LG4 to L69 conversion

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LG4 to L69 conversion

Postby Bandit » Wed May 08, 2013 1:25 am

Hello everybody,

I hope this is the right forum for this - I think it's a kind of "perfomance modification"... ;)

As I mentioned in this thread (=> viewtopic.php?f=29&t=2228), I currently have problems with the LG4 engine in my 1982. First of all, I want to say, that I will fix this problems because I want to keep this engine running. I will keep you updated in the other thread, maybe it is interessing for a few people in the future.

As a kind of "crazy project", I wanted to convert to LU5 (Crossfire injection) in the future. I primarily thought that it is only necessary to replace everything from the intake manifold up, the wiring harness, the fuel pump in the tank and the ECM. I've got all this parts, including a 1983 LU5 body shell with gas tank and exhaust system. It's a big puzzle, but it should be possible.

After reading the gorgeous (!!!) information from brother al (=> viewtopic.php?f=30&t=1907) about the different engines, I found out that pistons, camshaft, heads, etc. are different on the 1982 LG4 compared to the LU5. This information saved me a lot of trouble, because I did not know that there were so many differences between the long blocks! :) I know for now, that there is no way to "convert" my 1982 LG4 to the LU5 setup.

I am working on this cars for about 10 years now. In Germany, this is a kind of "unusual" car and hobby, but for me, it's a passion. I love these cars since I was a kid and so I still want to go my way with the LU5 conversion. I know this is unusal, too - most of the people get rid of the crossfire injection and replace it with a carburetor setup.

To keep a long story short, I've had working on a lot of cars and I've got a lot of parts in my garage. I've got also a 1986 Firebird V8 with LG4 in the past and saved the engine. It needs a complete overhaul, but I think the components are ok, solid and usable.

So when I look at the information from brother al above, it seems the big puzzle could be solved by combining the things this way:

  • Cylinder Block: 1986 LG4
  • Pistons: 1986 LG4
  • Crankshaft: 1986 LG4 (?)
  • Camshaft: No idea (1986 LG4 is different than 1982 LG4 and 1983 LU5)
  • Heads: 1986 LG4 (?)
  • Intake Manifold: 1983 LU5
  • Distributor: 1986 LG4 (?)
  • Gas Tank: 1983 LU5 (Fuel pump only)
  • Exhaust system: 1983 LU5 (preferable: a new aftermarket system)
  • ECM: 1983 LU5
  • Wiring harness: 1983 LU5
What do you think? Did I oversight something? I know that I have to replace the tachometer in the dash, but all of the other gages should work?

Of course, this is not a project done in a few days, this is a huge thing. I've got all the parts above lying around, so there is no need for a hurry.

I will highly appreciate every kind of input! :)

Marcel
Marcel from Germany. Addicted to 3rd Gens since 2003.

1982 Trans Am (5.0 l LG4)
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Re: LG4 to LU5 conversion

Postby eightytwo » Wed May 08, 2013 5:28 am

Well that's a really crazy project :shock: Wouldn't it be wise to just fix the LG4 issues?
>>> 08/82 Norwood <<< Pontiac Firebird Trans Am 5.0L V8 3-speed auto.
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Re: LG4 to LU5 conversion

Postby Bandit » Wed May 08, 2013 5:34 am

eightytwo wrote:Wouldn't it be wise to just fix the LG4 issues?

Bandit wrote:First of all, I want to say, that I will fix this problems because I want to keep this engine running.

Yes, I will!!! :) This here is just a project for the future, I just want to check out if my thoughts are realistic.
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Re: LG4 to LU5 conversion

Postby L695speed » Wed May 08, 2013 6:19 am

Honestly, I think you may have an easier time converting the LG4 to L69 specs. L69 parts or alternatives are easier to come by I think. And you get a more fun car to the boot..
Chris__1984 Trans Am. Working on a 383, and LT1 T56 swap, Eibach Pro Kit Springs (isolator delete), UMI suspension, 36mm/23 mm sways, rebuilt front end, Polys all round. LS1 Front brakes, PBR rears. 16 inch formula wheels. Otherwise will be bone stock.
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Re: LG4 to LU5 conversion

Postby eightytwo » Wed May 08, 2013 8:22 am

eightytwo wrote:Wouldn't it be wise to just fix the LG4 issues?


Bandit wrote:First of all, I want to say, that I will fix this problems because I want to keep this engine running.


Bandit wrote:Yes, I will!!! :) This here is just a project for the future, I just want to check out if my thoughts are realistic.

