Would it be tuff to get 250-275 emissions legal HP out of an LG4?? Serious answers please.

Tim

 

Sure, but it will be expensive, the big thing to do is exhaust, then intake, an hotter cam is cool too.

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--Steve S-- 84 Trans Am 305 HO 5 speed, completely stock will soup up when i get some $$$$$$$$$$

 

Well, there's technically legal, and then there's real-world legal.

Technically, you'd have to buy every emissions certified part ever built for the LG-4 and you'd probably STILL not reach your goal.

Real-world is a different story, though. Real world emissions they don't know if you have a weak-kneed 305 under th valve covers or a fire-breathing 383! As long as all the LG-4 emissions equipment is still on the motor and it passes the sniffer you're good to go!

It's gonna be a lot cheaper and easier just to buy a 250HP GM universal replacement 350 and stick it in there than it is to upgrade the LG-4 to the same power level. Just don't use the LG-4's exhaust- you'll want a set of headers (emissions certified 'natch) built for a same-year L-69 motor so you can use a 3" cat and 3" cat back. Stock LG-4 exhaust will strangle the life out of a 350.

 

I have been doing research on the board and in the archive and this is what I think it would take. If anyone else has any opinions please add for us LG4 guys.

1) SLP or Edelbrock TES headers, Random Tech 3" cat, Gale Banks or Flowmaster American Thunder cat-back.
2) World Products S/R torquer 305 heads
3) Crane CompuCam 2030
4) Edelbrock Performer-EGR intake
5) Upgraded secondary rods and hanger for q-jet
6) MSD 6AL box, HEI high voltage coil, 8.5mm wires

Instead of the World Products head and Performer intake, you could go with GM Vortec heads, but they need a dedicated Vortec intake and you need a something from a corvette set up to make the EGR work, in order to remain emission compliant.

This is all just based on research. If anyone out there has this set up or something better AND is emission compliant AND has real world experience (time slips/dyno #'s) I would also love to hear more opinions.

In the end, I am beginning to believe, it is better to just buy a brand new $1200 350 crate motor and...

1) SLP or Edelbrock TES headers, Random Tech 3" cat, Gale Banks or Flowmaster American Thunder cat-back.
2) AFR 190 heads w/roller rocker retro fit
3) Crane Compucam 2040 or 2050
4) Weiand Action + intake
5) Upgraded secondary rods and hanger for q-jet
6) MSD 6AL box, HEI high voltage coil, 8.5mm wires

Hope this helps.


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1983 T/A LG4 w/T-tops
Rebuilt/Modified E Q-jet
Custom Dual Ram-Air
Self painted cherry red w/ restored black/grey interior
Welded Comp Eng SFC
Tokico Struts/Shocks
Hotchkis LCAs and Panhard Bar
Energy Suspension bushings all around

 

Thanks Nightcruzer, that will be a big help

Tim

 

You should be able to do it. Another method is to use an ATI supercharger. They have kits (both intercooled and non-intercooled) that will fit carbbed cars. Before the s'charger though, get new heads, cam, intake, and full exhaust.

You'll probably want to upgrade your torque converter as well.

 

Have an LG4, I've looked into this. One interesting solution would be a stoker kit. I think you can get them for the 305 at Speed-O-Motive.

I also know that Pace Performance parts makes a conversion kit for the LG4 cars, includes a ZZ4 350 and works with the emissions equipment...for about $4k

Just some thoughts.
Mark

 

I replaced the LG4 in my '85 T/A with a 350. I bought an Edelbrock LG4 replacement intake and used a .441 lift .221 duration @.050 lift cam. I had the carb rebuilt by The Carburetor Shop to fit my engine specs. I then had Hypertech do a custom chip for me. I estimate I am now in the 275 horse range. I can run low to mid 14's and it cost me less than $2000 for the swap. I had already installed a complete SLP exhaust including headers.

[This message has been edited by LFN AT U (edited December 27, 2000).]

 

Hey "laughin' at you", do you pass smog? If so, how do you think you'd do in CA. What I mean is, are the emissions laws are more strict out there?

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'82 Firebird, dead stock, 9 bolt disc rear, over 200,000 miles and still going strong, more to come...

 

Your Gonna need a rebuild.

Flattop pistons (L69 style- the 86's used the same pistons) at appox 9.5 compression

"freshen" the bottome end.

Heads... the LG4 heads will work fine, Pocket porting, 3angle valve job, and bowl work. appox 350 bucks

Edeldbrock performer intake matched to the heads.
Cam... i had a Crane compucam.... the hydrualic variety and it wiped 4 lobes off.
I ran a summit 204/214 version, worked great, other options would be an XE form comp of the 206-212 variety, or the GM version of the 204 cam. stay away from cranes

Rebuild the carb, put some "quality" metering rods and hangers in the secondaries.
the DR or DH's worked for me with a D or F hanger.
Bump the timing up a few degrees.
let the computer do it's thing.

if the tranny's good a cheapass remaned vette converter will do wonders for ya for under a hundred bucks. it's no Vigilantee but it's better than stock.

my best time slip showed a 14.606 @ 93.26 mph. Unfortunatly the bottom end is shot.
3 light cylinders won't motor you down the track very well.
That combo i described, with the stock carb with the differnt sec metering, stock computer, a set of the TES edelbrock headers or the equivilent will get you around 14.flat on cheaters with a decent tranny, int the 95mph range.
that's a darn good running 305 for 1400 bucks

 

TimRS:

You may want talk with checkeye, another board member. He installed vortec heads, performer intake, and a another cam in his stock LG4. I believe he changed the carb jetting. He also has exhuast mods. Best to talk with him about the specifics.

Anyway, I personally saw him run a traction impared 14.58 @ 99.79 at Maple Grove. A good sixty foot time should put him in or darn close to the 13's. 99mph with a 3500lbs car roughly equates to 280hp.

Emissions legal? Won't pass a visual test due to the missing EGR valve, but I'd bet it would pass the sniffer.

 

I could hit the 275 horsepower mark on my Lg4 but all the parts I am putting on it will be xferred onto the new Goodwrench 350 i'll be dropping in, except for the 305 World Products 305 torquer heads. If staying with the 305 though, I can't see how these heads, a hotter cam and ignition system, underdrive pulley set, free flowing exhaust system with headers or tubular exhaust, after market chip, dual snorkel air cleaner with a k/n filter, dual plane intake manifold, and tweaked carb wouldn't put you in the ballpark. I'll take the 350 though.