Hey guys so I just picked up an 86 Trans Am for my son for a project car for us. Been on here searching and searching and covered the basics of why this thing is so slow. I know LG4's are dogs but this one is just ridiculous, I walked him in my 4cyl Subaru Outback lol. So far we change plugs, wires, cap, and rotor. Checked the EFE and although it is not hooked up it is not stuck closed. Fixed the choke on it and thought maybe that was causing the secondary lockout to stay closed but nope verified today secondaries are opening. Anything else I can check? The car runs good just has no oomph. It's killing him since his daily is our LT1 Caprice which will oit and out rape the Trans Am hahaha. I was trying to find a stamp on the rear as my RPO codes are gone to see what gears it has in it. Any other pointers or things to check out would be appreciated. Here are some pics of the ole girl needs work but runs and drives and the body is straight and interior pretty clean with a good center console and dash. All in all a great starting point He was hoping to recreate this picture of me in my Trans Am but nooooo prayer without a lot of bleach lol

 

Motor had maybe 170hp brand new in 86. Mine was a total dog as well. Best way to make an LG4 car fast is to yank the motor and drop in an LS.

 

Timing? Fuel filter? Is the carb working properly? Shouldn't be that slow.

 

That's what I thought too. Had an 85 LG4, although it was at least a 5spd, and it wasn't that slow lol. I did change the fuel filter and for now I set the timing at the factory 0 degrees it has listed. Was going to try and advance it some and see if that helps but was covering all the basics first.

 

Also check the rear end ratio. Mine was (heck still is) a 2.73. Low power + highway gears = sluggish.

 

Interesting that the timing spec is 0 degrees. The timing spec on my old 86' LG4 was 6 degrees, but it was a 5-speed. Possibly there was a different spec for autos, or maybe it was a California car with California emissions? Another member may be able to chime in to confirm if they have seen any other LG4's with a spec for 0 degrees base timing. I do recall that the later throttle body injected 305's (L03) motors did have a spec of 0 degrees base timing. I would confirm that the underhood emissions sticker is correct for the car. Maybe the hood was swapped at some point?

I agree with the other comments about going through and making sure everything is working correctly and to spec. You did plugs/wires/cap/rotor, so that's good. Verify proper base timing and set it there, make sure the transmission TV cable is set correctly and that the transmission is shifting at the correct RPM (should be around 5,000). The carb could be an issue. Even though the secondaries are opening, maybe not getting enough fuel? I would do all of the other things first, but it may be time for a carb rebuild given the age. Also, an old clogged up catalytic converter will cause a big drop in power. Could look into that as well.

With an auto, it probably has a 2.73 rear end. That will add to the sluggishness. But it should still be fun to drive.

 

They like 4-6 deg timing. If you keep the engine do 3.42-3.73 gears+posi, S10 tc, 3in exhaust + headers. It will make it lot more fun and carry over to your 350 swap later. I done this with my L03 except the headers and it was a peppy lil car burned tires up.

 

My 83 G20 van with 3.08s still ran like a 17.2 @ 74 with the stock 305. Got it into the high 15s with some maintenance, some cheap bolt ons and some adjustments. Tweaked Q-Jet, recurved HEI, performer rpm intake, factory catless duals from a 1-ton van with matching tubular shorty header style manifolds, dr gas x-pipe and a modified governor in the 700r4. Cam put it in the mid 15s.

 

Tiny cam lame gears choked exhaust.
212-218 .444-444 108 104/112 comp hyd. #12-310-4
Summit springs , 4.10 gears Headers 2.5" exh
1.6 rr optional.. Then fully port the heads. reinstall w / ..015" shim head gasket.

It will be a very different beast

 

I'm not sure if it's your intention but you're helping me make my point. LG4s are slow. If you put a ton of time effort and money into them they can be made nearly as fast as a modern base spec civic.

 

One knock against the pre-87 LG4s is low compression. Like 8:6 maybe. I put a Summit K1103 cam in an Lg4, headers, and Edelbrock intake +Holley Dp in aFirebird and it still wasn't any faster than a stock LB9 car. That's the last 305 engine I ever bothered fooling with internally.

 

Massive weight difference and massive aerodynamic difference. F-car should be atleast 2 if not 3 seconds faster.

 

Massive weight difference and massive aerodynamic difference. F-car should be atleast 2 if not 3 seconds faster.

 

85'-up LG4 had the higher compression (same as the LB9 and L69). 86' LG4's got the electric fan. Over their run from 82'-87', the LG4's gained some L69 parts and closed the gap between them some. Never got the cam and exhaust though.

They can be made to run pretty good with the normal upgrades, but yes, it's a lot of effort and it still won't beat a minivan.

I think the point of the OP's post is to see if his car is at least running the way it should. Upgrades cam come later, if desired.

 

Run a compression test, and then post the results ITT.

 

being slow is not new for the LG4 but if its below factory.. if its a Fuel injection change out your distributor.. alot of them go bad on these cars .. throw in a coil too

 

Thanks everyone for the tips! Yeah wasn't trying to make it fast just wanted it to perform as it should. I was thinking about a carb rebuild as the car was sitting in a garage for a good amount of years and I'm sure that wasn't good for it. It also still.has an issue idling sometimes and will throw a check engine light. Once you start moving it goes off so something still isn't in spec. I thought about the cat but the guy I got it off of had already replaced it and the car back exhaust as well. I'll check on the timing this weekend see if bumping it up helps any and see if I can pull the codes to see what it is aetting.