Is it possible to get an LG4 up to around 250 horses without blowing a lot of money and still getting relitively good gas mileage? What does it get mpg stock?

 

window sticker rates it at like 16-20, its different for different years though, ive got the lg4 block with stock heads, edelbrock carb and intake, open air cleaner element, stock manifolds with 3 inch straight back exhaust no mufflers, and i get like 10 city, and 18 highway, but in city i always put my foot into it so it depends.

 

The LG4 combo I put together:

Ported World Products heads; Hooker 2055 headers and 3" cat and everything to the muffler, dual 2-1/2" out; Crane Compucam 2050; ZZ3 intake; L69 dual snorkel air cleaner; Accel ignition module and coil. Everything else was stock, tuned, LG4.

That combo put out roughly 250 RWHP, based on drag strip data and sea level conversions for input in various HP calculators. I would typically get 18-20 mpg commuting, and although I didn't have it on the highway for a full tankful very often, it would get 24-25 highway. The LG4 stock was 20-22/25-27.

If all you're looking for is 250 gross flywheel horsepower (the typical crate engine method of rating), headers and a mild cam, along with a better flowing air cleaner than the stock single snorkel, will get you there. And, if your LG4 quadrajet has the AV limit, fix that so it will open completely (see the tech article linked from the thirdgen.org homepage).

As you can see from the sig, I'm still running most of that stuff. Still get 18-20 commuting, 23-25 highway.

 

ok thanks

 

i can get a set of 350 heads for free. Should i put them on to?

 

"Free 350 heads" usually translates to "smog era junk". Typically large 76cc chambers, poor flowing ports. Kills compression and kills flow. Stock 3rd gen LG4 are better than almost any 70's 350 head, and most likely better than any you would get for free.

Keep your LG4 heads. They're actually one of the best factory castings available for being turned into a performance head.

 

Ok, forget the heads then. Would it be worth getting them port and polished, and will ram air work with the carbeurator?

 

i have a 85 LG4 with a non cc q-jet and elderbrock performer intake,hedman 1 5/8 header...3.5in exhaust and no emissions....i was wondering how much hp im pushing..

 

Just thinking ahead on my own car, nothing I'd want to do now ... five7kid I enjoy your posts, they are very informative and I appreciate you sharing your knowledge on how to do things the right way.

What I am wondering is, if I were to upgrade my LG4 intake & exhaust and get some more horses out of her, should I be concerned much about my non-world class T-5 manual tranny with an HP increase? Any rough idea if I do the intake & full exhaust but leave the stock heads and cam roughly what increase I might expect to see? Is this even worth it without a new cam? I understand if this is difficult at best to estimate. Is it very hard to install new headers with the engine in place?

 

You'd be somewhere between the LG4 and L69 horsepower. Since they put non-WC T5's behind L69's, I wouldn't worry too much about it. Clutch dumps and speed shifting are what kill T5's.

 

I did a few mods to my 86 Trans Am LG4 car back in 2000. Put on an Edelbrock 1406 carb and 7101 intake with an open elelment air cleaner and got my little motor to push the car to a 14.94@92mph with a tad over 130K on the odo.

 

That's insane! You must weigh like 90 lbs.


You sure you didn't gut the interior or something?

 

yeah, thats sick. But isn't replacing the carbeurator a bitch because of the electronics, or do they make one that works with it? And like I asked earlier, does anyone know if ram air will work with the stock Q-Jet? I know i'd have to change the AV, but will ram air cause it to not get enough gas?

 

Interior was fully loaded, leather seats, power windows, doors, and mirrors.
The only thing I removed was the small 12" JL sub since I had run a 15.04 and wanted to hit a 14.9.
Car weighed 3520 with me and a 1/4 tank of gas (they have scales at the track). I weigh 150lbs.

The only thing the computer controlled in my 86 was the quadrajet, so I just removed the computer and harness.

this is the pass right before the 14.9 pass, which unfortunately no one video taped.
http://www.transamws6.com/video/manny-1504.wmv

 

I see in the pic above that you have a flowmaster sticker under the hood there, were there any mods to the exhaust? I'm not calling BS, but we are talking about 170-180 RWHP to pull off those numbers... which is 30-40 Hp over stock.

