I don't mean to step on anyone's toes, but it seems like in the larger automotive world the Olds 350 is not held in very high regard as a viable performance engine...

Hence, the end game for my '70 Cutlass S included an eventual swap to a 455 Olds... or a big block Ch_vy *ducks and runs*

I have HEARD however, that the '68-'70 Olds 350'a are actually somewhat sought after engines... any truth to this?

It'd make things a lot easier for me if the engine I currently have would be a viable build... or is it just better to "go big or go home" as per my original plan?

Thoughts?

 

My original 350 in my 70 was put thru hell. Was finally bored & stroked to a 380 that ran high 10s. Currently have a 425 DX block that runs mid to high 9s. So ya they work good.

 

That's because the "larger automotive world" is geared toward Chevrolet engines, hence all the aftermarket performance stuff is made for those instead of the other GM engines.

I do mean to step on toes when I say the reason for the outrageous aftermarket SBC support is because it took the aftermarket to make them perform.

Listen to 380Racer as he knows his stuff. BTW that 425 DX is an Olds 350 Diesel block modded up to 425 CI.

An Olds 350 won't be as cheap to build as a Chevy 350, but all other things being equal the Olds is every bit the Chevy's equal in performance.

It's also worth noting that it took Oldsmobile engineering to finally get the BBC design refined enough to both be reliable and make horsepower. The end result was the Olds DRCE. But those are not exactly compatible with a street driven car.

 

They make all kinds of cams, a few aluminum intakes, and headers plus everything in between to make them fast.
Plus they last a long time.
You add a stall and low rear end gears and it will more than satisfy you and your Olds!
Also an added plus is you won't get snubbed by people because you cross breeded a Chevy engine in your Olds!

 

The Olds 350 has a larger bore and a smaller stroke than the Chubby 350. On paper the Olds should have greater performance potential. Unfortunately, the it is handicapped by a restrictive head design, especially on the exhaust side. Aftermarket heads can help this.

The reason why there is so much more equipment available for Chevy motors is because there is a much larger potential market. Aftermarket parts companies are in business to make money. It costs just as much to tool up for a Chevy part as for an Olds part. Which one will have the greater return on investment?

 

It is the same old story. Every 350 and 403 used the same rod yet there is not a reasonably priced replacement available.

As always, it depends on goals and budget. You can certainly build a reliable, fun to drive, quick Olds 350. Would the same money spent on a 455 get you more performance? Probably, but I like my 350s

 

My 69 Supreme has the original 350 engine (rebuilt), runs like a top, but can't get rubber off the line. It'll chirp going into 2nd gear though. I just put Headman headers and a full Flowmaster exhaust on her in hopes of changing this fact, but still no go. It has the 12 bolt rear, but I haven't checked the gearing yet. Just comparing it to some of the other Mopar's and Chev's I had, it seems to be just a little lacking. Unfortunately I don't know what was done to it, still has #5 heads and all original parts on the motor..

 

Probably 2.73:1. BY the way, it's not a "12 bolt", it's a Type O with only ten bolts holding the ring gear to the carrier. Don't be fooled by the number of bolts on the cover.

 

I've told this story before. Back in the late 70s/early 80s I had a 71 Cutlass 350 2 bbl. I was a mechanic and I would let friends and regular customers borrow it while I worked on their cars. I canstantly got remarks on how peppy an fun to drive it was, and it had a 2.xx gear. When properly tuned with matching parts, it should easily turnn the tires over.

 

So what are some good sources to start looking at and pricing upgrades?

Let's say for argument's sake that I'm on the younger side of 30, but more importantly - am just getting my feet wet with this sort of thing...
Although I grew up with classic Oldsmobiles, my dad was never into hot rodding so I'm essentially a rookie

I am at least aware of Mondello, is that a good place to start?

Basically, where does one go to get into this sort of thing?

 

Well Coldfire, tell us what you've got, is it a 350 2bbl. with single exhaust, ect?

 

If you have 70, you should have 14cc dish pistons, #6 heads, and a compression ratio of 8.5 to 1. The stock cams are VERY mild, you can upgrade that and at the same time (since it is off) upgrade to a 4 bbl carb. If you can afford it, a quality valve job and a little port work would help. Then, it is pretty much basic-hot rodding, dual exhaust (personally, in this application I would not bother with headers unless you do up the heads including welding the center dividers and filling the crossovers, but your call), and a better gear ratio, like 3.42. Then, tune your carb and distributor, and off you go.

