VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc 305 TBI engine conversion

Hello All,

I am going to have to pick your brain's. . . .

I picked up an '86 K5 Blazer as a winter beater vehicle a few months back. After getting it road worthy, and using it for most of the winter, Unfortunatley, right before the big storm we had in the Northeast last week, the motor blew. I had a carbeurated 305 in it, however, I stumbled upon a an 87 K5 which would be an ideal donor, the only difference between the two is that this prospective parts truck has a TBI set up.

My question is that would I easily be able to make the swap froma carb to a TBI system? I prefer to keep the carb set up only because I had it rebuilt for the now dead-motor a week before it let go, so I just plan on using this donor motor for the block and heads. Right now I just looking for functionality!

Thanks in advance!

John Mahoney III

If you use the TBI it will require a higher pressure fuel pump (inside the tank), probably a tank, plus the computer will need to be changed along with all the various sensors, etc.
I would put the carburetor manifold on the 1987 engine.
Problem is that I am not positive the the 1985 intake will "fit" on the 1987 heads. Check and see if they both use the same intake to head gaskets.

VTJohn, knowing who you are and where you are coming from I believe that for this special question, you could get a lot of good input from this site(chevytalk.org). I know a couple of the moderators and they have been thru this mod. many times.
I go there a lot for questions about Chevy stuff not quite "stock" as we see here:

http://www.chevytalk.org

at the index page scroll down to the forum for your Vehicle type and model year.

Gene, Thanks. My father indicated that either you or Chip would have the answer. He is out of town still at the board meeting, otherwise he would be doing the posting. I definatley don't want to get involved with the tank. I planned on pulling the intake off the other motor, so I'll have to call the parts shop to see if it is compatible as you suggested. Would you happen to know if the holes for the carburetor fuel pump are drilled into the block? The other question I am wondering, is if BSing around with another potential motor is even worth the hassle, and perhaps should I just drop a crate 350 in for 1500. What started as a winter vehicle has slowly grown into much more than I planned!!!!

there are aftermarket harnesses available for the conversion from carb to FI. you'll also need a donor computer, sensors, etc. Edlebrock has a manifold that will bolt to the vortec heads and accepts your carb. the number is 2116, Performer Vortec. the manifold would be the most cost effective path.

John,
Often an apparently inexpensive part can require so many alterations that it is not the bargain anticipated. This seems to be one of them. If you plan to keep the vehicle for a long time then a crate engine likely will be the way to go. Or you can also likely find a local rebuilder to either fix yours or sell you a replacement. Make sure that they have a good reputation and will stand by their work. The closer you can come to what was originally in the truck will likely prove to be the best solution.

VTJohn,
There is another issue about using the TBI engine. Some years of TBI engines did not have a opening for the mechanical fuel pump. I don't know when that started. I do believe that some of the guys that modified their cars to run the TBI engines have found electric fuel pumps that are not mounted inside the fuel tanks. Many of them have changed their cars to the newer electronic shifted transmissions and also went to the TPI FI.

I don't know all of the details of the switch over but It may pay to buy a donar vehicle or why not check out the crate engine route?

fewer headaches would be with the crate motor. a couple of years ago the sb 400 I built for my 85 was on it's last legs. 80,000 miles I can't complain. Mr Goodwrench is the way I went.

Thats correct. Installing a 1987 engine in a previous year could open a whole new can of worms. 1987 is the year the block and heads were recast (note different valves covers) and it could be next winter and thousands of $$$ before its back on the road.

Thanks All! I knew that I would get some guidance here.

I more than likely going to go the crate route, however, I am kind of apprehensive about investing that amount of money into something I only paid 1200 for. As it stands now, there is a decent amount of rot in the usual trouble areas, and the transmission is pretty sloppy. The sole reason for getting this truck was to navigate long island in the winter, since my mustang was spinning out as soon as I touched the throttle when the roads were white. Needless to say, I don't want to pour all that much money into this thing. For the time being, until the weather warms up, I'm going to sit back and see if a better one surfaces and use the current one as a part's car. Its on the street now with a fresh inspection so I have some time to figure out my next move.

if anyone stumbles across a running 4x4 k5 73-86, especially you guys living out in the desert, let me know!!


John

I bought mine new in 85. it's had one repaint 3 years ago, never been in a garage except for repairs. I'll keep it till it won't go no more.

If its as rusted as most cars of that age are around here I would't put a dime in it.
If nothing else I would find a good rust free southern car.

I think I am going to go with what Gene suggested...this thing is pretty rotted, and hardly worth dumping 2K into a motor when I can get a better one for 3 or 4 thousand. Thanks for the help everybody!