Well i finally got my upgrades completed and took a short test drive. I went from a GM-3 to a GM-8 turbo, installed a 3" downpipe, upgraded crossover pipe, new injectors, glow plugs, fuel heater/filter/water sensor, replaced all fuel hoses anywhere near/on the motor, '97 style airbox, fabbed another turbomaster for the GM-8, pyro/boost/trans gauges, flushed coolant/cleaned radiator, upper/lower radiator hoses, new heater hoses, thermostat, lightly ported upper intake. Thing sounded god-awfull when i first started it but after a few minutes it was close to sounding normal. Took it for a short test drive, didn't really punch it but eased into it and i had 8-9 psi boost rather quickly at about 1500 rpm. I'll have to adjust my TM a little, i think it's a little tight. Very little smoke out the back and the pyro never budged above 500 deg. After fueling it up, and driving it back to the house (round trip total of maybe 10 miles) it still idled a little rough but overall i'm very happy with the results. A great big THANKS to everyone on here for the advice, help and information!!!:D
I just thought i'd post an "after" for my mods. I'll drive it some more, then post with the final results and pics.
Don

Outstanding, Don! Thanks for letting us all know - we love to see somebody get ahead!

Your welcome, with all the great info & help here i couldn't go wrong!!! After i drive it some and get the TM tuned in i'll have another update. Hopefully with some towing data. Only thing that concerns me now is i think i have the TM a little tight, didn't expect to hit 8-9 psi with 1/3 throttle at 40mph!!:eek: I used a spring off a GM rear drum brake retainer, seemed to be about the same as the spring i used on the GM-3 TM i made. I'll take some pic's of the -8 TM, another $10 / 15 minutes to fab. :D
Don

That spring sounds 'way stronger than what's on my Heath TM... I watch everybody building these and really wonder, because I see so many different springs.

Springs have a compression rate as well as a force... the force is variable depending on the rate, and it's a curve, not a straight line. Sometimes, I see people's homebuilt TMs and I wonder if they move at all, they are cranked so tight and the springs are so strong... I'd prefer to see a lighter spring with a larger lever arm, myself, but then, that's why I didn't build mine - I don't trust myself to get it right.

Good luck with it, though.

I compared that spring to the factory spring that came on my GM-3, and it was a little stronger but not much. Can compress either between my thumb & finger without too much trouble. I "cranked" it down some when i built it, i have several springs and will mess with it until it peaks about 10-12 PSI more or less. Love how easy it is to change, one lock-nut and it's off. ;)
Don

Sounds like you really uncorked the boost Jeanni with replacing that downpipe and that GM-8 can't hurt. I was suprised at how quick the boost would rise after replacing the stock exhaust on my truck as well. I'll be interested in hearing about the rest of your impressions.

Remember the wastegate spring will only effect max boost opening psi, your mid range 0-opening psi will remain the same. Bill heath reccommends 12 to 13 max boost psi for mechanical IP 6.5's, but then thats with GM-3 turbos, they get innefficient above that and just blow hot air.

Tracy, I didn't add that i have a straight pipe exhaust too. :D The 3" downpipe to a splitter into dual 2 1/4" pipes that go out behind the rear dual tires. I have 3" crome tips there as well. ;) With the '97 style airbox instead of the flat '93 one i had, the GM-8 & 3" downpipe it builds boost in a hurry compared to before. Can't wait to tune the TM a little to limit boost and see how it does at 75 mph on the interstate. I'll post some pics & further info in a few days if i get a chance and not working 65 hours/week. Thus far i'm a happy camper. :D
Don