There are some of you who may read this and ask, why is this guy working on such an odd ball engine. The reason is that this motor is an odd ball and there is so much untapped potential of this motor. From the reasearch I have done online, the tech used to develop the 3.4 went on to build the 4.6 northstar.

Even if this info turned out to be bogus, this thing is a monster waiting to be woken up and unleashed. They are finicky, but when mine was in top form I could keep up with mustangs, camaros and imports in my hometown feared my approach. I dont want to put it perfectly back to stock.

The people who love these cars and these motors know they are on the outside looking in. So I know its a chalenge, and thats one of the reasons Im doing this.

 

I recall reading somewhere that the Lotus developed LT5 from the Corvette ZR-1 was evolved into the Northstar. I could be wrong though.

 

Bought a new 94 Olds with this powerplant. Very impressive performance-wise, and good fuel economy to boot. Really set you back in the seat and deliver 28 mpg or so on the road. Sure not a trouble free engine. Head gaskets, seals, absurd alternator location that contributes to early failure and near impossible repair just to name a few items. I've always thought this engine would be awesome in a short bed S10 pickup though. That tranny might be fine for many thousands of miles. GM has a pretty rough standard for rating a transmission and they did de-rate that engine to suit from what I've read, but I'd guess you could up the power quite a bit without problems.

 

Head gaskets and seals? Not sure where you got that from, certainly it's no more prone to those failures than any other GM V6.

As for the alternator location, you just have it in the wrong car

4T65 > 4T80

Another popular mod is to take the upper intake from the 96-97 3.4 DOHC and keep the 94-95 lower intake, cams and heads because they flow at a much higher rate. The 94-95 intake is one piece and the 96-97 is either two or three (I can't remember which). The down side? You have to go with the OBD II computer to run it. This would mean (Yea! :hyper: ) more wires!

You use the 96-97 lower as well, and you can easily use the OBD1 or OBD1.5 computer (I'm running 96-97 manifolds on OBD1.5 right now, and have run them on OBD1 in the past).

The Question is how much would a turbo hurt my driveability and reliabiltiy? Yeah I know which motor Im talking about in terms of reliabiltiy.

The turbo is a real popular mod with some of the more adventurous (read: crazy) Fiero drivers. They say its less trouble that a super charger by half, or rather they say they it is on their message boards.

Mine started this morning, 8* out, and made it to work no problems. Drives just like a normal 3.4. Supercharger is a waste of time and money on this motor. We aren't crazy, we're just willing to actually do something, not just dream.

Hey,

You can ask me ANY question about the 3.4 DOHC, I know these inside & out and have Built even a wild N/A version. You CAN get a lot of punch out of these!!!!

Regards,
David

You don't know anything regarding the 3.4, understand that. Your "wild" version makes half the power mine does. Well, actually, we don't know that, you won't strap it down on rollers. Your pretty intake doesn't add any power, it's just a stock, restrictive manifold. Your motor is barely modified dude.

The biggest factor with any DOHC engine is that they are expensive to play with when building them up.

Parts ARE NOT CHEAP!

BUT,

You can get a ton of power out of them and I find they respond much better then OHV engines when adding a turbo & intercooler set up.
Thats mainly just because a DOHC engine design does allow more air in and exhaust out....

IF you are going to build a 3.4 DOHC you need the 3.4 DOHC Kent Moore tool kit.

Just watch for one on E-bay, etc

The DOHC is no more expensive than an OHV buildup. Turbochargers don't cost more if you have more cams, nor do intercoolers or headers.

How would you know how they respond boosted? Let's see your turbo 3.4.

By the way, I built my 3.4, and set the dyno record, without a Kent Mooore tool kit. That includes my timing belt.

I have custom ceramic coated mandrel-bent headers on one of my 3.4 DOHC's

Its crazy the difference headers make on these engine's.

With my set up, I gained 20hp, which was more then I thought I'd get.

There for the 96-97 3.4 DOHC head design with 1 3/4" primaries tapered to match the factory oval exhaust ports, v-band clamps (a.k.a. aircraft exhaust clamps), 3-1 collectors, and made with laser-cut flanges...

If I could get the "Manage Attachments" to work for me I'd post some pics.

Let's see the dyno sheets from these 20hp headers.

Oh and YES I completely port, polished and even port matched the heads, LIM, UIM, and Exhaust manifolds (prior to the headers), and bore out, bell shaped, and polished the TB.

Is it worth all the effort?

YEP!!!

You won't believe the difference!!!!
But, that is true with most engines.

Actually, I'd argue it isn't worth the effort. You see, I had better headers, a better intake manifold, a better throttle body, and my dyno numbers, although being some of the best N/A numbers posted, weren't that great.

What are your head's flow numbers? Wanna bet on whose are better?