BTW, stay away from Mondello, the horror stories are legendary.....

 

Ah, well I should've mentioned that a previous owner has already done several bolt-on mods so I'm not sure what it was originally

Currently she's sporting an Edelbrock 4bbl carb & Edelbrock intake with dual exhaust (true dual, not just a Y split) and an air cleaner off a 455 olds. It's also running an HEI distributor & coil (which I discovered here https://classicoldsmobile.com/forums...butor-cap.html)

But I believe the internals are all stock

Unfortunately, all the mods were done at least 2 owners ago - the guy I bought it from had also purchased it as-is and she just sat in a shed for 10 years before I bought it, thus there's no records of what's actually been done to the car other than what I can visually see

 

That's good! Which Edelbrock intake is on it? Can you look at the timing chain cover and tell if it has been off? How does it run?

 

This I've wondered about -- my car is definitely a "one wheel wonder" so I kind of assume the stock rear-end... what final drive ratio originally came with the '70 Cutlass S?

Really? I always thought Mondello was the go-to for Olds performance!?

 

I don't know! See, this is where I'm a newb lol. I can see clearly where it says Edelbrock, and on the other side it says "Performer RPM" is that the model?

Also, how could I tell if the cover has been off? There is a fair amount of grime, but again, most of this would have been done 10+ years ago

 

Yep, that's the model...Edelbrock Performer RPM. It's a step up from the regular Performer intake. I have 1 on my '72 Olds 350, also with a 650cfm Edelbrock carb and I'm very happy with it. Gearing is the name of the game with Olds motors. A nice posi unit, 3.73 or numerically higher will wake that baby up (I'm still bogged down by stock 2.56's! )
If your '70 350 was a stock 4bbl car, it should have over 10:1 compression, which is good for making power. Good luck with it!

 

Sorry Joe, yes type "O", stock intake and 4BBL carb, do you think it might just be tuning. Next week I'm having it put on the Dyno, so that should tell something.

 

Unlikely that it is a high comp 350. Possible, but unlikely, IMO.

Also, I kinda disagree about gearing. Thje torque curve is so broad that it is LESS of a factor than on other makes. I have actually seen stock-ish cars slow down in the 1/4 with 3.73s as they blow through the rpm range.

 

I bought a used ring & pinion from a friend a number of years ago for a Chevy 12 bolt I had installed under my Cutlass. They were supposed to be 4.11s replacing the 3.55s in it. Turned out to be 4.56s, but since I was racing I went ahead and had them installed. Never regretted that decision. In fact I had 5.13s for the 425, went down to 4.88s and finally back to the 4.56s again, but I also run 32" tall slicks now.

 

I guess what I was trying to spit out is that I prefer a deeper gear. But then I wouldn't frequent the interstate either.

 

IMO- Put a set of headers w/ decent exhaust system (if not already done), get a proper curve & timing ignition wise & tune the carb. That should get it running well & may allow you to put some hurt on those tires without opening up the engine.

Next step would be rear gears - 3.08 to 3.73 depending on the amount of highway driving you do & you will definitely need a limited slip diff @ that point or you are liable to set the rear tire(s) on fire.

The lack of low end grunt is a bit troubling - may be an "oversized" or improperly installed cam in it which gears will help with, maybe a whooped torque converter which would be another item on the shopping list after the above basics have been dealt with. Even a stock 2 bbl SBO should be able to beat up a tire peg legged, stock 4 barrel should be able to melt one.

A compression test would be a good idea to start with to see what you are working with for a foundation, get one done & post what comes of it so advice can be more accurate & helpful. If this is a healthy engine, even 2bbl/low compression based it will still respond positively to basic mods mentioned, just have to be very conservative on a cam, if higher comp 4 bbl base it will really like them. Would be nice to know if it is aftermarket cam but that takes a little extra work.

 

A stock 2bbl 8.5:1 comp motor will beat up a peg legged rear? I'm not sure about that. Not if it's a 2.xx. Not unless your starting off pre-loading the engine or trying to do a brake stand... I have 3.33's with a peg leg and I can't roost tires from a stand still, but I can jump on it at 20/25 and spin second, with a TH350.




What Edelbrock Carb is on the car? There should be a number on the passenger side front edge, right near the bolt to the intake. Could be a mismatched carb, mine came that way.


The RPM is only a upgrade if his motor has had some work, or the High Comp Version. On an 8.5:1 comp motor, it might be hurting.

