I have a chance to buy a 3.1L with 33,000 miles on it out of a Grand Prix for $350. My questions are: Is the block identical to the Fiero 2.8? Starter, Bolting to fiero trans, basically do I have to do any extra machine work. Can I use my 2.8 heads, intake setup? I just want to swap short blocks. How much Horsepower can I expect with porting, polishing, cam upgrade, roller rockers, Etc? According to the original specs for the car HP was at 150hp. How much HP can I get reliably out of it? Has anyone done a 3.1L swap? I know many questions but any help would be greatly appreciated. Thanks In Advance,
------------------ ~Oreif~ Fieroholic and proud of it!
Isn't the 3.1 the same as the 2.8 except a bore size larger? or does it have a longer stroke also? for some reason tho, I'm thinking they're the same exact block. if so, you <could> use you heads and intake, but I would suggest getting a valve job done to try and increase the intake a bit, and swaping the fuel injectors or increasing preasure. Note those last 2 wouldn't be necesary, but it would take more advantage of the larger bore/stroke and add to your power
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06:03 PM
Megafiero Member
Posts: 39 From: Oxford, MI, USA Registered: Jun 2000
As for your heads, you ask about porting and polishing, I'm not sure if you haved looked into the cost, but it's alot!!
You would be better off getting a set of GM performance parts Gen.II aluminum heads for about 500$ The stock heads have a intake valve size of 1.60 and exhuast of 1.30 the aluminum heads have an intake valve size of 1.72 and exhuast valve size of 1.42, a very nice increase in power. I'd say close to 20 HP with these heads and better cooling.
As for the cam since you want to use stock intake (computer controlled) your cam must work with the computer. I have found that either a Crane Compucam or a CompCams High Energy cam are the best out there. You could probable expect 10 Hp maybe 15 or more with rocker arms.
If you build the motor right (I would also suggest forged pistions) out of a 3.1L that is computer controled, you can expect close to 230 HP!!
Well good luck and if you have any other questions feel free to e-mail me.
----------- Megafiero megafiero@tir.com
------------------ P.S. yes a 3.1 will bolt up to your trans.
[This message has been edited by Megafiero (edited 07-01-2000).]
Are you certain of the valve sizes you quote? I thought the later model 2.8s such as the ones in out cars had the larger valves. I can't say I've ever purchased valves, or measured them, but most of the references I've seen refer to the larger valve specs. Just wondering....
Are you certain of the valve sizes you quote? I thought the later model 2.8s such as the ones in out cars had the larger valves. I can't say I've ever purchased valves, or measured them, but most of the references I've seen refer to the larger valve specs. Just wondering....
Don't expect 230HP from a 3.1L without NOS or a blower (turbo or supercharger). The GP Turbo 3.1L engine only produced 205HP. The Buick 3800 only managed 205, 225 and 240HP using M-62/M-90 Eatons.
At *best*, you will get 180HP at a reasonable RPM unless you plan on reving it to 10,000 RPM. Even the sequential 3.1L's only produced in the 160HP range.
Just trying to stay real here.
There truly is no replacement for displacement. If you plan on drag/stop light racing, get more displacement. For all of the work to get the 3.1L in there (yes, it will be easier than a Buick swap), get a Buick V6. Even the 3.4L DOHC at 210/215HP is a slug from a start, but it takes off like a <insert your favorite metaphor here> above 3000 RPM.
Otherwise, get a 3.4L Camaro long block. That will give you the most bang for a limited buck.
As far as the 3.1L GA swap goes, you will either need to swap the engine in complete and as-is or change the pistons to use the iron heads. No doubt, the 3.1L AL head engines run good. You will still need to work out the exhaust details if you stay with the complete 3.1L. In the end, you will spend another $200-500 doing anything.
Terry
[This message has been edited by terryk (edited 07-03-2000).]
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01:48 AM
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
Thanks for all the posts guys. Terryk, I'm not looking for a racing machine I would just like to bump up HP a little like the 180 range. I am going for better HP but mainly reliability. I plan on using just the 3.1L block,crank, rods, and pistons. You mention I need to change pistons going to the iron heads, why? My basic plan is Crane cam, roller rockers (1.6) porting and polishing intake system and exhaust, and the performance SI stainless steel valve's. My guess would be somewhere around 175/180HP. I thought about the 3.4L swap but I can do the 3.1L for under $1000. (parts cost) But I need to find out about the pistons Terryk talks about.
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10:29 AM
Megafiero Member
Posts: 39 From: Oxford, MI, USA Registered: Jun 2000
I would to expect 230 HP. I have planed out and engine build and had it dyno tested with a computer program (garanted within 5% acurracy. The engine you talked about with 205 HP was not built for this kind of performance.
Even the 3.8L engines yes they only make 240HP with a supercharger, but think!! GM can't produce a motor making tons of power, gas mileage and emisions would not be within regulation.
With the right heads, exhaust, increased comp. ratio, and so on 230HP is not hard to get. Me and a friend are building a 3.2L (3.1 .030" over) that will have 270 HP naturaly aspired!!!!
just like a 350, in a new camero they only make 305 HP that don't stop them from making 600+ HP on the right build. And about the valve sizes, I got them on mitchel on demand. It's a mechanics program. I worked at a shop that had it, and that was the valve size for a MPFI 2.8, also if you look in the GM performance parts catolog and look at the stock 2.8 heads they match up.
[This message has been edited by Megafiero (edited 07-03-2000).]
The combustion chambers are a different size for the iron and AL heads so you need the different pistons like the Silvolite 1486's. These are 8.8:1 for iron heads. www.kb-silovlite.com I believe.
You'll be pleased with a nice 3.1L engine. Port, polish, balance, add a nice cam, 1.6 rockers and you'll be happy. That's in sight of your budget. What is nice it not so much the low end torque, but the improved upper RPM range above 4000 RPM. With some 92 octane gas and more timing, you will approach the 170-180 HP range. Terry
[This message has been edited by terryk (edited 07-03-2000).]
Just my 2 cents- I LOVE my 3.4!!!! I am still getting some tuning done (Thanks!), but this thing is a DEMON! I drove my the 88 T-top GT that used to be mine again today- there is no comparison between the two. If you are brave enough to drill the starter holes yourself, getting a good 3.4 could be less than $500. I still have a new GM manual tranny flywheel for anyone that needs it for their 3.4 or 3.1 installation.
BTW- my 3.4: 70,000 mile engine, low geared 4 speed, functional Indy roof scoop, Camaro manifolds (maybe headers soon!), 2 inch true dual exhaust, gasket matched lower, upper intake and plenum, bored throttle body (+4 mm) and extra thin butterfly, MSD 6a and blaster coil (not the lower voltage GM style coil), now in the process of throwing out un-needed items like cruise, trunk carpet, leaf guards from rear vents, sub-woofer/amp, and other things I find no need for.
I took my ricer CRX friend for a ride Saturday- needless to say he does not want to race.
[This message has been edited by Cooter (edited 07-03-2000).]
That 3.1 out of a Grand Prix will probably be an aluminum head version which the Fiero intake will not interchange and it will have different pistons that won't work with the iron Fiero heads. The whole swap can be done, but you need the donor ECM and wiring.
