3.1 mpfi to dohc 3.4 swap

**91gpse** · 01-06-2012

Well its been awhile since I've been on here... and even longer since I posted. So I am going to make a thread showing the progression of the current project to the grand prix. It's a 1991 grand prix se coupe. I am converting it to a ste or in cavalier terms a z34. I killed yet another 3.1 so I'm saying eff it and I bought a dohc 3.4L and a trans for dirt cheap. I am going to post pics and explain the process of dropping it in.(along with adding a few accessories ie gauges along with it). Its going to be a slow process because of my job but it will be detailed down to which wire goes where and torque specs. I do not want to hear a just get a sc3800 this will be a how to not a slander thread.

**91gpse** · 01-06-2012

Heres the old engine

Heres the new one.

The manifold and crossover pipe. As you can see a bit rusty getting cleaned up the egr holes filled and ceramicoated.

The block. As you can tell still quite dirty haven't gotten around to cleaning it yet. Its getting a mechanical oil pressure gauge.

The intake manifold. Getting the same ceramicoat as exhaust manifold and possibly black pinstriping(undecided).

The wiring harness... This is getting probably the most attention. Its getting all new sleeves in silver splicing in an air fuel gauge (lowband for now cuz thats all I have). and a few other little things.

Bucket of engine bracketry and some misc. parts

**dsmuts** · 01-06-2012

A Z34 is a monte the cavalier was Z24. But what made you decide on a 3.4? Why not swap in an L67?

**ctracer** · 01-07-2012

good luck with the swap. are you gonna do any performance mods/engine mods while its out?

**91gpse** · 01-07-2012

update i did a bit of the painting will post pics when all the painting is done. including the steps of ceramicoat baking. the engine already has an egr delete im remapping the computer and im putting bigger injectors and a more efficient fuel rail. mainly though im doing cosmetic modifications to it. the goal is around 240-250 hp not too big of a gain when you consider its tops 220 stock. down the road it will see a procharger but not right now. and the reason i chose a dohc 3.4 over a 3800 is simply their less common and when built right can handle as much if not more power.

**91gpse** · 01-09-2012

i got most of the painting done. forgot to take a pic of the steps of ceramicoating but its not that hard just follow the can.

heres how the engine looks now after paint.

side view.

back and trans.

with the valve covers and intake plenum on. the valve cover ran so i have to respray it.

with the old heat shield i got a new one but it was too dark to take a pic with it on.

i especially like the way the exhaust came out.

**Z34Phoenix** · 01-11-2012

Ok coming from someone who had a DOHC for many many years... i ask too why? i know you said to be different, but your goal with that amount of HP is not easy at all. i probably had the most HP Na from one of these DOHC and it wasnt easy. further more, the trany just will not hold the power.

there are no mods left out there for this engine. i sold recently an under drive pulley and my ported intake manifolds.

what i can recommend to get the most out of it are the following:
-swap to a 96+ style intake manifold set (lower, upper, arm, and tb)
-port the lower to the heads, Upper to arm, arm to TB, and port the TB.
-Underdrive pulley if you can find one.
-get a chip from 60degreev6.com
-port heads?
-look into custom cams?
-have custom headers made?
and with all that it will still be hard for the goal you set

**ctracer** · 01-14-2012

its looking good man! you dont see very many of these swaps going on. you have to let us know how the actual swap goes

**91gpse** · 01-16-2012

Originally Posted by Z34Phoenix

Ok coming from someone who had a DOHC for many many years... i ask too why? i know you said to be different, but your goal with that amount of HP is not easy at all. i probably had the most HP Na from one of these DOHC and it wasnt easy. further more, the trany just will not hold the power.

there are no mods left out there for this engine. i sold recently an under drive pulley and my ported intake manifolds.

what i can recommend to get the most out of it are the following:
-swap to a 96+ style intake manifold set (lower, upper, arm, and tb)
-port the lower to the heads, Upper to arm, arm to TB, and port the TB.
-Underdrive pulley if you can find one.
-get a chip from 60degreev6.com
-port heads?
-look into custom cams?
-have custom headers made?
and with all that it will still be hard for the goal you set

Thats actually pretty similar to what I have planned. I'm taking the heads off soon to port them I'm putting larger valves in as well. Once I get the money I am doing all forged internals, boring the block out, and making a full 3 inch exhaust and headers. Down the road it will be powered by a procharger. When this happens I'm getting the cams custom made then having it dyno tuned. If I can't hit the power I was hoping for so be it, I set the goal high on purpose. Also it will be getting a getrag 5 speed once it gets the procharger so this trans doesn't have to hold the kind of power I'm looking for. Also I saw the newer style intake manifold at the junk yard so I may go pick that up.

