FAQ @ FastFieros


Facts Answers and more Questions


Low Mount 3800 ALT!

Low mounts in stock today. Newest design has tension belt assembly, cleaned, and blasted. 

3800 SuperCharged or 3800 Natural Aspirated engine FAQ for the DIY


This document is targeted to the consumer that needs to know how things work, and  wants to be educated in the swap process of putting a 3800 based engine to the Pontiac Fiero.


There are many places on the internet these days with information on the installation of engines in a hybrid environment. Its concept to take an engine from one car, and decide to put it in yet another car of different year model and even make. While some swaps have been around for years with lots of development targeted to this installation process, not all things are done the same way by everyone.

There are "opinions", there are facts, and then there are idea's. Everyone must try something in order to really find out accomplishment or failure. You learn something new everyday, or its a very boring day if you ask me. You learn from mistakes and help someone else not make the same mistake if you are a good person. We all learn a lot from bringing theory into real-world practice. Ask anyone who’s learned to fly a plane after using only a flight simulator — there are just some things that you can only learn from practical experience.

More about opinions: "UNLESS" you have tried and tested a method, or you have emailed the GM engineer team that knows the correct answers, then you have an opinion. I have both opinions, and I take the time to find the answers from the correct sources. There is one individual in the Fiero community that likes to brag about all his degrees and certifications in the automotive industry, yet he lacks practical knowledge and application. Being text book smart is great,  but actually doing the work and testing one self will lead to discoveries that either someone who wrote the book is wrong, or they just plain wrote what they wanted you to read, and not what was completely true. If you have an idea try it, but don't beat up on someone else's idea's because you think it is wrong. If no one tried to put 3800's in Fieros, we might not have this great install we have today. Someone is always first, then there are always follower's after that. Be an inventor and share your ideas. Here are my idea's and opinions about installing 3800's to Fieros. Please note that my project page is loaded with pictures upon pictures of my installs. You can clearly see that 2002 thur today, my installs have evolved to a very nice art, and cleanliness of the installation of the 3800 SuperCharged engine to the Fiero.

The most common questions are :

1. ENGINES: What engine do I find in the salvage yard for my installation. There are several 3800 based engines. I will cover what I consider the easiest to find and it has all the "right" stuff to start with. First, we want power and dollar for dollar value in what we do. The 3800 SuperCharged engine in Series II 99-03 from the Pontiac Grand Prix GTP is about the best you can buy. It has the correct oil filter housing, the correct supercharger tensioner assembly, the correct engine coolant temp sensor, and a few other small details that make this engine the best choice to look for.

2. TRANSMISSIONS: So now we have our engine thoughts. Next is the transmission. In the same GTP is the 4T65eHD. Again the 99-03 makes the best choice for ease of time and research on what transmissions are available. What if your Fiero is a manual transmission Fiero? You will most likely be wanting to keep that manual transmission. You will hope it is a 5 speed GETRAG from the 86-88 Fiero's. The Isuzu is an ok choice also. The 4 speed MY8 from the 84 Fiero is not that bad, but very hard to find these. The most popular manual I have installed 3800's to is the GETRAG 5 speed.

3. WIRING/PCMs: This one item is the "make it" or "break it" of the project. What computer will you run? Is OBDI or OBDII better? First thing to consider is that if you run a 4T65eHD automatic, you will have to run OBDII wiring and computer. If you run a 4T60e transmission, I am the only person to date I know of that has programmed a 3800SC to this transmission on OBDII. You have to use 1997 wiring, and PCM for this. I do the wiring for OBDII systems only. I do not support OBDI computers with programming, nor wiring. Why? OBDII is designed for the Series II and Series III engines. There are 4000+ parameters in a PCM to control the engine and transmission on OBDII. I am not sure the number on OBDI, but it far less. Do you really need all these parameters? No. Only the important ones that make the engine run the best, and the transmission shift the best. There are so many good reasons to run 99+ wiring, and 99+ code in PCM's. It all has to do with signal quality, and design of engine components working with the code they were designed for. Lets take the MAF (mass air flow) meter. This device contributes to the IPW (injection pulse width) alot. This device in a Series II engine is calibrated to the software code in an OBDII computer. The code in a OBDI is not calibrated to this device. You can cheat the tables in OBDI to a point to make it work, but you are cheating yourself in performance. Then there is IFR ( Injector Flow Rate) vs MAP. OBDI does not even allow for this one signal parameter, so modifying to enough power were 42 pound injectors are needed is going to be very difficult to get a proper tune. This one subject I could write a book on the differences, and what is an advantage vs disadvantage. Think about it this way. OBDI is dead. Zero development in GM or anywhere else for that matter. OBDII has about 2 more years and OBDIII will be on the way. CAN is already in the cars and trucks today, and this will be the future of OBDIII. Dont be left behind in your wiring and PCM controlling your 3800 Series II or Series III engine.

