Flow and superchargers...

[Fierobsessed]

Have you seen an Iron dukes crank? Its a piece of crap.

So far, the bottom end on 660's havn't been too bad at handling power. I think the forged crank will help a bit though. It's a lack of lube that causes the bearings to go bad usually. That or crank flex. A main problem usually causes the whole engine to explode. At least I think thats how it is...

[Mach10]

Oh, the 4-banger isn't perfect... But it's a solid cast-crank. I'll bet you a shiney dime mailed to your door that you can NOT find me an example of a broken duke crank that was NOT caused by rod bearing failiure.

Whereas, I've seen at least one broken 60-deg crank.

with respect to the rest of the moto, for every 60-degree you show me that's topping 300k, I'll show you a half-dozen Dukes with the same mileage.

The way the bearings wear on the 3 60-degree's I've pulled apart (2 2.8s, and a 3.4) they are pretty consistant; The mains don't wear badly, but the rod bearings start coming apart.

The 3.4 was the same, but with a slight difference; the top-shell wear on the 3.4 was consistant with the other 2.8s. This is from accessory drive loading.

But the 3.4s also seem to show a MUCH greater degree of bottom-shell wear than the 2.8s. This means that the pistons are forcing that crank down MUCH harder than the 2.8s. At double the power, I would expect this. BUT, given that these were all bone-stock motors, this is slightly disturbing, as it suggests that the DOHC is approaching the limit of power you can put through it without compromising seriously block or crank integrety.

This is just a suggestion, however. Once I pull my OTHER 3.4 apart, I'll be able to see if it was just a fluke, or if it's a pattern. I'd like to run a 300hp DOHC for a couple of months, and pull the mains apart to see how much force is being exerted on the bottom-end. Whether accelerated wear is due to the crank flexing, the block distorting, or simply from GM's pathetic idea of internally balancing... Hard to say.

Don't knock the duke (no puns!). It's got a shitty (and well deserved) reputation for being a gutless diesel substitute.... But you can NOT deny that they aren't perfectly solid commuter motors. Regardless of how ugly the cast crank looks!

[Fierobsessed]

As long as you treat the Iron duke like a gutless hunk of cast iron, it will behave exactly like it's designed to. Providing that the timing gear holds up. And for reliability, outside of a Fiero I give it a 9. In the Fiero, 7. Just don't rev it up too high.

As far as the 3.4 goes... well It's a good strong motor, I'm not particularly worried about the bottom end giving up from sheer power, as I would be with an Iron duke. But I suspect pushing over 300 horses is going to take it's toll on the bottom end. My concern isn't necessarily strength nearly as much as lubrication. As far as I've seen on the 660's they have a tendancy to fail from lubrication issues more then anything. Oil pressure is your best protection from metal to metal contact. So if your oil supply is weak, then it will take less force to cause contact. I believe this is the sole source for problems on the 660. Now, balance issues and crank flex come into play because the forces are far greater, and in a direction that oil pressure does not help fight at all.

There are so many solutions to the problem... and one time to another GM keeps introducing those solutions. Compare the 3500 to a 2.8. The 3500 block has a priority main oil feed system, a forged steel crank with MUCH larger 2.25" Pin diameter and cross bolted mains into a cast aluminum oil pan. These improvments obviously made the crank MUCH stronger, increase area on the crank pin witch helps distribute force across about 12% more area of bearing surface. The priority main oil system I'm not realistically sure how much it helps, but it seems to be desirable. Either way the 2.8 didn't have many of these strength improvments. The 3.4 DOHC has (I believe) only one oil galley below the dummy cam, again not sure if thats good or not, but it appears big. I do know that the oil pump on the 3.4 DOHC is rediculously huge.

Im inclined to say, solve the oil problems and use the latest and greatest from GM's parts bin, and you should be in really good shape. I really want to prove what this motor can do. (Once I get the rest of my life situated of course) I don't have any hard examples proving that lube is the real issue, just more of a hunch that seems to make sense.

My favorite example of GM using there head's is when they made the Quad 4. The crank is double counterbalanced, the block is deep skirted, the Oil pump is a gearotor (I believe that's what it is called) and the crank pins are super wide, over an inch, witch helped distribute the load from the rods across a large area. Quad 4 bottom ends are specifically designed to make 180 horses with 4 cylenders. They don't run into bottom end failures often. Now, if the head gaskets didn't blow, the heads didn't crack and the ignition modules didn't die... it would have been the best motor GM ever made. I don't know why they narrowed the crank pins with the twin cam 2.4 model. Oh well.