Just fixing the LG4 issues would be more realistic :) even tunning the carb and adding some better exhaust system for an example. L695speed's idea isn't bad. I would go for that 8-) But still you're free to do what you want to your car.
>>> 08/82 Norwood <<< Pontiac Firebird Trans Am 5.0L V8 3-speed auto.
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Re: LG4 to LU5 conversion

Postby Dens71TA » Wed May 08, 2013 8:35 am

As someone who took an originally LU5 car that a previously owner converted to carburetor after the CFI caught fire and then converted it back to CFI, DON'T DO IT! Crossfire injection sucks! Rough running, sometimes hard starting, vapor locks between the front and rear TBIs in hot weather, random hesitations, the torque converter locks up to early causing studdering up hills, the list goes on! If I was doing it again I would have converted the car to a factory LG4/L69 carburetor setup. It took GM until the late 80's to figure out TBI.
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Re: LG4 to LU5 conversion

Postby 8289ta » Wed May 08, 2013 11:31 am

I never had that many issues with my LU5. She finally took a crap due to a bad fuel pump, but all these years it ran like a champ. It is just a TBI setup. I never had vapor lock issues. The only time it was hard starting or rough running was when it had a problem - such as a vacuum leak.
I took the opportunity to make a few upgrades. If you need to change internal parts, I would use the opportunity to upsize the engine to at least a 350. I know if I ever need to pull the 305 for any reason, it won't be going back in. I am going to build up a mild 350 or 383 for her.

But they can be made to run good. But considering you already have the carb, it would be so much easier to get that set up to run properly. You could make some performance enhancements such as exhaust and intake changes.
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Re: LG4 to LU5 conversion

Postby Bandit » Wed May 08, 2013 6:10 pm

Thanks a lot for all of your input!

I always loved the look of this Crossfire engine bay with this dual air filters... but I heard that these engines got a few problems, too. And I know that such an conversion (LG4 => LU5) is a huge process involving ALL primary components of the car.

I never thought about an L69 conversion, that would be an interesting option, too. I will get some information about the L69 and then I will think about it. As I said, I am not in a hurry - before I start to build a second engine considering for a swap, I will get my car running properly.

Best regards,

Marcel
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1982 Trans Am (5.0 l LG4)
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Re: LG4 to LU5 conversion

Postby brother al » Thu May 09, 2013 6:43 pm

I imagine finding a good L69 in Germany will be a PITA! To make it easier, hunt out a complete/good '86/'87/'88 LG4 engine as the foundation... those LG4's got the same L69 Flat top pistons, but a much weaker cam profile. All of the other parts are cake after that. They were in a bunch of GM rear wheel drive vehicles in the 80's, Chevy Caprice/Impala/Monte Carlo/Camaro/El Camino/ Pontiac Grand Prix/Firebird/Bonneville, some Olds 4 door Cutlass models, and in a bunch of the Full Size station wagons... Stay Away from the Truck engines... many will have cracked heads and abuse issues.
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Re: LG4 to LU5 conversion

Postby Bandit » Thu May 09, 2013 11:03 pm

OK, first of all, you satisfied me all that an LG4 to L69 conversion (more or less) makes more sense than converting a LG4 to LU5... I think I will go this way in the future to get some extra hp. First of all, I have to get my LG4 work properly (seems to look good after doing a few minor works on it).

It started out to get real interesting because I currently HAVE a LG4 from a 1986 Firebird V8. It's complete with ECM, wiring harness, etc. if there were many differences compared to the 1982 LG4. So, no searching and finding necessary. That's good, because as you already said, it's nearly impossible to find a L69 around here.

Thanks a lot for all of your input!

Marcel
Marcel from Germany. Addicted to 3rd Gens since 2003.

1982 Trans Am (5.0 l LG4)
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Re: LG4 to LU5 conversion

Postby brother al » Fri May 10, 2013 10:57 am

The LG4 engine itself really didnt change much between '82 and '86, but some of the important parts used on/in them did. The intakes were aluminum. The Compression Ratio was bumped up in 1986 because GM added the flat top L69 pistons to the LG4. They also added ESC, Electronic Spark Control aka a Knock Sensor (all L69s had this). GM added an electronic fuel pump in addition to the mechanical unit (all L69's had this), The LG4 cam profile changed a little bit, leaving a lot of room for improvement and despite the compression bump, the '86 LG4 actually lost power because of the cam profile. The '86 ECM/PROM is a very good combo.

A lot of power is obtainable if you upgrade the camshaft to an L69 spec to the engine.
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Re: LG4 to LU5 conversion

Postby Bandit » Mon May 13, 2013 6:31 am

I've got all of this! That's great - are you able to tell me the numbers from ECM/PROM I need? I've got a few of them and want to put the right next to the engine for the further work... ;) So if I understand all the things correctly, I have to look for another camshaft and can use all other parts from the 1986 engine, right?

