: What years are compatible with my car year???

10-11-04, 08:23 PM
I have a 1999 seville STS.
i called the dealer and gave them my VIN number, accoridng to what they told me, only a 98-2000 cylinder heads would work with my car...
is that really true...i dont see why a 94, or 95 cylinder heads wouldnt work....
and the throttle body has to be off a 98-2000 only....so if i see a throttle body on e bay from a 97 or 95 or something it wouldnt work either?

so whats the deal? what about manifolds.....94 wouldnt work?


Anthony Cipriano
10-11-04, 10:16 PM
You're getting bad information. 2000 model year cylinder heads wont work on a 1999 Northstar no matter what the dealer says. I don't think any parts from a 2000 will fit your engine. Don't know what they were thinking when they told you that.

You're really limited to using heads from 1995 thru 1999. The 93/94 heads will physically fit on the engine and the head bolts will work but the intake manifold was significantly different for 93/94 and the heads had different EGR passages and provisions and different number of intake manifold bolts. You wont be able to bolt up your 1999 intake manifold to 93/94 heads so it would be a waste of time to get them.

The 95 throttle body was a bit different as that engine was speed density fuel injection and had no MAF sensor provisions. There were also differences in the MAF mounting on the throttle body and in the air inlet duct on the later years also. Some of these differences are minor and can be cobbled around but they wont look stock.

10-11-04, 10:20 PM
anthony why was the intake manifold redesigned from the many tubed/open to the two piece closed for 95+ is it that much more efficient? if so could one be adapted to work in say a 94 eldo :D ?

Anthony Cipriano
10-11-04, 10:47 PM
Actually the 95 and later intake manifold is a one piece part. The entire intake manifold - tuning tubes and all - is made as a one piece, injection molded plastic part.

It was changed to simplify construction of the engine. It reduces well over 100 parts that make up the complete intake manifold on the 93/94 engine to one single part. Functionally, the 93/94 intake and the later, one piece plastic manifold are equivalent. There would be no real reason to try to adapt the later model manifold to an earlier engine.

10-11-04, 10:52 PM
thanks anthony just curious. then where does the 95+ get the extra 5 hp

Anthony Cipriano
10-11-04, 11:06 PM
thanks anthony just curious. then where does the 95+ get the extra 5 hp

...from the intake manfold primarily - but before you rush off and start trying to change it realize that you'll never feel the 5 horsepower as it's just at the power peak and the gain was more on the order of 2-3 horsepower which allowed the horsepower number to "round off" to 300. The reason for the gain was the smaller plenum on the 95 and later manifold. The one piece plastic intake has a much smaller plenum volume compared to the large plenum of the open intake with the individual tubes inside. The smaller plenum tunes for peak power a little better.

The 5 ftlb. of torque with the 95 and later manifold came from eliminating the small "mouse holes" in the phenolic spacer plates. There's just enough crosstalk between cylinders with the small EGR mouse holes to cause a slight tuning loss at 4400rpm causing the 5 ftlb. loss with the 93/94 manifold system. Once again, not something to be worried about.

10-12-04, 01:28 AM
5 horses!?! That's worth like 0.00054 seconds in the 1/4 mile! :bighead:

10-12-04, 03:49 PM
oh wow good thing i asked.

so 95-99 will fit my car for cylinder heads.

and i guess the same for the throttle body? 95-99?

10-12-04, 09:39 PM
thanks again anthony, I am more interested in getting better gas mileage than HP of late and thought that a better flowing intake might help as I might be able to get a 97 intake cheap.

Anthony Cipriano
10-12-04, 11:05 PM
A better flowing intake will not give better fuel economy. At "fuel economy" operating conditions ie. light throttle cruising, a higher flowing intake would have absolutely no effect. The engine flow is so low at fuel economy conditions that there is nothing restrictive about the intake or exhaust system. Even a very "restrictive" one would not be restrictive at very low throughputs. That's why claims of improved economy with less restrictive parts is always suspect to me.

If you want better fuel economy air the tires up to maximum PSI that you can tolerate for ride quality (just don't exceed the maximum inflation). Take any unnecessary weight out of the car (weight is the enemy of fuel economy so hauling all that crap around in the trunk costs money), drive sanely (slower accelerations use less fuel), slow down at highway speeds (less aero drag), make sure the EGR system is clean and operating correctly, etcetera - and forget engine mods.

10-13-04, 01:20 AM
where is the egr on the 94 northstar located?

Anthony Cipriano
10-13-04, 10:40 AM
where is the egr on the 94 northstar located?

The EGR valve is on the right rear corner of the engine mounted on the water crossover. Look just under the brake booster on the drivers side near the firewall. The EGR valve is the can sitting on end with the wire connector on the end. Otherwise, the EGR is delivered from the EGR valve through the passages in the phenolic spacer plates to the individual ports.

10-13-04, 04:23 PM
sorry anthony but my manual is being borrowed and I havn't had a reason to look for the egr valve