r/EngineBuilding • u/Odd-Draft4494 • 3d ago

Olds Waking up the 403

Gallery image

Gallery image

I'm buying this 78 toronado for my first car. I was doing research on it and found that the 403 is surprisingly weak due to all the emission controling. I heard that swapping the cylinder headers for ones that have better compression, a mild cam and a Y-exhaust would wake the engine up but I'd like input from those that are more experienced than me. I don't want to make it a drag car but I'd also like a bit more power coming out of that 403.

6 Upvotes

88% Upvoted

9 comments sorted by

3

u/WrenchKing555 3d ago

Intake, Carb, Cam, Exhaust. Delete all the emissions, no cat exhaust, Edelbrock intake and carb, camshaft. Just doing the Intake, Carb, and Exhaust will make a difference. The camshaft is the icing.

1

u/East-Teaching-3104 3d ago

I agree that the intake / cam / exhaust recipe will definitely wake it up but man, those things have terrible compression. I think they end up having like, 8:1 or something like that.

Edelbrock apparently still sells 68cc heads for that motor- those plus a cam and intake would really be nice. They're only... $2600 a pair... 😬

You know there are a lot of other engines that would drop right in there...

1

u/WrenchKing555 3d ago

Yea I wouldn't go as far as heads on it. If it was my daily, I would remove the emissions, swap the carb and call it a day.

1

u/Odd-Draft4494 3d ago

I also plan to buy a winter car even though I'm going to treat the underbody for salt damage. So after I buy the winter/beater I'll probably do the cam. My friend just got this 4 barrel carburetor for his 67 Pontiac Catalina and I believe it's called the Demon? Would I get something like that since our engines are nearly identical (403 and 400) V8s

1

u/WrenchKing555 3d ago

That's a lot of carb for a stock engine. You would need to flow quite a bit more to necessitate that.

1

u/Odd-Draft4494 3d ago

Well I do save a bit of money since I'm trading instead of buying. So that's a bit of a plus for me to buy headers sooner

1

u/WyattCo06 2d ago

Is it a Holley Demon or Barry Grant?

1

u/Doctah_Whoopass 2d ago

8:1 is perfect for boost

1

u/Toomanycars6870 1d ago

Make sure to install a new timing set when the camshaft is replaced. Proper cam timing will return the low end torque that was lost from a worn timing set. The 403 is capable of more than many realize. It developed a bad rap from being choked by emission controls, low 7.8:1 compression, and weak webbing in the block. The block is nothing to worry about in a naturally aspirated format. Limit the rpm to 5000 and there will be no concern.