what is the diference between the lg4 and the high output engines, besides the intake? Is the difference in the engine components or the block itself?

 

The LG4 had dished pistons, lowering the compression. It may have had a different cam profile, and differente heads with smaller valve sizes and poorly shaped runners and valve bowls.

You should be able to determine exactly what the differences were for particular model years and engines by reading the FAQ section of this site.

 

The intake is the same. The heads are the same, 416 casting, including the 1.84"/1.5" valves.

The differences were the cam; the exhaust; carb; pistons in some years, creating higher compression int he L69 than the LG4; electric fan in some years instead of the clutch fan that costs 8 HP or so; chip programming; better timing curve, with a knock sensor; and the gears (3.73 was stock in L69 cars).

The exhaust difference was massive. Even the manifolds were different; 2¼" outlet instead of 2". Here's a pic of the cat inlet. The Y-pipe is the same as this. Compare to the drinking-straw LG4 parts.

 

I measured 2 1/2 when i changed the exhaust on my 87 t/a's manifolds and exaust pipes when i put them on my LG4. I was just wondering if it was worth the engine swap for the amount of horse power i would be gaining, and besides the 87's was just rebuilt.

 

The HO motor and the TPI motors used the same exhaust manifolds, except that the pass side one on the TPI motors isn't set up for the EFE valve like the carb motors had to have, and the driver's side one on TPI doesn't have the sheet-metal Thermac stove for the carb air cleaner.

The difference between 2¼" and 2" pipe is substantial. First, keep in mind that that's the outer diameter, and it's somewhat smaller than that in some places. So if you assume that the outermost 1/8" of the pipe's external size doesn't support flow, then the 2" pipe has an effective inner diameter of 1¾", but 2¼" pipe would have an effective diameter of 2". That gives a cross-sectional area of about 2.4" for the 2" pipe vs 3.14" for the 2¼". Much bigger difference than you might at first guess.

 

Connecting rods are supposedly forged on the L69, too.

 

All the small block chev connecting rods are forged steel.

The only connecting rods that are cast that I know of are
/were used in Pontiac V8's and Ford small blocks.

 

Hmm, well then I guess they were one step better than the "normal" connecting rods. Does X-type sound right?

 

actually ive heard alot that the l69 heads are 601 casting, not 416, but they are almost identical minus a few differences.

once again, l69 had flat top pistons (higher compression), better cam, better exaust, electric fan (most years), higher volume oil pump, more aggressively programmed ecm, more richly tuned carb,slightly higher stall torque converter on a4 cars, and much more aggressive rear end gears. I think I got it all.

edit: and ofcourse a search would have turned up the same results

 

My L69 had 416 heads, and X rods. I don't have to rely on "hearing" about it.

I still have one of the heads, the rods, and the stock cam, just because.

 

Yep....mine has the 416 casting heads too, along with X-rods. Maybe the TPI versions are 601 castings, but then again they were'nt considered "HO" AFAIK, even though the HP rating was higher on the TPI's.

My oil pump was a standard piece...not high volume like I have in it now.

 

https://www.thirdgen.org/techbb2/sho...hreadid=211160

heres where i heard about 601 castings, maybe depending on year there were different heads

rb83l69, your is an 83 right?
confuzed1, what year wre yours?

 

Mine's an '83 also.

 

No one has ever found any of these so-called "HO heads." They simply don't exist.

All L69 heads are common to 305s of the era, regardless of engine designation.

 

in the link i posted you say they exist but are only slightly different and two other people say they have had 601's on there 1984's. Ill pull my valve covers off some time and look at the casting number but until the i guess your right since i dont have any visual proof of 601's, not yet

 

My own heads are 601s, so I know they exist

They work really well once you port and polish them, as well as open the intake valve to 1.94".

The 601s have a smoothly outlined combustion chamber, rather like a kidney shape. The 416s and 081s are D shaped and very square in comparison.

 

Here is a picture of the 601.

 

601's are found on truck 305's, Vin H 305. Not bad heads actually 55cc compared to 58cc 416. They are actually a better head to port less garbage in the runners at least in the heads Ive seen.