The 4.9L Cadillac swap used to be very popular going back 15 years. Many Fiero owners still have them so it was time to get that powertrain out of storage and get in in my 85GT convertible project. After buying it 15 years ago I did a cylinder leak down test on this and it showed that the cylinders were in fine shape, actually in almost new condition. Finally started it up two weeks ago and it sounded great. A few more items need to be attended to and my 85GT California Convertible project will be road worthy, Some wonder why I did this swap when there are many more modern choices to choose from. All things considered this is why 1. Engine was purchased before the LS4 became popular. 2. Cost was very reasonable at $600 for the engine, trans, harness and ECM. 3. Install was very easy to do as it used GM mounts, one generic engine mount and a WCF engine mount. Axles were fitted. IIRC Cavalier std units. 4. This Cadillac aluminum block V8 engine weighs in at nearly the same as the Fiero 2.8L so handling won't be altered much. 5. It provides 275ft lbs of torque starting at a low RPM and 200 HP. 6. The 0-60 times are quick and this is where most of my driving will be, In stock form with a 4800 redline, its not a 1/4 mile engine. 7. Highway cruises are very comfortable and quiet with the short exhaust. At 70 mph the engine will see something like 1750 RPM. Hwy, gasoline mileage can be in the high 20's if not 30. 8. It uses regular gas but I will tune it for premium. Still have all the eprom programming tools here but we are using flash memory with a Moats adapter. 9. The 4T60e has a good reputation for reliability and its matched to the engine 10. The swap looks good at the shows. The negatives. 1. The distributors on these 4.9L V8 engines are very complicated. They contain the both the coil, trigger unit and a cam position sensor. They have a reputation for failure so I replaced it with a new one and ordered a spare just in case. 2. In general parts are starting to get scarce, New oil pumps are no longer available. 3. Performance upgrade parts are scarce and I believe this engine doesn't respond well to them. 4. Its just not an LS engine. 5. Rocket arm supports have been know to develop cracks.
Notice the battery power shutoff switch with the 5 amp fuse across it. There is a very good reason for using one on the 84-86 Fieros. ------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
[This message has been edited by Dennis LaGrua (edited 09-18-2024).]
Awesome Dennis and I'm ignorant on a "85GT California Convertible".....?
The California Convertible company was active in the late 80's and early 1990's They made a kit that you put on a Fiero notchback. It was a big job cutting off the roof welding a subfame underneath for support, attaching the header, the mechanism and then the canvas top. Here is one already finished. I thought that the look was the best of the convertible top options for the Fiero.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Hey Dennis, do you happen to have a picture of the car with the top down? I'd love to see it.
I have a friend that has done a lot of work on these engines. He built one that he ran off hydrogen, and another one that put out some pretty crazy power (NA)... both in Citation X/11s. If you did want to do any modifications to it, I seem to recall that the biggest bang for the buck was upgrading it with an Allante intake (runners?), that they were somehow bigger than what was normal on the 4.9s in the other Caddys, and also there's a specific porting job that can be done to the cyl heads to really wake it up. If you're interested in can try to get more information for you... but probably all stuff you can find online... don't know if that's of any interest. But I think it'll be cool to see this thing running.
Hey Dennis, do you happen to have a picture of the car with the top down? I'd love to see it.
I have a friend that has done a lot of work on these engines. He built one that he ran off hydrogen, and another one that put out some pretty crazy power (NA)... both in Citation X/11s. If you did want to do any modifications to it, I seem to recall that the biggest bang for the buck was upgrading it with an Allante intake (runners?), that they were somehow bigger than what was normal on the 4.9s in the other Caddys, and also there's a specific porting job that can be done to the cyl heads to really wake it up. If you're interested in can try to get more information for you... but probably all stuff you can find online... don't know if that's of any interest. But I think it'll be cool to see this thing running.
The top on my convertible is not attached to the convertible frame as yet. Its stacks up something as you would see on a 90's Mustang. I will put pictures up when complete. As for the 4.9L Cadillac V8; I don't view it as having real high performance potential. Porting the heads and adding a high lift cam could potentially help but I judge the aluminum rocker supports and head sealing as weak areas. It's recommended that you run a bit of cooling system sealer in this engine. I was told GM did this before it left the factory and recommends it when you change the coolant. All and all I like the engine and it will be a fun street, show and highway car, I will be happy with 200HP@275 ft lbs of torque.A subframe has been added but IMO the roof being cut off doesn't make the car solid for much more power than this. .
