I have n TA 85 with the lg4 engine. I am getting headers and 3"! exhaust. Now Im curious what differs between the lg4 155hp engine and the HO version, heads camshaft etc. Would it be easy to "update" the lg4 to HO specs? What about the carb and manifold. Would I need a new computerchip?

Hasse Olsson
Sweden

 

You're about half way there just replacing the exhaust. In '85, the LG4 had the same compression ratio as the L69.

Cam, air cleaner, chip timing curve, and carb secondary tuning were the other differences. The carb (other than tuning), intake manifold, and heads were identical between the two engines.

A dual snorkel air cleaner is a real must-do thing. Unless you do that, the effect of all the other things will be severely limited.

 

Oh, the L69 base timing was 6 degrees advanced instead of 0 for the LG4.

 

Well I guess you could say he's halfway there.

It's the compression difference that would be the most difficult thing to change. (9.5:1 compared to 8.5:1) You'd have to change pistons.

 

'85-'86 were 9.5:1. '87 was 9.3:1.

 

350 camshaft (I am running a federal mogul CS 1014R), different prom in the computer(more advance, more fuel, and higher speed for torque converter lockup), different metering rods ( a 1982-1984 van w/ 305 HO will provide you with a set of DR secondary rods) and a 1988 cadillac 307 will provide you with an F hanger) thats what is on mine. Compression, exhaust, and base timing were also different. I also noticed that most base 305s only had 1.74 valves and HO heads have 1.84. Dual snorkel or open element would help too.

 

US-sold 3rd gens all had 1.84" intake valves.

I don't know about Canadian or other exported 3rd gen LG4's.

 

Well by golly, I just looked it up and you're right!!

I never knew that! But only 5HP was gained by going up a whole point on compression??...... What gives?

I thought compression played a bigger factor than that.

Thanks for the info 5-7.

 

Compression plays a part in interactions, primarily cam but also exhaust.

When they raised the LG4 compression, they also added knock sensor and electric radiator fan. Since a lot of these things were driven by emissions and CAFE standards, the compression change may not have had as much effect on peak power as it otherwise would have.

Madison Avenue and insurance companies are other things affecting factory HP ratings.

 

I have a knock sensor too, and electric fan. Seems to me the only things you'd need to change to get to L69 standards (if you want to call it that) Is bigger exhaust, and a cam change.

HasseO - Sounds like your exhaust is in order....I'd run the cam I have - it's emissions legal if that matters too!! It woke my car up!! Of course, five7 kid will recommend the 2050!!.....

 

ive heard in certain years that the heads on the lg4's are all 416's and some of the ho's are 601's, but no one seems to be sure. So i'd just assume you have the same heads, either way, all 305's need new heads. One other difference not mentioned yet, the l69 has a higher volume oil pump, what ever thats worth.

This question is asked to much, searches would yield answers or maybe a sticky on the faq board.

 

Where do I get a dual snorkel air cleaner?

 

http://cgi.ebay.com/ebaymotors/ws/eB...tem=2458200118

EDIT: Holy he wants $22 for shipping

https://www.thirdgen.org/classifieds...tgo?adid=36059

 

105 bucks! I payed 10 for mine

Now all i need to do is fab up the rest of it

Brandon

 

I have an 85 IROC (LG4) that I would think is pretty much the equal of an L69 with the mods I've done. Note sig.

JamesC

 

I think it'd be fun to find out!!!

No doubt you'd kill me on the twisties though with the kind of suspension mods you list!!

 

My 86 LG4 motor had a carb and intake on it and I got it to run in the high 14's, not too bad I guess.

 

Air cleaner is the first thing I would change on an LG4... either to an open element or dual snorkel.

Dual snorkels came on '83-86(?) Camaros and Firebirds with HO motors. They also came on '70s small block Corvettes too, as well as early 2nd Gen Camaros with the LT1 or L82 motors (incase you wanted to look on Ebay for a dual snorkel).

 

Texas is a long way from Canada. I have never seen the 1.84 valves on any 305 except the HO heads on the L69s or the LE9s like I have. Look up the non 416 casting heads which were used on some early 80s third gens they had 1.74 valves. Most L69s cam with the 416 heads which are not as good as the 601s like the LE9 motors had.

 

Confused,

Runin'em would be a hoot, but truthfully, the last time I popped a clutch was around 1962 or 63. I ran my '54 straight-six Chevy (with dual carbs and flex-o-pipe into glass packs, Hurst floor shifter, etc.) against a Ford flat head. Got kicked at the end. My Camaro handles well, but I don't flog it much. I like those long straight Kansas roads. I'm lazy. The twisties are work!

JamesC

 

Look it up where? All data I've seen (particularly here) says 3rd gens all got 1.84's.


So much for everything being bigger in Texas...

 

Canadian LG-4's also came with 1.84" intake valves, the L-69's as well, I've seen both.

The only diff between the US and Canuck cars as far as the LG-4/L69 goes was the lack of computer controls, and for some reason we got cast iron intake manifolds - apparently US cars got aluminum ones?

Oh yeah, and our speedos read 140... nyah nyah, errr... km's, nevermind.

 

Here is one place I would sure think that the LG4 in the monte would be the same as the Camaro.
http://www.darklair.com/monte/l69.html

 

I wouldn't assume that they can be compared. The Monte L69 & 3rd gen L69 certainly had differences.

I would assume that an '85 3rd gen LG4 would be similar to an '86 3rd gen LG4, however, and I know what size valves an '86 3rd gen LG4 had.

But again, I'm not sure what they sent over the pond, so it's not a given. Most likely, though, Hasse's LG4 has 1.84" intake valves.

 

Did the Monte L69's come with the same dual snorkle air cleaner as the f-bodys?

 

Not that I've seen. Single (although larger than 3rd gen LG4) snorkel.

 

Interesting since I tore apart an 85 TPI L?? Whatever and swapped parts to an 85 caprice LG4 Friday which is Identical to out LG4's. The TPI and HO carb should be identical except for induction?Yes no?
Notes:
Heads 416's on both (601's are truck heads) exhuast though the claim is made their different there the same except for A.I.R. tubes pointing in the wrong direction. Of course knock sensor on the HO and the most interesting detail is the harmonic balancers and timing tabs are different. The TPI/HO balancers have a smaller width and the timing tab is located @ the 3 o’clock instead of the 12. Both stick out to 3 ¾ but the HO is lighter and will find a home on one of SSC’s engines.

 

Yeah, they're pretty much the same I think... same compression etc....

Maybe the lower compression LG4's had the timing mark at the 12 oclock position???

Glad to hear the HO balancers are lighter....I'll use mine on my 406 in a couple of weeks!!

 

I don't think you can... the 400s balancer is "unbalanced" so that it will balance the 400, which is externally balanced, so the 305 balancer won't work unless the 400's crank is an aftermarket peice that is internally balanced.

basically, if you use the 305 balancer on a 400, it will shake itself to peices.

 

You can when you're running Scat crank, rods, etc. and the whole assembly is internally balanced like mine!!

 

Cool... you didn't mention that before, so I just thought I'd make suer you knew just in case

 

No problem!! I realized that shortly after I started getting this engine built.......

Let me tell you, It added substantially to the cost to build this thing!!

But at least I can run the same balancer/flywheel or flex plate combo that a 350 can....