Has anyone played with the cam timing on the 3.4 DOHC? Chevy was nice enough to equip these engines with infinitely variable gears from the factory. I read a few years ago that retarding the exhaust cams 13 degrees will add about 30 horse on the top end. That is only recommended with a manual, as some low end is sacrificed. (I am playing with a manual.) I did some research and see the auto guys like +6/-6 for a smaller improvement throughout the rpm range. I am thinking of going +4/-10, as desktop dyno shows a gain throughout the rpms, and a pretty good one up top yet.
Unfortunately no. It uses a belt from an intermediate shaft to drive the cams. The gears (cogs really) use a split "cone" shaped washer and no key to hold them in place when tightened.
Now I am wondering if we can machine the Quad gears to accept a similar washer and get rid of the key... The first problem that pops into my head is how to time the Quad cams. The 3.4 has "flats" on the cams to lock them into "TDC" position. You then set the crank to whatever degrees you want (with the belt installed) and tighten the cam bolts. One would need a way to lock the Quad cams into a known position.
im gunna use a set of bushings that is typically used on the small block/big block camshafts. the only thing u have to do is have a machine shop drill a counter bore into youre cams that will fit these bushings. you then use what ever bushing to acheive the desired timing.... the kit comes with i believe +4*/-4* bushings. this is where i read about it----->reference http://www.nvmygtz.com/quad4/info_cams.htm
Only the later cars have the adjustable cam gears 94+ I think maybee 95-97. Anyways, there are no dyno's of anyone before and after 13* cam mod. Its all speculation. This issue is discussed in great detail at www.realfierotech.com
I'm quite certain they are all adjustable. I will be setting the timing today on a '92. I already loosened the cam bolts and can spin the gears. It is exactly the same set-up as the newer ones. I've never seen an actual dyno myself, but it looks good in Desktop Dyno. I am contemplating maybe doing +2/-8 or something, as +4/-10 or 0/-13 seems like such a radical change. I'll check out that link and hopefully it will give me some good insight.
Well, I managed to get a nice lope with the cam timing. It sounds like a 6 cylinder W41! It revs up a bit quicker now. Hopefully I can get it on the road by the weekend. The going has been slow since my heater was "reposessed." (I've been borrowing it for about 3 years and the owner finally took it back.)
Since you already got it together its a bit late for this but this site may help you out with any further problems w-body.com ,good bunch of guys over there.
*1990 Grand prix - Lawn ornament - Future: this car has no future
*1991 Grandamn - no motor - retired oval car - Future: undecided
*1986 Toyota Corolla (AE86) - 4AGE, 5 speed - Drift car - Future holds: Z20LET for 2009
*1997 Cavalier - 2.2 OHV, 5 speed - Oval car
*1989 S10, reg cab, short box - 2.5, 5 speed - Future DD Future holds: Built 2800 hyrbid, flat black paint and a drop
Last edited by Mr_Efficiency; 03-14-2008 at 03:39 PM.
I decided advancing the intakes was a bad idea. I think I will be going back in and setting the intakes to 0*. The low end and midrange are great, but it gets a little anemic before redline. That does not happen with factory timing. I guess I'll head over to w-body and see what they like.
OK, I know this thread is old .... but it raised a number of questions that went unanswered.
First off: The 95 and up motors had the infinite adjustability by just loosening the bolts on the cam sprocket & giving it a tap. In pre '95 motors you needed to swap out the sprockets & keepers for the later models to achieve this.
Next: On the pre - 95 motors it is possible to time the cams 180 degrees out. This is because the computer takes the cam sense signal from the INTERNAL cam (which really serves no other purpose on this motor other than as a drive pulley for the cam belt). (In the 95 + motors there was a cam sensor on the intake cam for the #4 bank that did this, so there was no possibility of timing 180 degrees out - it read the actual position of the overhead cams, not the internal "dummy"). In the pre 95' motors the paint marks on the "internal cam pulley" must be UP when the motor is at TDC to time the #1 bank. If it's DOWN then start by timing the #4 bank first. The motor doesn't really time to the #4 bank (no motor would, gang), unless the internal cam is in the "180 out" position. You have to remember that this internal cam only rotates once for every TWO rotations of the crank - and since it feeds the computer - yes, kids, there IS a "180 degrees out" setting (been there, done that).
Anyway - just thought I would pass that hard-earned knowledge along.....
Last edited by Dana Robbins; 06-08-2008 at 10:27 PM.
180 out still runs fine, since the plugs fire at every TDC with the waste spark system. It would only throw off the injection timing, which will still run fine.
People have told me that the earlier ones aren't infinitely adjustable, but my '94 Cutlass and the '92 Z34 both were.
Also, I ended up going back in and setting about 2 degrees retard on the exhaust, and the intake at 0 as my first attempt increased mid range significantly, but "narrowed" the powerband and lost a little top end.