hey guys, just joined, and recently decided that going to the tpi would be better than carb! i picked up an 88 iroc 305 engine, and i want to swap the tpi setup over to my 84 with the built 360ci in it. i am porting the base manifold and upper plenum right now along with my iron 194s, and hopefully i can find some high-flow runners to port too (if you know someone whos got some cheaper than new, or have some suggestions im up for them!!)

i need to know if i can convert the MAF system to the speed density/MAP style TPI. i also want to know if anyone has every machined out the center post on the throttle bodies and put in an oval plate? im a pretty handy fabricater, and have access to some machinery. i just dont know if this would yield anything good or not. i am going to buy a computer later, and a custom prom from a local speed shop, but i have the stock harness, and cant find newhere that will re-do it for a stand alone operation. im on a kinda tight budget, so im doing all the assembly and most of the fab work myself. i just hate wiring, and dont wanna try to do the harness myself.

any opinions, help, advice you guys could give would be great! thanks!

HK

 

I converted my TPI harness into a stand alone fairly easy, I studied the harness and the ECM pinout diagram for about 3 days before I finally grew big enough ***** to start hacking away at it. Everything turned out great and the truck runs well. As for converting to the speed density, I know that it can be done, but I think you will have to get an upper plenun from a Speed density car, the 85 to 89 plenums dont have the bung for the map sensor, or you could always drill and tap your own.
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Oh, almost forgot, 4 of your intake manifold bolts are not going to line up properly if you are using the lower manifold from an 88 motor. The centerbolt heads have the 2 intake manifold bolts in the middle drilled at different angles than the older heads.

 

i can drill and tap the MAP bung. i believe if i do some measuring/drilling/ grinding to the lower manifold i can get the bolts worked out. im not afraid to mod or fabricate, working in a machine shop for a couple years payed off greatly.

any more info you have on your wire harness mod would be great! i have to pull the motor again and yank the old half carb harness out, and i would like to know how clean your harness turned out.

lastly, correct me if im wrong, but the MAP setup would eliminate the MAF completely, correct? thanks for the help!!

 

Yes the MAP system completly eliminates the MAF system and the associated relays. The only info I can give you about the wiring harness is to study the ECM pinouts very carefully. Decide what you want to keep with the emmisions system and what you want to delete. It took 6 weeks of working on the truck until dark after I got off work mon-fri, and all day saturdays and sundays to perform the swap and 4 of those weeks were spent on sorting out the wiring. But the truck runs good with no CEL, I retained the MAF system, the EGR, and the charcoal canister. I had a prom adaptor programmed to eliminate the A.I.R. system, the VATS, and to set my cooling fan on/off temperatures. Even my electronic speedo works. You could also order this harness http://tpiparts.net/inc/sdetail/1052. I ordered alot of the stuff I used to perform my swap from TPIParts.

 

kewl, thanks for the continuing advice! i guess i should state the cars stats to help with less guessing on your part.

its a 5 spd (going to a t-56) 350 block, fully ported and pollished 88 305 heads (bumped to 60cc chambers and 2.02"/1.60" valves), fully ported and polished 88 tpi base manifold, ported and polished SLP runners, port n polished upper plenum w/ siamesed runner ports. hooker headers, flowmaster exhaust, HEI dist. 3.73 rear posi. im currently trying out a new throttle body setup (machining out the center post, porting it out and installing an oval throttle blade)

there are NO emissions on this at all. everythings stripped. no a/c, no anti theft (yet, later, will be stand alone.) no cruise. the bare essential hotrod.

i believe that i only need these sensors with my setup, but correct me if im wrong. * indicates needed.

 

The CEL is a definate must have, otherwise you will have no indication that something may be wrong. You will need the Vehicle Speed Sensor for it helps control things like idle speed, charcoal canister purge, and MPH fuel shut off. It you decided later to run an automatic, it als controls the TCC. You can take the star away from the oil pressure switch, you don't actually need it, it just serves as a backup in case you fuel pump relay takes a dump. The one thing missing from your list that I can see is the Electronic Spark Control Module. That is a must have and it probably won't even run without it. As for machining out the center post, you probably would have been better off just boring the throttle bores and putting in larger butterflys.. The single plate throttle bodys are generally reserved for Big Block applications as they flow about 1000cfm. 1000cfm is way to much for a small block. Do a little bit of research on the speedometer, I believe the computer gets its VSS signal from the speedometer itself, and the speedometer will remain cable driven.

 

many thanx again for double checking that list for me! i checked my harness a lil bit closer today, and it looks like someone got to hacking on it already. im gonna check it more, but i think its kinda boned. i studied a detailed pinout of it, and i may try to make my own harness with the parts i have. im still going to check to see what a custom made one will cost (finally found a shop thatll do it) but i speculate on the spendy side.

the throttle body is just a test really, i have a couple extras, one is a twin 52mm unit that just needs a clean n fluff job. are you sure 1000cfm is too much? ive been looking, and alot of the aftermarket LS throttle bodies are rated from 900 to 1200 cfm, and they say its for standard bore and stroke setups :S i know that LS engines are quite a bit different, but i guess ill see what this does, if it helps the high rpm (which i believe it should) then ill like it. guess ill find out!

thanks for the continuing advice!

 

I'm currently dissecting a wiring harness myself,and have found there to be very little info on the subject. One would think for as long as the 85-92 tpi system has been around someone would have done a write up on the process.( Trust me I've spent hours on Goggle looking)
But about all you can find is people who pay the big bucks for a aftermarket harness to do the conversion (non Camaro). Well hell what's the fun in that?, kinda like paying someone to build you a car.

 

haha, yea, i see what your saying, but sometimes paying someone to do the work for you isnt about "them building your car," its about getting a professional product that is taylored to your app. im like you, a DIY'er, and i can do the wiring, its just that with chassis and engine wiring, theres alot of crap a bumbler like me can screw up lol. im a "cut first and find out later" kinda guy unfortunately, why im now more prone to researching :P