I read through the specs page for this site, and this is my first post... so be gentle on my stupidity. I have a lot of questions so I apologize in advance, I'm loco!

I have an 87 LT carb'd 305 w/ auto (slooow). I would like to build a single turbo setup and swap in a 350 with EFI using megasquirt to control fuel mapping. My thinking is it would be easiest to get a harness and ECU from a 350 car. It's a budget build and I can fabricate almost everything myself. I've done it before for smaller engines.

For wiring, should I get a TBI/TPI 350 harness?
Would I need a new gas tank, or just HP fuel pump for the EFI?
Is it cheaper to go auto or manual gearbox, and which can handle 500hp?
What kind of rear end and gear is needed?
If keeping heat/AC, will space be an issue?
How streetable is 500hp in an F-body?

A lot of these topics could be solved by seeing some pics, which I've onyl yfound 1 or 2 of engine bays and header systems with a turbo. Any help would be appreciated! Thanks

 

Welcome aboard thirdgen.org.

What harness you use depends upon the injection type you use. If port injection, then use a port injection harness.

Your '87 should have an in-tank electric pump. A pump upgrade is a must, but you're also going to have to upgrade all of the rubber connections between the tank and engine. Getting all that from an EFI donor car may be the easiest way.

You shouldn't use the word "cheap" when discussing 500 HP. Nothing will be. Whether you go auto or manual, you're going to have to spend some coin. If all you do is drive it and don't expect to maximize track performance, you'll probably spend about the same on either choice.

Rear end choices are all aftermarket. 9", 12-bolt, or Strange S60 are the typical choices.

The streetability of 500 HP depends upon your level of discipline.

You might be better off asking this in the Power Adder forum. So, I'll move it for you.

 

First off, it depends on what you're doing. I'm not an expert at third gen harnesses by any means, but if it were me I'd probably swap harnesses or even go for something like the break out harnesses that are sold by several EFI places. With the Astro/Safari vans (what I really work on) They have a bulk head connector that's universal between the TBI/CPI vans and you just swap the engine side. Not a biggie. The one thing I will say about harnesses is have documentation (FSMs, Chiltons, print outs from the internet etc.) and plan things out if modifying an OEM harness. This makes a harness a success or failure typically along with verifying after changes are made. I would peacemeal a set of connectors from JY harnesses if you go the third party harness route.

If you're going port injection, it's probably NOT going to be a huge deal to swap to the TBI bulkhead versus the TPI one. You have a slightly different pinout versus the Speed Density TPIs but not a huge deal since you'll be adding the Megasquirt anyways and likely doing a few other customizations to change from a carb. I would avoid a MAF setup though, there is a lot of extra junk in it you won't need.

Besides this, if going with a TPI intake be sure to get accessory brackets. The TBI ones won't work due to the belt placement, at least not the truck ones. It's a pain in the neck quite frankly and I found out the hard way. Honestly I'd probably buck up and go with a single plane carb style setup.

Turbo wise, can you fabricate? If not I would find a centrifugal supercharger and go that route. Cheaper and easier in the long run. If you have a MIG and skills with it, then a turbo should be more doable.

Cheap, well cheap is a bit of a mis representation honestly. Nothing cars is cheap and turbo stuff isn't cheap either. If it was me, I'd do it this way:

-First off, take your stock 305 and leave it in. If it's healthy, there's no reason not to toss some boost at it first. People don't pay squat for them, it's a good way to learn the EFI system and it will take mods fairly well. The cam is very conservative which means it will be easy to tune compared to the thumpity one you'll try to toss in.
-Secondly, get the EFI system in and tuned N/A. I would learn the computer before doing the turbo stuff, there's a fairly steep learning curve to it. Find a mentor if you can. Hell, even if you get a TBI setup and put that on with the Megasquirt it will do while saving your $ for the rest of the parts.
-Third, turbo what you have. You'll be surprised what power it will make honestly.
-Fourth, don't forget the powertrain. It sounds like you're concerned about the axle and trans. This is a good call, turbo setups tend to be high torque. If you want streetability a 200R4/700R4 may be a better choice, but if you want real durability and/or have limited street miles swap in a TH400 and forget it. I have a 4L80E, it has its ups and downs. I did the Megashift trans controller, I'd go for something else honestly. For $400 you can supposedly get an awesome unit and it's way more than $150 worth of headaches to use the Megashift honestly. I'd check documentation for these swaps I know on a fourth gen a 4L80E swap requires cutting.

Leave gearing for later, with as much torque as you'll have 4.10s etc. will not be altogether useful and aren't required.

-Don't cheap out on a converter. All the power in the world isn't going to serve you if you're losing 20% on the top end because you're blowing through the converter.
-lastly, read read read. Can't say this enough.