4. Axles: Get the axles from the GTP if you are running the 4T65eHD. They dont fit the Fiero directly, but one of them (drivers side) will be used to make the right side axle. If you are using the Fiero manual transmission, then you will use the axles from this. I will try to expand more on this later with pictures.

5. Mounts: Yet another problem to decide on. Poly or rubber? Rubber will NOT hold a 3800 SuperCharged engine in a Fiero that is used to launch from a red light like you are drag racing. With gentle street driving, there are some rubber mounts that might work. I dont use rubber mounts in my installs. I use Poly Urethane with nice steel casings. These mounts should hold a STOCK 3800SC with no dogbone support. If you add a 3.4 pulley to your engine, this is not stock, and you will need dogbone support on the top side of the engine, or lower side at the tailshaft housing.

6. Dogbone: Yes, you need one if you do not stay with a completely stock engine.

7. Exhaust: Another area I can write a book on what works, and what really works great. Point A to B solutions using the stock Fiero routing method is no longer accepted by me. I dont like the CAT or any part of the exhaust running behind the gas tank area, and under the cradle. This causes so many heat related issues, and other problems. I perfer to use the stock 3800SC exhaust over headers that were designed around specs that hurt the performance of the engine vs helping it. The only 2 products that I really like are SLP headers, and TOG headers. TOG just went out of business either short term, or perhaps long term as of 1-15-06. SLP makes a great header, but I dont like the coating they use, and I dont like the slip joint connection for the cross over. I have lots of pics of different exhaust on my website project page http://www.fastfieros.com/projects .

8. Low Mounting Alternator: There is some speculation documented on the internet about the heater core support of an engine, and what it does. I say heater core support because there is one area that effects another area. The alternator sits on a large aluminum bracket assembly. This alternator conflicts with the decklid of the Fiero. This gets complicated here, so please read carefully. The 97 and some 98 GTP alternators are large. This will not clear the decklid on the coupe nor the fastback models. Now, the 98 had a change to a smaller version, and this will clear the coupes, but not the fastbacks. Same with the 99-06 GTP or about any other model of car the 3800 comes from, the alternator is smaller, and it will clear the coupes decklid, but not the fastbacks. So, in comes the idea to move the alternator to the lower area where the power steering pump was at. We call this "low mount alt" assembly. I build two different types of low mounts. Each supports the different alternators, and it also has some different function of tensioning. Low mount alt bracket for using the Fiero alternator is one way. I build this assembly out of the Fiero V6 alt bracket, the 3800 alt bracket, the 3800 aluminum dogbone bracket. We are using the Fiero alt as the piviot point to tighten the belt. The old tensioner is welded stationary in this application. Now, the second version supports the 99-06 alternator found on the 3800 engines. This alternator is smaller, it is stationary, so the tensioner is used to keep the belt in tension. I build both versions usually based on what the customer wants to use for an alternator and what is available to the customer for usage. Alot of engines do not come with accessories, so the consumer will want to use the alternator from the Fieros 2.8 V6 engine. Now we move to heater core support because if you low mount, it will change this alot.

9. Heater Core Support / Why that little transfer port is in the alt bracket assembly: This area has created some opinions to be publicly targeted as "improper" method of installation procedures. Why attack someone with your opinion about how something is done? Why not apply a proper test environment and back that opinion up with test data showing it is right or wrong to do something? Well, here at FastFieros, I do test all aspects of my procedures and methods of application. When this attack started coming from one of my competitors, I decided to email the GM engineers I was talking with about the EcoTec projects I was working on. They in turn got me in contact with the support group for the 3800 engines. I cannot overuse my communication with GM people, as they tend to not answer emails very often anyway. So, what is the problem? The low mount delete's the heater core input and outputs of the bracket assembly. You ask so what... Well, the bracket assembly has a drilled water passage. Its a 5/32nds hole in most of the brackets, and 3/16ths in others. I remember the first day I saw the thing cutting open those brackets to make the low mount assembly and thought, humm, must be there for some reason. It is drilled and plugged from the backside where you cannot see the plug. Why go to all that trouble for a little hole smaller than a typical pencil. My first thought was water circulation to prevent pressure from building in the system. However, it made no sense to this because the routing of the cooling system as a whole. Picture attached here >