Ive been a Chevy tech for 18 years and worked on alot of 3.4s and in my personal experience I would not recommend hot rodding these motors since I dont believe it will support it,at least not for very long.As far as putting in a 4t80 good luck,remember anything can be done with enough patience and money but in the end is it worth it? If you feel it will be then go for it,I just feel theres alot better places to start with.

I'm pushing 417rwhp on a daily basis, seems to be doing well so far.

The 3.4 DOHC is a great motor IF you know the details on it and have the Correct Kent-more service tools needed to CORRECTLY change the Timing belt, when needed.

I have seen one of these engines STILL running great with 495,000K on it. But the guy knew the engine well.

The #1 problem I have always seen is that most people that own one and have problems is people that don't or have very little knowlege about these engines, or about cars (eg, when to change the timing belt, etc.)
Also, to have the belt changed is either expensive, or in many cases done wrong, simply because to do the job right you NEED to understand the details on the Cam timing, and have ALL the correct special tools. Even a experienced Mechanic can do it wrong IF they DO NOT HAVE all these things....

I installed, and changed, multiple T-belts without the K-M tool set. I guess you could argue mine isn't done "correctly," but it runs a helluva lot better than your's. The K-M tool set is not that great. $10 at Home Depot, and a ******* welder, and you can do everything that kit can.

 

Best of luck to you.

I don't think you picked an easy upgrade, but think of all you'll learn.

Let us know what kind of aftermarket support you come up with.

 

A little expensive but can you cam it?

 

Well so far I have found that it’s possible to re-grind the stock cams. A couple of years ago there was also a local dealer with a performance parts window who told me that GM performance parts made a hotter set of cams. There is a timing mod for the 94-95 heads that sets the timing 13* BTDC that is said to get more low end at the cost of a really rough idle. If I went with a custom grind I'll probably be looking at about 2 grand, and for a 20 or 30 hp (if I'm lucky) gain that’s a lot of green to shell out.

Another popular mod is to take the upper intake from the 96-97 3.4 DOHC and keep the 94-95 lower intake, cams and heads because they flow at a much higher rate. The 94-95 intake is one piece and the 96-97 is either two or three (I can't remember which). The down side? You have to go with the OBD II computer to run it. This would mean (Yea! :hyper: ) more wires!

 

Wish I could help. In the meantime, I say go with the tried and true hot-rodding methods. Do you know any good cylinder head porters?

 

You know you can turbo just about anything. Not saying it'd be easy.

@Tom3 3.4 dohc in a shortbed S10 you say, hmm. Nah, I don't have that kinda money.

 

You know you can turbo just about anything. Not saying it'd be easy

@Tom3 3.4 dohc in a shortbed S10 you say, hmm. Nah, I don't have that kinda money.

The Question is how much would a turbo hurt my driveability and reliabiltiy? Yeah I know which motor Im talking about in terms of reliabiltiy.

The turbo is a real popular mod with some of the more adventurous (read: crazy) Fiero drivers. They say its less trouble that a super charger by half, or rather they say they it is on their message boards.

 

Hey,

You can ask me ANY question about the 3.4 DOHC, I know these inside & out and have Built even a wild N/A version. You CAN get a lot of punch out of these!!!!

Regards,
David

 

I have a 3.4 dohc the car in the morning idles high then low high then low.running really rough when low.runs great when idles high.after car is warm it runs great.any thoughts.

 

The biggest factor with any DOHC engine is that they are expensive to play with when building them up.

Parts ARE NOT CHEAP!

BUT,

You can get a ton of power out of them and I find they respond much better then OHV engines when adding a turbo & intercooler set up.
Thats mainly just because a DOHC engine design does allow more air in and exhaust out....

IF you are going to build a 3.4 DOHC you need the 3.4 DOHC Kent Moore tool kit.

Just watch for one on E-bay, etc

 

http://www.denlorstools.com/home/dt.../home/dt1/page_12802_520/kent_moore_spx_camshaft_sprocket_holder_-_j-38614.html

Had to look that up.

I would first go with the traditional ways of increasing power such as having the heads ported for flow, clean up and port match intake.
I dont belive anyone makes a set of headers for it, but one with enough time, money, and a good welder could make himself a set.


And no, the LT5 was not the father of the Northstar. LT5 is one of thoes engines that will go into GM's history books as just one crazy engine.

 

I have custom ceramic coated mandrel-bent headers on one of my 3.4 DOHC's

Its crazy the difference headers make on these engine's.

With my set up, I gained 20hp, which was more then I thought I'd get.

There for the 96-97 3.4 DOHC head design with 1 3/4" primaries tapered to match the factory oval exhaust ports, v-band clamps (a.k.a. aircraft exhaust clamps), 3-1 collectors, and made with laser-cut flanges...

If I could get the "Manage Attachments" to work for me I'd post some pics.

 

Oh and YES I completely port, polished and even port matched the heads, LIM, UIM, and Exhaust manifolds (prior to the headers), and bore out, bell shaped, and polished the TB.

Is it worth all the effort?

