is there anyway to get a lg4 to have the same compression?

Paul

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1987 Trans AM
305 LG4 5.0L
WS6
700R4
137,000km or 91,333miles
Black on gold trim
t- tops
K&N
Flowmaster 80 series
Sony X-plod deck
prestige 6 x 9s
2 crunch 10" bandpass subs running off the uq7 amp from the factory subs (which i blew with those amps)

 

L69s had 9.5:1 CR.
'82 - '84 LG4s had 8.6:1 CR.
'85 - '87 LG4s had 9.5:1 CR.

You're already there my friend. The extra .9 came from flat top pistons as opposed to dished.

 

is there any way easy way to bring the lg4 to the same hp im a beginner at engine mods

 

The L69 actually had a bunch of extra goodies to account for the extra 40hp. Bigger exhaust manifolds and pipe, better cam, better intake, specially tuned carb, aluminum flywheel... just to name a few.

Your flowmaster is a good start, but unfortunately it can't really do it's job because it's being choked by your stock exhaust manifolds and pipe. I got some headers and a catback last summer and they totally opened up my mid-high range.

If your cam is stock (peanut cam) that'll hold you down bigtime. A cam is pretty cheap for the hp increase you'll get over the stock cam.

 

Paul,

I'm curious how you got a Trans Am with the LG4...

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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader

 

the lg4 was the base engine in a trans am

 

any easy cheap mods i could do now?
remember i am only a beginner

[This message has been edited by Paul_Hughes_87 T/A (edited March 10, 2001).]

 

Paul,

Thanks for the info. I was under the impression that the carbed LG4 engine was last available in 1986, and the L03 replaced it in '87. I must be a year or two off. I stand corrected.

One thing to remember is that some of the Tech Articles on this site are not exactly correct. They don't even list a 2.77 Borg differential in my '86 TA, but mine has one - bone stock.

As for modifications, the door is open farther for you than for some of the EFI owners. The ECM has even less control over the engine on a carbed vehicle, so will be very tolerant of modifications. You should be free to use nearly any reasonable cam profile.

With the lower static compression, your timing can be advanced more with less risk of detonation and ESC retard. You should easily be able to adjust to 6-8° BTC without problems on 90+ octane. I'm running 10° BTC on 93 in the TPI.

Your carburetor can be re-jetted to provide different mixtures, the power valve can be changed to one with a lighter spring, the secondary metering rods and operating cam (hanger) can be replaced with a set that enriches the WOT mixture better.

The down side is that the heads on the LG4 are even more restrictive that the other 305 engines. Since you want to raise static compression and get more flow, you might consider changing the heads. If you are budget conscious, check your casting numbers and make sure your heads are the 58cc chambered variety. If not, you might be able to get a pair of used-but-nice 305 heads from someone who has done the swap, or a recycler. With a little port work and some slightly enlarged valves, these heads can flow prety well on the smaller engine. A little milling can bump up the static compression numbers at the same time. If you don't do the machining work yourself, and for what you might pay someone to do the heads you could buy a pair of World S/R Tourquer 305s. These are low-buck performance heads, but I haven't heard a lot of complaints about their use.

The intake restriction of the air cleaner is something that's been talked about a lot, and there is a Tach Article on overcoming that on this site. If your K&N is an open element type, you've already addressed that one.

The exhaust restriction of the heads and manifolds is easily overcome on the manifold side with a pair of 1-5/8" headers. This would be a nice compliment to the free flowing muffler installed.

There is always some free hoprsepower in synthetic oils.

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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader

 

ive been thinking of making my own version of the performance induction system intake with dual intakes