As we can see here, the flow is from the intake manifold to the alternator bracket, to the heater core, back to the alternator, and into the water pump housing on the suction side. Now, why have that little hole there if the flow is in a circle. Well, the heater core is not always circulating coolant. Also, I have received so many of these alternator bracket assemblies, there are versions out there that are plugged on the inlet side, and one version where it is plugged on both sides of the inlet and outlet. So, if we plug the inlet and outlet of the alternator bracket assembly, the little transfer hole is all that is left for the coolant to flow from the intake outlet to the water pump return side of that housing. What does this little 5/32nds hole do? Pressure relief? No. It keeps circulation when those inlet/outlets are blocked so a cooling effect is maintained on the alternator bracket assembly. The alternator creates alot of heat. Aluminum is a great heat dissipater but, when you have 200 degree coolant circulating in the material also, it creates a better cooling effect. Remember, some heater cores have valves to stop coolant flow completely, and some applications of the 3800 in cars do not use the inlet/outlet of the alternator bracket assembly. The flow is kept by this 5/32nds hole drilled between those two points of water circulation. GM engineers have always looked for ways to cool items in cars. Heat is a car worse enemy inside the engine, and outside in the engine compartment. Lets look at the Fiero. GM engineers put a blower fan in the right rear of the V6 85-87 cars to blow cooler air on the alternator, and the coil. It does not seem to help much, but hey, they tried. In 88, they left this device out of the car to reduce production costs, and it did not work very well anyway. Then another example of GM engineers using coolant to heat a device. The throttle body. They have coolant passing though tubes on the Fiero to heat the throttle body. Same way on the throttle body of the 3800's. They have coolant passages that pass coolant from the intake to the supercharger, then to the throttle body. All these efforts to cool and heat at the same time. Cool the supercharger, heat the throttle body.

Ok, now the return side. On 87/88 Fieros, you have it made. The return is built into the right side coolant tube. 85/86, you will need to tap the return at the water pump housing with 3/4 NPT TAP, and use a 3/4 NPT brass fitting, with a 5/8 nipple. Then a nice piece of copper tubing bend in a couple of ways to match the existing line running on the right side frame rail coupled with a short piece of 5/8 heater hose. Looks great and functions very nice.

10. Thermostat housing: Here we discuss what thermostat I use and why. The Fiero thermostat housing is a nice unit. It provides easy access to the thermostat, and it allows a fill point at the engine. The 3800 thermostat is under a housing that does not allow easy access, and it does not provide a fill point. I modify the Fiero thermostat housing to provide 3 functions. Fill point of coolant to engine with ease, change thermostat or remove for diagnostic purposes, heater core support output to heater core. These 3 functions are critical to a happy cooling system on the Fiero. Air in the system creates steam, steam causes extreme hot spots in the cylinder heads and leads to blown head gaskets. You must get all the air out of the cooling system in a Fiero, and it is difficult. Heater core output to heater core is just that. It allows coolant flow in a easy way to of hooking up to the Fiero existing 5/8ths heater hose. Thermostat to use. I like the Fiero thermostat because it can be purchased in several different temperature ranges. I use 180's. There is a huge difference in quality of thermostats sold for this style of housing. The stainless steel version is the strongest. The brass version is the weakest. DO NOT use the brass version if you can find the stainless steel ones. The brass versions have been known to collapse. It pushes up on the cap hard enough to bent inside the housing. This leads to another point of problem I have heard many times. The cap is bending the housing. Well, the housing is getting weak from rust most likely. I have seen about 300 thermostat housing for the Fiero. I can tell you I have seen some thin enough I can bent the lip edges with my fingers. These housings rust when a V6 engine sits for long periods with no coolant in the system. The coolant has rust inhibitors to keep steel from corroding. Please check your thermostat housing carefully. I bead blast all housings for the welding process, and repaint every one I build.