YEP!!!

You won't believe the difference!!!!
But, that is true with most engines.

 

The Kent Moore kit for this engine has like 15 different tools in it.

Its a large Kent Moore box

 

try hosting the pics on a site like photobucket.

 

Ive been a Chevy tech for 18 years and worked on alot of 3.4s and in my personal experience I would not recommend hot rodding these motors since I dont believe it will support it,at least not for very long.As far as putting in a 4t80 good luck,remember anything can be done with enough patience and money but in the end is it worth it? If you feel it will be then go for it,I just feel theres alot better places to start with.

 

Before Bonnevilleclub.com got shaken up a dude there built a supercharged AND turbocharged Bonneville with a 4T80. Might want to do a search with it

 

I was reading through this post as I have a '96 3.4 DOHC engine ready for a project car I am workng on and I wanted to build a set of headers for the engine. I would be very much interested in seeing the headers hayesperformance built as well.

Any way we could get some pics for these?

Does anyone else have pics of how the headers are configured on the engine? Always better to start from pictures than to start fresh but not impossible.....

Thanks
Don

 

I got pictures of the headers, but I can't seem to up load them.

I'll E-mail them to you and you can post them after......

 

Hi there i have a 94 Cutlass with the 3.4 motor I have seen some reports on this motor and seem to be negative.I do realize no matter what car you but you may just get the lemon package.What are your thoughts on this motor.Are they realiable.Most new cars are a major problem to work on.Unless you know the tricks.

 

The 3.4 DOHC is a great motor IF you know the details on it and have the Correct Kent-more service tools needed to CORRECTLY change the Timing belt, when needed.

I have seen one of these engines STILL running great with 495,000K on it. But the guy knew the engine well.

The #1 problem I have always seen is that most people that own one and have problems is people that don't or have very little knowlege about these engines, or about cars (eg, when to change the timing belt, etc.)
Also, to have the belt changed is either expensive, or in many cases done wrong, simply because to do the job right you NEED to understand the details on the Cam timing, and have ALL the correct special tools. Even a experienced Mechanic can do it wrong IF they DO NOT HAVE all these things....

 

haynes performance,
how about a link to your website and a #. Please,would you do the honor of emailing the pictures of the headers for the 3.4 dohc. I thought someone was making headers
a while back. I can't seem to find that company. How about some coming up with a set
of header flanges; it it true there are 2 or 3 different flange patterns for this engine.
Hell if I had a set of flanges I could make a damn good 2 or 3 peace headers using
Headers By Ed stuff and their header advice. It turned my 92 achieva scx into a
torque monster and gained 35/40 hps as well at a altitude of 8000 foot altitude.

new member
W41duvernay@yahoo.com

 

The headers were custom made by Milzy Motorsports, there were only a few made and they were STUPID expensive. He doesn't make them now from what I know.

Yes there are 2 Exhaust port patterns the 91'-95' are square with rounded corners and the 96'-97' Are double the width and "pill" shaped.

Here is the link to my Grand Prix's site.

http://www.cardomain.com/ride/2453344

 

hey,
Why didn't you go to headers instead of ported oem manifolds. I had a huge argue-
ment over this point w/mantapart on the Quadforum club on yahoogroups back in the
day. According to miltzy website they are selling the headers to this day. I know it
cost me $750 to make a 2 piece header for my w41 quad 4 .
I love what you did to the ride. What are your quarter mile times versus stock,
what are you running for a plug gapp. What plugs are you running. I've tried a bunch
on my 92 achieva scx ; the best that I ran w the DIS2 were the torquemaster
www.extremespark.com ($25 a plug s-version equal to a plug gapp of 60s).Man did
my throttle response go nuts with those plugs.
Great mod with the msd box.

 

I run the OEM Plugs. The AC Plugs for the 3.4 DOHC have a large special electrode (the AC Part code lists them as a "Plug for High Performance Use"), and when I have tried others they made it run like crap, even when trying different gaps.
These plugs you use sound great, I'll try them.
I had a DIS-4 in the Grand Prix Till it went on me.


The reason for the ported/ port matched/ Ceramic coated manifolds were because I didn't have the headers at the time.


Thanks!

 

I can say though that I'm VERY pleased with that motor done up!

It really pulls hard and is lots of fun, it easily spins the tires, in a straight line, on dry pavement.

 

haynes,
What is the stock plug gapp on those tdc 3.4 engines? If the msd coils are worth
anything, combined with ther DIS4 should allow an additional .015s plug gapp over
the stock setting.
I know Msd told me I ahould be allowed to go up on my stock plugg gapp (which
was .035s) an additional 015s over stock with the spark box. Platnum plugs are horrible for the Quad 4.
The torquemaster are made for lifetime use.
The Msd box went on you. It only cost me 150 to get the Msd box on my repaired by msd.
They are a really great company. Get the box fixed then go for the S-plug torquemaster plugs.