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1995 L67 junkyard engine exploration


2seater

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Yes, the pistons are a puzzle. The tops are relatively clean and my estimation is there isn’t a lot of time on the engine after repair. On the other hand, the sides and near the rings look like baked on buildup. Run hot or the tuning way off. I don’t know but it has come to the end of the line for now. I need to work up a pair of heads for the other block destined to get the supercharger so these will get some disassembly and evaluation

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I guess this is loosely related to the L67 exploration and honestly I found a bit of a surprise, at least to me. I have posted engine power curves and such in the past and I thought perhaps a comparison of the LN3 to the later model versions, particularly the S/C engine I am dissecting. Along the way, regarding the 1995 N/A engine in a Riviera, I discovered why the hp curves looked suspect to me. I had to look for other sources to find out the N/A engine is the first of the Series II engines and the Supercharged, is the previous Series I. More trivia I guess. 

 

The yellow lines are our beloved LN3, and even against the Series II and the S/C Series I, it has more grunt off the line. It is quickly overshadowed as the rpms climb with the S/C engine building a big torque lead at fairly low rpm, and the Series II power advantage is most evident at higher rpms. 

wykres_power_por_lbft.jpeg

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Interesting. I think the '95 NA engine would be a good choice for the Reatta. Close to the same power but a lot less complex. I like the low RPM torque of the LN3 and the chart shows why.

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I took the heads apart today. Most of the valves are in surprisingly good shape, except a few that apparently trapped moisture. Even the machined seats on the valves are in good condition with almost no pitting. The heads themselves will require more cleanup work, and likely a light porting and some reshaping, just because. I will get better shots of the heads later. The heads were not cleaned up at all, save for using a shop vac on the chambers and ports to get rid of loose material. It is evident on close inspection a couple did have water in them. I would like to save these heads for use on any engine no matter if LN3, L27 or L67.

 

I found a small tag attached to the frost plug on one head. As near as I can make out, it says "void if removed" and a number. Perhaps this entire engine is not original to the donor but is a remanufactured replacement?? It would explain why many items are fresher than they should be.

 

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17 minutes ago, 2seater said:

I would like to save these heads for use on any engine no matter if LN3, L27 or L67.

 

I wouldn't have thought they would fit the LN3. Would need to use the other SC top end parts to do so?

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4 hours ago, Ronnie said:

I wouldn't have thought they would fit the LN3. Would need to use the other SC top end parts to do so?

They are physically the same as the LN3, being the last of the Series I engines, aside from the slight difference in the rocker arm mounting. They have an extra approx. 5/8" hole, on each head, in the rail into the valve cover for the built in PCV system which works with the TPI naturally aspirated manifolds too. The LN3 doesn't have the same pcv system so the hole would need to be plugged, easily done, and an external pcv system installed. Beyond the roller rocker pivot difference, there is likely no advantage to using them. I will do a cleanup and mild porting, check the chamber cc's and try a flow test, but I suspect little to no difference. What I find advantageous would be the more universal nature of them when used on a Series I engine rather than cleaning up and porting for each engine. They would not work on a Series II engine, nor the reverse. 

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