 

How much money is 'a lot'?

 

All stock exhaust except for the Flowmaster muffler on the back of the car, stock manifolds, stock Y, stock cat, and stock I-Pipe.

 

you should get an exhaust too. put anther 15-20 horses on, the Y-pipes were made really bad.

Anyway, does anyone know if i put a hood on that works like the 1982-83 Z28s will it get more air. They had ram air flaps instead of the pointless louvers. Don't get me wrong they do look good.

 

SWEET, I knew some lg4's where strong!

My car would probably have ran a 15.1 at like 93 mph with just catback, !air

probably 14.9 with full exaust, !air !a/c !jack !spare tire

but we will never know, freakin carb fire.. I have an Xe262 sitting here, for some one to try out in there lg4

 

Can't you just cut the louvers and make them functionable? I plan to do that... maybe its pointless?

 

yeah i want to do something like that. This is really pissing me off though. Why is the 305 such a crappy engine. Is there not enough bore for the stroke or what? They made these engines for fuel economy, but they don't even do that. I love my car and i want the original engine in it. There has to be a major flaw in the 305 or something. Ford 5.0's are way better. Is there a way to increase the compression on my LG4 without having to get new heads? I want to be getting 20 miles to the gallon and have at least 200 horses.

 

basic upgradews will get you to 200HP
EG: Intake, Full exhaust from headers to tip (atleast 2.5"), Holley 650DP, HEI distributor w/high volt coil and high flow air filter (K&N).
But if you want to go faster without ripping youre motor apart start swaping heavy OEM parts with lite aftermarket ones.
EG: gear reduced starter, Air-Con Delete (if you don't use it), smog delete plus heaps more and youre new headers will be lighter than the stock cast iron exhaust manifold.

The 305 is not a crap engine it is just the **** emissions laws that killed it power from the factory, A 305 can be made to put out some nice numbers.

 

my camaros completely stock with a k&n airfilter and i get like 10 city and 16 highway when i drive hard. driving a little slower she gets about 13 city and 18 highway

 

I doubt you will get that with a 305, the only way you will get good power and efficiency is with a LS1 or a larger engine.
Yes a larger engine will burn more fuel stock but it will be working less to do the same job as a smaller one so there for it will be less.
Rough example:
305 = 190HP@4,700RPM (Peak = 190HP@4,700RPM).
350 = 190HP@3,000RPM (Peak = 320HP@4,700RPM).
Less load + less RPM = less fuel evan tho it is a bigger engine.
This is the main reason I was talking about weight reduction because less body weight = less engine load.

 

250 HP and 20 mpg highway should be a piece of cake for a hopped-up CC LG4. I did a lot better than that with both (as stated in post #3).

 

What exactly did they put on for the emmisions sh*t. I notice that the engine is covered in a jungle of tubes, but what does it all do?

 

Well they did everything to the engines to make less emissions out the exhause so they limited the flow, 305 arnt so bad asfar as i know but if you look at a set of mid 70 350 heads you will know what I mean, But the heads are one thing that can improve if you port them that will increse performance a fair bit because they are restricting the flow atm also I have been told there is a performance gain by removing the cat. the main problem is over there in the US use have kinda strict emissions laws so I don't know if they can be removed where you live.
our emissions laws are nowhere near as strict as over there (i think) but in 1 year there was a 20kw drop from factory 180kW (308) in 1976 and 161kW (308) in 1977 then go forward to 1984-85 117kW (308) that is a 63kw drop!

 

I wouldn't put it that way at all.

More than anything, they were faced with fuel economy requirements. They went with a long stroke/small bore configuration in an attempt to maximize torque for the size - torque tends to provide better economy, while giving the best "seat of the pants" feel. Since this design started in the late 70's, we aren't talking about the heyday of Detroit with regard to performance, design, or quality.

With the standard SBC head configuration, the small bore tends to shroud valves that are large enough for performance flow. The Ford 5.0 doesn't have either problem - small bore or flow issues - but what they gain in performance they lose in reliability (with higher performance levels).

