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 Rebuilding 3800 L67

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dbriviera
Amateur
dbriviera

Name : Dave Derhak
Location : VANCOUVER ISLAND
Joined : 2014-07-08
Post Count : 36
Merit : 4

Rebuilding 3800 L67 Empty
PostSubject: Rebuilding 3800 L67   Rebuilding 3800 L67 EmptySun Oct 18, 2020 2:59 am

So recently I had the intake manifold gaskets blow out on my 98 Riv with about 200,000 kilometres on it. Opening up the intake I wasn't surprised to see that they're made out of plastic and they finally died, great idea General Motors. The engine developed a knock and I replace the lifters and the con rod bearings hopefully to solve the issue. However this didn't solve the problem and upon further inspection of removal and dismantle of the engine I found the two pistons on the left side or the front of the engine as it sits in the car missing the crown all the way down to the first ring land on the first two Pistons. My gut is is that these first two Pistons are struggling to get the exhaust out because of the restrictive exhaust ports that these cars have on the manifolds especially the front manifold and I think that at the time that the intake went I ended up with severe detonation. Anyways the engine still ran but developed a pretty significant knock. The block and heads actually are still in good shape; the cylinders didn't get damaged despite the Pistons losing little chunks of aluminum that eventually ended up going out the downpipe likly lodged in the cat. I'll post a few pictures here of the engine dismantled and I'll let you now how things go. I have a couple of questions if anybody's rebuilt one of these: what head gasket do most of you guys use, multi-layer steel or composite. I priced out the parts on rockauto.com. They currently dont Have a full engine gasket set but I can piece together the gaskets that I need. I also ordered the replacement bolts that I need from ZZP including an ARP stud kit for the heads and the mains. I was looking at forged pistons however they're quite expensive so I'm opting to go to hypereutectic pistons for about one-third to cost. I've also got new LS1 lifters , pushrods and upgraded rocker arms from zzp..1.9:1 vs 1.6...the gaff is " It is a lightweight replacement rocker arm, (over 27% lighter than the OEM rocker arms!) however this is the higher 1.9 ratio version, the stock rockers are 1.6 ratio. These are intended to maximize the performance of the stock camshaft by increasing the lift of the stock cam lobe. Increasing the lift of the valve will improve airflow through the heads resulting in about 5-7% more horsepower. They will reduce the boost a bit in supercharged applications which will reduce knock."
I was shocked to see how restrictive the stock front exhaust manifold is with it having a pretty decent restriction as soon as the exhaust hits the guts of the manifold so I will put a power log on the front... the rear actually is pretty well made from the factory so I think it will remain in place. I believe that I'm going to add an oil cooler to it and a 180F t-stat and then maybe at some point I'll look at getting an intercooler kit from ZZP as well ...they're out of stock right now and I haven't quite figured out how the actual heat exchanger is going to mount as it's just kind of large for sitting anywhere on the front end of a Riviera ...I'm wondering if anybody tried this intercooler route on the Riviera and what they use for the heat exchanger.. here are some photos so far...Rebuilding 3800 L67 20201012
Rebuilding 3800 L67 20201010
Rebuilding 3800 L67 20201011Rebuilding 3800 L67 20201012
NOTE ... the cylinders are really shiny so the picture shows the reflection of the damage piston area making it look bigger. The top of the first compression ring is visible..

Rebuilding 3800 L67 20201014
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LARRY70GS
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LARRY70GS

Name : Larry
Age : 64
Location : Oakland Gardens, NY
Joined : 2007-01-23
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PostSubject: Re: Rebuilding 3800 L67   Rebuilding 3800 L67 EmptySun Oct 18, 2020 8:51 am

PM Aaron (AA).  He rebuilt his and found a guy that did a great job.  His high mileage engine was damaged from detonation, the rod bearings were hammered by it.  The PCM can only protect the engine so much with KR.
Hyperutechtic pistons are even more susceptible to detonation

_________________
98 Riviera SC3800  All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
Best MPH, 116.06 MPH, Best ET, 11.54
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albertj
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Location : Finger Lakes of New York State
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PostSubject: Re: Rebuilding 3800 L67   Rebuilding 3800 L67 EmptySun Oct 18, 2020 2:50 pm

A Plog would be great, but you will get joy *just* from porting the front cast exhaust manifold. I did that.

It'll be nice to see what you do about a heat exchanger for your intercooler.  I'd probably mount something behind the front air dam with the plumbing coming through the drivers side front in vicinity of the existing air box.  You could get some space (and noise) going to a mustang-type cone filter for the air intake and bung the air sensor into the existing air horn somehow.  I've never tried that, however, no interest, but it's fun to think about for a moment.
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dbriviera
Amateur
dbriviera

Name : Dave Derhak
Location : VANCOUVER ISLAND
Joined : 2014-07-08
Post Count : 36
Merit : 4

Rebuilding 3800 L67 Empty
PostSubject: Re: Rebuilding 3800 L67   Rebuilding 3800 L67 EmptySun Oct 18, 2020 3:48 pm

LARRY70GS wrote:
PM Aaron (AA).  He rebuilt his and found a guy that did a great job.  His high mileage engine was damaged from detonation, the rod bearings were hammered by it.  The PCM can only protect the engine so much with KR.
Hyperutechtic pistons are even more susceptible to detonation

Ok thanks i will contact him
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AA
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AA

Name : Aaron
Age : 43
Location : C-bus, Ohio
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PostSubject: Re: Rebuilding 3800 L67   Rebuilding 3800 L67 EmptyMon Oct 19, 2020 10:25 am

Hi Dave. We used fresh OE cast aluminum pistons (L67). These are fine for running quite a bit of boost. I was at 13-14 PSI, and have run up to 16. Problems occur when you go lean and severe knocking ensues, which is what happened to mine.

For what it's worth, I've read hypereutectic pistons are brittle, and not recommended for boost, but there may be exceptions here.

Diamond makes a set of forged pistons for a pretty penny, which can tolerate lots of knock, but a downside is they have piston slap when cold. It's just something I read numerous times from those running them. Not a huge deal for a race car, but not something I wanted for my daily.

Also the OE head gaskets are very good in the L67. We used these and of course the updated OE metal LIM gaskets for the rebuild.

If you've never had your fuel injectors cleaned and flow tested, this is a good time to do so. https://www.mrinjector.us/

Love the extra mid/high power from 1.9:1 rockers. One of my favorite mods for these engines!

_________________
'98 SC Riviera • 281k miles • 298 HP/370 TQ • 0-60: 5.79s • ET: 13.97 @ 99.28 • 4087 lb • 20.1 avg MPG • Nelson Ledges Lap: 1:30
3.4" pulley • AL104 plugs • 180º t-stat • FWI w/K&N • 1.9:1 rockers • OR pushrods • LS6 valve springs • SLP headers • ZZP fuel rails
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