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Engine SwapEverything about swapping an engine into your Third Gen.....be it V6, V8, LTX/LSX, crate engine, etc. Pictures, questions, answers, and work logs.
I've been planning out this swap for some time myself. On the engine mount issue, there is a sure fire way to make sure they are bolted in a the right place on the subframe. All one needs to do is cut out the template from any 78-87 G body frame. I was fortunate enough to have a 78 Pontiac Grand Prix equipped with a 301 Pontiac V8 at my disposal. All the necessary brackets and mounts were already there for the taking. As has been discussed here before, the Pontiac V8 clamshell mounts differ from the SBC mounts. The Pontiac mount is longer, narrower and more shallow than the SBC mount. The mounting holes on the frame as a result are slightly different. The G body frames were drilled for many different application due to the engine sharing that was going on within the divisions of GM at the time. The F body was drilled for only two mounting positions. Using the SBC holes as a starting point, once you obtain the template from the donor car, lay the template over the subframe and modify your holes to accept the Pontiac V8 mount. This will ensure the engine sits at the right location and that the engine geometry is correct
I've been planning out this swap for some time myself. On the engine mount issue, there is a sure fire way to make sure they are bolted in a the right place on the subframe. All one needs to do is cut out the template from any 78-87 G body frame. I was fortunate enough to have a 78 Pontiac Grand Prix equipped with a 301 Pontiac V8 at my disposal. All the necessary brackets and mounts were already there for the taking. As has been discussed here before, the Pontiac V8 clamshell mounts differ from the SBC mounts. The Pontiac mount is longer, narrower and more shallow than the SBC mount. The mounting holes on the frame as a result are slightly different. The G body frames were drilled for many different application due to the engine sharing that was going on within the divisions of GM at the time. The F body was drilled for only two mounting positions. Using the SBC holes as a starting point, once you obtain the template from the donor car, lay the template over the subframe and modify your holes to accept the Pontiac V8 mount. This will ensure the engine sits at the right location and that the engine geometry is correct
Unless you plan on running some conventional heads and custom intake, you're going to be hard pressed to make power out of that 301. And 2nd gen engine mount brackets fit over the mounts perfect, you just have to relocate the mounts slightly.
I am going to use a 1975 vintage 400, not the 301. Since the 301 uses the same basic geometry as the 400 including mount bosses, it will be a natural fit. The Pontiac clamshell mounts will allow for another half inch of air cleaner to hood clearance. By using the SBC mount it puts the engine slightly forward of where it should be had Pontiac used their own V8. See the below pictures. The first one is the template I cut out of the G body. I laid this on the F body subframe and used the SBC bolt holes to hold the template in place. I used a white spray bomb to mark the holes on the subframe. Note the template shows where the SBC bolt holes go after marking the subframe. The template can be used to mark both sides of the subframe.
@Wonderbird 84: I'd be careful with the '75 blocks. They have thinner castings. They're good for their purpose, but as for building a power machine you'll want a different year. My block is a '75 but heads and rotating assembly are from a '69, and I'm going for more of a show car than a rocket ship.
As for progress on this thread, I am currently buying a house, and plan on having this beast breathing this summer, but it is put on the back burner for the next couple months. Don't get me wrong tho, this won't be forgotten, it'll be 3-4 months max before I make some progress again.
@Wonderbird 84: I'd be careful with the '75 blocks. They have thinner castings. They're good for their purpose, but as for building a power machine you'll want a different year. My block is a '75 but heads and rotating assembly are from a '69, and I'm going for more of a show car than a rocket ship.
As for progress on this thread, I am currently buying a house, and plan on having this beast breathing this summer, but it is put on the back burner for the next couple months. Don't get me wrong tho, this won't be forgotten, it'll be 3-4 months max before I make some progress again.
My engine will be a fairly mild build. I'm using 6X-8 heads and a Q-jet with no more than a RA-III spec cam. I want a fun driver, not a full tilt race car. Part of my goal is to make it look like the engine belonged in this car from day one. I saved all of the G-body spec brackets, A/C components and wiring harness to help facilitate this.
Well It seems about time to start posting on this thread again. Have had a very busy year between buying my first house and losing my mother, and the Firebird moved to the back burner for a while. After moving into my home and getting my Bird up to my house, it's a new chapter for the thread here.
