by "My bird IS the word" (mybirdistheword)
Published 12/31/2017 at 12:03
by "My bird IS the word" (mybirdistheword)
Published 12/31/2017 at 12:03
Tags: Tech questions
STARS: 0
A new year comes with new challenges and projects! this year will be the year of the Oldsmobile 403: the best worst engine ever.
Before I get to the questions, my situation for those who arent familiar: My trans am is junk. the engine ran fine when it was in the car, but was leaking like a sieve. all of my surfaces are nice inside (minus the inch of oil goop in the intake valley) which isn’t strange for the 403, but indicates that it was definitely sitting for some time. My present circumstance means that I can’t really throw money at this thing, but I am willing to ballpark around $2k for the rebuild over what I have already spent on new oil pump, water pump, timing ect. Clearance issues also mean that I am stuck with stock heads and intake.
What does that leave me with? well, I can get high compression pistons that should remedy the 403's miserable stock 8:0:1 compression. combined with a cam and I would not have to go far into the serious expensive shit to get my engine in decent shape. The real question?
On stock heads, am I just pissing my power away?
Concerned about flow mostly. This engine is seriously under-stressed for what it is designed for which will actually enable me to use stock everything for the most part, so I think I will be fine.
but if the stock heads will bottleneck it I might as well not screw with things.
I am not looking for racecar power here, just something that isn’t embarrassing for a 6.6l.
I know I can get my stock engine rebuilt just fine in my budget. If I start going into cylinder head porting, that is going out the window. I don’t love this engine. I don’t love my whole drivetrain for that matter. I could ls swap the thing and lose zero sleep. the problem is that I want to drive it, and that won’t happen unless I put this thing back together. I would be fine keeping it, but I want it put together properly, and I only want to do this once. I don’t want a $5k 403. I just want ~300hp which I know this thing can make.
"jimz" (jimz)
12/31/2017 at 12:44, STARS: 0
guy next door to us when I was in high school had a ‘79 with the 403. Built up a bit, but AFAIK was on stock block and heads. y’know, cam/intake/headers. Don’t know how much hp he was making, but it felt fast when I rode in it. ‘course, this was 1990 and the Malaise era was just ending.
http://www.texastransams.com/articles/2002ron_l_403_article.htm
"HammerheadFistpunch" (hammerheadfistpunch)
12/31/2017 at 12:44, STARS: 1
Well there is a rebuild cost and a performance gain cost. Is there a junk yard engine with a better compatible head you can source? I don’t know squat about these motors unfortunately.
"slipperysallylikespenguins" (slipperysally)
12/31/2017 at 12:49, STARS: 1
One thing I’ve heard with these is that you can put on heads from an older Olds 350 to raise compression to 9.5-10 without a new cam or pistons.
"AMGtech - now with more recalls!" (amgtech)
12/31/2017 at 12:53, STARS: 2
What about a junkyard LS out of a truck? Like a 5.3? I bet you could get engine, trans, wiring, and control module for that same $2k. Sure, there would be some effort involved on your part and downtime would be greater, but it’s winter, and you’d be happier at the end.
Or do the bare minimum to get the 403 running, as in no performance mods, just reliability fixes. Then save up to swap in something better in a year or two or whatever.
"WilliamsSW" (williamssw)
12/31/2017 at 12:57, STARS: 0
I’ve heard this too, and might even flow better?
"Alfalfa" (alfalfa-romeo)
12/31/2017 at 13:27, STARS: 0
I’d say stick with the stock heads and maybe replace them later.
Another possible option is to port your heads, but if you’re unsure about the process you’re likely to just fuck them up. So you know, that’s entirely up to you.
"crowmolly" (crowmolly)
12/31/2017 at 13:29, STARS: 4
Preface: honestly $2k can probably get you what you need for a 5.3L LS swap right now. Cheapest way to reliable power.
That said, if you want to stay original looking or want to learn how to work on older stuff I understand. To some degree LS swaps are like 383s and Torq thrust wheels from a few years back.
