Twin-charged Bonneville Update - Page 5 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

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Old 12-15-2009, 01:47 PM   #41
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Very nice. You obviously have a ton of time into that beast. Great work. So, you gonna drive that thing around with street slicks on the front or what? LOL
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Old 12-16-2009, 03:10 PM   #42
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Interesting new development:



Look real close in the mirror, right between the head and block... that little burned spot in the head gasket. Right now it'* just a slight tick, not even enough to create a misfire code! it still made 380whp after four runs on the dyno. I drove the car all weekend and this week. I guess I need to order a set of Cometics for it.
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Old 12-16-2009, 11:32 PM   #43
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Cometic hg'* are on the way. i am thinkng I will polish the combustion chambers while the heads are off. I also plan to radius the chaber around the spark plug... that seems to be where the gasket keeps popping. And from what i have seen, everyone else has a problem in the same area. there seems to be a sealing problem right behind the plug... one of the 3800 vendors contributes this to relatively thin deck thickness on the heads. Iam going to look into adding a steam hole in the block and head, see if there is water under there. I know the older 3.8/4.1 had sealing problems in the turbos and steam holes fixed it, for a while till boost went ever higher. That'* when the RWD turbos added two extra head bolts.
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Old 12-23-2009, 12:52 PM   #44
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Tearing it down today, I'll post some pics later.
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Old 12-23-2009, 12:54 PM   #45
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Good luck.
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Old 12-23-2009, 04:57 PM   #46
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Yo.. Jeff I'm moving to ATL by July.. You think you can work on my 88 SSE. I want to Turbo this [email protected]$%T !!
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Old 12-24-2009, 02:55 PM   #47
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Pictures tell the story.

Burned thru #4:



Large amount of oil in cylinders, primarily #3 and #4:



The culprit, intake manifold machine finish is crappy. Look close at the machining "swirl" marks. The thin rubber around the ports was not sealing and they were sucking oil in at the bottom.







I think I finally found the source of my oil consumption! This also explains why even with a totally different engine, it blew #4 three times. This ported LIM was used on both engines! ot only is the affected cylinder lean, but oil fouled. Oil does NOT compress and it burns hot as hell, both contributing factors in pre-ignition and detonation. I had oil problems on the first engine, too. I also have an idle issue where the IAC is closed and the engine still runs at 850-900rpm. I could NEVER find any external vacuum leaks, so I knew it had to be internal, just never had the time to trace it down.

I am going to have the LIM skim-cut to smooth it out. I'm going to polish the combustion chambers, too, while it is apart. The chamber will receive a radius cut on the affected (blown-out) edge to bring the chamber wall to the edge of the h.g. This will reduce the tendancy to create a hot spot in the chamber. I'll radius back the heart behind the valves, too.

Everyone have a good Christmas! See you back here next week.
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Old 12-24-2009, 03:00 PM   #48
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Good job finding the problem. I'll have to remember this and check any LIMs I pull off a engine.
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Old 01-04-2010, 11:46 PM   #49
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Quote:
Originally Posted by huntsville88SSE View Post
Yo.. Jeff I'm moving to ATL by July.. You think you can work on my 88 SSE. I want to Turbo this [email protected]$%T !!
Hey Man, sorry I forgot to reply. I think the Series I engine would LOVE turbocharging. Remember, it'* essentially the Series I FWD engine that propelled the '89 Trans Am turbo to unheard-off performance for a V-6 at that time! Pontiac engineers used the FWD heads on the venerable 3.8 RWD block due to clearance issues with the F-body strut towers. With an intercooled T3 and copious amounts of boost, the '89 TTA was the fastest production car GM had built in decades (if not ever!)
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Old 01-04-2010, 11:52 PM   #50
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I disassembled the heads today. I had a more than a few bad valve seals... lesson learned: if you pull the heads, change the seals. I did not last time around and they are no good.

I am planning to install new stainless steel oversize valves, re-shape and polish the combustion chambers, and port-match the intake ports and manifold. I was having a problem with boost-stacking at 5600rpm, hopefully this will help it breathe a little better at higher rpms. I'll post some pics as work progresses.
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