Decision help for my Fiero - V6/60.

[82-T/A]

Hey guys, I'm sure a lot of this has been discussed before, so I apologize for anything I might be beating to death.

I'm in the process of restoring / rebuilding my 1987 Pontiac Fiero SE / V6, and I'm at the point where I have to make a decision on the engine.

What I have now is:

2.8 that's undergone a 3.1 crank / rod swap.
- Hypertectic (sp?) pistons w/ .040 overbore
- 1.52:1 roller rockers
- Port / Polish
- 17lb injectors, slight tune.

I ran that motor breifly before I started tearing it down, and it ran "OK" but really took a performance dive as soon as it hit about 4,800 rpms... I mean, hard-core. The car would accelerate quite well, and then it fell off a cliff so to speak. I figured out that it was the cam selection I had, which was predominantly more for a truck. I ended up being a Crane Cam 272, which I was going to put in, but haven't gotten around to it. I only put about 1,000 miles on that motor, and supposedly it had 9.2:1 compression based on what the machine shop (who assembled it) told me.


Now, looking at some threads on Pennocks, I'm entertaining another possibility. As I understand it, I can basically use a 3400 bottom end, and the entire Fiero top-end. This will give me more horsepower, but more important, I'm hoping it'll be a smoother running motor. My 2.8, when stock, ran quite well... really ran like a top, and I'm hoping the 3400 will be even better than that. So here's where my questions are:


1 - What is the difference between a 3400 and an early 3500 block? Can I actually use a 3500 block with the gen-1 heads?

2 - If I do go with a 3400 or 3500, what cam shaft can I use? Only real reason I want to go with a 3400/3500 is for the larger displacement, and the roller-cam. Is there a difference between cam specs on a roller cam vs a flat tappet cam? I'd like to get something that's similar to the h272 in terms of duration, etc, since as I've been told, the larger the duration, the more air it will allow into the combustion chamber... which is better considering the restrictiveness of the Fiero's plenum.

3 - If I go with a 3400/3500, can I still use ALL the stock Fiero stuff, as in, the distributor, the single ignition coil, etc?

4 - Finally... what am I better off doing in terms of reliability, performance, driveability, and fuel economy. Try to re-work my 3.1 conversion motor, or put that on a stand to look pretty, and go with my 3500 idea?


Thanks guys, and just for the record... my goal is really to keep my Fiero looking very original / stock, but improving performance / quality. I'm hoping with the roller cam, the motor will be smoother running, have a nicer smoother sound, etc. I know the Fiero intake will be a huge restriction, but I'm OK with it. I'm not expecting something that'll run 13s... but if I can break into the high 14s with this set-up, and a Getrag, I'll be very happy.


Thanks guys,

Todd

[trotterlg]

You just can't get iron heads to flow well enough for any serious high rpm power. A larger displacement may make things ever worse if you keep the stock top end and intake. Going to a bigger cam will end up decreasing the effective compression ratio due to more overlap, so, unless you up the compression some what you gain with the cam you may loose with the lower compression. This is why there is a recommended compression ratio listed with hot cams. Larry

[82-T/A]

You just can't get iron heads to flow well enough for any serious high rpm power. A larger displacement may make things ever worse if you keep the stock top end and intake. Going to a bigger cam will end up decreasing the effective compression ratio due to more overlap, so, unless you up the compression some what you gain with the cam you may loose with the lower compression. This is why there is a recommended compression ratio listed with hot cams. Larry

Thanks Larry, I probably wasn't very clear. The swap to the 3400 with the 2.8 top end would also entail going with a set of 3.4 DOHC pistons, which when used with the 3400 would give me a pretty high compression. Most of the guys who have done this, have basically shaved down the center of the piston somewhat, and a nice range is usually around 9.6:1 that most people who have done this, are looking to achieve.

The iron heads in this situation, aren't the bottle-neck... it's really the Fiero 2.8 intake that's the problem. It flows better than any other stock 2.8 intake, but that's not really saying much. I never noticed it when the Fiero was totally stock, or even when I improved with bolt-ons (better exhuast, etc)... I finally noticed it when I bumped displacement from 2.8 to 3.1 (or 3.2 I suppose). That's when it really hit me. That said, I've converted my car from an automatic to a manual... so I'll have better control of when it shifts in order to keep it in it's range. I say I've converted it to a manual, I've actually done EVERYTHING except swap out the actual transmission. But I just haven't gotten to the engine compartment yet.

[Kaiju Senso]

Personally I don't see the point (sorry.) As you've noticed with your 3.1 build, the Fiero top end just falls on it's face by 5k rpm and what you want to do is make it faster without addressing the main issue? Seems like a lot of work to end up with a little better bottom end power but the same top end issues. I'm assuming you're not updating to the 7730 ECU because you want to keep the distributor right?

I just skipped all of that hassle and went straight to a 2005 3400 with OBDII.

