I am considering a 3.4 DOHC swap and would like input from anyone who has done the swap, drives this swap regularly, or offers parts or info on the swap. Tell me the good, bad, and ugly.
The plan is to purchase and install a basically stock DOHC with a Fiero Getrag on an 88 cradle. Anyone selling a complete low mileage take out, or if you have a crate motor collecting dust, PM me with pictures and a price. I know the 3800's are faster but I want the broad rpm range of this engine, and have heard they sound great. Any sound clips you can post would be appreciated too.
I loved the DOHC Formula I had and would have to say it was the most fun swapped Fiero I have driven and that's beating out modded 3800s. The DOHC on the 5 speed is the perfect engine setup for the Fiero when u want a car that handles and drives damn near perfect. I loved being able to bring the RPMs up to 7K and the exhaust not just got sweeter the higher the RPMs went. It is probably one of the few cars I sold that I actually hated see going but the herd had to be thinned and being an AC delete car it went. I DD for some time and to several events in Tx and OK with no issues at all. The buyer flew in an drove it 750 miles home to Las Cruces New Mexico with no issues and said he loves the car. The only down side to me is iit's size as any work done to it is gonna be a pain cause of the tight fit.
The swap is actually very easy and straight forward as not a lot of special order parts r used. The 88 front engine mount is moddemodded for the DOHC and then u pic what type mounts u wanna use. U use a 88 flywheel along with a Getrag clutch of ur choice. The wiring needs to be integrated but there are several on the board that can do that.
I have a aluminum flywheel with about 1500 miles on it that is for sale of u decide to do the swap. I pulled it off the 3.1 in the Formula I picked up when I swapped the clutch out...
I plan on doing a DOHC swap into my empty 88 GT in the future..
[This message has been edited by MstangsBware (edited 08-02-2014).]
I have a 3.4 DOHC in my 86 and have daily driven it for the last 3 summers.
I agree with pretty much everything MstangsBware said. It's not the fastest swap out of the box, but IMO it's the most fun of the common swaps when mated to a manual trans. Winding this thing out to 7k is an absolute blast and the exhaust note while doing so is downright orgasmic.
IMO the biggest task to overcome is finding one in good shape these days. Solid used engines are getting scarce. Crate engines are still floating around, you just need to have the patience for one to pop up.
I would recommend starting with an OBD2 (96-97) engine if possible. The others are fine too (mine's OBD1) but there are benefits to running the later year engines such as the redesigned heads and intake as well as SFI and better tuning options.
I have sound clips but I'll need to find a way to post them. The clips sound good, but just don't quite portray it as well as hearing it in person.
I loved the DOHC Formula I had and would have to say it was the most fun swapped Fiero I have driven and that's beating out modded 3800s. The DOHC on the 5 speed is the perfect engine setup for the Fiero when u want a car that handles and drives damn near perfect. I loved being able to bring the RPMs up to 7K and the exhaust not just got sweeter the higher the RPMs went. It is probably one of the few cars I sold that I actually hated see going but the herd had to be thinned and being an AC delete car it went. I DD for some time and to several events in Tx and OK with no issues at all. The buyer flew in an drove it 750 miles home to Las Cruces New Mexico with no issues and said he loves the car. The only down side to me is iit's size as any work done to it is gonna be a pain cause of the tight fit.
The swap is actually very easy and straight forward as not a lot of special order parts r used. The 88 front engine mount is moddemodded for the DOHC and then u pic what type mounts u wanna use. U use a 88 flywheel along with a Getrag clutch of ur choice. The wiring needs to be integrated but there are several on the board that can do that.
I have a aluminum flywheel with about 1500 miles on it that is for sale of u decide to do the swap. I pulled it off the 3.1 in the Formula I picked up when I swapped the clutch out...
I plan on doing a DOHC swap into my empty 88 GT in the future..
Hey Mstangs,
Las Cruces is just up the road from me. Can you PM me contact info on the guy that purchased it. Maybe I can get him to be part of our Fiero group here in El Paso. Who here can build a harness for me?
I have a 3.4 DOHC in my 86 and have daily driven it for the last 3 summers.
I agree with pretty much everything MstangsBware said. It's not the fastest swap out of the box, but IMO it's the most fun of the common swaps when mated to a manual trans. Winding this thing out to 7k is an absolute blast and the exhaust note while doing so is downright orgasmic.
IMO the biggest task to overcome is finding one in good shape these days. Solid used engines are getting scarce. Crate engines are still floating around, you just need to have the patience for one to pop up.