The 305 was the product of an unfortunate time in Detroit history, and although it served GM well as they used it, it really isn't well suited to performance. That doesn't mean you can't get one to perform, but it does mean that what you do to it for performance doesn't give you as much return as other configurations do.

In my case, my stock 305 ran a best 1/4 mile of 16.85/80 mph. With intake, it ran one 16.80. With heads/cam/exhaust/air cleaner, it ran a 15.70/90 mph, more than a second off the stock time. When I put the 350 shortblock in, I expected another half second improvement - imagine my surprise when, with my son in the passenger seat, it took more than another second off of the hopped-up 305 time! With only driver, almost a second and a half, and 5 mph faster. All of these times were at 5800', by the way, with 3.08 gears and no AC with the stock 305, and 2.93 gears, higher stall, and AC reinstalled for the hopped up 305 and current 350. Oh, no 2-3 shift with either 305 config (very tired tranny).

The difference between the stock LG4 and the hopped up one was huge (I started a thread to the effect of, "So this is how a 305 is supposed to run"). The difference between the 305 and 350 is even bigger, with a much bigger smile on the face every time I drive it.

The emissions talk is a red herring. It doesn't make much performance difference at all, and actually helps fuel economy.

 

Ah ok, I don't know mutch about US emissions systems but the Aus emissions engines had a large power drop from the pre-emissions engines.
But I thought there would be a small power increse from the smog pump delete because of less load on the crank, Also I thought emissions system flowed less that made them more fuel efficiant in return would make them less powerfull?

I know a 5.0L can be made powerfull because my friend has a 307 that will kill anything it goes up against but 5MPG is the downside.

How would you go about getting 250HP @ 20mpg? with a 305, I don't have a clue what HP im getting out of my L69 but I know I aint getting 20mpg. (I get 170Miles per tank)

 

I get 18 mpg commuting, and at least 23 highway with my current ~350 horse (~280-300 net) 350. It's close to but not quite as thrifty as the souped up 305, which was around 300 horse.

Letting the feedback computer controls do what they do best is the key.

 

ok, so emissons controls are ok. Mild Cam, intake manifold, dual snorkels, port and polish, tune the carb, a new ignition system, and exhaust system headers back is all i really need according to everyone. I'm still in high school, and this is my first car. I want to be able to say I have a camaro and actually be able to smoke the ricers.

 

How big is a 3rd gen fuel tank?
I want to try workout what MPG im getting.

 

3rd gen fuel tanks are ~16 gal. If you're going by your fuel gage, don't believe it. Divide the miles between fill-ups by the gallons to fill since the last fill-up, that's your mpg.

Emissions controls such as the A.I.R. pump don't take enough power to even measure on the engine. Other than that, it's just weight.

 

and when i say new ingntion system i mean a high performance coil... and how much does a port and polish cost? And what would be the best intake manifold for my situation?

 

What would I have to do to convert to an L69 from an LG4.

 

https://www.thirdgen.org/forums/faq-...5-engines.html

 

thank you

 

It depends on how much you're willing to spend. If the bottom end of your engine is relatively good and doesn't have a lot of mileage on it (maybe 80k or less), or you know it's history and it was maintained well, then you could pretty much build up a decent motor off the 305 base. I didn't see your year car, but you're probably putting out somewhere in the neighborhood of 135-175hp (depends on the year of the LG4).

It's hard to say really what the worst items are on the LG4 because there are many horrible flowing parts on it.

I guess you should decide first how far you want to go into it. If you're willing to remove the heads, you could make some decent horsepower.

Not all 350 heads from the 70s are crap. There are several GOOD cyl heads that were available in the 70s that have higher compression. They made heads like the "camel heads" and the "HO heads". The camel heads are so called because of the dual humps that they have on the cyl head casting.

The best thing you can do is search eBay, or if there are a lot of local junkyards, you could try printing out a cyl head identification chart and take it with you as you look through the older junk cars. I have found several powerful 350s hiding under the hood of 80s Jaguars and a number of other cars (popular swap). There are always lots of Trans Ams and Camaros where someone has already done this work maybe 10 years ago (and now the car is in the yard). The local yard here in Fort Lauderdale charges $25 per cyl head.

