I have a GM-4 Turbo and a set of 6.5 exhaust manifolds for my 87 GMC 3/4 ton with 6.2 J code engine. I do seriously hope I can make this work. Wastegate doesn't seem to have any preload on it.


Questions galore..... Can a wastegate acutator from a Garrett t-3 be made to fit? and the accutator is to open the wastegate, correct? Do the others like the T-3 have an internal spring in the accutator that puts pressure on the flap gate?


Should have researched beter but got a GM-5 with NO play for $200 and a new set of 6.5 manifolds for $140, do not yet have a turbo intake manifold. Head swaps nopt practicle, this engine has 73,000 original miles (documented) and new injectors. Where does the 6.5 turbo dump return oil from turbo, and is the stock line an AN-3 fitting?





Edited by: thevirginiadude

The vacuum actuator uses vacuum to hold the waste gate closed to build boost. You can check it with a vacuum pump. You can replace the vacuum actuator with a spring adjustable version. Turbo Master is one. You can also make your own pretty easily.


The stock 6.5 turbo (at least on my 93) dumps oil into a plate that bolts over the "old" mech fuel pump location.

Truck manifolds put all the heat on #6 & 8 cylinders. Headgasket repair and cracked heads will result from engine coolant temps over 240*F, EGT over 1200*F, and IAT ~250*F. Moniter Boost and pyro guages and consider adding intercooling.


The adjustable mechanical spring arm would work well for you. 10-12 psi boost is max before intercooling.


If you have to get into the engine again, rebuild with 19:1 pistons, 6.5L heads.Edited by: quantum mechanic

Truck manifolds put all the heat on #6 & 8 cylinders. Headgasket repair and cracked heads will result from engine coolant temps over 240*F, EGT over 1200*F, and IAT ~250*F. Moniter Boost and pyro guages and consider adding intercooling.


The adjustable mechanical spring arm would work well for you. 10-12 psi boost is max before intercooling.


If you have to get into the engine again, rebuild with 19:1 pistons, 6.5L heads.


I have a pyrometer on it now (was running a Banks stinger kit). Have every intention of putting on a boost guage too. With a boost controler to make sure it is in limits. Trying to find an intercooler that will fit behind the grill.


Heres a question for the experts. What is max intercooled boost level that can be considered safe. With stock internals on a low milage engine.

If your making 15+ psi with intercooling it should be more than enough for your stock internals, and it's about all a GM-4 will make.

OK, my concern was ariving at a boost level that is certain to be unsafe for the motor. And that is something I am seeking to avoid.


Its no Cummins 5.9 I have no delusions about that. But I do want the most that can safely be made with stock internals. I do have the GM TH400 transmission, not the 700R4 that is far weaker. I do wish I had a 4L80 but since I have a 1987 GMC 2500 4X4 it would be expensive any way around to swap a equally robust OVERDRIVE transmission into it.








Edited by: thevirginiadude

before you tear into it you might want to address space issues with the heater box on that 87. thats why the banks system sits so low. don't give up though i have a buddy with a 90 blazer that wants turbo and we are currently trying to figure out how to re-engineer that box to maybe use a smaller core to get clearance. the van and hummer top mount turbo set-up is an option but is harder to find, requires different heads, and would be more $. gud luk!

Wifes gonna kick my but if I have to sell the parts I already got. Wanted to buy the Banks sidewinder 2 years ago but she went off on me. I got the stinger system because I was able to prove to her it was cheaper than muffler shops around here. Anything that is big bucks is out. Truck see's little use and until the telecom sector rebounds excess spending money is in short supply.


How bad is the interferance issue with the heater box? Before I break off manifolt bolts trying to take off my manifold and get in this over my ears?

First - no additional heat is put on any cylinder by any manifold.


#8 cylinder has usual Chevy problems, found on any Chevy V8 block, but has little to do with the turbo, or un-balanced exhaust, or any other misconception.


There is some theory that intake plenum swirl, where flow comes around the upper intake plenum elbow and blasts directly into #8 port, may have some consideration, but naturally-aspirated Chevy engines, Diesel and gasoline, exhibit similar cylinder wear from hotter coolant temps.


(Wanna do some free-thinking? Water swirl in northern hemisphere is opposite direction of swirl in southern hemisphere - same with tornados, typhoons, and hurricanes. Do Chevy V8 engines in southern hemisphere show excess cylinder wear in #7 cylinder in opposite bank? Think about it........)


The oem turbo-mount exhaust manifold is massive, radiates and retains much heat - the entire passenger-side bank is subjected to more radiated heat than the driver-side bank, effecting the valve cover sealing, and possibly some of the plastic parts in the valve train.


Does not cause any failure difference than on driver-side bank.


The dual-element tin heat shield between the manifold and head is extremely functional and very necessary to minimize heat radiation.


Second - head down to the local boneyard, check out the S-10\S-15 trucks, to about '93.


Put an eyeball on the ac evap housing, noting the similarity in general size and shape to the C-K housings.


Also note the angular relationship to the firewall, compared to the C-K housings.


C-K and S-10\S-15 housings are of two distinct materials thru the years - fiberglass and PVC, or some such.


Man with a slow hand can adapt the two housings together, such that interested spectators do not notice any peculiarities.


Use the fiberglass versions, due to the heat from the turbo, and it will need the foil-over-glassfiber insulation, as in the Astro van doghouse.


Finish up with R-134 conversion, including plastic expansion-screen tube, and you're cool to go.


Third - use the 6.5L electric lift pump - the factory turbo drain can be bolted in place of the original mech pump, allows use of factory drain tubing.Edited by: gmctd

gmctd,


We have one member from south africa. We could ask him if he's heard of the #7 cylinder getting excessive wear.

http://www.dieselplace.com/forum/smileys/Wink.gif

I have no intentions of swapping in newer heads. This motor and the truck has only 73,000 original miles. Was originally a county vehicle (fire Dept) till it was sold to a dealer at auction 4 weeks before I bought it. Called the county garage and had them pull maintenance records from file and confirmed the milage.


If this one blows and I keep it I am dropping in a 12Valve 5.9 Cummins.


But I don't see that day comming any time soon. I don't drive it a lot either.