PFF - Pennock's Fiero Forum, PDA Edition

4.9 or 3800sc? (Page 1/1)

allansmithee

APR 14, 11:30 AM

Hey everyone, I'm thinking of swapping my fiero with a 4.9 or 3800sc but Im not entirely sure whats involved in either swap. I've only done one engine swap before so I have limited experience with such affairs. I'd also like to keep it manual. I've looked around and the benefit I see from the 3800 is upgradability, but this is going to be my daily. So which engine would be best for my application

Spadesluck

APR 14, 12:20 PM

First, welcome to the forum!

Second, there is no "best". It will all depend on your wants. Both motors can be done with a manual and both motors are pretty reliable. Beyond that they are very different. The 4.9 is an older platform now and could be a bit more complicated because of that. If it were me and I only had to choose between these two motors, I personally would go with the 3800SC. The 3800SC also has a lot more power capability if that is what you are after as well.

treborerellim

APR 14, 03:35 PM

Go with a 3800, I sure wish I would have.

Dennis LaGrua

APR 14, 05:22 PM

The way I see it the 4.9L is a significant upgrade at the lowest cost and is a fairly easy swap. The typical Cadillac owner drove them gently. The 3800SC offers more potential for upgrades at a higher cost but getting very hard to find with reasonable mileage. IMO the folks that owned the supercharged engines drove them hard. Both will get you hwy gas mileage in the 25-30 mpg range.

------------------
" 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 "

allansmithee

APR 14, 07:29 PM

Getting some good info so far, but I still have some questions. What kind of milage should I look for in either engine? I actually have a deville in the yard with a 112,000 mile 4.9 that I don't drive much and was considering selling it.

hnthomps

APR 15, 10:06 AM

I cannot answer on the 4.9 but do have two 3800 SC engines (Series II and III) installed with manual transmissions. Tunes on both cars are conservative but the Series III has a lot of extra goodies and the Series II is basically stock except for the pulley. Either of these cars appear to give me about 25-26 mpg when driven in a somewhat reasonable manner while running the A/C. I do use 91 octane gas to help prevent potential engine knocks.

Nelson

Dennis LaGrua

APR 16, 10:32 PM

quote

Originally posted by allansmithee:

Getting some good info so far, but I still have some questions. What kind of mileage should I look for in either engine? I actually have a deville in the yard with a 112,000 mile 4.9 that I don't drive much and was considering selling it.

4.9L Cadillac 200HP @275 ft lbs of torque. Like the 3800SC the engine uses premium fuel. As for usable mileage, it all depends on how the engine was maintained in both cases. IMO the 4.9L is less subject to wear as they are not revved that high. Its a high torque engine. Before I do a swap I do a cylinder leakdown test on the engine. In the case of my 3800SC 61 miles I expected and received like new readings but I also got them on my 4.9L with 61K miles. If you just want high torque at the lowest cost the 4.9L will provide it and offer good hwy mileage. If you are building for the 1/4 Mile then the 3800SC is better.

olejoedad

APR 17, 09:04 AM

In a Fiero application with proper gearing (manual trans or Seville automatic) the 4.9 runs on 87 octane with no spark knock.