Other than that, you'll want a good camshaft, a set of roller rockers, a good intake manifold, and a proper carburetor to match. It's at this point whether or not you want to decide if you want to keep your factory computer control, or trash it for a vacuum advance distributor and non-cc carburetor.

Depending on what you end up doing, it's a good idea to get a new distributor, preferably one that has a built in multiple spark discharge feature. A high energy ignition coil, some good plug wires, and the correct temperature range spark plugs (steel tipped) for your cyl heads.

The 305 motor itself really is not THAT small. And it's not JUST the horsepower you should be focusing on, but also the torque. I have a 2002 Crown Victoria that's JUST breaking into the high 14s. It's probably (guess) putting out about 240-250hp with a 4.6. I've been trying to find a dyno, but all of the shops around here only let you use the dyno if they are doing work ON your car (if anyone knows of a dyno in South Florida that rents dyno time with the use of a professional, PLEASE let me know...).

Anyway, the motor itself is really only the half of it. There are several other aspects that you'll want to consider.

You'll want a good set of headers, you can get a decent set of Edelbrock Test Headers for a few hundred, or you can get a set of cheap FlowTech headers for practically $200 shipped with the Y-pipe.

You'll also want to get rid of your factory catalytic converters if you still have them. They are HORRIBLE. The early 80s cats are practically worthless. The newer hi-flow cats that you can purchase from Summit or Jeggs are far superior and use a ceramic honey-comb instead of charcoal pellets.

I guarantee to you that any stock Camaro or Firebird will see a bigger performance improvement by replacing the OEM cats with high-flow ones, than you'll see by replacing the stock "cat-back" system.

Other things you'll want to consider are the rear-gears. Since you have a 5-speed, you can probably go to a higher final drive without affecting your fuel economy. If you do a LOT of highway driving, you may want to keep a 3.08:1 or something along those lines, but if you do most of your driving in the city / town, you'll actually see an improvement in fuel economy by going with something like a 3.73:1.

In my opinion, it's a good idea to keep the EGR system functional, although you can easily simplify it without needing all the extra hoses and crap (depending on whether or not you keep the computer control). All EGR really needs is the EGR valve / diaphram, a thermostatically controlled intake sensor, with a vacuum port going to the sensor and the EGR.

I would recommend getting rid of the smog pump. It's crap, and with the newer cats it doesn't do anything anyway. You'll get far cleaner emissions with newer cats and a properly tuned carb than you will with ALL of that AIR injection crap, the smog pump, and the old pellet cats. Of course, if you're in a state that does those kinds of emissions testing and requires the original equipment, then you may want to keep it on there. Although, you can easily block off the AIR fitting tubes and modify the pump to just be nothing more than a dead pulley.

If you're still using a clutch fan, you can also replace that with a newer radiator fan and shroud. All you'll need is a port on your intake manifold for the temperature sensor and a positive "switched" feed.

Lets see... what else.

It's a good idea to have all new motor and tranny mounts, they can really help how your car launches and responds to throttle.

You'll want a good exhaust system too... preferably something that takes advantage of the additional flow of the entire system.

You'll also want to port-match everything... this does help.

And last but not least, you'll want to make sure you have the carburetor and timing properly tuned for the type of driving you'll be doing. You can get a little bit more power by advancing your timing and going with a higher octane fuel, but I find it better to just stick to normal timing which allows for normal 87 octane fuel.


If you do all of this stuff, you should have a pretty decent running vehicle. It doesn't take that much really, and you can have excellent gains whether you do it on the cheap, or you spend a lot of money.

Most stock LG4 Camaros and Firebirds are total pigs. I mean, when new and on a good day, they ran mid / high 16s. On the street with some wear, you'll be lucky to be breaking into the 16s.

I had an 82 Trans Am about 8 years ago, and I was running consistent low 15s with not much more than maybe $1,000 in parts.