[Mach10]

True dat about the timing gear. Nylon teeth? Ugh... And yes, you can in fact kill a duke pretty quick if you rev the snot out of it (like, much past idle!). I've got a friend who's building a HO duke. Not quite the SD version, but he's got a REALLY nice intake and TB setup for it, and we're going to hog out those heads for him. See how it stands up to some real abuse!

GM's "progress" on this motor is nothing more than a LONG series of bandaids to cover glaring engineering errors that were obvious from the start of the run. Economics dictated that they would fix them in small steps, rather than bang out a bunch of well-built and sturdy motors.

I would disagree that all the 60's problems stem from oiling issues. There's a few things. I won't comment on the newer (series 3? the 3500s ect) motors, since I know almost nothing about them. But problems that plague the earliers:

-Balance, Balance, BALANCE. Is anyone else puzzled as to why it's almost always the #3 or #6 rod bearing that tears itself apart first? And that it's the furthest from the vibration dampner?

-Related to balance is the fact that the mains saddles are too small. There's WAY too much room for flex, which when combined with the existing balance problem, makes for some really funky crank distortion. The crank's forged, and it seems to be able to take it ok, but the bearings suffer.

-Did I mention balance?

Oiling is definitely an issue, and I won't argue that larger kingpins wouldn't significantly help. Personally, I plan on pinning the oil bypass on all of my filters, running thinner oil, and making sure that the drainbacks on my engine are clear.

Even when GM started internally balancing motors, their quality control was so bad that for some motors, they might as well not have bothered.

Once I get the old motor out of my fiero, and the junkyard runner in, I'm starting up a half-decent build. We'll see how far out of balance the factory assemlbly is, and how well it runs once it's been balanced.

[timg]

(Again, there is a point where the right turbo is, JUST RIGHT, so shh. if your a turbo guru. )

I agree. Turbo stuff makes my head hurt sometimes. It's quite hard to find proper setup. Many use turbos that are too small for a 2L engine, much less the 3.4. Mine has a significantly larger turbo than all of the others (that I know of) and does sacrifice some response (huge turbine) and yet also sacrifices some top end (small compressor). It can have full boost by 2500 rpm in higher gears, but in first there is lag until around 3500 rpm. I think my dyno chart is pretty self explanitory- I always assume full boost from 3000-7000 rpm. The one turbo I would love to see on a 3.4 DOHC is the GT35R. The compressor is absolutely perfect. The turbine side is a bit small compared to what I'm running now, but should be good for over 600 horsepower, spool faster than the P trim T4, and flow just as much as the P Trim T4. I'm really considering upgrading to one, but the smaller turbine is holding me back a bit. I've considered a GT40R, but I'm worried that the turbine side on it is too big and will cause too much lag... It's not a very easy process- superchargers are definitely MUCH simpler. I'm even considering trying to have a custom turbo spec'd (GT35R or GT40R compressor and center section, but with the GT37 turbine wheel in a T4 housing). I'll throw one thing out. If you want lots of power and really quick spool, the GT35R is the ONLY turbo you should consider. There are others with more potential, but it should be the perfect street/strip/track turbo.

A disclaimer- turbos are NOT for the weak of commitmentment and heart. A turbo setup can be really fun, but you will always be looking for more and constantly working on it. They're also VERY easy to blow up Most guys who go SC can set it up and forget about it. I've never had a turbo setup like that...

Centrifugal superchargers are a perfect cross between a turbo and a supercharger. They spool strictly based on RPM and have a progressive (non linear) output. In other words, if your engine puts holds back 10 PSI of boost, your flow will be a curve based on RPM. These superchargers are known for good Adiabatic Efficiency (in otherwords, they don't heat the air much past what the compression does). These are perfect for a pushrod motor, helping it make a fairly linear slope of torque. They work quite well on a DOHC engine, however the power curve will be a steep ramp as opposed to a good range on a DOHC motor. Simular to a turbo.

Sounds like we agree again. Personally, I don't care for centrifugal SC's, except for large displacement motors that need help in the high end and not down low. On a DOHC or small displacement motor, they wouldn't help the engine where it needs it most and would result in a peaky torque curve with virtually no gains down low. In general, their compressors aren't as well developed as a turbo and the boost curve sucks- i.e. 0 psi @ 0 rpm, 3.5 psi @ 3500 rpm, 7 psi @ redline. They only make full boost at redline...

Lysholm = I really like these.