**91gpse** · 01-16-2012

On another note.... I killed the old engine.... exploded the piston and put the rod through the oil pan and took out the starter.... epic way to kill a motor if i do say so myself... I'm parting it off as well as selling the old trans so if anyone is looking for parts for a 3.1 mpfi pm me. Will port the heads if you want(for more of course).

**ctracer** · 01-16-2012

good luck finding that getrag 5 speed. they are rare and usually abused. on top of that, idk if the getrag will handle the power either. but hey, gotta try right?

**91gpse** · 01-17-2012

Originally Posted by ctracer

good luck finding that getrag 5 speed. they are rare and usually abused. on top of that, idk if the getrag will handle the power either. but hey, gotta try right?

I actually know where one is. its sitting in a fiero thats been parked for a few years. the guy said hed sell the whole car for 600 so i might get it sometime down the road. If it doesnt work I will just get a modern 6 speed out of a g6.

**Z34Phoenix** · 01-18-2012

More Power to you if you pull it off. i have heard over the years so many people talk and talk about doing this and that to this engine and it never pans out. I do hope you complete it. but i dont have my expectations high...

where are you getting larger valves? i have never heard of anyone tearing this engine down that far... but if you do go down that far wait and do the internals then. i dont think it is really needed though, just like the 3800's the bottom end is strong and not the failure point. the only think to kill these engiens is the timing belt... in my case it was the chain between the crank and the timing drive gear/sprocket. the failure i had was very rare and i have never heard of it happening to anyone else.

for the power level your building i would say skip the getrag as they were never designed for that amount of power and with limited parts i think it is just asking for problems. your best bet is to get it swapped to OBD2 and run a 97 pcm and harness so you can run a 4t65e. then you can drop in a built trany from TEP or some of the people running around who are known for building the strong tranys that can handle the power. not to mention there are and will be plenty of parts avalible.

further more a full 3" exhaust is pointless. you will be killing low end tq on a motor that already is lacking there. a 2.5" is plenty. as for headers... it all comes down to your ability to make them.

if i were to build a Lq1 from the ground up, this would be my plan:
-96-97 bottom block. cleaned/ tanked, new internals, and walls honed but not bored
-port the heads and polish the chambers
-95 or older heads because the bolt pattern will allow to run a front log manifold on the rear bank.
-build my custom upper intake manifold i designed and recalculate volume for turbo
-single turbo not looking for more then 7psi
-3" dp off the turbo thru a 3" cat then 2.5" the rest of the way back
-97 harness with a built 4t65ehd and 3.69 gears

**91gpse** · 01-19-2012

The timing belt is the major problem with the motors... I have a solution just trying to find a way to pull it off, yet to find the conversion kits but I want to eliminate the belt and go with a chain.

**Z34Phoenix** · 01-21-2012

I have never seen a conversion kit to replace the belt. and im not sure it is a good idea. this engnie already has alot of rotating mass because its an over head 4 cam. if you add in a chain vs the belt it already has and replace the tensioner system, and pullies it will add even more weight to the system! and a chain long enough to replace the Tbelt would have soo much slack and be prone to breakage. and if you try seprate chains you are adding even more weight! When replacing the belt you replace all the idler pullies and the tensioner with the belt. if you do this correctly it will last another 75-100k miles! my last timing belt job lasted from 98,000 miles until the dummy chain jumped a tooth and the belt and pullies were still good at 224,000 miles! after 75,000 you check the belt every 3k to look for signs of wear and tension. the timing belt isnt as bad as people make it out to be. yes it is the main failure for the engine just because most dont replace or watch it like they should.

to be honest, i have heard people come and go talking about doing radical builds like you and never completing them. what is said about moding the 3800 holds true for this engine as well. Set a Budget and a Goal. then make a plan. considering some of the ideas you mentioned will require extensive fabrication and rarely ever done on an engine that is even more rare.... I have been in the DOHC community for 10+ year and there have only been 3-4 people who have tried making cams for this engine no specs were ever passed on nor were any results. all who tried ended up switching engines. this should tell you something.