In your case (if you don’t want to go LS or want to put that off until you’ve at least enjoyed the car a little bit on the road) I’d keep the short block as is. Retorque the bottom end, get thinner head gaskets, and reassemble. If you upgrade the exhaust (which you’ve done IIRC) and add an aftermarket intake/tuned carb/non-shitty distributor curve you will be on your way. If you want to attempt a new cam you can do that too- it will make a big difference. You just need to make sure your ducks are in a row as a flat tappet cam break in has little tolerance for fuckery.
"My bird IS the word" (mybirdistheword)
12/31/2017 at 13:33, STARS: 1
Not without work since they are designed for a smaller engine.
"My bird IS the word" (mybirdistheword)
12/31/2017 at 13:33, STARS: 0
You can do that but it requires substantial mods and still suffers from issues with valve size and porting which would both put it over budget.
"My bird IS the word" (mybirdistheword)
12/31/2017 at 13:35, STARS: 0
that would require a new transmission, driveshaft, special parts like crossmembers. not necessarily a difficult swap, and one I may do eventually, but is very $$$ even with a junkyard engine.
"AMGtech - now with more recalls!" (amgtech)
12/31/2017 at 13:37, STARS: 1
That’s disappointing. I had no idea. More oppos should live by me, I would totally help with these kinds of projects.
"My bird IS the word" (mybirdistheword)
12/31/2017 at 13:38, STARS: 0
The stock heads are fine, I just can’t afford the porting as that would be at least $1000
"WilliamsSW" (williamssw)
12/31/2017 at 13:39, STARS: 0
Makes sense with that big bore in the 403. What I’ve heard probably skipped over the head work needed.
"My bird IS the word" (mybirdistheword)
12/31/2017 at 13:40, STARS: 1
the 2k could get me the engine (and maybe trans) but it requires another $1500 in accessory parts. I probably will put an LS in at some point but it’s too much right now for a car that is full of holes.
Edit: also I can’t do intake or a carb because it will screw up my shaker clearance. I should probably get new ignition stuff after I get it running again.
"crowmolly" (crowmolly)
12/31/2017 at 13:45, STARS: 1
I guess the BOP bellhousing adapter alone is a few hundred.
Anyway, that’s what I’d do with what you’ve got.
"Alfalfa" (alfalfa-romeo)
12/31/2017 at 13:46, STARS: 0
Yeah I meant doing it yourself. It has been successfully done with die grinders, but it’s certainly not the most ideal method.
"My bird IS the word" (mybirdistheword)
12/31/2017 at 13:46, STARS: 0
Whats nice is that an ls is in my relatively piss poor skill level because there isn’t any fabrication needed, but it requires special headers, an oil pan from x car, bracketry, ect ect. But I wouldn’t feel right doing that until the body work is squared away. Possibly considering a manual swap as well since the floor pan will probably get replaced.
"My bird IS the word" (mybirdistheword)
12/31/2017 at 13:49, STARS: 0
more of a time thing. I am trying to eliminate frustration on this thing so it actually gets done. would have to get heads to practice on, tools, you know. I already have to do brake and fuel lines as well as body bushings and subframe connectors and do all of this with a new job this summer.
"AMGtech - now with more recalls!" (amgtech)
12/31/2017 at 13:53, STARS: 0
That’s what I mean. I can fab, and do paint and body too. The only automotive related thing I don’t feel comfortable with is custom upholstery.
"AMGtech - now with more recalls!" (amgtech)
12/31/2017 at 13:54, STARS: 0
I had a friend who used to live near me that would help me get my “custom and old stuff” fix, but he moved away a couple years ago. Don’t have any projects of my own
"sdwarf36" (sdwarf36)
12/31/2017 at 13:57, STARS: 3
You don’t need any porting. You aren’t changing your gear so you aren’t going to be revving it any higher. Those heads will flow fine to 4k rpm. That motor is built for torque. The fact that the rings will be sealing properly-and the head aren’t bagged out is gonna add all the hp you’ll ever need. I’d maybe go 1 size up on the cam-other than that go back to stock. (Former automotive machinist for apx. 30 years.)