 

# on the carb is 1407, a quick google search tells me that it's 750cfm

Again, I have no idea if the internals have been changed at all... what are some ways to tell? It does appear to still have the factory heads

 

What did you have done to it?


One wheel wonder meaning it'll peel out and put on a good one wheel show?

I wouldn't think it's got 2.XX gears in the rear if it's peeling out from a stop. Without help of the brakes that is.



Have you taken a vacuum reading at idle, in park and in drive from manifold port on the carb? High vacuum indicates a milder cam. If it's high, I would guess you have the 8.5:1 comp motor, and the 750 cfm carb might be too much. I have a 600 cfm carb on a 72 motor, with different metering rods etc, and it's too rich at low loads.

 

You can mod the engine until the sun comes up but without gears its going to be a dog.
I would get some 373s and a posi and then install a 750 vacuum 3310 vacuum Holley and be happy burning off the tires sideways.

 

Nothing, bone stock, it was just well tuned. An 8.5 to 1 355 with the stock cam does not need gear to be peppy.

 

Agreed. But I feel peppy and "spinnin the tires over" are different. My 72 350 is peppy, but it cant brake the tires loose from a stop. Sure I can roll around a corner, nail it and swing the rear end around, but I'm not slaying tires stop light to stop light. Maybe tires have come a long way in 30 years, I dunno. You owned that car before I was born. :/

 

My 72 cutlass with a 350/TH400, 2bbl and single exhaust would spin the 275/60/15. One wheel wonder with 2.73 gears. Nothing impressive but it would get you a ticket.

 

Sorry to Hijack OP, but was this recently? Stock motor, no rebuild no nothing? This is from a dead stop to wide open throttle, no preloading, no brake stands, in a straight line, correct? q-jet factory carb?

Now mine has a TH-350, not sure how much of a different 1st gear is between them...

 

Yes this was last summer. No preloading, stock motor with 170,000 miles on it. Stock rochester 2bbl carb. Straight line. TH400 has a higher 1st gear. Oh, it had a stock HEI and open air filter.

20 yrs ago with my Supreme I would light up 235/60/14 with a stock 350/TH350, 2.73 one wheeled wonder with 4bbl and headers. I could never leave the line floored or it would spin too much.

 

WTF!? Is all I can say. I have HEI and an open air filter, the generic one from Edelbrock. a performer intake and a 1405 carb (600cfm). Coppercutlass ran a 1405 on his hopped up motor and it ran great down the track. I think my tires are 235/70/14, but they are pretty worn. And I've got 3.33 gears in the rear. Higher first gear, numerically? Mines an "S" model, not sure if that could/should change anything.

So OP, it appears a 350 can really perform pretty well with minimal work. If it's done right. Clearly mine wasn't done right.

 

1st in a TH350 is 2.52 and in the TH400 is 2.48. The supreme ran a 15.6 1/4 mile @ ninety something mph which is not real impressive but it would spin the one tire. The 350 can be made to run good.

 

I ran 13.9 on a mild 355, but like coppers, it was nowhere near stock

It could be as simple as a pump shot/accelereator pump tuning issue. Don't assume the engine combo is bad just yet, though I do think a Performer intake is a better choice.

 

I have the performer intake. Do you mean the rpm variant? That was on the motor originally. The regular Performer is def. better. Transmission downshifts better, car doesn't hesitate/bog like it used to. Swapped to 1405 carb too. Still a 600cfm, but bigger idle circuits etc. car has 15/16 " Hg at idle so I have steel e-brock springs for the metering rods. Top notch on accelerator pump doesn't do much. Put richer metering rods in it, but now it seems to "stutter/surge" at 30mph just maintaining speed. like just off idle rolling. Maybe 1/2 down on the peddle. So I'm guessing to much fuel there. But it accelerates way better at WOT. So my car needs less fuel at idle, but more throughout the RPM range. I'm guessing. But I really should figure out the timing part first, otherwise I'll just be redoing everything on the carb.

There's something wrong with my timing. I don't know if the cam is off, the dizzy is screwed or what. But I couldn't figure it out, and had to pause the troubleshooting for my intake leak, which turned into 3 intake gasket changes, and a radiator flush/removal. And wiating for new intake gaskets each time.

Base timing is ~43* all in around 3600-3700 ~55*. See my thread here:

https://classicoldsmobile.com/forums...-mild-cam.html

OP I feel bad, I keep derailing your thread.

