Does anybody that got the 3.1 rebuild have any performance numbers? I am hearing a range from 190-220 HP on the 3.1 rebuild with competition cams. What torque numbers did you get? Any 1/4 mile times with the 3.1? How does it feel in the car? Is it a nice pull? ( Push :-) ) Thanks for the info.
IP: Logged
09:30 AM
PFF
System Bot
Eric Member
Posts: 916 From: Columbus, Ohio Registered: May 99
All I know is I am not satisfied with the present amount of power in my 88 GT and think a performance 3.1 rebuild is the way to go with cheap reliable drivable horse power. Torque as a percentage of horse power, goes down with a more aggressive cam. And from what I have heard, after 2500 rpm is where most of the power can be found.
Cool Greendano. I'm thinking of getting that same cam. Did you get your springs, retainers, and lifters with it? How much did the whole thing cost from GM?
IP: Logged
06:26 PM
Eric Member
Posts: 916 From: Columbus, Ohio Registered: May 99
Greendano, are you using the Federal Mogul part#h562p 3.1 pistons? These are the pistons Shaun told Lee to get and Lee told me to get. I don't think those guys are sure of the compression ratio, but I imagine it's around the stock 8.5:1 because they are dished pistons. Do you have any concrete numbers on your pistions?
IP: Logged
06:38 PM
RFMike Member
Posts: 255 From: River Falls, WI Registered: May 99
Has anybody out there done a 3.1 rebuild, and have experience with its affect on fuel economy? I may consider it this winter, but I put a lot of miles on (2,500-3,000 a month); I love power and speed, but I need the mileage, too.
Here's all you need wanted to know. Fuel economy...I used to get 200 miles a tank, I get 170 now. Parts...I used all the matching GM valve train gear with my cam Springs, rockers, retainers ect... Cam comes with lifters. Pistons...I used second overbore '91 Camaro pistons. It comes out to 0.040" Here's the bad news, I work at a GM dealership and am good friends with the parts manager....So some of my parts I got at cost. I guess the thing to do would be get your hands on a GM performance catalog and go to any local GM dealer that you want to spend your money at. The car idles with a nice lope. It by no means is a beastly idle, and the computer can keep up with it no problem. Dan-O
Eric, The Federal Mogul pistons you were asking about are available in two different compression ratios. The ones you want are from a '90 Camaro 3.1. The compression was higher on this engine than on other cars that were available with the same engine. the book lists the compression for this piston at 9.0:1. the ones that you were talking about are,in fact, rated at 8.5:1. The only physical difference between the two is the depth of the dish. Also, F.M. offers these in hypereutectic alloy, which cost me $18.00 a piece at my friendly neighborhood parts store. This is a SUPER alternative to stock cast pistons. They are stronger than cast but weaker(and WAY less expensive) than forged. In contrast, Keith Black hyper pistons are basically the same, but cost quite a bit more than the F.M. ones. Hope I helped a little.Stroker
IP: Logged
09:09 PM
PFF
System Bot
Jun 8th, 99
Eric Member
Posts: 916 From: Columbus, Ohio Registered: May 99
Dan-O, Thats roughly a 15% drop in mileage. Do you drive any differently now (I know I probably would). 200 miles per tank? I always hesitate to give mileage out. Most people bs blatantly about it. that said, here goes: i just got back from a job site trip of 308 miles. All highway, but no freeway, across Minnesota prairie. Headwind there, tailwind back. Speed of 72-85, when in the open, with a lot of passing. Yes, the radar detector was on. Air conditioning on both ways. Filled up when i left (to the top of the fill tube), and put in 12 gallons when I got back. I know, it "only holds 10 gallons". That's what will go in, when I'm at empty. That's about 26 miles to the gallon. I have regularly gotten 28-29 on these trips, and I don't drive slow. True, NO bs. Is this unusual? Would anyone recommend a cam that isi a good combo of hp/ fuel efficiency?
Mike, It gets even better. Before I did the motor swap, the CE light was on regularly. No EGR and bad O2 sensor. So my mileage was even worse. Plus I will have to compute my mileage later once it cools off here. We are in the middle of a huge heat wave for late May, early June, so Yes, the AC has been on almost all the time. Dan-O PS I think my gas tank is dented or has displaced volume somewhere, because I can never get more than 10 gallons in it, even when I stutter going up hill towards the gas station as I run out of gas I still can't put nowhere near 11 gallons.
