) to tap into the extra hp, torque converter, gearing, posi, etc. So sure more hp is what matters when taken to the nth degree but otherwise it can lead to disappointment.

Here is a fellow members disappointment in 4k as they say.
As you can see he lost 30 lb ft of torque while he was expecting 30+ and was irate about it.

His dyno specs of 203 and 346 was stock 403 but true dual exhaust.

All 3 of those quotes are from 3 seperate posts in this thread here. https://classicoldsmobile.com/forums...esults-103967/

Bottom line, depending on your wants you may have to "really" pay to play...

 

Yeah, it isn't cheap for a proper build, at all. My motor will actually be 9.3 to 1 at best with the new Edelbrock heads. Hopefully the under 220 duration roller cam will help bottom end. I assume he is running the stock torque converter? You definitely want something 2000+ with that cam off the line. With my 9 to 1 Olds 350 with the 214/214 custom cam with a 2350(2200 to 2500 rated) stall 2004R with a 2.78 open rear, easy 1/4 block burnouts. It felt stronger than the 403 thanks to the better first gear and more stall.

 

Curious on his cam specs and RPM intake?