Page 1 of 6


Posted: Thu Feb 08, 2018 2:38 pm
by Rettax3
This is happening. FINALLY. :roll:

Re: Finally...

Posted: Thu Feb 08, 2018 2:52 pm
by heavywoody
Ecotec swap?

Re: Finally...

Posted: Thu Feb 08, 2018 3:04 pm
by Rettax3
Look closer. 3.4 TDC. :D

Re: Finally...

Posted: Fri Feb 09, 2018 12:37 pm
by 3X00-Modified
A 3.4 DOHC? are you insane... they are hard enough to work on in a Grand Prix... never mind that small engine bay. And add in the little to no aftermarket that exists for those... Way too much hype on those engines for not much HP output.

Re: Finally...

Posted: Fri Feb 09, 2018 1:08 pm
by woody90gtz
But 4 cams!

Re: Finally...

Posted: Sat Feb 10, 2018 12:15 am
by Rettax3
3X00-Modified wrote:A 3.4 DOHC? are you insane...

Jon, I thought by now you wouldn't have to ask... :P Hey, this is possibly one of the ultimate engine-swaps... Twenty years ago.

I actually do agree, too much hype over them, but that also goes for the maintenance requirements as well as the performance. This car will not out-perform either my turbo 3.1/3400 hybrid, or my modded L67 SC 3800 GTU while the engine remains stock. But, it will be unique, and have its own character -that is what I am after. With +50 HP and a higher red-line, it will also rip-up a stock version of itself, so I am good there too. I wanted this engine in one of these cars since I pulled it from a wrecked Z34 maybe ten years ago. The car was a good donor, 60-something thousand miles IIRC. My biggest complaint is that it was an automatic car, and the engines were tuned slightly differently. I do have a rebuilt Getrag 284 from a GP GT, but it is slightly bigger than the 282, and uses different inner CV splines, I am not interested in messing with that after the whole F40 Six-Speed swap in the GTU.

I have wrenched and service-written for long enough now that everything starts looking like a repair estimate to me. I spent an afternoon test-fitting this engine, and looking over everything for real-world feasibility. The plugs (all six!) will actually be easier to change than a stock 3.1 MPFI or 3100, but my 3.4 DOHC is the last year of the older intake style too. The timing belt will be interesting to change, to say the least, but I'll put in a fresh one before final install of course. Considering that the belt does not go all the way down to the crank on this engine, it may not be that bad. I can't think of another timing belt engine that I would deliberately go out of my way to install, and I don't know if I would do it now if I didn't already have this engine, I really don't like T-belts overall. Water pump sits very close to the frame-rail, and yeah, it will be a PITA to replace that too. Same pump used on the other 60-degree Gen-2s and 3s though, so easily available and cheap to replace. Dito for the P/S pump. The T-Stat will be far easier to service than a 3X00, about the same as a MPFI engine. The accessory belt will be difficult, but considering that GM decided to make it necessary to pull the engine mount on the later V-6s to do that, a lot of our cars are harder than they need to be -I remember doing the belt on my old '90 'Retta in a parking-lot without any tools at all, thank goodness the tensioner was getting a little weak... Alternator will have to be done from underneath, but there is actually a good amount of room -an automatic trans would make it harder for sure. Clutch changes will be about the same as they are on the 3800 -I've written a procedure for this on my GTU, it is pretty straight forward (I don't even need an engine-support bar on the 3800 due to the excessive mounting braces I used on that car). Any other major repairs, the engine will likely have to come out. Not sure about radiator replacement -that might be removable from the bottom, some OE cars are that way too.

This isn't a weekend bolt-n-go swap, but so far it doesn't look too bad. Hopefully, I'll get more time into it this weekend, complete the front lower mount, start (or complete) the tranny mount (unless someone has a '95-era Getrag 5-speed mount they want to sell, cheap?), and begin the mid-mounts and strut-brace...

Re: Finally...

Posted: Mon Feb 12, 2018 1:58 am
by Rettax3
Got the timing belt done yesterday -used the short-cut method for now. Not bad at all, and although my engine wasn't fully installed at the time, I think it will be doable by dropping the left sub-frame to allow the top right side of the engine to tilt away from the strut-tower. The belt drives nothing but the cams, and does not reach all the way down to the crank, so in some aspects this is easier than most T-belts. The tensioner is beautifully simple and effective. I would do two of these over a Sienna T-belt any day, and three of them over a Mitsubishi DOHC 3.0 Eclipse... Later, I may retune it -this engine has infinite cam-timing option do to its' unique design (not the only one to use un-keyed slip-gear adjustment, but this was not common back then), and there is some documentation proving a 6-13 degree exhaust-cam retard and some intake cam advance improving low-end and mid-range, but it sacrifices some top-end performance past 6600 RPM (yep, past 6600). This may be with the newer, larger intake though, I will research that more later. For now, I am retaining original cam timing.