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Originally posted by Dennis LaGrua: ... Porting the heads and adding a high lift cam could potentially help but I judge the aluminum rocker supports and head sealing as weak areas.
The Allante rocker supports are made of steel, but are a bit uncommon. (Edit - there are two sets on ebay right now.) One of the guys near me has ported his heads to a fare-thee-well. I think he said he got a total of 7 lbs of metal out of the ports. He let someone (a performance engine builder) look at his work. Apparently, this builder was impressed. I don't think the engine is back together yet, but it's gonna be interesting.
[This message has been edited by Raydar (edited 09-19-2024).]
The Allante rocker supports are made of steel, but are a bit uncommon. (Edit - there are two sets on ebay right now.) One of the guys near me has ported his heads to a fare-thee-well. I think he said he got a total of 7 lbs of metal out of the ports. He let someone (a performance engine builder) look at his work. Apparently, this builder was impressed. I don't think the engine is back together yet, but it's gonna be interesting.
Yes the Allante 4.5L did have steel rocker supports. The set on ebay is being advertised as aluminum..... Hmm. While the 4.9L engine should have potential for more power, again those aluminum rocker supports are IMO a handicap. AFAIK, many of the 4.9L performance builds that we have read about over the years have not done well. The only mod that I will add is an MSD ignition. That system really add wider double sparks below 2000 RPM. I have the box and the quick install harness. The other mod is my exhaust that is Spintech and nearly a straight through. Since the build is a ragtop I'll stay with the stock engine and just tune it for Sunco 94 octane gasoline that available here. Figure that I could bump the timing up a few degrees. IIRC you own one of the original Ed Parks builds. How is that doing ?
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
The valves in the 4.9 heads are not large enough to support much porting work from what I've read. I would think that a turbo sized to build boost above 2500 rpm would be of good benefit.
Dennis, is the tranny working properly on the convertible?
Yes the Allante 4.5L did have steel rocker supports. The set on ebay is being advertised as aluminum..... Hmm. While the 4.9L engine should have potential for more power, again those aluminum rocker supports are IMO a handicap. AFAIK, many of the 4.9L performance builds that we have read about over the years have not done well. The only mod that I will add is an MSD ignition. That system really add wider double sparks below 2000 RPM. I have the box and the quick install harness. The other mod is my exhaust that is Spintech and nearly a straight through. Since the build is a ragtop I'll stay with the stock engine and just tune it for Sunco 94 octane gasoline that available here. Figure that I could bump the timing up a few degrees. IIRC you own one of the original Ed Parks builds. How is that doing ?
I remember back in the late 90s when a lot of convertible kits were being offered. I was seriously considering one, even though at the time I was in no financial position to get one. But... I'd always heard the frame / chassis flexing was almost unbearable, and very noticeable.
I'd imagine you'd almost have to weld in some serious frame supports from front to back, and then a bolt in cross-brace if you wanted to really overcome that flex. Can you see / feel the doors moving as you're driving around?
Honestly, I wonder how the 3rd and 4th gen F-bodies did it... since it's basically a monocoque body with a front subframe. When I cut the roof off a 1978 Cadillac Eldorado back in the late 90s... the car was already designed to have been made a convertible from years prior (even if was no longer offered that year)... so the "subframe" went all the way back to and behind the doors.
The valves in the 4.9 heads are not large enough to support much porting work from what I've read. I would think that a turbo sized to build boost above 2500 rpm would be of good benefit.
Dennis, is the tranny working properly on the convertible?
Have no plates on the cars as yet. Engine starts right up, there is no smoke and sounds pretty good. Still need to attend to a few items on the top kit like smoothing in the header and attaching the weatherstrips. Then its off to a top shop to get the canvas installed. Car will move in drive and reverse so we will know about the trans come road test time. The trans was rebuilt by a guy from a transmission shop so we can only hope that it shifts properly. The stock power, torque will be enough for me and if a different ride is needed the 3800SC is 100% ready. Yes a turbo will wake up additional power and while having a full chip program setup I'm not a great OBD1 tuner so we will let that be. OBD2 is really my programming forte. Years ago PBJ ran 12's in the 1/4 mile with his turbo setup. That car seems to have disappeared along with all the swaps John (Rockcrawl) did. To answer the question about a subframe, I welded together a special frame from 1 x 3 square stock that goes from front to rear with a removable cross member. Should do the job for the power that the car will have. Hope to have her on the road by late fall.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
I remember back in the late 90s when a lot of convertible kits were being offered. I was seriously considering one, even though at the time I was in no financial position to get one. But... I'd always heard the frame / chassis flexing was almost unbearable, and very noticeable.
