3800SC Rebuild (Page 1/1)
ChuckLS1 FEB 10, 07:41 PM
Within the next couple of years I'm planning on doing the 3800SC Swap in my 88 Formula. The 3800SC is currently in my daily driver (2000 Grand Prix GTP) with 176k miles. It will probably have close to 200k on it when I do the swap. As far as rebuilding it what should I look out for? I plan on having a shop do the work as long as I can find a good one. I have read on here that if the bottom end looks ok, don't touch it. I plan on using the stock automatic transmission which I plan on getting rebuilt with stronger parts if possible. Thanks!

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Chuck
88 Formula W/fastback
2000 Grand Prix GTP

DimeMachine FEB 11, 09:52 PM
First question - why are you planning to rebuild?
Dennis LaGrua FEB 12, 06:15 AM
For some reason the 3800 has a tough reputation to rebuild correctly and is known for spinning rod bearings. I do not know why this is so but it could be that bearing clearances are very critical in this engine or it could be that oil pressure must be carefully maintained within spec.

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" 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 "

MarkS FEB 12, 02:28 PM

quote
Originally posted by Dennis LaGrua:

For some reason the 3800 has a tough reputation to rebuild correctly and is known for spinning rod bearings. I do not know why this is so but it could be that bearing clearances are very critical in this engine or it could be that oil pressure must be carefully maintained within spec.




The old 3.8 was the same, bearing clearances are critical. From what I was told by Buick engine machinists, there is a tendency to set up these engines like SBC's and they absolutely do not fair well like that.

[This message has been edited by MarkS (edited 02-12-2021).]

ChuckLS1 FEB 13, 09:43 PM

quote
Originally posted by DimeMachine:

First question - why are you planning to rebuild?



Well its going to have close to 200k on it. I want to make sure it lasts. Plan on putting a smaller pully on the supercharger for more power.
Dennis LaGrua FEB 13, 10:09 PM

quote
Originally posted by ChuckLS1:


Well its going to have close to 200k on it. I want to make sure it lasts. Plan on putting a smaller pully on the supercharger for more power.


Rebuilding a high mileage engine is a good idea but on the 3800 I would just make sure that the bottom end is built to exacting tolerances. Some builders here have enjoyed success and maybe they can chime in, while places like ZZ Performance stopped selling rebuilt short blocks as guys were blowing them up.
All we know is that they worked well from the GM factory, millions were produced and they lasted a long time. If the same formula is followed then you should be OK.

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" 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 "

olejoedad FEB 14, 07:38 PM
Unless you've had a lower intake gasket failure/coolant leak, the bottom end should be good.

However, 3800's have a tendency to make the round cylinder bored egg-shaped. At that point, it's toast.
ChuckLS1 FEB 14, 10:18 PM

quote
Originally posted by olejoedad:

Unless you've had a lower intake gasket failure/coolant leak, the bottom end should be good.

However, 3800's have a tendency to make the round cylinder bored egg-shaped. At that point, it's toast.


I did have that gasket and the supercharger gasket replaced last year in addition to the coolant elbows. I also got a rebuilt supercharger snout installed.

I want to do it the right way, replace all the gaskets, new water pump. Want to make sure it can handle additional horsepower.
BadNewsBrendan FEB 15, 10:59 PM
On top of what others have said would recommend replacing main seals and if there's a ridge worn on the harmonic balancer where it touches the seal id replace that too. First L67 I refreshed dumped oil out the main seal at high rpms and spun rod bearings.

I rebuilt the engine with a reman crank, new rings and everything and has made it a couple thousand miles so far but I think it's too early to say if the bottom end rebuild was a success or not.

Good luck with the swap! Its fun and wish I had an 88.