I also pulled the old spark-plugs, my engine has a LOT of corrosion in the front bank of plug-tubes. It shouldn't hurt anything, but it was sad to see -this engine has been garaged since I salvaged it about a decade ago -too bad it never went into a car earlier than this. The plugs were in great shape internally however, and a quick bore-scoping showed nothing of concern on the front bank. I poured some 5W20 into the cylinders and let them sit a little before turning the engine over, and it moved fine.

Clutch is in, an LUK pressure-plate, with a Clutch Masters ceramic Stage 3 puck-type disc (from the 3800 GTU's earlier MG282 -the first clutch I had in that car that could hold its' torque), and an original GM flywheel, freshly resurfaced. SKF throw-out bearing completes it. Everything (except for the ceramic disc) including the transaxle was donated by an '88 GT, which also gave me a spare Z51 setup... 8) Got the tranny bolted-up after chamfering the input-shaft splines with a Dremel for easier install. Front lower engine mount is in, might need some adjustment though. Looks like I can use the stock exhaust manifolds, the rear outlet will clear the firewall how I have the engine positioned (until I am ready to put in a turbo with custom headers... :twisted: )

Re: Finally...

Posted: Sat Feb 24, 2018 11:16 pm
by Rettax3
Another afternoon on the DOHC Z... I've been shifting the engine around in the bay, lowering the front, lifting the rear, pulling it forward more, putting it all back again. I really don't like how close the alternator pulley sits to the rear unibody framework as it arches down to the central sub-frame mounting point. I have maybe millimeters of clearance as it also angles inward as it arches down. I finally made the decision today that rather than hard-mount this engine in the bay as I did the GTU's 3800 to ensure that it doesn't hit things while shifting in the bay, I would relocate the alternator. The compromise will be losing the A/C system. Where I live now, the weather is pretty temperate, and A/C is really not necessary. I would have preferred to keep it in place, but I would rather delete it in exchange for a more functional engine install. So, now I will have to fab-up some adapters to mount the alternator in the A/C compressor spot, and take a little time to remove all unused A/C parts that are practical to remove. I will also re-align the tensioner assembly, and will have to measure-out for a shorter belt. Lastly, I will have to notch the plastic timing-belt covers for the serpentine-belt to drop down to the crank from the P/S pump instead of routing down and back to the alternator. As a note, pulling the alternator was pretty easy from the original position (more so than with this engine in the original Z34), so building this car that way and retaining the A/C would still be valid, just a really tight fit. Another plus is that I should be able to drop the engine a tiny bit more, thus lowering the center-of-gravity a bit.

Re: Finally...

Posted: Sun Feb 25, 2018 11:48 pm
by Rettax3
Done with most of the alternator relocation work. Much happier with this as it sits now. The alternator will have to be pulled from underneath, but that was the same as before. Probably about as tight -not too bad. The front engine mount has now been changed-out from the stock Z34 piece to a Mopar big-block mount (an extra I had sitting around in case my '70 Plymouth needs it, once I finally get around to finishing its' build), and two tabs welded to the right sub-frame for the bolt to go through. I'll get pics this week. Still a long way to go, but it is at least moving forward. :pardon:

Re: Finally...

Posted: Tue Feb 27, 2018 2:16 pm
by themixer
this is going to be really interesting

Re: Finally...

Posted: Wed Feb 28, 2018 7:37 am
by woody90gtz
Never realized they put the alt down low. Seems ripe for corrosion in northern cars.

You should do an IROC style sticker down the side that days DOHC-Z. Haha

Re: Finally...

Posted: Wed Feb 28, 2018 2:38 pm
by weba
I remember reading that these engines were significantly detuned because of transmission worries. But I'm sure it will fun to drive as DOHC engines tend to be :) Even if not it would not be that fast.

Re: Finally...

Posted: Thu Mar 01, 2018 9:59 am
by EPfiffner
Sweet man, I'm following this. Many motivated members here, I'm impressed with all of the swaps. I feel like my stock 3.1mpfi is hard enough to work on, I can't imagine swaps, adding a turbo, etc.

Re: Finally...

Posted: Fri Mar 02, 2018 6:46 am
by Rettax3
Exhaust parts are rolling in. I'm going 3-inch on this one. I've always run 2.5 or dual 2-2.5, so this is a little different for me. I'll start with a 3" in/dual 3"out Flowmaster, mostly because I already have it (used, needs cleaned-up, but otherwise very good), but I might neck the outlets down if I retain the dual outs -I don't see much point to the current sizing. Not sure if I want to run pipe all the way to the back, or continue on with my typical side-outlet style (very effective both in weight savings, and surprisingly in performance with the short-run pipes). I don't have much more to wait for, except for time to work on it. Unfortunately, work is calling on me heavily next week...