My 86SE V6 will get 180 miles out of a full tank of gas.(heavy footed city driving) My new 88 coupe got 330 out of its first tank of gas. BIG difference. Almost makes me want to leave the 4 banger in...but i doubt it:)
I just wanted to throw my two cents worth in to the discussion. Before I bought my V8 Fiero, I seriously considered swapping a V6 into my other 4 cylinder Fiero, so I did a bunch of research on hopping up a 2.8 liter into a 3.2 liter. Stroking it with a 3.1 crank and boring it out equals about 3.2 liters. That GM high output cam is a great cam, I've heard many great things about it from other people, I would have used that cam too. For anyone considering hotrodding the V6, you just have to get the book called "Chevrolet Power" published by HP Books. It has a whole section in there about the 2.8, 3.1, 3.4 series V6's. Yes, they are really Chevy motors even though they put them in Pontiacs (and other GM cars too). I have a really cool computer software (Desktop Dyno) that is an amazingly accurate engine simulation program. You can play around with different cams, compression ratios, induction setups, etc...and see what it does to the torque and horsepower numbers. Unless you're building an engine strictly for high rpm racing, forget the horsepower numbers game. Horsepower is a function of torque and rpm. For a mainly street driven car or even road racing, you want to build a high torque engine. That's what sets you back in your seat when you pull away from a stop sign. Build a maximum horsepower engine and it will be a dog at low rpm, the ricegrinders will spank you from stop light to stop light. At 6,000 rpm or more, it will scream, but it sure won't last long if you do that very often. Torque will naturally increase with bigger displacement engines. That's why big block V8 have so much pulling power. Ok, end of sermon. If anyone wants me to plug numbers into my computer program to check out how different components may effect power output, feel free to contact me.
IP: Logged
08:13 PM
Eric Member
Posts: 916 From: Columbus, Ohio Registered: May 99
Batboy, Isn't the GM performance cam built more for upper RPM horspower? The bigger displacement should compensate for the loss of torque from the cam. I've never really heard torque numbers on a 3.2 rebuild, so I don't know what to expect. Around 200 hp with the GM cam. Torque should be around 240 ft/lbs, right? Also, freeing up the air flow in the heads and manifolds does more for horsepower than for torque. Maybe someone like Dano or Stroker can clear up this issue.
IP: Logged
08:43 PM
PFF
System Bot
lowCG Member
Posts: 1510 From: seattle,WA U.S.A. Registered: Jun 99
Batboy,did you do any research on the 4cam,3400 motor that they put in the monte carcasses? Been thinking about that one,as I don't want to put any more weight in the back. I guess it makes a bunch of torque all with only 9:1 compression,and stock exhaust.Thought that it should spin up real nice with some good headers/huge exhaust,some good headwork,aftermarket fuel/spark control/larger intake runners(like a tunnelram),11:1,good headwork,stock cams.
I forgot to mention in my last long-winded post about building a performance V6: make sure you use the HO aluminum heads with the splayed valves. Power is made or lost in the heads. Have a good machine shop completely rebuild the heads right and do a three angle valve job. If the shop knows what they're doing, some minor pocket porting increases flow too. However, the easiest and best way to increase flow and power (and even add better fuel economy) is to install a good set of headers and a good flowing exhaust system. Improving the exhaust system increases both torque (up to 20 ft/lbs) and horsepower (up to 25 ponies) over a stock engine, probably the best bang for your buck and often overlooked. Modified engines can see even greater power gains. The best part is that you don't have to pull the engine to do it.
Eric, you're pretty sharp. Yes, that GM hipo cam does sacrifice some on the low rpm range, but makes up for it in the mid to upper range. And you are correct about the larger 3.2 utilizing it better. In fact, that cam was really designed for the 3.4 engine. I don't recommend using it with the 2.8 (using a stock crank) because it kills the mid range too on the smaller engine. Horsepower and torque is probably about in the 200 range for both. But, I didn't have the exact cam specs handy when I did my calculations just now. Actually, if you can afford it and can find one, swap in a 3.4 engine, they are lot more work to fit, but they do put out great torque numbers. Ed Park's web site has some good info about that swap.
LowCG, the dual overhead cam engine that you are talking about is a high reving, high output engine that sounds like an ideal motor to use, if you just look at the numbers. But, and this is a big BUT, it just doesn't hold up well, especially to rough usage. Those heads and cams (four of them) are very expensive and temperamental. The timing belt needs constant replacement, because if it breaks at speed, you toast the engine. I would personally avoid them, too many headaches in the long run.