IMO look at ZZ3Astro's build threads(there are a couple.) It's a GREAT example of a streetable 350 turbocharged engine and it's way more stock than one would think. See point 3 again after you read.

It makes great power too, even with the TPI choking the top end off. Something like a single plane EFI setup/cam would likely change the dynamic of the combo and make yet more power on the top end.

 

I appreciate all the info, lots in there!

One thing I realized is the exhaust setup would actually be the same regardless of which engine is in there. So I could definitely do the fabricating and fitting on the existing motor. I've built complete turbo pipe setups before on fwd V6 mazdas. I have some steel ban-saws, sawz-alls, a 220 Millermatic Mig welder, big vices, lathe, mill etc. I don't see it being a problem to build it from scratch.

I've heard horror stories about trying to boost the carb setup so I'd likely wait until the EFI IM was in place. It would be easier to use an oem intake plennum but I've consider building my own sheet metal intake as well from sheet metal with velocity stacks inside. It's pretty easy and would only cost ~$140 for the materials and sensors. Not sure which route I will go yet on that if I do this.

I'm not even sure I want to stick with an auto tranny because I think there's less trouble with a manual but I haven't priced out the cost of a TH400 and converter versus the cost of a manual gearbox with a good clutch. But if I'm doing an auto to manual swap I have to deal with master/slave cyl nonsense as well... more work! heh

I think I actually saw ZZ3Astro's vids on youtube a while back. I didn't know he was on here so I will look up his build threads for some info. Thanks partner!

 

first thing i would do is the tpi swap and get the ms installed and tuned on the 305 to get a feel for tunning, then build the turbo system on the 305 and tune it, this way if u blow anything up its just the 305. once ur good to go there then swap the 350 in and put the turbo system on that

 

project89, that's the most logical approach. The EFI switch will be a big chore and some cash so that's a good place to start.

This is the base LT model and according to the 87 data page, it's the 165hp 305 with an A4 tranny. What is an A4?? I can't find much data on it or any clues to how much torque will shatter it. This one has never shifted normal and refuses to downshift, almost like it's stuck in overdrive. My gut tells me it needs worked over anyway. If I stick with automatic, is the TH400 and 700R4 the only ones capable of withstanding 450-500 lb-ft? I'm not into drag racing so high RPM launches aren't what I'm worried about, just reliability. The drive train dictates the budget the most so I want to do my research there first. Thanks all!

 

Agree 100% with the EFI swap first.. get your EFI in and get it driving. While you are learning to tune, your engine will have a much higher tolerance to mistakes without boost!

I'm running a 700R4 and it's been going for two and a half years so far. I built it myself with Pro Built Automatic's pro-street kit. I'm having issues getting a converter that is stalled low enough for me, so it's not seeing max torque from my combo but I've been running 94 mph in the 1/8 for a long while. It's supposed to be good for 650 crank hp. I drive it on 150-200 mile round trips a lot plus I have a huge stack of time slips, so it's holding up under all conditions.

 

i too agree with project89 . i'm doing the same thing only i'm using a tbi instead of a tpi plus i'm tuning with ebl flash but same concept . one step at a time ...

 

Steve, I've been studying over your website and watched a lot of your vids. I appreciate you chiming in since your car is basically the poster child of my power and reliability goals.

freaky, is there a specific reason why you chose TBI over TPI? Ultimately the boost is the power adder so I'm not concerned if TPI or TBI have a 5-10hp difference because a half pound of boost makes up for any loss. BUT if one of these systems is easier to convert to from a 4bbl setup, I'd be interest in the easier path.

 

i would choose the tpi over the tbi anyday of the week for a boosted build

the nice thing about a tpi turbo build is that u are rpm limited by the tpi power will drop off around 5k-5,300 with a bone stock tpi system, so u can get away with a bone stock engine and not abuse the bottom end to bad.
witht he low end tq of the tpi and turbos suited to make tons of mid to upper mid power it makes for a very bad *** street car

the 700r4 can be used when u first get started but once u start making some good power the stock trans wont last , u will have to spend the money on a proper build kit or just go th400 or 4l80e and be done with it

im not sure how much cash u have but if the pending sale on my twin turbo system falls threw ill offer it to u for 2,200 bucks + shipping , incudes the turbos/wastegates / headers , downpipes and some cold side plumbing , but no intercooler(reusing it on my twin turbo 427 im building), also includes all the oil lines

 

Not to familiar with tbi setups but i am a firm believer a port inj setup is much better for 500 hp. I dont see many high hp tbi setups.