I'd imagine you'd almost have to weld in some serious frame supports from front to back, and then a bolt in cross-brace if you wanted to really overcome that flex. Can you see / feel the doors moving as you're driving around?
Honestly, I wonder how the 3rd and 4th gen F-bodies did it... since it's basically a monocoque body with a front subframe. When I cut the roof off a 1978 Cadillac Eldorado back in the late 90s... the car was already designed to have been made a convertible from years prior (even if was no longer offered that year)... so the "subframe" went all the way back to and behind the doors.
i had a 1989 camaro convert.they doubled the width of the rocker panels.i added subframe connectors.and then someone slammed into the back.
Yes the Allante 4.5L did have steel rocker supports. The set on ebay is being advertised as aluminum..... Hmm. While the 4.9L engine should have potential for more power, again those aluminum rocker supports are IMO a handicap. ... IIRC you own one of the original Ed Parks builds. How is that doing ?
Mine is just fine. Charged up the A/C about two hours ago, since it's going to be in the 90s this weekend (I saw 93 today), and 80s most of next week. I have added the Allante intake and rocker rails, and a NV T550 5 speed (aka "Beretta Getrag".) Tweaked the tune to accommodate both. Of course the gearing is not optimal, but it's still an absolute riot to drive. The automatic did nothing quickly. I disliked it so much I almost sold the car.
Good luck with yours. That's a cool car. I still think the 4.9 is a viable swap, even though not many people are doing them any more. We'll have to see what my buddy's does, when he's finished with it. I may try to borrow some of his porting knowledge/skills, but he's also going waaaay beyond with other mods, too.
Gotta finish my LQ1, first.
[This message has been edited by Raydar (edited 09-20-2024).]
The 4.9L Cadillac engine is an easy and inexpensive way to 200HP and a whopping 275 ft lbs of torque. Its seems to have faded from popularity. I would guess because this is so because powertrains are becoming scarce. Its an all bottom end powerhouse, that doesn't lend itself to performance mods real well, and it may be a dinosaur but the engine has a reputation for light weight, torque, reliability and great HWY mileage. The weak spot only being the inside distributor cam sensor but that is easily replaced. On the street the 4.9L Caddy is fun to drive and on the highway it cruises effortlessly, quiet, and comfortably at speed. You might not win very many 1/4 mile races with it but on the 1/8 mile it is fast. Today where LS4, LSX9, LZ9, LZ4 high value engines are now becoming popular (but difficult swaps) the 4.9L engine swap is no longer in vogue but I would venture to say that dozens if not hundreds of 4.5L/4.9L swaps have been done and are still out there. I probably have only $2000 in this swap ( due to rebuilding the transmission) but with a solid low miles powertrain you could do it for less than $1000. I only paid $600 for mine as there is low demand for this engine. I will do a separate build thread on the California Convertible project when it is done,
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
The 4.9L Cadillac engine is an easy and inexpensive way to 200HP and a whopping 275 ft lbs of torque. Its seems to have faded from popularity. I would guess because this is so because powertrains are becoming scarce. Its an all bottom end powerhouse, that doesn't lend itself to performance mods real well, and it may be a dinosaur but the engine has a reputation for light weight, torque, reliability and great HWY mileage. The weak spot only being the inside distributor cam sensor but that is easily replaced. On the street the 4.9L Caddy is fun to drive and on the highway it cruises effortlessly, quiet, and comfortably at speed. You might not win very many 1/4 mile races with it but on the 1/8 mile it is fast. Today where LS4, LSX9, LZ9, LZ4 high value engines are now becoming popular (but difficult swaps) the 4.9L engine swap is no longer in vogue but I would venture to say that dozens if not hundreds of 4.5L/4.9L swaps have been done and are still out there. I probably have only $2000 in this swap ( due to rebuilding the transmission) but with a solid low miles powertrain you could do it for less than $1000. I only paid $600 for mine as there is low demand for this engine. I will do a separate build thread on the California Convertible project when it is done,
I don't know what happens "really" when a car ends up in the junkyard. I've seen it... most times they take the engine out with a claw (which seems like it totally destroys the engine), but I know a lot of these motors end up in rebuilding lots where you can order them from a re-manufacturer. I assume there's enough of these cars that the motors are still fairly prevalent.