Todd, @ http://www.PontiacPerformance.Net
2006 Pontiac Solstice
2004 VW Beetle Convertible (Wife's Car)
2002 Ford Crown Victoria LX-P74
1987 Pontiac Fiero SE / V6
1984 Porsche 944
1981 Pontiac Trans Am WS6
1973 Volkswagen Type-2 Transporter

 

We already established that LG4 heads are a good starting point. In fact, they're better than camel humps. And any 70's head is going to lower compression beyond any possible flow improvement. Stick with LG4 heads on a 305.
Roller rockers are a waste of performance $'s, especially on a mild 305. The computer controlled carb is one of the best things about an LG4 - trashing it is the same as throwing more performance $'s away.
Again, the computer distributor is a good piece. The module and coil aren't; if you go with a box you can eliminate the module, but a simple module and coil change is all it really needs.
We already covered that. However, Flowtechs are junk, and should be thrown in the trash even if given to you free. Edelbrock for LG4 aren't much better. "Test Headers"? Exactly what is that? In general, aftermarket exhaust for the '86-'90 TPI single cat application is the way to go - it'll all bolt into the car, no cutting/welding/shop install required, and it'll give you all the flow you need for a mild 305, wild 305, or if you eventually upgrade to a 350.

The A.I.R. system doesn't take away any power that's measurable on the engine, and does help reduce emissions - even with new cat types. Besides, it's required to be in place in some regions of the country. The only excuses for removing it are opening up space under the hood and weight savings - and the weight savings is negligible.


I hate to have to go through posts like this, but I can't ignore misinformation.

 

Not all camel heads, or HO heads have 76cc chambers. There were many cyl heads made during the 70s. Not all of them were made after 74. Some of the highest compression motors offered in production cars were produced in the early 70s. Camel heads are significantly better flowing heads as they typically come with 2.02:1 intakes with 1.6:1 exhaust valves rather than the 1.85:1 vs 1.5:1. If the heads are free, yes, they're probably garbage. But... like I mentioned (which you failed to quote), if you go to the junkyard, you can often find excellent cyl heads in some junked cars (many of which I've found in junkyard Jags). eBay is also a great place for some classic cyl heads.

For one, I'm going through the COMPLETE list of things I can think of that you can easily do to your motor to improve horsepower without breaking down the short block. Second, roller rockers are a great way to decrease the drag on the rotating assembly. A set of 1.52:1 or 1.6:1 roller rockers are barely more expensive than a new set of stamped rocker arms.

Roller lifters are equally as great. They are just one more way to make the engine perform just that much better. Less friction, less heat, more power, less drag on the rotating mass, better fuel economy... there are excellent alternatives to replacement OEM parts.


Again, I'm listing every single possible thing that you can do to the motor without tearing it down that will give some improvement. A hotter ignition coil will improve emissions and idle quality, and will restore performance where an old coil can lose some of it's capacity to charge.

I don't know what your point is. I'm not suggesting that he eliminates the CC distributor unless he decides to go that route (which is entirely dependant on whether or not the entire CC setup is actually there)


TES headers... so you've never mispelled a word? Thank you for pointing it out. You get a gold star.


Sure, I never said it wasn't. I'm not really sure what your response was here? If you're going to tell me that the older factory pellet style catalytic converters aren't holding back the performance of the car, then you need to do a little bit more research.

GM has to make very specific calculations when it comes to exhaust ID, and the ID of the catalytic converter. THey have to take into consideration noise, emissions, cafe, and all the other standards. Completely eliminating the catalytic converter will cause you to lose SOME low-end power in most V8, but you'll typically see a significant improvement in the top end. But by having the cataltyic converter that's exactly at the correct CFM that meets that sweet spot in the exhaust flow that gives you the least amount of low-end loss for the greatest amount of top-end flow, then you get the most benefit. I can assure you that the olders style pellet cats are NOT optimal.

With newer ceramic interal catalytic converters, there is absolutely no need for AIR injection. When you have the carburetor properly tuned, this additional air is completely pointless, and just more unnecessary crap under the hood, and more things to break and spread heat.


I guess you missed the part where I said exactly the same thing, even though that's what you were responding to.




I made 1 mispelling on a particular brand of Edelbrock emissions legal replacement exhaust headers. I don't see anywhere else where I've given mis information.