Try conversion to tpi based setup using any efi intake but retain a map based tpi harness. Try to find a 91-92 ecm and run code $59. Use it for n/a use for now to get used to tuning efi and then add 2-3 bar map and turbo for boost.

With stockish 305 you can import alot of settings from tpi bin file like timing and ve tables into code $59 and play with the egr/inj constant in that code until it actually runs. Then fine tune from there.

Its a big learning curve. It will take time.

Blow thru carb can also yeild good success when done right. Hangar18 has a diy mod for any carb to make it boost capable. May be an easier task

But efi is abit better for driveability. Keeping stock tpi style harness is as budget as it gets

 

if he does go with ms there is no reason to get a factory harness the install is so damn simple, if u can read , u can install an ms harness , hell its only 12 wires to hook up basically

12 wires without iac
16 wires if u use the iac
then +1 wire for each thing u add like tcc lockup or fan control etc


the bonus is u get a brand new harness that isnt hard or a mess of wires and everything is new and u can run it exactly how u want it , not to mention the ms harness are labled ever 2-3 inches down the lenght of the wire

 

my car came with tbi an i didn't want to go through the trouble of changing the wiring harness .plus i'm only looking for 400-500 hp . tpi will be a better an easier system to tune foresure . hope this helps

 

This one has a carb, so either way I have to run new wires, new intake and injectors. It's a real shame this is a carb'd LT lol.

The TPI's individual ports/injectors would likely be more efficient and will definitely be more torquey due to runner length and plennum design. The SBC is going to produce massive torque with FI anyway so I could lose a little torque in exchange for HP. I was thinking of making an intake with shorter runners and velocity stacks so you gain more mid-high HP and balance the torque so you aren't just roasting tires. I would be using street tires so traction is a big concern.

I have done MS on a FWD V6 and it wasn't too bad because I tapped most all the wires on the factory ECU, except IAT and CPS. Since I will have to run wires for injectors I might as well do a custom IM ahead of time with a big throttle body. I'd probably have to pay $100+ for a used TPI IM, where I could build one with stacks for $120ish. And it may even free up some space around the top of the motor and be lighter.

Lots of ideas are spinning here and I have a hunch I'm going to get even more confused as time goes...

 

Honestly, converting a carb to blowthrough and running that is probably the all time easiest way to do it. Not as accurate or controllable as EFI, but there have been reliable, stupid fast (like making a few times the power that you're hoping to) blowthrough carb cars

when you get into high torque applications there are better, more reliable parts out there for autos. You'll find that parts do exist to build a high torque T56 or similar setup but they tend to be $$$ and clutches become a bear. I've blown up a couple of Macleod twin disk clutches in my 4th gen (to which Mcleod said "huh, that shouldn't have happened, and sent me a new one, but the work involved swapping and parts broken... made it almost as bad as if i had to pay for another one) and was never happy with the way they worked, durability...

I think that people's experience on this board with 700r4's varies on the extreme. there are people that have run them forever and beat the crap out of them with no problem and others that have had them repeated die. I've had both, I had a '83 (one of the weakest of the 700r4's) that i beat on for 17x,xxx miles and got hundreds of slips with that never wimpered, and then I had an '87 that I blew up 3x with good parts in it in less than 17K miles (behind a stockish + spray 350tpi, though the interesting thing is that 2 of those times it let go without the spray)

I would love to see a reliable, bolt in 700r4 for these cars, I would spend good $$$ to get one in a second. They tend to be nice trannys for street use and perform well. I wonder if TCI's ultimate setup is that tranny but I haven't heard of anyone running it yet.

The big problem with using TBI for blow through is that really big injectors don't really exist for it. The slight advantage is that it is a lot like a blow through carb, you don't need big CFM and adding the fuel to the airstream further up results in a slight intercooling effect (a lot of very fast blow through cars do not use intercoolers). I actually think it's a good setup for as much as you can find fuel for, which is probably somewhere around 500hp at most.

What do you do for plugs? I've resisted this on my car running an MS on a TPI, build an adapter board, custom case... for it, but some of my plugs are getting old and brittle... if I break a few more I might seriously consider this as a way of getting better reliability and cleaning things up immensely.

 

diyautotune sells all the new sensor and injector plugs if u want all new plugs

on my cars i just reuse the plugs of the factory harness and buy new ones to replace any that are damaged

i belive diyautotune even sells the plugs without the pigtails so u dont have to solder, just strip the wire from the harness crimp and install the pin into the plug and ur done

obviously if u start with a engine that isnt fuel injected u will have to source all new plugs but its not exspensive


the relay board is nice for cars that were original carbed since it houses all the conections and relays for the fuel punmp, fans, main power that u would have to add to the car anyways