Exhaust and Driveline Engineering Questions

[TamuFD]

Got a few ideas to play with:

First, would like to add overdrive to the beast (87 K30 crewcab 6.2NA/SM465/NP205/3.73) Ive researched under/overdrives, the NV4500, and regearing options. But i've got a bug in my brain. Would it be possible to take a divorced NP205 (or other gear driven t-case), flip the whole thing around, and run it right behind my factory NP205. This way instead of engaging 4Low to get a 2:1 ratio. I can get a .5:1 ratio. A little high for overdrive, however Ive got plenty of gearing choices to play with. Have to make/borrow a crossmember and shorten the driveshaft, but there's no shortage of driveshaft length either. I can find a t-case for a couple hundred bucks, and wont have to sacrifice my gearing. Sounds like a plan to me. Any insight would be appreciated.

Secondly, I'd also like to turbocharge the beast. I have considered putting a pair of turbos to keep the dual exhaust... dual. as well as power-balancing the engine. Mount them under the truck, not worried about a little lag. My concern is that Ive heard the 6.2s cant take much boost due to the high compression ratio. Also heard a recommendation to change head gaskets when adding turbos. Too much work, not enough time. Therefore, would it be possible to direct the compressed air, into the exhaust, drawing or pushing the exhaust out more quickly. This will (or i hope it will) create a vacuum drawing more air into the engine inductively. It should only allow the engine to take in as much air as it can, and hopefully save my headgaskets for another time. My fear is the possibility of a vapor-lock-esque situation from having a vacuum on the exhaust, or that between the opening and closing of valves, no real amount of air will be allowed in inductively. Dunno, any help would be great.

Third, I'd like to put a high idle system on my truck. How would i go about this (where can i find the right solenoid)? Thought chevy had a hi idle system on the 6.2s, apparently i was wrong...

Finally, I'd like to know if there are any vehicles (readily junkyardable) that had hydraulic clutch set up. Wanted to buy new master/slave and fab a bracket for the bellhousing. But Vato-zone wanted near $60 for the slave alone. Heard the LUVs had a hyd clutch, but i havent seen any. Once again, your info is the only opposition to my insanity. Lemme know whatcha think.

You guys have saved me more headaches and stress than you'll ever realize. Thanks for your time and wisdom. (Sorry its a little long)

 

[Hogback Fabrication]

You can run the t-case backwards to get an overdrive. You may be better off using a 203 range box. Kinda like a doubler, but with the 203 range box mounted backwards. It wouldn't be shift on the fly either way.

The 205 idea sounds too big, heavy, and long to me but it would work.

 

[TamuFD]

Thanks

 

[tRustyK5]

I like thinking outside the box too, but it can get spendy and often enough not net you the results you wanted. For turbocharging the 6.2 I'd stick with either a 6.5 factory turbo set-up, Banks, ATS or similar. As long as boost stays reasonable and the 6.2 is in decent shape it'll be fine and give you the extra power you want without having to get into internal mods. The big upside is the lack of having to R&D the whole thing. Single turbo is more than enough, if you want dual's after the turbo you can either split it after the downpipe or run a single in and dual out muffler.

Backwards 203 has been done sucessfully...and is probably the easiest way. Cost versus going with an NV4500 is probably similar. I went with an NV4500 and doubler behind my 6.2. Great combo at both ends of the scale.

As for high idle, the 6.2 does have one. Otherwise known as the HPCA (high pressure cold advance if memory serves me). There is a temp switch at the rear of the drivers side head, and up til it reads approx 120 F coolant temp the HPCA should be on. This effectively bumps the idle speed up a bit and makes the 6.2 noticeably louder as far as clatter goes.

Hydraulic clutch stuff was from '85-87(91 in sub's and K5's) You'll need the specific bellhousing, clutch slave, fork, clutch master, line and hydro pedal assembly. Yeah, it's a PITA and the parts can add up quick but it's very worthwhile IMO.

Rene