"Shift24" (the-nope)
12/31/2017 at 14:05, STARS: 0
Sounds like 301 turbo time. Seriously though these were rare and parts are scarce. Only made between 1977-79, but it did use olds standard block so as stated by others a olds 350 head might be better
"Rock Bottom" (rockbottom81)
12/31/2017 at 14:14, STARS: 2
I know you said you don’t want to port the heads, but it’s really a cheap and easy win on a smog-era engine. These heads were made to be cheap (instead of good), so they usually have all sorts of extra casting ridges and lumps in the runners that can be taken out on a Saturday afternoon. Of course, it requires an air compressor, a Harbor Freight die grinder, and an iron burr, but all of those things can usually be borrowed. Just a thought.
80% of the easy gains are on the intake side, and most of that gain is at the bottom of the runner near the valve. If you reach your finger up through the runners from the chamber, you will probably feel casting ridges on the runner floors as the runner turns. Remove those ridges, being careful not to walk the die grinder burr over the valve seat. Also, all smog-era heads also yield decent gains in cleaning up the bowls. The last turn the intake air makes before hitting the back of the valve is usually a mess from the factory. You don’t need to go way up in the runner, the biggest gains are had in the bowl. This guy did a pretty good job, though I would prefer to leave a little more meat around the guide on a street engine:
"AestheticsInMotion" (aestheticsinmotion)
12/31/2017 at 15:12, STARS: 0
I just so happen to have a ticking time bomb 350,000 mile BP engine just begging to be replaced...
"Die-Trying" (die-trying)
12/31/2017 at 17:21, STARS: 0
the lower 4 bolts on all those gm transmission bellhousings were the same, could always do some of the same ol’ same ol’ and go BBChevy....... provided a guy had enough confidence in those 4 bolts.....
"AMGtech - now with more recalls!" (amgtech)
12/31/2017 at 20:09, STARS: 0
Do tell...
"My bird IS the word" (mybirdistheword)
01/01/2018 at 12:44, STARS: 0
most of the stock parts are available believe it or not, and most if not all the performance stuff is built for the 350 and the 455 olds and can be adapted, but there isn’t much selection in either case.
"My bird IS the word" (mybirdistheword)
01/01/2018 at 12:46, STARS: 0
No old (pre 80s) junkyards in my area. Any new engine will cause clearance issues with my hood and come with it’s own problems. mostly availability unless I went with a chebby 350
"My bird IS the word" (mybirdistheword)
01/01/2018 at 12:50, STARS: 0
thank you, this is very helpful.
"My bird IS the word" (mybirdistheword)
01/01/2018 at 12:51, STARS: 1
Its just a bit outside my comfort zone, and more of a time thing. Given you can take the heads off without pulling the motor I may still have this done in the future when time allows.
"AestheticsInMotion" (aestheticsinmotion)
01/01/2018 at 19:03, STARS: 0
Well, the Miata needs something soon. I’m hoping to make it through the winter, but I can smell coolant while driving, oil is covering the bottom of the engine bay, and even my local race shop which is fairly cheap wants quite a bit for a rebuild, which doesn’t seem worthwhile considering other options.
Once business picks up again in a few months I should have the cash to buy the same engine with lower miles, a slightly newer VVT Miata engine from the NB generation and possibly have someone build it up slightly, eventually adding forced induction... Or do a budget LS/LFX swap. That’s looking better and better because I like the idea of going with an understressed naturally aspirated setup so I’m not tinkering with it every day.
Unfortunately I don’t have the space/tools/knowledge for something at this level, so right now I’m at the mercy of the handful of nearby places willing to do work like this
"Rock Bottom" (rockbottom81)
01/02/2018 at 10:20, STARS: 0
Totally understand, port work is pretty intimidating. If you have a chance, grab a spare head to practice on. It’ll give you a feel for how the burr bites. Next time you have the engine apart, you’ll be ready to add power for cheap! Keep in mind that iron and aluminum cut very differently, so plan accordingly :)