Hi Guys,

From what I have read (no direct experience), it seems that the caddy 4.1, 4.5, 4.9 engines simply cannot be modified to avoid falling flat above about 4500 rpm. It seems people have tried porting, changing valve diameters, and changing cams....all with little success.

Now back nearly half a century ago, I had a '64 corvette. It originally had a 300 hp, hydaulic lifter cam. I swapped in a 365 hp, solid lifter cam. The high end was great, but the low end sucked (by comparison to the original cam). Then I ran across a device called a Vari-Cam. It was basically a cam gear which provided variable cam timing based on RPM and the principle that advancing the cam will increase low speed torque, retarding the cam will increase high speed HP and torque. It was somewhat adjustible but generally advanced the cam 6* at idle and slowly retarded the cam as RPM increased...straight up at about 3000 rpm and retarded to about 6* at the high end.

It completely changed the character of the engine! Drastically improved autoX performance!

All this makes me wonder if Cadillac has severely advanced the cam in the 4.x engines to maximize low end torque at the cost of high end horsepower.

Has anyone tried installing the cam in the 4.x engines retarded about 6*?

Curious as to you engine experts opinions.

Larry

No, I have not, but it is a good thought.

Back in the day, I raced a MonteCarlo big block with the Crower VariCam setup. (and a few other goodies he didn't mention....) He got me by a half a fender in my L79 Nova after surprising me off of the line - wouldn't race me again.

But, I suspect that the Caddy's biggest limiter to high RPM operation are the painfully small ports and runner design in the heads.

Olejoedad,

I am sure you are correct that the ultimate power will be limited by the size and design of the ports. But I would surely have expected better results from those folks who have done flow increasing modifications, wouldn't you? Seems to me that porting and related are necessary but not sufficient changes to wake up that engine family. Something else just has to be going on.

Oh, and I am delighted I am not the only old fart who remembers the Varicam!

Larry

To me it seems that chasing high-end power from an engine that was designed from the get-go as a low RPM, wide torque band powerplant is a waste of time and money.

The engine was designed to haul a heavy load, and the engineers rightly figured that torque was the answer.

Back when I raced R/C cars, some electric motors were written off by other racers as 'slow', because they didn't make good peak RPM numbers. Using my home-made motor and chassis dynos, I was able to use the good torque numbers that these motors made, gear the car properly, and regularly beat the guys running the 'fast' motors.

Same thing with the 4.9 - gear it to use the torque the motor produces, and don't worry about making anymore RPM than its designed (purposely) to make. Don't try to make it act like a SBC. Shift it at the proper point in the torque curve and let it pull through the next gear. Repeat.

Most Fieros running the 4.9/4T60E combo are using Deville drivetrains with the 2.73 overall final. My Formula uses the Eldorado drivetrain (same motor) with the 3.33 final. Having driven both variants, the difference in performance is staggering - the Formula, with the 3.33 gearing (Mattwa) is a beast, whereas the 2.73 swaps are not much better than a really good running 2.8.

I have had two Sevilles with the N* as well, the first was an SLS, the current one is an STS. Althought they both used the N*, the SLS was the VIN 'Y' (275 HP, 300 TQ) and the STS is the VIN '9' (300 HP, 295 TQ). the biggest difference between the two is the gearing, the SLS was around 3.23, the STS is at 3.73 - huge difference in performance, huge.

I would like to gear the Formula just a tad higher (numerically) to about 3.45, I think that would be a better ratio for pulling the car up through 3rd and into OD, and get the top end charge that is a bit lacking as compared to a 3800SC modded Fiero.

I think your idea about the timing may be correct; I'm wondering why, however, they didn't play with that when they did the Allante.

quote Originally posted by olejoedad: I would like to gear the Formula just a tad higher (numerically) to about 3.45, I think that would be a better ratio for pulling the car up through 3rd and into OD, and get the top end charge that is a bit lacking as compared to a 3800SC modded Fiero.

3.43 4T60e was stock in the W-body 3.4TDC cars... it's a 3.06 diff and 33/37 chain ratio...

Its also just a chain sprocket swap on a 2.73 4T60e... 3.06 with 37/33

[This message has been edited by carbon (edited 01-04-2012).]

There you go Mattwa, a low cost option for your 4.9 car!

quote Originally posted by imacflier: ...All this makes me wonder if Cadillac has severely advanced the cam in the 4.x engines to maximize low end torque at the cost of high end horsepower. Has anyone tried installing the cam in the 4.x engines retarded about 6*? ...

I've wondered about this myself, since I installed my 272 "retarded" in my 3.4. I was really happy with how it ran.
Too bad that the Cloyes timing set with the adjustment isn't available for our engines, to make it easier for us "fabricationally challenged" folks.

I am, by NO MEANS, an expert at all, but having read Fieroaddiction's performance page several times, I think he does a good job explaining the functional limits of the 4.9 drivetrain. I am also in the middle of swapping a '92 4.9 into my Fiero and will likely be heading to the U-Pull-It yard to grab an Eldorado trans to eventually install (thanks OJD, you gave me the "more power" bug).

Fieroseverywhere has also spent a LOT of time thinking and exploring the limits of performance modification to the 4.9 in an effort figure out what would best wake up the motor. His conclusion is that the only real option aside from the modifications outlined by Fieroaddiction (and possibly using the Allante springs Raydar discovered) is a "roots-type" supercharger or a turbo along the lines of PBJ. And even at that, its a large expense at little gain. Unless you're committed to the 4.9 drivetrain (as FEW and I are) there are far more cost-effective options in the SBC, LSx and 3800 options to high-power motors.

The 4.9 is just plain fun to drive, is a beast stoplight to stoplight, yields the bragging rights ("hey, I got a V8 in there!") and sounds awesome. It also provides great driving characteristics and decent MPG along with some fun for those of us not looking to blow the doors off everything on the road.

http://fieroaddiction.com/caddy49h.html

Thanks for listening...

Josh