I've been on the Fiero site, since this engine was such a popular swap for those cars, and have dug-up a lot of info from there. I will be getting another front exhaust manifold, as it can be lightly ground-out, flipped upside down, and mounted to the rear head -thanks to all the Pennocks folks that got this all figured out. This will save me from having to fabricate headers -as I recall, the original manifolds flowed really pretty well anyway, so until I decide the engine needs major head-work, the logs should be enough.

I'm also researching ECU tune info, although it is a '95 (like the car), it uses an EPROM chip, so it looks like I might be going emulator on this one, although I am very open to burning new chips -anyone have some old equipment they aren't using any more that they want to let go of?

According to the info I've found, redline on the DOHC is 7200 RPM -that might take a little getting used to! It doesn't seem hard to reset cam timing to make a more streetable, flatter power-band that kicks more life into this thing up past 6500 -I seriously doubt I'll be pushing this engine that hard often anyway, but nice to know how to make the most of it.

Woody, Ha- yeah, that would actually be pretty funny. Kind of fits, actually..
Weba, thanks for chiming-in, I appreciate your input alot. Yes, I've read the same thing about this engine being detuned due to then-available transaxle limitations -apparently the 4T60E was designed in large part to support this engine, but didn't come up to snuff in original form, so the engine's performance had to be hacked-down by something like 25% -that is huge. :no: Most of that was taken from spark timing I've read, and clearly cams were retimed away from optimum. Regardless, if I see no more than 210 HP before the turbo is added on, it will be fun to drive -that is still a 50 HP boost from stock to my car, and higher redline too! :D

Re: Finally...

Posted: Mon Mar 05, 2018 4:34 am
by Rettax3
Found a factory GM brace in my box-o-braces that fit almost perfectly between the right frame-rail (as it arches down to the right subframe's mid-mount point, just behind where the CV comes out) and the engine's rear alternator support bracket (which is no longer being used). There are several holes in the frame rail there, and the inside is accessible from the side, making it a perfect mounting point. Unfortunately, as I've lowered the engine, the holes no longer line-up so perfectly -I had to drill an extra hole. Ultimately, I will be adding structural plates both inside and outside of the frame rail (bolt-on pieces).
RgtRr Engine-Brace.jpg

The right-side will be supported by this brace in the rear, the factory Z-34 mounting bracket on the front with a big-block Mopar engine mount between it and the subframe, and the original '95 3100's dogbone brace bracket (which bolts perfectly to the 3.4 DOHC, of course) modified to bolt up directly to the subframe instead of just using a flexible dog-bone torsion-brace.

I started the rough-cut on the radiator tie-bar (upper core) support, using both the GTU's 3800SC swap and the Teal Indy's 4.0 L47 Aurora swap components as models. This will have a brace holding the engine from the front left (original Z-34 torsion brace/lifting eyelet). I will have a hard time making an H-brace framework, like I did in both of the other cars which attach both strut towers together in the rear and brace into the upper tie-bar at the front, due to the height of the throttle-body on the 3.4 DOHC and the future planning of a turbo install, but I think I can attach the ends of the support directly to the strut-towers instead.
Here is the GTU, showing the H-brace that ties the radiator core-support and both strut towers together.

Also got most of the transmission's mount done -a slightly modded variation of the one I designed for the '90 Turbo 'Retta that supports the Muncie from underneath and bolts into the left sub-frame.

Finally, the rear of the engine will have a bracket off of the EGR pad on the intake with a small torsion-brace pushing against the strut-tower brace (sourced from a GM H-body, like the GTU and V-8 Indy have), but while fairly stout, that whole thing is cast aluminum, so it will have to be the most flexible of all the mounts.

I like supporting the engines in these cars at several points, suspending them from a 'web' of lighter mounts and braces, rather than using two or three big, bulky mounts to hold the drivetrain in place. Basically, these cars have too much flex in them as it is, and the engines I'm putting into them are physically too big to go slapping around inside the bay. Using several small mounts makes the engine more of a stressed component of the car's structure, like a motorcycle engine, and distributes the stresses into the car more evenly, rather than having a burdensome lump thrown into the middle. So far, the GTU has performed flawlessly in this regard for years and years.

Now I am looking seriously at moving the battery to the passenger-side of the car (again, due to the turbo), and finding that GM stamped this side differently, more like a step up to the strut tower than a ramp, and the original passenger-side engine mount frame obstructs the battery placement. %) Considering seriously attacking this piece with a grinder, to avoid having to dump the battery into the trunk... =@ But I'll wait until I know for sure how the turbo will fit in the bay with the 3.4...