These are the numbers my computer program came up with for a high performance street 3.2 liter engine using: 3.1 crank, bored out to 0.030 or 0.040, 9:1 compression ratio, "fast burn" splayed valve aluminum heads, 1.72 intakes valves, 1.42 exhaust valves, .426/.454 lift GM performance hydraulic cam, headers, and low restrictive mufflers. Torque is about 200 ft/lbs at 2,000 rpm, peaks at about 220 at 4,000 and is still at about 200 at 5,000. That's a great flat torque curve, just what you want for a street engine. Horsepower peaks at about 200 ponies at 5,500 rpm. In other words, this engine pulls extremely strong all the way from 2,000 to 5,500 rpm. That's a nice broad range, especially in a light Fiero.
I'm going to retract what I said about that 3.4 liter crate motor earlier. Everything being the same, the torque and horsepower gains were only another 10 or so more. That's not enough to justify the amount of work, modification, and money spend on the swap. The 3.2 option is a no brainer for the budget minded. Just remember to use a 1985 or newer block (with the one-piece rear seal). The older ones had smaller main bearings which were weaker, plus the 3.1 crank will not drop in without a lot of additional machining and expense.
IP: Logged
11:43 PM
Jun 17th, 99
lowCG Member
Posts: 1510 From: seattle,WA U.S.A. Registered: Jun 99
Didn't know about"big block"style heads for the 60deg V6's,that has got to help out alot. I've had modern engines for the last ten years or more and have had no problems with cogged belts/direct valve actuation,actually have more bad memories of worn timing chains/gears, bent pushrods,and pulled-out rocker studs! Do you know of or have you spotted a source for info(ie.valve sizes) on these overhead cam motors in the course of your travels? Need to find out a few things before I commit to making headers and who knows what else.
hey I have a few comments to make. The HO aluminum V6 heads are good but they wont work with the stock fiero intake manifold. The intake port spacing is different. Externally the 3.4 is identical to the 2.8 so I cant see any additional problems with this swap.
LowCG, I can't find much info in my "auto library" about that 3.4 twin double overhead cam engine. I don't know for a fact, but they may use that splayed valve head? Does anyone else know for sure? I do know that replacing the cams and valve train will cost you a mint during a rebuild on those puppies. Those HO aluminum "fast burn" heads also have bigger valves than the cast iron ones and flow much better. Just remember to use the proper head gaskets. If you use regular cast iron head gaskets on aluminum heads, you'll have bad sealing problems.
PaUL, I didn't know about the Fiero manifold not matching up to those HO heads, but that doesn't surprise me. Just use a manifold that is designed for it (it won't look exactly factory, but who cares) or go to a carburetor setup (which I guess you did). Thanks for the info and I'm sure some of the others are really glad you mentioned it too.
Ok, here's another thing I forgot about. It you use a different manifold than the original Fiero's, you may have to change the fuel pressure regulator and change or modify some of the computer stuff. My advice is to do a lot of research before attempting it.
Here is another thought: supposedly, the cast iron 3.1 liter engines from the early 90's front-wheel drive GM minivans will bolt right up to a Fiero and use all the existing Fiero engine accessories and parts. About the only thing to change is to use an adjustable fuel pressure regulator and a neutrally balanced flywheel/flexplate. If you could pick up one of these cheap enough and if it was a real good, low-mileage engine, that might save you the trouble and expense of having to completely rebuild your tired old 2.8 motor.
how much does a 3.1 rebuild cost? and is it that much trouble to do the work your self or do you get better results from a professional? i know my way around motors, i race motorcycles, but i usually tear down motors and have most of the performance work done by a professional, but i have never done it on a car. is it that much harder? i know my moms mini-van blew a camshaft so we tried to replace that but something went wrong, ended up getting a 97 taurus wagon... anyway how hard is it to get timing right?
IP: Logged
03:09 PM
Eric Member
Posts: 916 From: Columbus, Ohio Registered: May 99
I'm going to start my 3.1 rebuild next week. My car has zero modifications so far. I'll post all my parts and what they cost me as I go through this ordeal. Shouldn't be that hard, I hope.
A 3.1 rebuild costs about $1,000-$1,200 about the same as a 2.8 rebuild kit. You just get around 30 more hp and it LOOKS stock!! SLEEPER. The kit is available from PISA http://www.cybercars.com/fierohq.html
