Well... no more 425 for me.... damnit I miss that car so much now... never realize what ya have....until its gone...
Anyway, my list of, well, cheap power improvements to the 425...
- full tune up. This includes fluids changed, plugs, wires, cap and rotor, air filter, fuel filter, PCV valve etc....
- 14" open element air cleaner. Mine was made by Edelbrock, it looks really nice. Free flowing, and sounded sweet, especially when the secondaires opened
. It also greatly helped to clean the engine bay up.
- drain cat. conv. If your car still has the origanal cat... its plugged. Pry out the drain cap on the bottom and drain the beads... make sure they all come out... then take it to a shop that has those plugs... when I got an inspection on the car, the guy had a bunch of them laying around (old GM part) and charged me $5.... it was loud, but got annoying fast with the plug missing.
- rebuild carburator. The Qudra-Jet is a sweet carb, don't let anyone tell you otherwise... but obvisouly a ~30 year old carburater is going to have problems. Rebuild it, and if you know about carbs, or a shop does, then dump the emmisons settings from factory and go for a little performance, a stock Q-jet can be worked over to squeeze more out of it. Keep in mind this is an 800CFM beast that fits the engine perfectally, keep it. A good book for the Q-jet is Doug Roe - Rochester Carburators.
- find a 1968 472 intake manifold. This intake manifold, stock, flows alot better then the 425 intake. The '68 dosn't have EGR either, so the 425 now dumps EGR. While I don't mind EGR, with an old valve and lines, it is more of a problem then anything. Then, take the manifold to a machine shop and have them totally cut the center section under the carb out, so it is 1 big opening. You now have an intake manifold that flows 95%+ of the Edelbrock intake, for a whole lot cheaper. Sure it still weighs 45lbs, but it looks stock. This intake manifold will flow just as well as the Edelbrock until around 5,500RPM.... seeing as how these big blocks don't rev past 4,000RPM stock, you have to do alot to really get out of the effective range of it. It is also a low-riser intake, no more hood clearance problems. Perhaps the biggest thing is, you can still use the factory AC, not so with the Edelbrock. The A-4 from the 425 has a different mounting bracket, so to correctly mount the compressor, you need the 472 AC compressor bracket. Swap that over and she bolts right in. Revs smoother, sounds more healthy at WOT and noticeable power boost. The BB Cads are so cool, there is no coolant to mess with
.
Another non-engine related performance boost that really helped the car in handling and overall driving, was installing a factory rear sway bar. Mine was from a '79 Fleetwood, but I have been told 70's G-bodys use the same bar. Very nice mod.
The stock '79 DeVille with out 472 intake or rebuilt carb ran a 17.5@78mph. She was noticeably faster after words. I gotta say, the car was actually fast by the time I was done with these minor things. Floor it at 30 and she'll downshift into 1st, put you in the seat and you see the nose of the car jump up.
Other cheap things I had in mind was a shift kit for the trans... that would really help since the trans is calibrated for excessive slipping for smooth shifts.
Another thing that was going to be sweet, since the factory 2.28 gears don't offer much for performance, I was going to swap a cam in... not a hot cam, but a cam that brought the power band lower then stock... an RV cam. More low end torque at the expensive of high RPM HP. The neat thing is, the cams power band is idle-4,000RPM... well, it would shift at 3,900RPM going in to 2nd and 3,400RPM when going into 3rd, when in drive. It was perfect. The cam is the MTS #3, stock valve train is fine. It is also the gas saver cam and is very possible to get 20mpg+ on the open road... that was going to be the project. I wasn't ready to swap the rear end just yet, and so being stuck with the 2.28 gears, I was going to make a torque beast, a whole lot meaner.
Also, find the cross member from a Caprice 9C1, that way you can easily run true duals. True dual 2.25" exahust on a near stock 425 would be sweet, unleash a few ponies too, and with the MTS #3 cam, really open it up...
while on the exhaust note, the 425 manifolds are junk. Find a set of 472/500 manifolds, while not the best, they flow alot better, direct swap in for the 425, that and the true dual exhaust would be sweet.
There are all the basic plans I had for my '79... I had lots of plans. Hopefully this will help anyone else that just got a 425 and wants to bring the life back. Mileage dosn't effect the BB Cads much at all... meaning a 425/472/500 with 100k, if mainted thru its life, will show minimal wear and be ready for any plans you may have. Same goes for the Turbo 400.
- BTW from an appearance standpoint, something that REALLY helps the '77-'79 DeVille is to run a 2nd pin striping down from the fender and follow the body line that ends at the door. That right there is the missing link, without it, the car looked bland and missing something... I added that and DAMN those 2 pin stripes really set the car off like nothing else, it looked soo nice.
She will be missed....