With this project sitting for so long, I had some rust in the tank. And my fuel tank was in a pretty sad state to begin with. So I ditched the factory tank and bought a 4th Gen tank from a 2000 Camaro 3.8 Liter. As of right now, I'm running a carburetor, so the 50-60 psi the 4th Gen pump would put out would be wayyyy too much. AND the fuel level sensor on the 4th gens read 40-250 ohms (I know this has been covered numerous times) when our 3rd gen gauges read 0-90 ohms. So I had to "engineer" my fuel pump together. I started with taking the whole pump apart.
Disassembled GM fuel pump module.
Last edited by firechicken1992; 10-24-2015 at 01:14 PM.
At this point, you may notice the 4th Gen pump has two lines coming out of it. One goes to the top of the module to feed to the motor. The other routes to the bottom of the module. This keeps the "pocket" full of fuel to prevent starvation. Well the lumbering 3rd Gen pump has only one output. This is where I had to get a 'lil creative.
I used a vacuum tee: 3/8x3/16x3/8 part number 717663 from O'Reillys to create the second feed for the pump module.
The part that connects to the bottom of the module needs a male connection, so I cut a portion of the original line to secure to the 3/16 hose.
The 3/16 hose going to the bottom of the module. With the pressure being so minor, I felt comfortable securing it with a good zip tie.
Now, mating the two together is perhaps the easiest part.
I had to trim and position the hose clamps in a way to make sure they wouldn't contact the wires when installed. Don't want them rubbing through the insulation.
The 4th Gen pumps have two wires for the level sensor, a hi and lo signal. The 3rd Gens, of course, have one wire. This is an easy fix.
A quick 3rd Gen fuel pump and level sensor diagram. Note how the wire leaving the level sensor splices to the same ground wire as the pump. This then grounds out under the center console.
One of these tools is really handy to have to remove terminals from connectors. You may be able to achieve the same results with a micro screwdriver or small paper clip.
I simply removed the wire I wasn't going to use.
What I did with the wire leaving the level sensor, was combine it into the same terminal as the motor's ground wire. On the left is the motor's power wire. Not shown is the pink/purple level sensor input wire.
I bought the new terminals from NAPA. Part number: 725157.
At this point, I'm glad I still had my 3rd Gen pump, as the connector to the actual pump is different on the 4th Gens. I used two more of those terminals from NAPA and recycled my connector from the original 3rd Gen pump
Fired the motor up. Im able to regulate it down to a nice 8-9 PSI and with 5 gallons of premium in the tank, my gauge reads spot on at a touch over 1/4 tank.
Fired the motor up. Im able to regulate it down to a nice 8-9 PSI and with 5 gallons of premium in the tank, my gauge reads spot on at a touch over 1/4 tank.
Not recently unfortunately. Been tight on finances around my house and life has been kicking me in the rear. Hopefully as we pull out of spring I can get some more work done on it. Nearly there.
Are you at all concerned about how that plastic T will survive in gasoline?
I am very much concerned hahahaha. Im hoping this will last for just the summer. I need to throw a driveline under it and a shifter and I should be good to roll, and I want to convert to EFI so I'll be able to use the higher pressure pump in the future with the 4th Gen tank. I'm hoping since it was rated for vapor it'll survive.....but I know liquid gas is a different animal.....
Nothing as of late. Been buried with life and house work.
Hoping to revive this thread this spring. When I started this project I cut a lot of corners. I've been going through the car and fixing anything janky I had previously done. Been accumulating parts to continue this project when I can.
So it's been quite a while since I've touched this car or this thread.
Some back story:
When I started this project I was 17. I had taken a few highschool shop classes and thought I had the knowledge to do an engine swap. Between looking at my past posts and undoing all the shortcuts I had taken....boy.....was I wrong.
Now having proper knowledge, technique and financial means, I'd like this to be my official start on this project. There is enough ratty and chopped up 3rd Gens, I don't need to add to it, especially when there are so many other skilled and knowledgeable owners on this forum.
So here is my first post as an educated and passionate gear head.
1992 Firebird Base
Pontiac 400 Swap with MPFI powered by Megasquirt. Just got my intake manifold. The Gold Box should be in next month.
I am extremely interested in seeing any report or information about how that SPFI system works on your poncho block. I was planning on doing something similar and I've got so many questions. How is it at idle, on cold start ups, at the light, sitting in a parking lot? How's the throttle response? Would you say fuel efficiency is better or worse? Do you think it's a big, marginal, or minimal improvement over a carburetor, or is it not as good? Does it sound any different, or is it impossible to tell the difference? All the little things that you notice while driving a car around, you know? The kind of things most people take for granted when building a car.
11-23-2014, 09:32 AM
