turbo charged 3.4 dohc....430 rwhp!

[FerrariFan]

That's what I'm going to do. Stock crank but forged rods, forged pistons, HD bearings and ARP bolts on the bottom end. That way I can run 15 PSI all day and not worry about it.

[TGP37]

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.

That is exactly what I did. Bottom end is stock except for ARP rod bolts, stronger bearings, stronger rings and a crank scraper. Been running 8-12psi for a while now, occasionally hitting 15 max from creep and mbc fine tuning.

The bottom end is pretty strong for stock and the pistons can handle a good deal heat....just do NOT hit detonation, they shatter.

[NateD4]

FerrariFan,

The reason I mentioned running the block is because there is a slight chance that the castings have not been stress relieved fully. About 10 years ago we had a 3.1L that warped the block after an over heat. It required the heads and block to be machined flat again. The old racing thought on this one is that its better to get all the stresses in the block relieved before investing in machining them. I'm sure some might argue that blocks should be stress free from the factory, however my experience and those of people I know in the engine building circle is contrary.

As for the rods, there is a math formula that takes your stroke and rod length to calculate the acceleration of the piston pin which can be translated into a force load if you know your piston assembly total weight and the upper half of the rod.

I'm working on a build that I plan on running up to 8500 RPM. So I did a preliminary analysis of the bolt clamp loads required to keep the rod together. For the most part the only time the rod bolts see load is when the piston is decelerated at the top of the bore. In my case the inertial loads were about 3000 lbs while the compressive loads from the turbo are estimated to be nearly 18,000 lbs in compression. Which means the rod bolts won't be taking much if any of that load.

With that said you only need rod bolts strong enough to handle the max RPM you plan on running (and any over speed allowance you give for missed shifts or lack of traction etc..). The rod strength for turbo is then a requirement of buckling loads due to compressive forces pushing the piston down.

If you are looking for a set of rods, I had a set of 60 degree V6 Carrillos listed for sale last week on e-bay. These are 2" journal long rods to the stock 60 degree width. They also have 7/16" SPS CARR multiphase steel cap screws rated to at least 250KSI (comparable to ARP Custom 625+ cap screws). The guys at Carrillo told me they are virtually indestructable. They use stock width 60 degree bearings. If you're interested PM me. The only reason I'm selling them is because my new crank has small block rod widths (which is really weird) so I needed actual small block rods to properly fit it.

As far as pistons go customs are probably a good idea, perhaps not required, but I'd rather know I have good parts than blow something up. Have you shopped the custom piston makers yet?

[FerrariFan]

Nate,
Thanks for the tips. My ultimate goal is to have an engine that I can romp on occasionally without worrying about something breaking. I had limited it to 12 psi without any problems but I babied it most of the time. Your probably right about the rod bolt upgrade. However while it's apart I think I'll go ahead and take it to the next level with sbc rods and custom forged slugs so I can run the max 15 psi the 2 bar map $8f will be capable of. It should be able to run more aggressive timing and get more power. this engine won't be raced or held at high rpms for extended periods of time. Just the occasional full throttle run up through the gears.
The engine has been crated and in a warehouse for who knows how long before I bought it a couple of years ago. Since then it's been sitting in my unheated garage so I'm sure it's been though a few seasons of hot and cold.

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.

[NateD4]

Slappy you are right on the valve springs and lifters. I'll bet the valve train has a natural frequency above 650 Hz and is more then capable of shift at 7500-8000 RPM.

[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.

[NateD4]

Joseph,

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

[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.

[Mach 5]

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

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

[FerrariFan]

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

LOL

[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.

[SappySE107]

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

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.

[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, 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.