The new Eaton roots SC's have had HUGE improvements. They may not be the most efficient, but they're MUCH cheaper than the Lysholm SC's.

As far as what I plan on doing to the engine, other then the blower I have lots of plans, few of witch I have actually started, so it's all up in the air till I can actually work on it. I plan on using a 3500 crank, modified for the 7X reluctor to fire a relativly normal DIS system. The rods will be aftermarket Eagle H beam rods for the 4.3L, modified to accept 3500 bearings, and fit to the crank. The pistons will be custom forged slugs, yet to be determined. Compression ratio probably between 8.7 and 9.0, still undecided. Mains and oil pan will be from a 3100, unless I decide to just girdle them internally, in witch case I will stick with the steel pan. Oil system will be relativly stock, as I don't see a need to modify it. But I plan on opening up the drainback passages to keep the oil in the pan where it belongs. I will make custom headers... but I don't know weather I will make them equal length or not, it depends on space in the engine compartment. I do not plan on making any changes to the heads whatsoever, (unless the oil drainback passages need cleanup) I am actually not planning on doing ANY top end work, with exception to the intake manifold, and the cam timing, and injectors. Managing this beast will be a 1227730 ECM, with a highly modified 89-90 TGP code. I plan on running 12-15 PSI and no more. I am expecting 350 at the wheels, 26 MPG or better, two 11 second runs and pass emmissions every year. I expect it to stay a daily driver. Thats asking a lot from any motor. I've seen L67's that come close to pulling this off. but with the 3.4 DOHC, I can see it happening. If all else fails, I still have my Quad 4 pace car, its a lot of fun to drive too.

Thats about all. sorry for going on and on about what I'm doing and why, but it's something I am passionate about.

I really want to hear how your motor build turns out. It sounds very innovative and should work out quite well.

Good luck!

Tim

[series8217]

Once I get the old motor out of my fiero, and the junkyard runner in, I'm starting up a half-decent build. We'll see how far out of balance the factory assemlbly is, and how well it runs once it's been balanced.

I drove my Fiero with the stock 3.4 DOHC. When I rebuilt it, I balanced the bottom end on a Hines balancing machine. Everything (con rod big ends, small ends, pistons, etc.) was balanced to +/- .5g and the crankshaft was spin balanced with the flywheel using bob weights corresponding to a certain percentage of the reciprocating mass to represent what rotates with the crankshaft. Obviously GM doesn't do this; the balance pads on the connecting rods are untouched by the factory, and the crankshaft has a few small holes drilled in it. We also attached the pressure plate to the flywheel and balanced that after the crank/flywheel assembly was done. This is important because the pressure plate is like adding another 1/3 of a flywheel, and they are generally not balanced at all!
The connecting rods were pretty close in weight, but I did have to take at least a few grams off the end of 5 of them to get them to match the lightest.
Here's the scary part: we had to take 30-50 grams (I dont remember exactly, but it was greater than 30) out of the crankshaft.
The difference in the way the motor runs now after the rebuild is just nuts. I can literally hold it at 7k RPM and put my hand on top of the motor and NOT feel that it is running. It's that smooth. I'd love to tear it down someday and look at the bearings and whatnot, but ideally it will last longer than I'll ever need it to (150,000+).

[RedZMonte]

This setup looks very simmilar to the stillen supercharger we put on my buddies G35/350Z. The lower intake stays but the upper is replaced by a box that is sandwitched between the cam towers. pretty simple design. the new upper intake that the charger bolts too also contains a air-to-water Aftercooler before it goes down the lower intake and into the engine. maybe somthing for you guys to compare too and get some good ideas. And it did require some modification to the hood (AKA Chopping a big hole and bolting on a cowl)




Shane

[Husky]

So it turns out an L67 with an intercooler won't fit under our stock hoods... so there's something else I get to work on. I think I'll just use a short cowl induction style hood, and exaggerate the stock hood's tiny tiny cowl.

[RedZMonte]

I think the hood clearance is the least of the worries. you can allway make something work. I would be more worried about making the charger work and run reliably. From the looks of it you will need more then a tiny cowl. need like a 3" cowl or more. My Lumina had about 1/4" clearance with the L67 in it, and it sat between the heads. the blower above the LQ1 will sit quite a bit taller then the L67. I would focus on making the lower intake and bolt it to the motor 1st, get it running and worry about the hood last. if you can make a intake that works with the blower and replicate it i think you will have a pretty saught after setup. People will be willing to pay you for it and will surly give you plenty of $$ for hood clearancing.

S