11. Fuel Pump: Here is yet another area I have been attacked on from others on the internet. Again, they provide only theory's from text books and no real data to support their claims. I have taken the time to send a fuel pump to Kinsler Fuel Injection for flow data on my pump of choice. I use the EP376 AC Delco part. Why? Well, its a AC Delco part for one thing. I have never purchased a bad one, and never to this date had to remove one, nor any customer called and told me the fuel pump went out. So what is this EP376? It comes from the 94 Chevrolet Corvette with an LT1. Now, you would think if a fuel pump can deliver fuel to a V8, it can support a V6 easy. Well, that could be true, but we are dealing with a supercharged engine, with 38 pound injectors. So what is the data and what is so recommended beyond this EP376? The Walbro 255. Now there are several versions of the 255 to start with. NOT all are created equal in flow. Flow? What is flow compared to pressure? I could write a book on flow vs pressure, but it is beyond the scope of this FAQ at this time. Lets just say, we want about 204 lbs per hr on the injectors. How do I know this, and what is the flow data? I spent the money for the test data to make sure I was not creating a problem for someone, and know that my installs are the best I can make them for people. Here is the email directly quoted from Greg at Kinsler Fuel Injection....


Typical boosted engine on gasoline runs at approx. 0.6 - 0.7 BSFC, SO to produce 290 hp you would need approx. 175 - 203 lbs/hr.

Guess your injectors at 38 lbs/hr @ 45 PSI would mean with 48 PSI each injector at 100% would be 39.2 lbs/hr per injector X 6 = 235 lbs/hr ---- so at 75% duty cycle you would have 176 lbs/hr to the engine / 87% duty cycle you would have 204 lbs/hr to the engine.

These numbers should be well within a nice safety zone.



Greg Murchison

Fax # 248-362-1032

gregm#kinsler.com www.kinsler.com

Kinsler Fuel Injection

Now, the test data provided on this pump...


1) There are approx. 6- models of Walbro 255 pumps Earl is out of the

office till next week, I talked to Mike we did not run a Walbro at

your PSI spec's.

Here are the AVERAGE flows of three different models

PSI       lbs/hr      Amp

0            500         4.2

20          450          5.4

50          365          8.4

70          300          12.0

100        120           18.0

2) Injector flows MUST be based on the test pressure.

There is NO true standard. So when someone states a flow, they

MUST state the pressure which that flow was measured at.

Same problem with pumps - people give false info and even talk about

it incorrectly. They don't really understand how the fuel system works.

Biggest problem - people qoute flow numbers without any pressure load

on pump. Look at above numbers - you can see how important knowing

the pressure is.

Most OEM injectors are referenced at 43 or 45 PSI - BUT that does NOT

mean they are.

Most people when talking injector flow are referring to static, or full open.


NOW, the EP376 test data


All standard pump test are 13.2 volts

Your pump

PSI     lbs/hr     amps

0           363         6.2

10         325         6.7

20         298         7.2

30         275         7.7

40         247         8.1

50         217         8.6

60         188         9.2

70         148         9.8

80          80          10.3

Average Walbro 255

PSI     lbs/hr

0         500

40         368

80         230

If you need more info, let me know



Greg Murchison

Fax # 248-362-1032

gregm#kinsler.com www.kinsler.com

Kinsler Fuel Injection


SO, in conclusion to this issue, the EP376 supports the 3800SC to about 325HP with no problems. People who are modifying there engines to more than 325HP are most likely already going to know they need a Walbro 255, but the average consumer that wants a nice quiet pump, easy to purchase at any GM dealer, or even AutoZone carries these, the EP376 will work fine. I should know, I have put about 25 of them in 3800SC applications with ZERO failures or problems tuning. Its called practical application, and not text book reading.

I get asked very often... " How much of the engine, transmission, wiring do I get from the donor car." The best answer is ... ALL OF IT today. I buy complete drop outs. What does that look like ? Here is one...

As you can see, this is the engine, transmission, axles, wiring from the engine compartment, PCM, MAF, all sensors, all accessories.... these all add up if you dont get them in one place. The shipping will kill you unless you are going somewhere really local and getting the parts yourself. Then, please, with todays gasoline at $3.00 a gallon, this has to taken into consideration as part of your project plan if you are driving any great distance that burns alot of fuel. Get it all in one place if you can. I sell complete powertrains for this very purpose to eliminate that hunt for parts here and there concept.

There are many more questions I want to answer about the installation of the 3800 to the Fiero, but I need to end at this time. Please call me anytime 10am - 10pm central time, 7 days a week. My phone number is my cell phone number. I don't like to spend 75 minutes on the phone talking about installations procedures, but I certainly have many times. You have questions and idea's, I have answers and opinions to help you...

Good luck !







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