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Oldsmobile 403 (Olds 403) Engine - Ask Anything

Jeff Smith: We did a little digging and it appears that the low-coolant sensor on your car is located on the passenger side of the radiator tank. It is difficult to see and you may need to remove the battery to access the sensor.

Apparently the sensor is tied only to the light on the dash, so it does not contribute to illuminating the check engine light. It also is somewhat troublesome, and corrosion or debris in the cooling system may arbitrarily trigger the light. So if you want, you can merely unhook the connection and go back to manually checking the cooling system level.

As for your engine temperature concerns, it first sounded like the gauge you were using may not be accurate (which is a common problem, especially with factory gauges), but looking into the factory fan settings, it appears these high temperatures were intentional. The first coolant-fan-switch temperatures we found were in a Hypertech instruction manual that indicated the factory ECU triggers the fans full on at 240 degrees F and turns them back off at 225 degrees F. That's a bit warm for a typical summer day that could easily kick your under-hood temperatures well over 240 degrees F. The Hypertech Power Programmer III that we looked at has the capability, among other things, to reprogram the electric fans to kick on at two different temperatures depending on your choice of thermostats. With the 180-degree Hypertech thermostat, the fans will kick on at 213 degrees and shut down when the engine temperature falls to 205 degrees. Or, you can opt for the 160-degree thermostat, and the programmer will trigger the fans to come on at 192 degrees and shut off at 185. This second option seems to be the most ideal as it will keep your engine operating somewhere around the 190-degree mark.

The reason the factory intended these engines to run so hot was strictly to satisfy emissions demands. Higher engine operating temperatures reduces hydrocarbon emissions, but it's certainly not the ideal situation for making power. Higher coolant temperature also increases the intake manifold and cylinder head intake port temperature. This heats the incoming air and fuel, which may improve mixture vaporization, but more important, it heats the air, making it less dense. This makes less power and also makes the engine more prone to detonation. The only snag we see with the Hypertech Power Programmer III, (PN 345752) is its $399.95 price, which seems a bit steep just to change the fan temps. The programmer can also allow you to change the rev limiter, speedometer calibration, and shift firmness and timing along with a slight change in timing and air/fuel ratio to produce a little more power, but you didn't mention those items. Jet also makes a similar GM programmer that offers the same features plus it shows a slight gain in power with some additional tuning. The Jet Stage 2 Power Control Module is PN 19614S and sells for $329.95

We also spoke to Mark McPhail, an ex-GM engineer who has worked with us on many Car Craft projects and who now does aftermarket ECU programming and tuning. You can contact him about doing a simple reprogram of your ECU that will trigger the fans at the exact temperature you want for much less than $400. Plus, McPhail might also be able to pull a few other reprogramming ideas out of his electronic bag of tricks if there is something specific you need. Regardless of which option you choose, the engine should make a little more power just by running about 40 degrees cooler!

More Info
Hypertech

Barlett, TN
901/382-8888
HyperTech.com

Jet Performance Products
Huntington Beach, CA
800/535-1161
JetChip.com

McPhail Performance
Costa Mesa, CA
248/941-1948

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65 comments
Charles Nott
Charles Nott

I have a stock 1/2 worn out 70 455 w-30 in my jet boat. It still hauls. wish I could upgrade with a edelbrock top end and rebuild the bottom

Bill McBath
Bill McBath

I had this in my Nova for one last race before I retired, what a ride it was... Thanks to all my fan's ans supporters through the years.... The Raceway Hugger ---- signing off...

Thumper Stahr
Thumper Stahr

To me, Olds is second only to Pontiac. I love these engines.

Nathaniel Green
Nathaniel Green

Yup!!! Ev er since my lon.g gone 87 307 beat a mustang gt more i.nterested in burning out than racing. That 403 deserves to go into an oldsmobile. I suggest you guys dig up a late 70's cutty or something for it.

Herb Edgell
Herb Edgell

joe mondello is your olds power guru.

Jeffrey Roseling
Jeffrey Roseling

I got a 78 olds delta with a 403 runs good with 250,000 mile on it and never rebuilt

Larry Fogle
Larry Fogle

It pisses me off when they put a Chevy in anything that is not a shevy keep the Olds and make her run.

Christopher Shipes
Christopher Shipes

My Dad has a 403 olds in his 79 Pontiac Trans-Am. We still have to redo it. Haven't had the time or money to get it right.

Chris Welch
Chris Welch

Definetly, i had an 81' Olds Cutlass with an Olds 455 in it. That was a fast car, I wish I had it back.

Travis Kerns
Travis Kerns

Build a 455 race motor. Up to 500ci. All motor. Naturally aspirated.

Michael D Taylor
Michael D Taylor

403,307...... run for ever...R.E. Olds would have liked them.

Greg Reinarts
Greg Reinarts

With the added strength of H-beam rods these engines can now be run hard and make lots of torque, and you can find them in self service wrecking yards at bargain prices.

Shawn Dumas
Shawn Dumas

Damn! My first car had that engine they have power yes!

Scott Myers
Scott Myers

Yeah I need one for son's 79, its .030 over, ported heads, forged pistons, Compcam, and a 175 shot of nitrous..

Chip Wilson
Chip Wilson

I've used the Olds engine in a Camaro swap before, fits under the hood better than a Chevy engine and is a lot torquier. Also used the Olds engine in several Chevy pickups.

Marty Decker
Marty Decker

Had a 330 with a power glide in a 66 cutlass ran that thing forever. Pigtailed a pushrod one time was running 100 MPH in 1st gear installed a new one and she was running like new again.

Chad Bauer
Chad Bauer

I had one with a mild build in a 77 buick lowrider. It had no problem roasting those little wheels.

Frank Mahon
Frank Mahon

Big Olds freak. Just put a stout 66 330 in my 87 Cutlass Salon...have a 71 455 on the stand for teardown.

James Motor
James Motor

I'm a olds freak!!! Blaaaa!!! Yeah I had a 403 that was bad as hell !!! Dounuts for dayyyys!

Damon Stickney
Damon Stickney

I have a 403 .030 over in my 85 el camino and a 425 .030 in my 1976 cutlass and they both scoot down the road quite nicely Thank you

Doug Burks
Doug Burks

Love Oldsmobile I've had several olds torque monsters just like Buick were most everyone will bash and say Chevy is better I've had both they are all good but I like not being in the majority

Lee Atkinson
Lee Atkinson

GREAT motor for the street, super-easy to make into a 13-second daily driver. Not much harder to get into the 12's.

Zach Knouse
Zach Knouse

What's the deal with the gold edelbrock valve covers?

Greg LeBlanc
Greg LeBlanc

Olds 455 in my 1975 olds omega, bast to drive!!

John Royal
John Royal

I am just finishing up one for a customer

Aaron Lancaster
Aaron Lancaster

Lol not a 403. I have one in my Trans Am, I wouldnt give a plugged nickel for. It's going in the trash as soon as my big block chevy is done

Dennis L. Young
Dennis L. Young

I had a 77 Olds 98 Regency with a 403 it was to heavy to get off the line fast , but it was a cruiser on the open highway.

Jeffrey Ralph
Jeffrey Ralph

Hey I got a 383 stroker small block chevy in Chevelle what's a good set of headers???

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