turbo charged 3.4 dohc....430 rwhp!

[TGP37]

Nate, tri-metal bearings. I suppose the word strong isn't the best word to use. Better, newer bearings since I planned on the turbo. Remember guys, this is my first build sometimes I say things goofy. I learn as I go.....keep on going.

[NateD4]

Some people run more than 25PSI and want to do it for extended lengths.

I sure wouldn't want my bottom end to come apart because I decided to run at high RPM for a few miles... Beside a Bonnevile run sounds fun!

Any rod can bend when the fluid in the cylinder goes from compressible to incompressible. If the rod doesn't bend... Something else will. Engines don't make good hydraulic pumps at high rpm.

The reason I worry about the bottom end is because of some research done on the Ecotec with PM rods.

Story here:

http://www.turbomagazine.com/features/turp_0203_gm_racing_ecotec_engine/viewall.html

"However, as the Ecotec pushed through 283 hp at 4400 rpm, all four connecting rods simultaneously failed catastrophically and smashed through the side of the block. Laboratory analysis subsequently revealed a mid-beam compression fracture on all four stock powder-metal rods. All other components checked out fine. GM Racing installed a package of components you'd certainly install if you were taking the trouble to open an engine to upgrade the connecting rods: Super-duty forged Crower X-beam rods-plus 10:1 JE forged pistons with thicker top ring lands and Hastings moly ring packs. The GM Racing team installed larger fuel injectors, and continued to lean on the engine. Power advanced quickly to 350 hp, at which point the engine ran out of breathing room on the exhaust side. The ratio of Reactants (exhaust) to Products (inlet charge) is very high on a nitrous motor. GM Racing found the stock Ecotec exhaust manifold became sufficiently restrictive above 350-hp that injudiciously adding more nitrous could actually make less horsepower-due to dramatically decreased efficiencies in scavenging exhaust gases from the combustion chamber clearance volume. "We finally made 370-375 hp on nitrous," says Bothwell, "but the engine was really pissed off." "

[ForcedFirebird]

I remember this thread from years ago.

Over-engineering is fine, but to be honest the 660 has been proven to take boost and abuse just fine. I would be more comfortable with the early forged rods over the lat powder-forgings with snapped caps. I have never seen one break, but have seen them bent in BOTH directions on a Camaro that sucked up some water. Not sure if I still have the pics, but will look a little later.

In terms of bottom end, there are three things to be careful of. Boost, Detonation and RPM. Any of these can wreck a rod if it is extreme.

Not so sure on the boost part. Stock rods and short bursts of 21psi on Loner's car didn't bother the rods (9.1:1SCR 3400/3500), or the stock head gaskets for that matter.

[FerrariFan]

Lol. I know that's hilarious. try this link. Lol
what's even worse is that the website appears to be unattended and my repeated emails to change or edit the link have gone unanswered. LOL

https://picasaweb.google.com/103577966960525906703/AD355?authuser=0&feat=directlink

Lol. Here's a link to a Youtube video of a walkaround.

http://www.youtube.com/watch?v=H4ULcPq78v0

Thanks for letting my know about the broken link! LOL

[Dave96z34]

Lol the pics of your car the link is unclickable.

[FerrariFan]

Yep, that's my car. I can't sell it with a bad engine though.

[robertisaar]

http://www.kitcars.com/Classifieds/AdDetails.asp?classified_id=23338

came across this while trying to google for kit cars.

[NateD4]

It's really a toss up when we start talking rods. The stock rods have proven to hold up for many people. The stock rod bolts are probably fine if you keep the RPMs down. If you know the pistons weights you are looking at you can calculate the rod bolt loads based on your intended RPM range. For most people stock bolts are probably ok and ARPs make things safe.

IF you plan on really cranking the boost up you will want a different than stock set of rods for buckling resistance and detonation resistance.

You really have to define your reliability requirements and rebuild mileage. It is possible to make more then 500 HP on a stock bottom end, it may only last a few minutes or hours depending on how you run it.

Back in Corvette C4 days a few of the well known tuners (mainly Greenwood and Callaway) were messing with turbo chargers. I read an article that discussed the difficulty they had making a stock GM small block reliable. It mainly had to do with bottom end components. These engines had forged bottom ends because thats what it took to make them last. I think most of that discussion is valid today... however technology has improved.



TGP37 what do you mean by stronger bearings? More clearance? Tri-metal vs Bi-metal? or are you talking full race bearings?



FerrariFan, I agree on over building it. I guess it depends on your budget, patience and what you want out of the engine. In my case I've decided to put the best I can in it. I personally would rather be able to drive an engine and not worry about whether I can flog it. Now the transmission is a different story...

In terms of bottom end, there are three things to be careful of. Boost, Detonation and RPM. Any of these can wreck a rod if it is extreme.

[Dave96z34]

Nail in the coffin as in you have more problems you were not expecting. Stock bottom end can take a beating with a proper tune. more later its time to drink

[FerrariFan]

You should have no problem at 8 psi-12 psi. I have a Greddy boost controller and the "low" setting I have set at 8 psi and the "high" setting was 12 psi. I mostly drove it on the low setting and the high setting was only for occasional use. It ran great like this for two years. For whatever reason I decided to crank the boost up a few notches and I saw 15 psi on the boost guage and it was pulling like crazy! It was totally awesome until I got home and heard the rod noise at an idle.
Anyway, the lesson here is don't get greedy and just be happy with what you've got. Yeah right!