 

Exactly. It is too difficult having multiple conversations in one thread.

 

Okay,

So after I got home from work today, I jacked up the rear of the car to see where I'm at on a few things

1. Determined for sure it doesn't have limited slip (turn one wheel & the other goes opposite)

Then, raised only the driving wheel, made a mark on the driveshaft, and rotated the wheel 1 time

Driveshaft only spun ~1.25 times...at first I was like WTF, 1.25:1 gears? Then I read (on that interwebz) that with the 1 wheel method you have to spin it twice??? (Would love an explanation why btw) so I guess they're mid 2.xx:1's

Can you guys point me towards some rear-end sources?

I would LOVE to try that first to see about hooking this old girl up before tearing into the engine before I have to!

 

Also wouldn't mind some gear recommendations as well

This is my daily driver in the summer, not a track car so 4.10/4.11's probably way too high. Driving this car in the first place I'm obviously not OVERLY concerned with gas mileage though

Saw a few tossed around in the thread already... 3.33, 3.55, 3.73, 3.83?

As to what a few others mentioned, it's not that the car isn't "peppy" she does alright... but somewhat pedestrian in comparison to my buddy's bone-stock '69 Super Bee 440 6-pack. I know that's a big block, but with the mods to my car I'm starting to guess gearing is the biggest thing holding her back from really pushing you back in the seats at takeoff!

Edit: much less the new "modern musclecars" (stock GT Mustang comes with 420hp from the factory, SS camaro 426hp... and that's not even the crazy ones ones like the ZL1 -- 580hp!!!

I'd like to feel like if I theoretically pulled up next to one at the lights, I'd have a fighting chance, which I don't believe I currently do

 

@jpc647 I have ran in the past. The 1405, 1406 borrowed , and I rebuilt a 1407 for grins and giggles, I als ran for a very short time the 650 avs. p.i.t.a to tune. the edelbrocks need a good tuning. I ran the 1405 box stock with headers That is a key thing with the 1405 And it ran great box stock . 2 years ago I put my old 350 in my dads car with manifolds and it is now pig rich with that 1405 it ran perfect on my car ! I tried tuning it every which way and it was still rich. I talked to edelbrock and they said manifolds would not matter but I call bs on that since headers tend to lean an engine out. On my low 13 sec combo the 1406 really lacked the bottom end grunt then I bought another 1405 and it came to life some what. But for a car that ran 13.3 at 103 it could not do a burn out from a stand still. The following year I changed converters and went with a higher stall and holley 650 double pumper and it was a whole different beast. I then tried a 1407 on that same combo and base line was wayyyyyy too big , no matter where I adjusted the pump shot or what metering combination I tried it would bog horribly then take off and all you could smell was fuel. I learned a lot with my last combo on how crucial the correct parts are for performace. My car ran good but it could have probably ran a lot faster from the getgo if I had it all correct.

@cold fire. A 3.73 on a mild engine to stock engine will pep it up big time. I ran a 307 last year in my 72. I had a 1900-2300 stall with my 3.73 gears and the 307 could roast them from a stand still. It had a 650 holley and headers and good tune and exhaust but that little 307 ran good. If you plan on doing a mild build in the future buy a nice converter similar to what I ran. not too loose good on the street and it will have a nice launch. , So buying a rear gear and converter of your choice could be something to think about getting before you rebuild your engine That will give you the best bang for the buck., If you plan in advance and get something that will work down the road. You could add some headers and a nice exhaust and it will be a nice street cruiser and best of all all those parts can be re used in a future build. You have to find out what you have and figure out what it needs to run good or your best bet might be to find a good running stock 350 and drop that in and start with a converter and a rear gear etc. messing with an engine that you really don't know whats been done could be more expensive and then you could rebuild the one you took out and maybe reuse some of the parts and build it to suit your needs.

 

Some good advice

Remember, I'm quite green to all this, so bear with me... when you buy a new rear, do you just replace the differential or the entire rear (axles & everything) ...in which case would this also be an opportunity to upgrade the rear brakes? (she's sporting discs out front, but drums in back)

Are there some gear manufacturers that are held in higher regards? Any I should avoid (i.e. they are known to detonate after 10k miles lol)?

Also, how hard is it to install a torque converter I picture having to pull the engine/tranny!

Speaking of the transmission, I see guys throwing around th350 & th400... is there a visual way to tell what transmission I have?

So many questions!