I'm not really sure why you felt the need to be abrasive and nasty in your response. I gave him every single thing I could think of that would improve the performance. It all clearly depends on what his goals are, and what his budget is. You seem to have compeltely missed that very critical point and picked apart my post, responding to things out of context.





Thanks...


Todd, @ http://www.PontiacPerformance.Net
2006 Pontiac Solstice
2004 VW Beetle Convertible (Wife's Car)
2002 Ford Crown Victoria LX-P74
1987 Pontiac Fiero SE / V6
1984 Porsche 944
1981 Pontiac Trans Am WS6
1973 Volkswagen Type-2 Transporter

 

 

Ah, "TES". Now I get it. Not particularly impressed by them, but they do offer more 3rd gen applications than others. Dual cat version is probably the best they have, but I still prefer Hooker 2055HKR's or the Hedman dual cat version. Most any header will be better than the stock exhaust manifolds, but you can avoid low quality, installation headaches, performance loss, and extra expense (read: exhaust shop work) by picking the exhaust components carefully.

The originator's question stated "not a lot of money". Roller rockers is a lot of money, in my opinion, for the return you'd get in a mild set-up. Ditto looking for "classic" performance factory heads, especially when you've already got a good set of factory heads in the LG4 heads. Roller lifters in an '86 block would be an expense that would take forever to break even on.

Josh, we seemed to have missed one of your questions: Yes, "ram air" does work with a carb. In fact, the factory set-up qualifies, as long as you understand that "ram air" really is "cool air intake". The best set-up in that regard is a dual snorkel air cleaner with a duct going toward the headlight on each side - the factory made such a set-up with their L69 HO engine, but they're getting harder to find. You can fabricate one yourself by adding another snorkel to your stock air cleaner - there's a tech article on the subject linked from the thirdgen.org homepage.

As for how much is "emissions crap", not as much as you might think. The A.I.R. system is purely emissions related, and if you can get by without it, it can be removed without any effect on the system at all. The EGR system is close behind, but disabling/removing it can lead to part-throttle pinging problems. The vapor canister is emissions related, but I advocate keeping it to vent the tank, as any alternative is less effective, even though the vacuum lines for it contribute mightily to the snake pit under the hood (one of these days I'm going to relocate that control valve so it is out of the way). The rest is there to give the computer information it needs to get the most out of the engine, both in terms of power and economy, while keeping emissions to a minimum - and it does a very good job of that. To the best of my knowledge, there is no replacement carb for the factory piece, although I understand Ford used a computer controlled Holley for a year or two (I've never seen one myself), but I don't know if they would be compatible with our system.

By the way, the '86 LG4 had 9.5:1 compression, the highest ever offered in a 3rd gen engine. No need to raise it above that.

Todd, with regard to getting abrasive: I read at least 50 threads a day, which adds up to several hundred posts a day. First I make sure people are obeying Board rules (usually do). Then I check to see they are staying on topic (thread hijacking, mostly). Finally I look for technical accuracy, within my knowledge base (I know I don't know everything, and really do resist commenting on a lot of stuff). With all that, a huge post like yours takes as much time to go through as some entire forums do, and when I start seeing information that doesn't pertain to the originator's situation (he wasn't asking for every last thing he could do to improve performance, for instance), I need to do something. So, my apologies for appearing "abrasive" and "nasty", as that's not my intent. If this was a face-to-face, you would know that is not the case at all. "Terse" I'll admit to, that's the curse of trying to say the most with the fewest words.

I do prefer keeping things as friendly as possible.

 

I have learned so much from being on this site. You guys arguing just seems to help, haha. I definetly now have a plan of what I need to do to my LG4. 250 horses no longer seems so far off. Torque I was never truely concerned with torque because its a V8 and torque is pretty avaliable. The more horses i try to get out of it the more torque i will obtain to. Thanks guys.
----------
Is there anything I need to worry about when replacing the intake manifold. Or will everything come off of the old one and fit on the new one such as vaccum lines or anything?

 

and what is the stock camshaft specs for a 1986 LG4 M5?

 

I think I got the link to this site from a different thread, but maybe you can find something useful here. http://www.popularhotrodding.com/eng...cks/index.html

It made me believe in my LG4, although I would love to put something bigger and less emissions bogged....