I would recommend starting with an OBD2 (96-97) engine if possible. The others are fine too (mine's OBD1) but there are benefits to running the later year engines such as the redesigned heads and intake as well as SFI and better tuning options.
I have sound clips but I'll need to find a way to post them. The clips sound good, but just don't quite portray it as well as hearing it in person.
Thanks for the info. I have found a 95 OBD1 SFI crate engine. Since this motor is SFI can it use an OBD 2 harness and ECM? Unless there are any 96-97's engines out there this one should work for me. My car is an 88 Mera 5-speed and I thought this engines sound would be perfect coming out the back of my car.
[This message has been edited by Rick 88 (edited 08-04-2014).]
Go to Google and type this: site:fiero.nl 3.4 DOHC
it will return all the threads in Pennocks that have 3.4 DOHC in them. I tried to start each thread with 3.4 DOHC so it will help the search. You should find everything your looking for with that search
I followed little ferrari's build almost to the letter, and must say that it is spot on. Now if Darth and I can figure out why it is running pig rich, I may be able to chime in.
I have a 96 DOHC in my 85 Fiero. Love the 7k red line with the manual trans. Had the swap done for 5 years and only had one problem with it when tensioner broke on the highway. No damage to the engine ( supose to be a interference engine).
Joe Sokol
------------------ 85 SE Daily driver with a 3.4 DOHC OBD II 88 Formula/GT 4.9 Allante Intake (My Baby) www.fieroking.com
I am glad everyone that has one seems to like this motor. Does this motor sound fairly European? I am going to be putting it in a Mera. I'm hoping it has a bit of an Italian sound going thru the gears. Thanks for all the tips. Any one you recommend to do the harness. From all the research I have done, Sinister Performance is the place.
I also need tips on exhaust systems, A/C, Cruise, plumbing, etc. PM me or post away. I am reading everything I can find.
Taken with a smart phone, unfortunately the microphone really doesn't do it justice.
Specs 1992 3.4L DOHC 1996 intake swap Internally balanced and bored .030" over FFP underdrive pulley Stock front and rear exhaust manifolds with 2.5" mandrel bent exhaust into a DynoMax muffler with Corvette C6 tips.
Disregard the slow shift, my Isuzu does not like going into second at anything higher than the original Duke's RPM range.
[This message has been edited by Silicoan86 (edited 08-06-2014).]
I've ridden in a 3.4L TDC engine Fiero and these are my ,observations and opinions based upon research, discussions with owners The engine seems to fit the Fiero engine compartment but looks quite massive in there. I do not know if it is possible to change plugs without dropping the cradle The swap appears to be a bolt in with a stick (that also lends itself best to the power curve). The engine is an early attempt by GM at making a DOHC engine based on the 60* V6 block design. The design is quite old, low mileage examples are difficult to find but crate engines pop up every now and then There have been some oiling reliability issues and the timing belts must be changed at 60K miles. The gas mileage and power down low is average but in the 4000-6500 RPM band it really talks off. Over 400HP is possible using boost. ex: Matt Hawkins This has never been a very popular Fiero swap but there are a small amount of Fiero owners that love this engine.
Originally posted by zzzhuh: I figured that transmission would blow up the second you give it any gas.
I recently acquired a Getrag to replace it, so I've been driving it pretty hard now that I've got a spare on hand. It seems to hold up pretty well actually. Like I mentioned, It's really hard to shift into second until the rpms fall back down to Iron Duke levels, and that may be helping the matter since I can't shift that hard into second gear which is known to be the Isuzu's weak point.
IMO the 3.4 dohc tends to be easy on transmissions due to its high rpm powerband, at least compared to engines like the 4.9 which has a full 270+ ft-lbs of torque from the moment you slam it into second gear and let out the clutch.
The crate engine I will be using is a 95 SFI version, I am going to be installing it with a Getrag.
I also have an NOS export Getrag with the 3.91 final drive. There have been posts on here about building a hybrid close ratio gearbox using the 1/2 gearset of the Fiero Getrag along with the remainder of the export gearing and 3.91 final drive. The export box uses a Quad 4 bellhousing which would need to be swaped. The export first to second gearset in it is supossed to be very short compared to the Fiero first and second since this trans was used in a GM minivan. With the additional DOHC power would buiding a gearbox like this be a benefit or not?
On the cruise control, it is better to use the Fiero system or the electronic cruise these motors came with? Also I am going to need recommendations on an exhaust system. I don't want to cut the trunk as I actually travel in my car on occasion. Since my car is over 25 years old it no longer has to have an emission test. Would the DOHC perform better without the convertor?
[This message has been edited by Rick 88 (edited 08-22-2014).]