[RedZMonte]

I have put ~75K Turboed miles on my DOHC all stock 8psi and beat to piss... She sees Red line quite often.. My valve seals are toast from sitting so long and my front HG appears to be starting to leak a little. I cant complain the car now has 165K miles (turboed at 90K miles). Hell my stock 4T60-E lasted to 130-140K Miles before it broke (~50K of it turboed) which is awesome even for a stock LQ1

S

[3400-95-Modified]

You make it sound like nitrous is worse... lol, I've been running that since around 06, started with a 50 shot and quickly went up to a 100 shot... I've yet to have any issues running that on a fully stock 3400 bottom end(first engine was a standard rebuild done by me nothing special at all). Just two years ago I did Clevite bearings in my 05 3400 and thats it at the time it had probably 35-40k on it, I should probably move to ARP rod bolts but I didn't think it was necessary, since I have yet to blow a piston or spin a bearing, all my stock bearings came out looking brand new.

[FerrariFan]

I think your over thinking it yes having forged rod and pistons would be a good thing or possibly a nail in the coffin. That may or not go as planned. My sc LQ1 has done 48k miles on at 8-9 psi on a engine that's that now has 196k miles. I drag race it weekly in bracket with 30-50 other cars and way over 200 passes. Iv beaten the hell out of it in the proses granading 2 trans in 3 weeks time. Took 1st between the failure weeks A huge plus beats being towed home. Way I look at it my last comp test I did was normal and the only thing im having issues with is failed valve seals. You spun a bearing it happens get another short block or long block. The Lq1 is a tank you didn't bend the rod, shatter a piston or blow a head gasket. Day you break a rod I will be shocked. But I do agree under boost 6k is a better rev limit ARP bolts and a soft rev with a MSD would be help full. Also keeping a spare engine wouldn't be a bad idea but mines been siting untouched for almost 5 years when I yanked it from the donor with 85k. Time to start building another car with that one.

Wow, that's an impressive amount of flogging on that high-mileage engine! Give's me hope that I'll have many trouble-free miles when mine is done. I'm of the mindset that as long as the engine is getting yanked why not over-engineer things while we're at it. I'm not adding nitrous or a bigger turbo just a few more lbs of boost. I like your idea of the MSD ignition to add a soft rev-limiter.
By nail in the coffin are you referring to adding stress to other drivetrain components like the transmission? I'm running a 282 5 speed now. I've heard that they're pretty tough. As long as I don't run slicks, the rear tires are the fuse that will burn-out (spin) before any drivetrain components hopefully.
I like your comparison of the LQ1 to a tank. Let's take the analogy a bit further. If you've ever looked at military hardware compared to civilian stuff it's over-engineered and sturdier than it needs to be to survive a lot of abuse. The down-side is that it's a lot more expensive than similar civilian components. Who cares if it's not your money right? LOL
My plan is to take this M60 and turn it into an M1. How can that be a bad thing?

[TGP37]

Dave96z34 speaks good advise.

The connecting rods you have are strong compared to other stock motors. I too would be shocked if you bent/broke a rod with anything under 15psi. The crank is also strong and will handle the abuse. The pistons, well, if you have a great tune they will hold up to the boost. They are hypereutectics and shatter under detonation, they wouldn't last long in boost with excessive knock. But if you tune well and the knock sensor is working well you should not worry about that either.

If you have the money to spend, forged pistons are nice. But if you want to save some $$$ for other mods and plan to stay under 12psi, the bottom end will be fine with the addition of arp rod bolts & stronger bearings. I run hyper pistons, stock rods & crank and had hit 12-15 psig range often, 8-9 psi steady over a year. The only warning I have with hypers is using a ring with tight gaps. If they butt, the piston is gonna rip apart. Though I feel that is only a real concern with fresh rings and LOTS of heat.

in short: the bottom end on these motors are good enough for 8psi all day everyday for years, if taken care of properly. Stock rods and crank will handle 15 psi, though I would want forged pistons at that amount of boost.

[Dave96z34]

I think your over thinking it yes having forged rod and pistons would be a good thing or possibly a nail in the coffin. That may or not go as planned. My sc LQ1 has done 48k miles on at 8-9 psi on a engine that's that now has 196k miles. I drag race it weekly in bracket with 30-50 other cars and way over 200 passes. Iv beaten the hell out of it in the proses granading 2 trans in 3 weeks time. Took 1st between the failure weeks A huge plus beats being towed home. Way I look at it my last comp test I did was normal and the only thing im having issues with is failed valve seals. You spun a bearing it happens get another short block or long block. The Lq1 is a tank you didn't bend the rod, shatter a piston or blow a head gasket. Day you break a rod I will be shocked. But I do agree under boost 6k is a better rev limit ARP bolts and a soft rev with a MSD would be help full. Also keeping a spare engine wouldn't be a bad idea but mines been siting untouched for almost 5 years when I yanked it from the donor with 85k. Time to start building another car with that one.