Sparky SpeedoQ I'm getting ready to do an engine/transmission swap on my '92 Chevy C1500 truck and I see a potential problem. Hopefully you can help. I'm taking out the factory 4.3L V-6 and the five-speed manual transmission and replacing them with a mild 355 and a TH400 trans. The problem I'm going to have is with the speedometer. The factory speedo (which I would really like to keep) is electronic. The old TH400 is a geardriven cable style. What is the best solution for me to get correct speedo operation with these components?
I've done a fair amount of research and made a dozen phone calls, all with no real good answer. I did find that in the early '90s, Chevy used a TH400 in many applications (a G30 van, for example) that had electronic speedos. I found the GM part numbers for the vehicle speed sensor (PN 8655291) and rotor (PN 8655315) for these vehicles. I'm just not sure if I can use them on my trans or not. Will they work, or was there a difference in the transmission tailhousing to accommodate this change? Thanks for your help.Mark HussVia e-mail
A You're right on track to spark up your electronic speedo. We checked with Tom Woodside at GMCOPO to see what he had to say about your swap. Tom fills us in that you have the correct list of GM components to get the proper signal to the speedo. He reminds us that the speedo-driven gearhousing is in the transmission case, not the tailhousing. He said that when you replace the speedo drive gear with the reluctor ring (PN 8655315) make sure that you install the ring in the same axial location as the stock speedo drive gear you removed from the output shaft. Reinstall your tailhousing and bolt in the vehicle speed sensor in the standard speedo drive port in the trans case. This will give your speedo the signal it's looking for.
Looking For TroubleQ My '93 1-ton crew-cab dualie with a stock 454 is having trouble towing my 28-foot trailer. A friend says to replace the cam and dished pistons. He is giving me a set of '77 oval-port heads to install, but I must use a special Fel-Pro head gasket to accomplish this. He says Edelbrock makes a TBI-to-oval port intake manifold. Will this all work? I need more torque for the fuel used! Should I just look for an earlier block? Any suggestions or ideas are greatly appreciated. I can't afford a new diesel! Thanks.Dave ZimpelVia e-mail
A Don't we all wish that we could afford a new diesel? My '96 Vortec 454-equipped 31/44-ton truck, pulling my 24-foot Pace enclosed trailer with all my junk, doesn't drive by too many gas stations! My buddies with late Duramax trucks kill me on fuel economy to the tune of double the mileage. Maybe someday.
GM released the Gen V big-block Chevy in '91. This updated big-block had revised water passages in the deck surface of the block and the cylinder-head castings. These water passages were increased in size to facilitate getting the core sand out of the castings after the pour. With these larger passages in the Gen V block and the scalloping of the Mark IV ('90-and-earlier) cylinder-head mating surfaces, the head gasket has very little-if any-material to seal on. Yes, Fel-Pro makes special head gaskets to help alleviate this situation; however, it's sketchy at best! Back in 1990 I got my hands on a preproduction Gen V engine. We swapped on a set of Mark IV heads and ended up with a slight water leak in the valley. This is why when the Gen VI big-blocks were released in '96, they added a little more material to the deck to allow the use of early heads.