just like the 3800 says too... i wouldnt recommend tearing down and rebuilding the bottom end. its best to find a low miles block. to properly build a bottom end, you need to have a shop hone the bore, balance everything and even still people have engines that die when all this is done. also the DOHC never looses pistons or throws a rod or spins a bearing. the only one i heard of with bottom end failure was ez112 who rebuilt his engine and it lost a piston at the track. this engine is popular in the fiero crowd and many have run turbos and put 325-350 whp.... there is one member of another forum who has a 95 Z34 who also was runing a turbo and put down 325 hp on 7 psi i believe. so i honestly think the DOHC has a stronger bottom end then the 3800 series engines.

I dont want to discourage you, but im just tired of hearing people dream up these plans and never follow thru. it just adds to the notion that this is a bad engine when it really isnt. what ever help i can give let me know. my best recommendation would be put the engine in don not go any deeper then the lower intake manifold and timing belt. and enjoy the engine. the cost of what you are saying/planing would be not practical at all. even doing the work your self you are way up there...

at least 2-3,000 for the bottome end to be replaced with forged parts and properly installed and balanced.
4 custom cams and hoping to get the specs right on the first try 1,200-1,500
procharger 2,000 once done if lucky
300+ in valves
??? making headers
???? tuning who knows ... deff hard if your not OBD2 or stand alone system.
???? finding a getrag in good shape and installing it.
that is about 6,800+ all the unknown ???? + any stumbling blocks! this could easily be $10,000+ into the engine! (not talking about labor, suspension, brake upgrades or paint).... resting on a getrag that wasnt designed for more then 200hp to begin with!

If i was told to tke 10,000 to build a 1st gen Wbody, and the restriction was not to use a 3800 engine... i would say go with the 3400 and go turbo. it might be possible to use a getrag with it or upgrade to a 4t65e and have it built for the power. and it prob will come in under budget. heck you might be able to squeeze an LS4 V8 in there! and not do anything to the engine.

**91gpse** · 01-28-2012

Originally Posted by Z34Phoenix

I have never seen a conversion kit to replace the belt. and im not sure it is a good idea. this engnie already has alot of rotating mass because its an over head 4 cam. if you add in a chain vs the belt it already has and replace the tensioner system, and pullies it will add even more weight to the system! and a chain long enough to replace the Tbelt would have soo much slack and be prone to breakage. and if you try seprate chains you are adding even more weight! When replacing the belt you replace all the idler pullies and the tensioner with the belt. if you do this correctly it will last another 75-100k miles! my last timing belt job lasted from 98,000 miles until the dummy chain jumped a tooth and the belt and pullies were still good at 224,000 miles! after 75,000 you check the belt every 3k to look for signs of wear and tension. the timing belt isnt as bad as people make it out to be. yes it is the main failure for the engine just because most dont replace or watch it like they should.

to be honest, i have heard people come and go talking about doing radical builds like you and never completing them. what is said about moding the 3800 holds true for this engine as well. Set a Budget and a Goal. then make a plan. considering some of the ideas you mentioned will require extensive fabrication and rarely ever done on an engine that is even more rare.... I have been in the DOHC community for 10+ year and there have only been 3-4 people who have tried making cams for this engine no specs were ever passed on nor were any results. all who tried ended up switching engines. this should tell you something.

just like the 3800 says too... i wouldnt recommend tearing down and rebuilding the bottom end. its best to find a low miles block. to properly build a bottom end, you need to have a shop hone the bore, balance everything and even still people have engines that die when all this is done. also the DOHC never looses pistons or throws a rod or spins a bearing. the only one i heard of with bottom end failure was ez112 who rebuilt his engine and it lost a piston at the track. this engine is popular in the fiero crowd and many have run turbos and put 325-350 whp.... there is one member of another forum who has a 95 Z34 who also was runing a turbo and put down 325 hp on 7 psi i believe. so i honestly think the DOHC has a stronger bottom end then the 3800 series engines.

