I'm sure this has been gone over 1000 times, so I'm sorry. I tried searching for this topic and couldn't find the thread that discussed it.

Anyway, I have a 455 smog motor and was just curious how bad are they really? I'm not looking to build a track car or anything. I just want something that will spin the tires and something that I can blow the doors off those stupid rice burner imports. Thanks for the input.

 

"Smog motor" usually refers to a low compression engine, mostly built in the mid to late 70s. A 455 still displaces 455 cubic inches and makes a ton of torque. Are there "better" 455s? Yes Is a later 455 still a good candidate for a mild street build? Definitely! As always, it depends on your budget and goals.

 

No. They're not that bad. Pistons may suck a little but 300hp to the wheels is a reasonable goal with an intake, cam, and headers. Just no J heads. If you really want to transform the car, start with the rear axle. Short answer, if you have one that runs fine, leave the bottom end.

 

BrownBomber sidesteps the question by suggesting ways to modify a smog motor, but in a way, he answers it as well: Stock, these motors will drink fuel like a Bowery alkie, while moving your car like a staggering junkie.

You will not beat any rice burners with a stock one of these in a '70s American car, unless that American car is a Chevette, or that rice burner is a '72 Datsun B210.

- Eric

 

And definitely not if its in a 65 Jetstar. you need to find a different goal.

 

The one I have has "J" heads. I have the opportunity to pick up a backup generator 455 with "K" heads. I don't have a bunch of money to dump into either one. I just don't want to waste money on the "J" head motor if it's not gonna be worth it. Thanks guys.

 

Trust me, if I had the money to get a cutlass I would have. Down the road that is my goal. I got a damn good deal on that jetstar, plus its in really good shape. So for now, that's what I have to work with.

 

I didn't say anything bad about the Jetstar and I think they are awesome cars. It was your goal of smoking a rice burner with it, that ain't happening.

 

Ya, that damn thing is a freaking boat! Lol. Thanks for being honest. Will it spin the tires at least? And not just going around a corner on wet pavement?

 

You should be able to shred tire/s with a 455 in it.

 

Doing a quick search, I found the smog engine 455 puts out roughly 190 HP, & 250 Ft/ Lbs of torque. That's pretty pathetic and the chief reason it's so low is the lack of compression, as others have stated. I agree that your best bang for buck would come from changing the rear gear ratio. Without doing anything to the bottom end, it's going to be hard to get your compression ratio up to decent levels.
Even if you were to do just the upper end, it will still add up fast. I'm going to throw some numbers at you that you can just call "guesstimates".
1) Core "C" heads - $200
2) Valves, Springs, Guides, Mill heads, Machine work - $850
3) Used intake manifold - $150
4) Used headers - $200
5) Rebuild Carb - $250
6) Cam, lifters, push rods, chain set - $450
7) Used Comp Cams roller tip rockers - $150
8) Gasket kit - $80
You just spent slightly over $2300. At least this is a good start to a respectable power plant. You could bolt this on, and start building a good short block. Those "J" heads don't flow worth a darn, but some guys have ported the snot out of them and had good results. If you're handy and have lots of time to kill you might want to do some Home Porting. This thread might be right up your alley -
https://classicoldsmobile.com/forums...echniques.html


Another option for you might be to take advantage of the low compression/ restricted ports, and build a twin turbo set up. It would be more money, better gas mileage, different than anyone else's, & probably not as reliable.
Keep us posted on your progress. Good luck, Dave - The Freak

 

Depending on what these motors are costing you could have a pretty good build
What's wrong with the 455 with the k heads ? Or the motor with the j heads ?
455 after 71 usually have low compression pistons

 

The one with the j heads came with the car but is j it st sitting in the engine bay. I'm planning on pulling it out this weekend to see if it will even run. The one with the k heads was a backup motor for a generator. The guy said it ran great the last time they needed it, but used oil. What is the most cost effective way to upgrade the rear end?

 

I like the Ka heads. If the purchase price is reasonable you might pick it up and do a rebuild putting in pistons to increase the compression.

I don't know how common gears are for your rear end. A member called monzaz has a business that includes rebuilding rear ends of this vintage. You could create a thread asking about what would fit, but if nobody replies you could send monzaz and message.


John

 

I say whether you have a 68 engine or a 76 engine, and then do a complete performance rebuild with good pistons and earlier heads or aluminum heads, that you essentially get the same result, right?

I helped a friend do a performance rebuild on a 73 engine and installed earlier heads and it was a very strong motor.

 

That k head motor is $300, but I stumbled on to 455 with C heads. The guy is asking $400 but I think I can get him down to $300 also. Thanks for all the info guys.

 

Those are okay prices for a complete engine maybe missing carb
The c heads could still be small valve same with the Ka heads
I have bought 4 engines and have taken the best parts from three to have two builds ready

Just to list a few
72 block big car gave me a good std block with N crank
The marine engine was cracked but had a fresh rebuild gave me a good rotating assembley std crank and big valve Ka heads were checked and had been rebuilt
You can always mix and match tell you get the best parts as long as your picking them up cheap

 

I think the c head motor came out of a late 60's two door hardtop of some kind. I couldn't understand the make. I believe he said 1969. I'm going to go look at it Friday as long as we don't get a lot of snow. Will the date be stamped on the back of the motor?

 

Driver side if engine just under the head there is a pad stamped it will tell you 3xxxxxx

These number/ letters will tell you make year and factory and the last few of the vin of the car

3=oldsmobile
If it is 69 9=69
M= Lansing
Just to give you a idea

 

If the 1969 is a runner it will have higher compression pistons. If it needs rebuilt with new pistons, it may not be better than the marine engine. Ka heads were large valve only whereas the C's could be large or small valve.

Here's where the number is located that oldstata was describing.

PA221821.jpg

PA221822.jpg

 

A low compression 455 can run really well. I had a 71 Toronado engine (my grandfather bought the car new) in my 74 Omega street car that weighed 3980 lbs. with me in it. The engine had 120,000+ on it when I put it in, 100% original, and ran 13.50's with open headers. I put a cam in it and ran a best of 12.86. In my 73 Omega race car (3550 lbs.), I had a 76 455 with a cam, headers, stock intake and Quadrajet, stock TH350 converter from the Omega, and with mildly ported J heads it ran 12.50's. I freshened it and switched to E heads and ran a best of 12.18. Timing helps a lot. I ran 45° total with all my low compression engines.

 

My stock '73 455 4v with J heads and 2:73 rear, destroys tyres..

[botmbulb], 45° total eh. What was your initial timing set to? (vac advance disconnected)

 

22-24 initial, no vacuum advance.