I've also found a set of 305 TPI exhaust manifolds including the Y-pipe... ;)

Marcel
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Re: LG4 to LU5 conversion

Postby brother al » Wed May 15, 2013 11:10 am

Sounds like you are well on you way..., but almost all of the info you need is in a thread I wrote:
viewtopic.php?f=30&t=1907

I will dig out my parts list and give you the rest of the part numbers missing from that article, just give me several days. If I dont respond by Monday, PM me to get my butt into gear.
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Re: LG4 to LU5 conversion

Postby Raptor » Fri May 24, 2013 7:26 am

The guy who gave me many parts from his L69 in France may still have the heads, pistons, intake, carb and other stuff (the exhaust manifolds and HEI are on my car though, the dual snorkel intake is on a knight rider replica near Paris). He rebuilt his motor completely and upgraded it quite a bit just to notice the block had a huge crack :/ So he went with a 350, here's his car : http://www.youtube.com/watch?v=eqzWqSapUPI (yeah he's nuts :D )
You should ask him if he still has some parts you may need for the conversion, tell him I sent you if you do so. ;)
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Re: LG4 to LU5 conversion

Postby Bandit » Thu Aug 08, 2013 5:30 pm

Well - a few days ago, I decided to put my 86' engine on an engine stand. I just wanted to check out if this engine would be a good foundation. Well, it seems that it is!

It went from this...

Image

... to this...

Image

... and this...

Image

Image

Beside putting it on a stand, I removed a few parts and vacuum-cleaned the block. I thought it was in a real bad condition, because it parked outside for years with removed spark plugs, etc. - but I was wrong, all the plugs are there and everything seems to be good. I tried to turn the engine with my ratchet - it worked! :)

I also noticed the mounting position of the valve covers - I thought this redesign was made for the '87 model year?! Is there a chance that this engine was replaced?

Maybe one of the moderators could rename this thread to "LG4 to L69 conversion" - because I think this will be the way to go for me! :) I am not working on this engine the next weeks, but I think this could be the next "big step". For now, I just have to find out if I have an engine harness for this engine - and if there are any differences from LG4 to L69 in 1986.

Best regards! :)

Marcel
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Re: LG4 to L69 conversion

Postby TAdan » Fri Aug 09, 2013 6:38 am

Marcel, I agree, those are the 87+ style heads.
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Re: LG4 to LU5 conversion

Postby eightytwo » Fri Aug 09, 2013 6:38 am

Bandit wrote:I also noticed the mounting position of the valve covers - I thought this redesign was made for the '87 model year?! Is there a chance that this engine was replaced?

The valve covers are mounted in the right position. If it's an LG4, it should have the stamped steel ones (picture below).
Looks like someone swapped them with the 1987 up ones.

Image
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Trans Am video: http://www.youtube.com/watch?v=4XIXKIld6XE
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Re: LG4 to L69 conversion

Postby brother al » Fri Aug 09, 2013 3:47 pm

The '87-up SBC valve covers are physically the same perimeter shape/flange as the '86-older ones. The only differences in the valve covers are the "rib design" and the '87-up ones have centerbolts that hold them onto the head. The '86-older ones have 4 perimeter bolts to hold them to the heads... they do not interchange without special adapters that were not available until about 10 years ago and those adapters are not common/cheap. Those appear to be original to the engine and as TAdan said, very well could either be an original '87 LG4 or a GM replacement LG4, LO3 TBI 305, or even an LO5 TBI 350 crate motor.
(all '87-up Non-reverse flow series SBC engines look like this).
The idea was part of Chevrolet's updating to reduce warranty repairs because of oil leaks, this included switching to a one piece rear main seal ("1pc RMS"), the revised intake manifold bolt pattern, and the changes to the valve covers. The idea behind the centerbolt valve covers was that by placing the downward clamping force onto the centerline of the top of the valve cover, the perimeter would seat evenly. It would also prevent damage/bending of the perimeter flange of the valve cover from people over-tightening the bolts. On '86-older valve covers, if people do not torque them down properly, the mounting bolts will continue to crush down onto the valve cover and gasket, causing the gaskets to cruch, deform/push-out, and leak and the lip of the flange on the valve cover deforms as well helping them to leak even more.

This is a part of the problem with finding good used GM valve covers in the States... many of them have damaged flanges if you look carefully because of improper torqueing.

Cast onto the upper back of the transmission flange is the displacement of the engine, this can either be in Cubic Inches or Liters:
"5.0" "305" "5.7" "350"
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Re: LG4 to L69 conversion

Postby eightytwo » Sat Aug 10, 2013 3:59 am

Below some pictures of the older '86 valve covers brother_al is writing about.

1986 Trans Am LB9 engine
Image
1986 Trans Am LB9 engine
Image
1986 Firebird LG4 engine
Image
>>> 08/82 Norwood <<< Pontiac Firebird Trans Am 5.0L V8 3-speed auto.
Showroom: http://www.earlythirdgen.com/forums/vie ... =25&t=2132
Trans Am video: http://www.youtube.com/watch?v=4XIXKIld6XE
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Re: LG4 to L69 conversion

Postby brother al » Sat Aug 10, 2013 7:30 am

Another Tell tale of the '87-up motor is the distributor... GM went to that design in '87. (Less reliable IMHO, lotta folks seem to need to replace them.) Also, yes, I didnt mention the '85/86 TPI engine valve covers, they had the rib design but perimeter bolts.

Image
Image

Also, there is a possibility that it may be a factory roller cam engine if its a replacement engine...
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