I dont want to discourage you, but im just tired of hearing people dream up these plans and never follow thru. it just adds to the notion that this is a bad engine when it really isnt. what ever help i can give let me know. my best recommendation would be put the engine in don not go any deeper then the lower intake manifold and timing belt. and enjoy the engine. the cost of what you are saying/planing would be not practical at all. even doing the work your self you are way up there...

at least 2-3,000 for the bottome end to be replaced with forged parts and properly installed and balanced.
4 custom cams and hoping to get the specs right on the first try 1,200-1,500
procharger 2,000 once done if lucky
300+ in valves
??? making headers
???? tuning who knows ... deff hard if your not OBD2 or stand alone system.
???? finding a getrag in good shape and installing it.
that is about 6,800+ all the unknown ???? + any stumbling blocks! this could easily be $10,000+ into the engine! (not talking about labor, suspension, brake upgrades or paint).... resting on a getrag that wasnt designed for more then 200hp to begin with!

If i was told to tke 10,000 to build a 1st gen Wbody, and the restriction was not to use a 3800 engine... i would say go with the 3400 and go turbo. it might be possible to use a getrag with it or upgrade to a 4t65e and have it built for the power. and it prob will come in under budget. heck you might be able to squeeze an LS4 V8 in there! and not do anything to the engine.

The point about the belt vs chain is noted so I won't touch that will just continue to maintain it. Ls4 will fit with a northstar trans bell housing.(too easy) I want something different, something complicated(bit of a masochist). I have the time and the money and the means. I got a set of heads for it that I'm going to experiment with, I wanna see if I can cut out the little piece in the exhaust ports for better flow. The headers are just gonna cost me materials same with the exhaust seeing as a buddy of mine has a welder already. I know full well how much work it will take. Didn't say it was gonna be a quick and cheap process. Actually I remember saying that it will be a lengthy process. And 20 hp more than stock shouldn't be that hard considering I'm doing the heads I'm putting the newer intake on it. I'm doing a number of little things that will add up. Egr delete, ect.... The bigger mods are down the road when I have more money. The trans I'm looking into a 6 speed. Also if you say the bottom end will hold up to psi then I will leave that just will do a headgasket when I boost it.

Update... Due to unseasonable weather my entire yard is flooded from rain..... In the middle of winter... in Michigan... So I can't get to the car because its on the other side of a lake(not kidding....were talking a good 6-8 inches deep in some parts). Anyways I picked up a block heater... Not too hard to install pop out the freeze plug and put it in... Going to do that tomorrow.

**91gpse** · 01-29-2012

Noone can knock experience when it comes to building hence why I'm taking the advice. Yeah I had a dohc 3.4L but I never really did anything with it. I want to build this one to its full potential.

**Z34Phoenix** · 01-29-2012

I will enjoy seeing the progress and what it can become. on the heads... removing the divider in the exhaust port is not a good idea... before making any changes to the heads please do more research on porting of heads... too many people feel they can just make ports bigger and they will flow better.... this is not the case when it comes to porting heads. you want to remove restriction and maximize the flow velocity. if the port is opened up too much, it will greatly reduce the velocity at which the air can flow. the best analogy i can think of is taking a paper towl roll, coffee stir, and McD's straw. try to blow thru the paper towel roll... cant get much force out of it can you? then try the coffee stir.... same thing but if you get a McD's straw you can get a good velocity at a descent flow. its the same thing with the heads... if the ports are too small there will be too much friction and restrict flow... if they are too large, the air wont move far at all. if you have just the right size you will flow the right amount at the right velocity to make power.

there is a head porting guide on here and other forums as well read up and you will be better prepaired. the divider in the exhaust allows each of the exhaust ports to flow faster then if they were combined. the only thing i would do is just at the exit, i might consider filling them down to a knife edge to allow the exhaust streams to mix with less turbulence.

**91gpse** · 01-30-2012

Hence why I got a set of heads from the junk yard to try on first. Because I know I will screw up the first shot. Basically I have 2 heads to practice with before the real deal. As well as an intake manifold to mess with because I'm getting the newer one like you suggested. My main problem right now is the upper mount... the one that attaches to the core support.... the bracket is hitting on the head and wont line up with the holes correctly. It's sitting pushing up against the end plate of the head(which I don't think it's supposed to.

**91gpse** · 02-08-2012

Update. I got the old engine torn down to the point where its ready to come out. Next week is the pull with any luck. Then hopefully selling off parts of that motor/trans then raiding a junk yard for more parts.