'99 L31/4L60E into 71 C20: Observations

[Tim240Z]

Well, I got the engine fired and running. I haven't driven it yet as I have some more yet to do, but I found some interesting things during the conversion:

1: The PCM needs a brake switch that is open when the pedal is depressed. The regular brake light switch is closed (provides current) when the pedal is depressed. So I need to run 2 switches....no biggie, but one more thing!!

2: The L31 sounds pretty sweet with open headers

3: The Helms FSM is written and organized like a Taiwanese VCR manual!! The "Carline" FSM that I have for the LT1 is wayyy better.

4: After hours in the back reaches of two parts stores, there is no possible solution for oem radiator hoses for the L31 and the 71 radiator. I had to use one of those crappy flex hoses for the top, and splice 2 hoses together for the bottom. Not ideal, but I want to eventually get an aluminum radiator, so I am not too concerned about the cosmetics of the setup right now.

5: The L31 runs the oil through the radiator in the Suburban. So, since the truck did not have that provision, I was faced with a choice. Either block off the external oi lines, or run an oil cooler. I chose the latter and mounted it under the radiator on the core support. It will get some air flow, but not much. I was worried about keeping the oil too cool.

6: Driveshaft. Had it shortened 3.25" and overhauled. All I can say is that I am very very very glad I did that. One universal had 4 needle bearings (for the whole universal!!!) Center bearing was toast too!!!

Well, I have all the gauges working except the speedo (needs to be electronic). I think I will make a new dash panel with all aftermarket gauges though......later though.

7: Tilt Column: This was very easy!! Since all the transmission activity for the 4L60E occurs at the tranny, I could just bypass the PN lockout and the reverse light switch. Made the install very simple!!!

8: Fuel system: I got ALL the hard lines from the Suburban, so I used them. I used the original truck feed line for a return. I drilled a hole in the bottom of the tank and welded a fitting to it and ran some 3/8" Aluminum fuel line to feed the L31. Used the MSD 2225 inline fuel pump that I used with the LT1 in the Z car with a high flow filter before the pump and the OEM suburban filter after.
That's about it for now, I guess.......now that everyone is asleep