With no education on these motors at all, my first impression is: - Big heavy old Cadillac V8 - 90s horsepower, why bother - It's going to be big, and if I'm going to do that, why not go with an LS
Of course, I realize now (as you've mentioned) that these engines are actually pretty light, and weigh about the same as a fully outfitted 2.8. It seems like an awesome engine swap. I wonder what the difference is between the 4.5 and the 4.9? The 4.5 in the Allante seems more performance oriented... odd that they get more power from a lower displacement motor... but I guess that's the same as the W41 Quad-4 vs the LD9 Twin Cam.
In short this 4.9L swap has been a learning experience. I tuned for a few extra degrees of timing (using 94 Octane gasoline) and will add an MSD ignition that really helps to about 2000 RPM that is in the middle of the power band, With the improved ignition and a free flow exhaust I expect to be pushing 210-220 Horsepower and still at 275 ft lbs of torque. Thats plenty for a street/show/cruise night V8 convertible car. I would have preferred the more modern LS4 but this engine was in storage for about 15 yrs and it was time to do the swap. The aluminum, block engine only adds 50 lbs to the car as Joe has stated. Hope to share some driving impressions soon.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
In short this 4.9L swap has been a learning experience. I tuned for a few extra degrees of timing (using 94 Octane gasoline) and will add an MSD ignition that really helps to about 2000 RPM that is in the middle of the power band, With the improved ignition and a free flow exhaust I expect to be pushing 210-220 Horsepower and still at 275 ft lbs of torque. Thats plenty for a street/show/cruise night V8 convertible car. I would have preferred the more modern LS4 but this engine was in storage for about 15 yrs and it was time to do the swap. The aluminum, block engine only adds 50 lbs to the car as Joe has stated. Hope to share some driving impressions soon.
That's only 5 laptops in the trunk worth of weight!
Now you just have to update your signature, Dennis!
Originally posted by 82-T/A [At Work]: ... With no education on these motors at all, my first impression is: - Big heavy old Cadillac V8 - 90s horsepower, why bother - It's going to be big, and if I'm going to do that, why not go with an LS
Of course, I realize now (as you've mentioned) that these engines are actually pretty light, and weigh about the same as a fully outfitted 2.8. It seems like an awesome engine swap. I wonder what the difference is between the 4.5 and the 4.9? The 4.5 in the Allante seems more performance oriented... odd that they get more power from a lower displacement motor... but I guess that's the same as the W41 Quad-4 vs the LD9 Twin Cam.
The 4.5 in the Allante and the 4.9 in the Deville both make ~200 HP. They even use the same injectors. The 4.9 with the Allante intake is guesstimated at 220 HP. I'll let you drive mine when you're here this weekend, if you want.
The 4.5 in the Allante and the 4.9 in the Deville both make ~200 HP. They even use the same injectors. The 4.9 with the Allante intake is guesstimated at 220 HP. I'll let you drive mine when you're here this weekend, if you want.
I haven't been around here much in the past many years, but it looks like a lot of the same user names I remember from years ago. I stumbled across this thread looking for information on a car i just picked up. I haven't thought about the 4.9L in about 20 years, and now somehow I ended up with 2 of them. One of them is an 88 coupe that I am trying to get restored.
[This message has been edited by Jncomutt (edited 12-20-2024).]
While "normal" mods are not well received by the 4.9, it doesn't mean it cannot be modified. Folks just need to thing outside the box and spend some money. (that's the kicker, at the end of the day there are of coarse better ways to spend money) Send the heads of to a machine shop and install bigger valves and better springs. Get a custom cam built to your specs not just an off the shelf delta cam. Make your own headers to flow, not just a muffler. Have bigger injectors built for your application. Then on top off all that, run a stand-alone ecm to control everything.
Is that all worth it, probably not, but you can very well have a stronger performing 4.9.
Steve, I took out 3lbs of material out of both heads.
