Engine Mods for a 3.4 pushrod turbo

[BrianC72bgt]

I've got a 3.4 out of a 94 Camaro that I'm swapping into a 72 MGB-GT. I plan on building a twin turbo setup, my question is, What internal weak links need to be addressed for this engine to handle 12-15lbs of boost? The last DIY turbo I did was in a 90 miata. That engine was derived from a factory turbo motor so it already had beefy rods and oil squirters on the piston undersides. The internals were good to go.

So, where is (are) the weak link(s) in the 2.8 - 3.4 family of pushrod engines? (Assume I'll take care of proper intercooling, engine cooling, ignition timing and fuelling for boost)

Pistons?
Rods?
Crank?
Valve Train?
Oil pump?
Studs?
Heads?

I know the ignition system is strong enough and easily upgradable with higher output coils. Thanks in advance for sharing your collective wisdom.

Brian C.

[bszopi]

RE: Engine Mods for a 3.4 pushrod turbo

http://www.60degreev6.com/modules.php?op=modload&name=Pushrod&file=index&req=viewarticle&artid=33&page=1

Its more centered around the 3x00 engines (aluminum head), but I think most of it can be applied to the 3.4L Camaro engine. Heads and cam are things that jump out in my mind as being different.

[StudlyCamaro]

RE: Engine Mods for a 3.4 pushrod turbo

i dont know of anyone that has taken a 3.4L to the edge with a turbo, however i know ive seen many people spray 'em and the pistons never hold up long.

im not saying that the pistons are the weakest point, however they tend to be the first thing that fails from what ive seen (ive been around for a while)


there was guy (tiago) running 12 lbs on a stock bottom end a while back (although i havnt heard what he's up to in a long time) making near the 350HP mark, so that will give ya some hope.

[Sardonyx]

What is the weak link for the 3.4L? pistons(I know) but what will/has the other parts hold/held?

[ezrollin]

Get forged pistons,the rest will hold together

[ForcedFirebird]

Cast pistons are NOT a weak link. The 60* pistons are eutectic from the factory and the rods are forged. Tuning is the enemy when boosting ANY engine.

If you want I can give you a link to a cast piston 4cyl that was pushing 32psi and a dual 4" core intercooler

[Guest]

Cast pistons are NOT a weak link. The 60* pistons are eutectic from the factory and the rods are forged. Tuning is the enemy when boosting ANY engine.

If you want I can give you a link to a cast piston 4cyl that was pushing 32psi and a dual 4" core intercooler

FF, the weakest link in the 660 IS the piston. any cast pistin is considered "eutectic". That's just a measuerment of silicon content in the aluminium. Eutectic being IIRC 15 PPM, Hyper being more than that, Hypo being less.
The weak part of the stock piston seems to be the skirts. The top ring land seems to be another failure point, but it seems this may be more due to the use a ring gap more suited for N/A engins than a gap suited for forced induction, and because of this may be creating a pressure point and breaking that top ring land off.

Next to that, and being far less failed I think would be the valves and then rods. Valves have dropped, seems to be higher milage with a stiffer spring at higher RPM when they fail, rods, seem to fail when another component fails, like a piston or valve, or too much fuel/liquid in the cylinder and the rod will bend.

Thes engines really are quite robust however, and have taken a lot of abuse even in stock form.

In the 3400 I'm building for my truck, I will be replacing the pistons with hyper-eutectic pistons, adding oil squirters and replacing the valve springs, due to also wanting to run about 15 PSIG boost. I'm looking into different valves, but overall, I'm not really worried about too much else as a failure point.

Another consideration that I will be trying to find something different for is the timing chain, not so much for a failure reason, but because the stock replacment units seem to stretch quite a bit, and would prefer for the cam to stay in the same position it ws installed.

[Sardonyx]

Get forged pistons,the rest will hold together

That is what I wanted to hear

Has anyone heard of something else failing and at what point and/or boost level. I am not looking for the freak of GM, 1000HP on stock. But more like the gen avg.

[boostedrs]

ive gons as high as 18 psi on stock pistons,ran it rich and not a whole lot of ign timing, and they have held together.though i didnt have many passes on them before i swaped them out.so i cant tell u how long they would have lasted.

but as far as ive seen the top ringlands seem to be the weak point on the factory pistons

[gtmattz]

I am also planning on putting a 3.4L into an MGB, but was looking at a single turbo setup, and not planning on any insane boost, just enough to get a bit more efficiency and power from the car. I am planning on buying the HT 3.4 Crate Engine to work from, as I really prefer to start with a known good base.

I am new to turbocharging, so I dont really know how I am going to go about this just yet. My 'big plan' so far is to use a single turbo t70 through a holley commander TBI system with the edelbrock performer intake.