Can you offer any info on building a harness. I have been told any 85-88 Manual Transmission V6 harness will be able to be tied in to the DOHC harness.
I want to build the swap on another cradle and be able to have it pretty close to complete before it is installed in the car.
Did any of you guys run you exhaust system without a convertor? If so did you notice any power improvement? In Texas you don't have to meet emissions once the car is 25 years old.
I have over 60k miles on my 3.4 DOHC swap. I first swapped it in 2005. I have run dozens of track days in the California heat. It's a great engine for the track due to the broad powerband and high rev limit. When I first did the swap I had an Isuzu 5 speed and I sheared all the teeth off 2nd gear.. so I don't recommend that transmission for anything. A Getrag with the long 5th will get ~27 mpg on the highway on an otherwise stock Fiero.
Spark plugs are easy if you crack the rear wire holders in half so you can remove them without hitting the rear firewall shelf. You will need a magnetic spark plug holder and some short extensions to feed in one by one. The rear spark plugs are very straightforward.
Don't buy a used motor. Get a crate motor or plan on doing a rebuild (budget ~$3500 -- so get the crate motor instead!). When these engines aren't taken care of the intermediate shaft bearing can fail and send debris through the rest of the oiling system. Sound familiar? Google Porsche IMS bearing... The fix is to disassemble the motor and replace the front intermediate shaft bearing with the longest one that will fit. I think it's an SBC camshaft bearing or something. If it's a new motor you do not have to worry about this.
quote
Originally posted by Dennis LaGrua: The engine seems to fit the Fiero engine compartment but looks quite massive in there. I do not know if it is possible to change plugs without dropping the cradle
It takes about 10 minutes to remove and replace all 6 spark plugs. Actually, all of the maintenance is very easy except the timing belt.
quote
There have been some oiling reliability issues and the timing belts must be changed at 60K miles.
The timing belts are annoying. I'm not aware of any oiling reliability issues. I've been running my car hard on the track and the only issue I've seen is high oil temps, but that's a problem with everyone's car out here in the 105*F heat without additional coolers.
I have purchased a 95 SFI crate motor. I plan to keep the install as close to stock as possible for increased reliability. I hope to be able to drive it regularly and take some trips in the car. I plan to keep A/C and cruise. My car is a Mera, and I thought this engine would make the right exhaust sound for the Mera bodywork. Any tips on what kind of muffler to run? Or should I just keep the stock V6 Fiero muffler. I have always liked the sound it produced.
Another question. What did you guys do concerning the oil fill cap being on the firewall side of the engine. Can another cam cover be installed with a cap on the trunk side?
[This message has been edited by Rick 88 (edited 08-26-2014).]
a lot of the stuff you need are in the old posts, I know I asked a lot of questions and got some great advice. Use the google search method I posted above to find things here fast.
My setup was: 88 Coupe. 96 Motor, stock 88 Isuzu trans. (wish I had a Getrag, but i had no issues with the isuzu)
My 96 was wired up as a 91 (OBD 1) system. I used the ECM and harness off an 91 Cutlass that was originally a 5 speed car. I wanted to start with a 5 speed trans and not have to modify an Auto harness. I had to replace a few sensors because the 96 - 91 had some differences. Nothing to bad. I built my harness on my kitchen table using the pin outs found online. A few years ago, there was a DOHC website that has a lot of great info on it. One of the pages had a pin out diagram that was 97% spot on. In the end, I purchased a 91 Cutlass Service Manual off the web and used the pin out pages to trace every wire (54 of them) I also removed the stock 91 relay center. It cleaned up the harness and it looked great. For exhaust I ran headers, they were custom made so I can't offer any advice, however, I also used the cat-back system from WCF, I bought the 2.5" set up and Spintek muffler. I sounded great and I had no option but to use a "high flow" Cat. The new high-flow cats offer almost no back pressure issues so I would not worry that much about it.
Can you guys post some pics of your exhaust systems, and let me know why you made them that way. My engine is a 95 SFI. I understand it is better if you change on of the exahust manifolds for one from the other side. Which one do I need? If any of you have a built system for sale, send me a PM.
I know I am late to the party for this swap. For you guys that still have them how have they held up? For those that pulled them, whey did you do it? I drove a new Grand Prix 5-speed with a DOHC back in the day, and the engine pulled very well and was extremely smooth.
On the rear suspension did anyone install stiffer springs due to the added weight on the engine? Is the additional weight that noticeable if you are just using the car as a driver?
Anyone else have swap parts they want to sell?
[This message has been edited by Rick 88 (edited 09-17-2014).]
