turbo charged 3.4 dohc....430 rwhp!

[Joseph Upson]

Sorry to hear about that, not sure what main bearings you have but there are 3 types now, ~135 degree upper groove, 180 deg groove, and the latest 270 deg grooved main bearing. The greater the groove the better the rod bearing lubrication at a little expense in less problematic areas of crankshaft lubrication. Connecting rod failure in early model 60 degree motors isn't a surprise considering the number of Fiero 2.8s that did it.

I still have a stroked and radiused forged crank 3.43" if you're interested. I used clevite HN bearings in my last rebuild and loosened my bearing clearance to ideal .0024" and use 10W40 for the increased loads. Unless you plan on running a lot more boost I wouldn't lower compression unless you've found it to be problematic already.

I'm at 4psi until I open the exhaust up and ~11.0:1 compression on 93 octane, I'm spraying water but I don't need it at the moment. The bearings in the last motor took a hit because I gave 5W20 a try with tight bearing clearances .0018" that caused intermittent oil light tripping at idle. I didn't consider the extreme compression at the time ~11.6:1 with the tight clearance at the time of that experiment which probably would have been fine with stock compression and clearances.

[pontiacjeff]

I'm building the engine for Lance. I was thinking of putting the valve reliefs in a set of forged 3400 pistons, Sappy, what do you think about that? Or with that big ol dish, will valve notches even be necessary? I'd like abt 9.0:1 for this, don't know the cc of the dish on the 3400 pistons, do you?

[FerrariFan]

First of all, thanks for the quick and informative responses! This is really going to help. Sappy, thanks for the PM. I'll try to get those measurements for the ARP head studs to you. No, unfortunately I wasn't using ARP bolts on the bottom end and was actually surprised I didn't have this problem sooner.
My goal isn't any more horsepower than I can get from 15 psi since I still plan on using $8f with the 2 bar map and ECM I'm using now. As it was, I could break the rear end loose very easily in second gear. Any more power would just tear up my tires or grenade my 282 tranny. 15 PSI will probably require a bit more fine tuning from Jeff. What is the advantage of the lighter lifters and springs? I don't plan on revving the engine any higher. If anything I think I'll reduce the rev-limiter a couple hundred RPM to be safe. Jeff also suggested incorporating a programmable MSD ignition for a soft rev-limiter instead of the ECM fuel cutoff which is pretty harsh. BTW, what is the difference between the 3.4 DOHC pistons and the 3400 if one will fit in the other? Do you have the 270 HD degree bearings that Joseph mentioned?

Joseph, even though I hadn't run into any detonation problems think just a bit lower compression would help the reliability, especially if I'm going to use a new block and pistons with tighter clearances than the high mileage engine I'm using now. Tell me more about crank. Where did it come from? Why aren't you going to use it?
Lance

[SappySE107]

If you aren't wanting any more power, you are wasting your money on a forged bottom end. Get the ARP rod bolts in and HD bearings. Don't bother with the springs or lifters if you aren't looking to squeeze more RPM or boost either. Just rod bolts, and bearings.

[pontiacjeff]

If you aren't wanting any more power, you are wasting your money on a forged bottom end. Get the ARP rod bolts in and HD bearings. Don't bother with the springs or lifters if you aren't looking to squeeze more RPM or boost either. Just rod bolts, and bearings.

He's gonna end up with more power...

[Joseph Upson]

Joseph, even though I hadn't run into any detonation problems think just a bit lower compression would help the reliability, especially if I'm going to use a new block and pistons with tighter clearances than the high mileage engine I'm using now. Tell me more about crank. Where did it come from? Why aren't you going to use it?
Lance

I wouldn't go with tighter tolerances with the power level you're at, it may create more problems than it solves. I wouldn't touch the current compression ratio either, if anything I'd increase it. 2 years before a problem developed with parts you intend to replace with better parts, leave the compression ratio alone, a number of production boosted cars have in excess of 9:1 compression. The rod bearings gave you a problem, fix them, leave the compression alone.

The crank is a forged 3900 crank that was offset ground to a longer but, shorter stroke than what was intended for my combo, so I started with another crank.

[FerrariFan]

I wouldn't go with tighter tolerances with the power level you're at, it may create more problems than it solves. I wouldn't touch the current compression ratio either, if anything I'd increase it. 2 years before a problem developed with parts you intend to replace with better parts, leave the compression ratio alone, a number of production boosted cars have in excess of 9:1 compression. The rod bearings gave you a problem, fix them, leave the compression alone.

The crank is a forged 3900 crank that was offset ground to a longer but, shorter stroke than what was intended for my combo, so I started with another crank.

yeah, I guess I should have explained that a little better. When I said tighter tolerances I meant tighter just because of the fact it will be a new engine isn't worn or loosened up like the current engine.
I don't know a lot about the 3900 engine. How does the 3900 crank compare stroke-wise with the stock 3.4 dohc crank? What would need to be done to get it to work?

[Joseph Upson]

yeah, I guess I should have explained that a little better. When I said tighter tolerances I meant tighter just because of the fact it will be a new engine isn't worn or loosened up like the current engine.
I don't know a lot about the 3900 engine. How does the 3900 crank compare stroke-wise with the stock 3.4 dohc crank? What would need to be done to get it to work?

You know this by now but the 3500 nonVVT-3900 have a 3.31" stroke just larger crank pins and a different crank trigger wheel than 7x that is removable. My stroked crank is already prepped needing a 7x ring and balancing with the chosen parts to go with it.

[SappySE107]

That crank isn't going to be a good idea.

[FerrariFan]

That crank isn't going to be a good idea.

Your right. I think I'll stick with stock crank. Should be plenty strong for my target HP range.

[FerrariFan]

He's gonna end up with more power...

LOL

[Mach 5]

That crank isn't going to be a good idea.

Im curious as to why this crank wont be a good idea??

[SappySE107]

Im curious as to why this crank wont be a good idea??

Stroking a high rpm motor is counterproductive. His setup is excellent with 3.31 stroke and 5.7" rods. Using a heavier crank with no 7x timing sensor that needs custom rods, pistons, or both will gain near as makes no difference, nothing performance wise, and most likely introduce more headaches than the build is worth.

[NateD4]

Joseph,

Who makes the main bearings you are talking about? I need a set for a crank with radiused main journals.

[NateD4]

FerrariFan what are your goals for the next build?

Unless you are trying to push extreme RPM or plan on hanging at high RPM all you may need is a rod bolt upgrade (if that) and some race alloy main bearings (perhaps a high eccentricity bearing). If you plan on adding more power you may want rod upgrades and custom pistons and a better crank.

I do recommend custom pistons to get a piston properly designed for your application even though they are somewhat expensive.

Also if your new crate 3.4 has never been run, I'd consider running it for a few thousand miles to heat cycle the block so when you tear it down to rebuild the block has been stress relieved and will have a minimal chance of stress relieving after the build up.

Where was your crate engine stored? Sometimes if they have seen summer/winter storage the hot and freezing cold can thermal cycle the block. However if that has happened you'll want to inspect for condensate surface corrosion on things like cams and valves prior to throwing extreme power to it. I'd probably still run it stock a few thousand miles though.