[trotterlg]

I just don't think you will be very happy staying with the iron heads in any case. Even the best port job going doesn't come close to what a stock set of aluminum heads will do. But then yours will look stock. Having more displacement will just compound the breathing problem most likely. Larry

[robertisaar]

i'll repeat what others are saying.... bumping up to even more displacement while using the gen1 heads is going to limit your RPM range even further.

the 7730 can drive a distributor quite easily. the 90-92 3.1 F-bodies are one place to look for settings/wiring.

[82-T/A]

Thanks guys, I really appreciate the advice. But just for posterity sake... the iron heads will most definitely not be the bottle-neck here, it's absolutely 100% going to be the Fiero's factory intake. I'm simply hoping to relive my late teens and early 20s when the Fiero was my first car, and I drove it everywhere... to the beach every weekend, other stuff... hahah.

I'm only looking to get high 14s out of this car, but more importantly, I really want the most reliable, driveable, stock looking 87 V6 Fiero I can get. So the stock heads and the stock intake are going to be definite for this situation.

Don't feel bad for me, I've got a 1969 Olds 455 big block putting out 600ft-lbs of torque that I am looking to put in something, and I also have a really low mileage 2002 Crown Victoria LX that runs mid 14s all day long. So I'm not just looking for speed... just to make the car really smooth, lots of decent power, and something that's going to be reliable.

I am very interested in the 7730 though. A lot of people on the Fiero list are swapping to this ECM. As long as I can get it to work with my stock harness (where all I have to do is swap around pins), and maybe add an extra sensor or two, this would be awesome. Does it still make use of the MAP? Or is it a MAF system, because I was hoping to keep my intake totally stock looking with the plain old rubber boot from my Holley TB unit to the air cleaner.


Thanks again guys, really appreciate it. still would like to know though if the 3400 and the 3500 blocks are still basically the same, meaning, can I still bolt on the cast iron heads to a 3500? I know that I'll need 5.56 pushrods... but just wanted to make sure everything else was still the same.


Thanks!

[TurboGTU]

The 3400 block will help unshroud the valves if you decide to go with larger valves and a hefty port job. If you have a spare intake manifolds and know a good aluminium welder have him make the ports bigger.
I know iron heads are the worst but even a good porter can make some flow. Take for example the ford 2.3l Lima head. Those flow pathetic but a guy on Turbo Ford.org named boport makes them flow like a 3*00 head.
3500 lx9 should be the same as 3400. You'll need new mounts

[caffeine]

Unless you need to have the stock heads for looks, I would just go to a full 3400 or 3500 swap. It should be a high 13 sec to low 14 sec car with a stock 3500. It's really not much extra work if you already have the engine out, and IMO its also more reliable.

I ran my fiero for two weeks with the stock 2.8 and had problem after problem so I ditched it. I've now put 30,000 kms (since a little less than a year ago) on my 3500 and it never let's me down.

I agree with what others are saying; increasing displacement will only make the high-rpm power worse if you're keeping the stock top end, because it will have to flow even more air at all rpms. In fact, the power may drop off even sooner than before.

[trotterlg]

But, if you go with your swap with the stock Fiero top end and big bottom end, you may be able to enter it in some tractor pull contests and have some good pulls. Larry

[Purple pit]

http://engine-parts.com/

That will be a fun site for you.
Your power fall off is normal do to the stock cam and intakes.
A 3400 or 3500 would be a worthless engine with 2.8 intakes on it. Plain and simple. If you have a junkyard near you go there and take a 3400 upper of and look at the size of the ports. They are twice the size of a 2.8/3.1L. Even the early 3100's have bigger ports than the 2.8.

It would be like putting a stock 350 intake on your high powered 455. You might be able to get away with some Extrude honing on the 2.8 intakes, but that would be pushing it still. The TB and plenum will be a bit small too. Really you are down to building the 2.8 or dropping in a 3400/3500.

I don't understand how more compression will help a 3400(with 2.8 heads) when you can't get enough air to the cylinders in the first place.

[Kaiju Senso]

3500 lx9 should be the same as 3400. You'll need new mounts

The block will mount right up to the stock Fiero location without issue (give or take some grinding to the bracket or oil pan ridges depending on what oil pan is used.)

As you can see 82-T/A, people seem to agree that it's a whole lot of work for nothing and in my opinion what you seem to really want to fix is that power drop off at 4800 rpm.

[ericjon262]

82 ta, I hope you're not another lost cause like 85% of Fiero.nl...

[caffeine]

Ya, you will NOT need new mounts. Some minor cutting is needed and the stock motor mount bolts up. Dog-bone mount may need to be custom but you might be able to use the stock one with a low mount alternator.

[ericjon262]

Ya, you will NOT need new mounts. Some minor cutting is needed and the stock motor mount bolts up. Dog-bone mount may need to be custom but you might be able to use the stock one with a low mount alternator.

Don't even need to fab a dogbone if you run the fiero timing cover and accessories... the brackets that bolt to the head have to be re-drilled for the earlier drive, but that is simple enough.