2wd-k5

hey everyone im new obviously, i searched and searched all over the web, and here, but i can find any info on anything lol, i am planning on building a twin turbo propane setup using 2 impco 425 mixers, i want built it with junkyard parts (turbo intercooler from diesel, turbos from chrysler 2.2)
so im just going to explain what i want to build and i hope i can get whatever help i can get, if anyone sees any problems, just say so lol

first off i have a set of cast .60 over pistons, most likely i will just buy some dished forged ones, the heads are 2.02 double bump closed chamber heads that will have new hardened valve seats installed once i get rolling on the build. from there, it goes to stock small block chevy exhaust manifolds turned forwards facing the front of the truck and up, mounted on themwill be the adapter (i will fabricate) that will let the chrysler turbo mount to the manifolds (underhood room is not an issue as i have a late 70's k5 blazer) for the drawing side of things, i have 2 impco propane 4 barrels which will sit beside or on top of the turbos depending on height.
after the turbo, each one will have its own intercooler running either side to side or up and down depending on how much the sideways style blocks the rad, and each of these will be junkyard units, with the kind depending on size, avalability and price
from there i will either fabricate a box for both inlets to go into to bolt to a carbureted intake, or ill buy one depending on price
i dont need huge power, i just need about 450 ftlbs to tow a racecar on a trailer, and do it relably, i am trying to use readilly available parts to keep prices down, and junkyard parts where available
i am planning on using the threaded hole at the back of the block where the oil pressure guage is normally located for my oil supply
obviously i need a few more things like a wastegate, boost guage and such, dont think i have overlooked them, i just want to get the big planning out of the way first for this, i can sort out the small things myself through searches, but i have never seen anything like what i want build, all i have seen is a draw thru big block on propane, and i couldnt study it

basically i just want feedback on my system, does it sound good? what should i change and what should i be looking out for?

one last question... i have buy an oil pump anyway, so should i get a high volume one?

thanks for any help given

Matt Cramer

I don't like Chrysler turbos for junkyard setups - they're pretty tiny, and the proprietary flange limits future upgrades.


Sorry, I have no idea how the propane mixers will work in a blow through; they'll probably be OK for draw through though. Just don't like the thought of a boost leak under those circumstances...

2wd-k5

awesome to know man, i mean to have the propane setup built as a draw through, with both turbos feeding into a fabricated hat on a regular carb style intake (i am trying to keep it cheap as possible)
good to kow about the chrysler turbo setup though, i should have realized, those 4cyls dont rev high, and simple math of the 4 banger size (2.2) vs a 350 (5.7) should have told me that
the blazer the setup will go into will be meant as a general beach cruiser, but also as a tow rig for a 1/4 mile car, so high rpm isnt the goal, low end torque is, and on top of that, the camel hump heads are out for a set of smog 1.94 that are hogged out

2wd-k5

ok, now what about the chrysler 2.4 pt cruiser setup? looking around, the turbops dont seem to spool until 2k rpm, and at 2.4l x 2 = 4.8l, but with their turbos spooling at 2k rpm, by guestimations on a 5.7 it should spool at 1500 rpm and probably top out at 4500 rpm (maybe less no big deal) to give me some awesome torque (what im looking for)
my main thought on this project is torque and turbo availability, as i live in canada so selection is very limited
in another school of thought, an early gm 6.5 turbo single may work also
and one more thing on this post, while searching, i noticed something about carbon coating or something for draw thru designs, i cant find it again, but is it possible to get non coated turbos coated?

lost of questions i know, but there is so much info that is non specific to my setup, that it makes planning very hard

Matt Cramer

Biggest problem with the 2.4 Turbo? They cast the turbine housing as an integral part of the exhaust manifold. I'd rather use something like a pair of Holset HX35s, or maybe two Mk III Supra turbos.

2wd-k5

doing dome searching, it seems like the holset would be the best choice for me. a huge part of my problem is availability, i live in the BC interior up in canada, so selection is very limited.... until it comes to diesels, doing searches, it seems the holset is very reliable, and cummins are everywhere in the junkyards, so with 2 of them, rebuilt i think i could be fine, thanks very much for your help matt, now i just ned to figure out the carbon part for the draw thru

2wd-k5

been searching for a bit, cant find the carbon seal kit for a holset, so im just going to hold off and do some reseach on blow thru propane for a bit and get back on it, and as i build it i will document and post, for info on the build

2wd-k5

ok, so i spent all day checking it out and checked out every google link for v8 propane turbo (much to the dismay of my wife) and everything i see with propane turbos has a single turbo and single mixer, i still want to go twin turbo, but at least i can see how their set ups are
first off, most of the setups are blow thru, as carbon seal turbos are a thing of the past before EFI turbo setups (the reason for it is the oil fron the crank case gets into the turbo, goes thru the bearing and out the exhaust till it drains the crank case. And it turns out the impco 450 propane system doesnt need a vaccum (but i would have to buy a vacum pump and i think ill have to figure out an exhaust scavenging system for the crank case vent) and under boost conditions, the 450 impco design will flow up to 950 CFM!! so only a single mixer is needed, i still want to go to a twin turbo setup though, because what i am after is low end torque because this truck is going to be a cruiser/tow rig for a racecar (think diesel power) so 2 small turbos are still the ticket for me vs one big turbo that wont spool till 2500 rpm
i will be spending the next little while putting the parts together, and i plan on fully documenting the build for other people who plan on building the same setup.

while dooing my searching i found many many people asking about the twin turbo propane setup, but there is absolutely nothing in terms of build, parts or theories on TT/prop out there
i am going to source a lot of information from a car guy who lives down the street from me as he has a 32 ford truck with a 46 cadillac flathead v8 with a superchager on propane (i know freaking crazy right?) as well as a "winter beater" 81 ford fairlane with a 408 stroker race motor on propane so he may be the one to help me set up my prpane system as well as give me first hand knowledge on the boosted propane subject, thanks muchly for your help Matt, and i will post about my build as soon as it starts

Deputy Diesel

Digging up an older one here. Just wondering how this is going.

Im in the okanogan as well. And always building something.

Current project. 350chevy. single Holset HX35 12cm exh housing. Single Impco 425 mixer. Dual model E convertors. Colt cams custom turbo propane grind. Performer intake. built up 882 casting heads.

In a 89 chevy 2wd shortbox Lifted 35inch tires. welded 14 bolt and 4 wheel disks. built 700r4. 5 linked rear with f150 front coils.

1972K20

Is this build still active ? Sounds interesting !!!!