Olds 307 to Olds 403 engine swap info please?

Couple of things;
This whole thread would go real good on the Classic Olds Forum, rather than here, as we have many noobies asking about this swap!
I believe there might be some internal and external balanceing issues related to changing the dampener and flexplate between a 307 and 350 - check it before installation, please!
I do know you can't mix and match the pulleys, and there might be a difference in the length of the water pump, between the two, and they must match!! I'd install a new pump, anyway, as the cost isn't worth the problem, after installation.
If you find a early A-body rear 'double-hump' crossmember, it'll be a lot easier for exhaust! Simple mods for a bolt-in!
Your current gear [7 1/2"] is gonna be your weak point - GN [bolt-in] was 8 1/2", and usually 3:42 gears! Will last at least twice as long.
Good luck!

 

Thanks for the tips. I kinda posted it here because the 307 to 350-403 swap is so popular on the 80's full-size GM wagons, and it's all the same.

I am going to use a new 8 1/2lb 350 harmonic balancer, but everything else is going to be from the 307...well except I pulled some a/c brackets from a 79 Toronado, which did not have the smog pump, since I'm not putting all the smog stuff back on. I'n looking into this I've been told everything will bolt up with the 350 balancer....we're about to find out!

I'm retaining the computer to control the transmission torque converter, a.c compressor cycling, and the electronic carb. I am modding the carb so the secondaries will open fully and adding 350 metering rods.

The exhaust is staying basically stock for now because the car has to go through state inspection one more time (25 years in Texas).

Such fun!

-Mike

 

Exhaust will sniff the same - now or later!
They're so stupid up here, I put a dual exhaust muffler on a '86 GP 2 + 2, and they checked one side!!
And a 180 thermostat will help everything!!

 

I reread the entire thread Mike. Interesting. I still say go with Gold paint. :2_thumbs_up_-_anima
I have a 2004R in the 55 Chevy wagon. They are tough trannys they just get bad publicity. Some hot Buicks had those.
About the electric shift, I bought a kit with a sensor. Very clean and simple. Even added a shift lite to show when torque converter kicks in or out. Used one of the 55 Chevy idiot lites. Other is for brake warning.

 

That's so funny!

This is the last year they do a visual exhausr inspection here. Next year, at 26, it's a "beep the horn and show me the parking brake" inspection. In other words I have to retain the cat converter until August, run it through inspection, and then it's true duals for this car.

I do feel bad the 350 will be choked through single exhaust until then.

-Mike

 

Good to know about the trans, hope it holds up.

Too late on the engine, put the first quote of black on last night!

-Mike

 

One of the guys on Classic Olds was selling a 8 1/2" axle, and I questioned him about a drum to drum assembly.
He has one, 3:42 Posi for $1150 - all new everything!!
Won't effect emmissions, either!

 

Ouch! Love to have it but that's way out of my budget, sadly! Wives and kiddos are expensive!

 

Here's Eddie standing next to the Cutlass last night, for it's final drive under 307 power (307 power... :lol: ).

ANYWAY we made it the 15 miles to the shop, but it was scary! Car fired right up and had over 40psi on the gauge. Eddie rode with me and Misty and Tuck followed.

Got on the highway and watched the gauge drop from 40 to 30 to 20 and then head for the red. Took my exit and BAM got stuck at a LONG light. As soon as I came to a stop the gauge dropped to zero, and VERY BAD SOUNDS began to come from up front.

I popped the car into neutral and gave it some gas and the gauge moved from zero into the red...but not above it. FINALLY after what seemed forever the light changed, and clanging away we made it the last mile to Troung's shop.
I was never so happy to shut a car off.

SO it's backed in and locked up behind his gate, waiting for the cherry-picker to pull the 307.

Oh Man!

-Mike

 

Quoted for maximum ridiculosity...

 

I had a classmate in school with a nice black over silver '85 442 that he thought was the baddest thing on 4 wheels. Yes they are a damn sexy car and I always loved ALL G-Bodies. I, at the time had bought my parents '87 Grand Prix with a factory ordered HO 305, with 2004R tranny, 3.08 limited slip, Rally Tuned suspension with the big front and rear sway bars, Dual (after Cat) exhaust, roller cam/lifters and low friction crank(according to dealer options and build sheet), high volume fuel and oil pump, oil cooler, tranny cooler, 795cft Qjet, dual snorkel air cleaner. Dealer estimated it close to 210hp. Be it true estimate or not, it was a VERY impressive runner. Basically a 2+2 in plane ice blue clothing. Split bench, AC, Crank windows, AM/FM radio, it came with some ugly hubcaps but Firestone F480 205/70/14 RWL tires. Everything was exactly as my dad ordered it.

It was bone stock as dad had ordered it and I just bought it from them with 132K on it and took it to school. I just blew up the 350 in my 80 regal and dad offered it to me on weekly payments, because they just bought a brand new '92 Grand Prix. I pulled into the school parkinglot and Matt was already there and laughed at my GP coz of the hubcaps with white lettered tires. He was a total ass and always had been, spoiled by mommy and daddy his entire life. I told him after school, bring that Nutless with its 307 boat anchor to the west side of town and I will give him something to cry about. He said NO PROBLEM, care to wager, I said nope, you are gonna want your money to replace that puke motor when I shut you down. 3 car lengths was what I had him by at the end of our strip where we been racing for years. He was not so smug after that day. I did run it every Sunday at the local strip after that and the best time I got out of it completely stock was 14.84@ 91.9mph. Not bad for a 5.0 in a 3339lb fully dressed car on street tires and full exhaust. 3 years later it had a mild 350 out of a 77 Blazer, it ran better but I never ran it at the strip.

You will love the 350 Olds motor, the torque will be the most noticeable, even with the choked exhaust. IMO, the 307 is not much of an improvement over the Buick 3.8, just sucks more gas and has a little more torque. Its a shame that shoved them in so many cars when they could have gotten better mileage out of a 350 because of the higher torque and less need to shove the peddle to the floor to get them moving off the line.

 

Great write-up, enjoyed reading it! And I totally agree, the 305 Chevy will eat a 307 Olds for lunch.

Thought you might like the pics below. This is one I let slip away. When I was first dating Misty, who is now my wife, this '85 Grand Prix LE was her daily driver. Chevy 305 V8, posi rear, buckets, floor shift, full gauges with tach.





Here's my '93 S-10 and GP in the parking lot of our first apartment together:


I replaced the goofy aftermarket wheels with 15-inch Pontiac Rally II wheels.

MAN that was a sharp GP!

-Mike

 

Made some good headway this weekend! Engine is all painted and ready to be taken to the shop.

Pics!






And coming together!




Can't wait to hear it run again!

-Mike

 

Lookin' GOOD, Mike!

 

Oh and here's the tag number from below the head on the block: 32R18284..and one I can't read


Interesting breakdown....
3 = Oldsmobile
2 = 1972 ...? So my heads are 71 and block is 72? Confusing...
R = Arlington Assembly (Texas engine from new!)
18284 = Last digits of car's VIN #