I am planning on replacing the cam/lifters/vale spring/timing chain/sprokets with higher quality components. I was initially planning on leaving the bottom end alone, until reading this. Should I replace the pistons as well, seeing as how they seem to be a weak link? I would also welcome any suggestions regarding cam grinds that would work well with my intended setup.

[ForcedFirebird]

Just how much is that 3.4 crate (if you don't mind my asking), I just picked up a 3.4 short block for $150 w/120k on it. Plan on refreshing with rings/bearings and have a 3400 top end to mate as well.

I have a t3/t4 hybrid turbo, with 6psi I hit the rev limiter (that pulls fuel) and ran into detonation. If these rods weren't forged, the mess would have been bigger, lol.

[gtmattz]

I have been looking around online, and that HT 3.4 crate engine is usually around $2000 shipped. The HP/Torque #'s that are listed are a little off, as GM is specifying that this engine is for replacement in carbureted s-10 pickups with all the emissions equipment installed. In my resarch so far, I have seen both hp and torque numbers above 200 with the holley commander TBI, 1.5" headers, and 1.6 ratio rocker arms. With a proper cam and 6-10 lbs boost I am thinking that this could be bumping against 300 hp.

As for hitting the rev limiter... When the turbo 'spools up' do the revs start climing alot faster than than N/A? I have never really driven a turboed car before (I am not counting turbodeisel trucks and tractors here), so I do not know what kind of behavior I am going to be experiencing. I do not plan on driving this car like I stole it, but I will probably be taking it to the annual legal street drags (1/8 mile) that are held here annually, and really dont like the idea of grenading anything lol. Are there certain types of rev limiters that work better to help avoid detonation? I know I have a bunch of silly questions, but it seems that there are some knowledgeable people here, so I am trying to exploit that

[Joseph Upson]

The 3.4 camaro pistons are pretty strong and eutectic also suggests that they are stronger than the 80s v6 pistons because I actually broke a ring land on one and it showed no damage to the top of the pistons as you see in these from the 3.4.

What happened here on what was a twin turbo 3.4 in a Fiero was a simple mistake, a ground strap was left disconnected and some how it caused the computer to apparently go haywire and excessively advance the timing almost instantly on giving the engine throttle. The damage is extensive but it occured right after the engine was installed and after several brutal detonation cycles audible inside and outside of the car while I was trying to figure out what was wrong. I gave up and decided to convert it to single turbo and during the dismantling process found the disconnected ground strap.

I'm also considering now since a mishap last year the possibility of a chip data problem being the cause. I found several hiccups in the spark table of a chip I burned once after rechecking it. It was off by double digits in several places. I don't recall whether I suspected the chip years back when the 3.4 disaster happened, or a may have ruled it out by trying an OE chip.

After it was converted to single turbo it ran fine and strong with the pistons looking just like they do in the picture for months. What led me to the discovery was a broken piston ring and more detonation abuse finally cut about a .050 groove in the cylinder wall and boost pressure started blowing oil out of the engine.

Amazingly, there was only slight damage to the turbine wheels on the turbo, eventhough they processed bits of piston and piston ring. Only the top of the piston chipped, the ring lands remained intact.

The pistons from my 3900 look a lot shinier than those so I wonder what kind of changes they made in the casting metal and if they are stronger yet.

Also I have a picture of a 3400 piston from an 03 Alero and noticed that it does not have the antifriction patch so it must be the first design, it also is a little dull in color like the 3.4 pistons instead of a shiny silver aluminum color like the that in the 3900 and most likely the 3500 also. I suspect there is a possible bit of truth contrary to the apparent insistance by MAHL and a GM tech that GM said the pistons in the 3.6 DOHC are aluminum Forged pistons by mistake. I haven't seen any other V6 pistons that shiny and I can't see how they would make them weaker at the same time the power demands are going up.

[ForcedFirebird]

I have been looking around online, and that HT 3.4 crate engine is usually around $2000 shipped. The HP/Torque #'s that are listed are a little off, as GM is specifying that this engine is for replacement in carbureted s-10 pickups with all the emissions equipment installed. In my resarch so far, I have seen both hp and torque numbers above 200 with the holley commander TBI, 1.5" headers, and 1.6 ratio rocker arms. With a proper cam and 6-10 lbs boost I am thinking that this could be bumping against 300 hp.

What fuel delivery do you plan on using? This willl determine what kind of limiter you will have.

I'm using a stock 7730 ECM, the limiter pulls fuel.

[gtmattz]

What fuel delivery do you plan on using? This willl determine what kind of limiter you will have.

I'm using a stock 7730 ECM, the limiter pulls fuel.

I am going to be using a holley commander 950 TBI system (not yet sure if I will be needing the 2bbl or 4bbl).