3100 into 84' S10 Blazer

[Axelsmancave]

Hi All,

I have myself a 1984 S10 Blazer, 2.8, with BW 4 speed and its carbureted. I also have two 1999 3100 SFI Malibu motors. I have read and am capable of making the FWD to RWD conversion (I've noticed the MG guys do it all the time). Everything I read says that I am going to love fuel injected 3100 motors and I agree. What should I use for my ecm?

Andy

[2.8-350TBI]

What exactly have you read about swapping in a FWD motor to a rear drive app?

You will need an electric fuel pump that is capable of the pressures needed for mpfi. (4.3 CPI blazer pump maybe?)
Then you will need the motor, which you already have two of lol.
Bell housing from second gen 2.2 s10, but idk if it will swap onto the BW tranny...
The ecms you should consider are the 1227730 and it has a weatherproof underhood brother called the '7727, and there is another more capable ecm: the '9396.

I went with a 7730 since those are easy to find in my area, and the swap chip I will use is meant for a 7730/27.

[Axelsmancave]

Here is some of the info I've read off of various forums:

I will need custom engine mounts. I did notice that my 3100 blocks have mounting bosses on both sides of the block but they may be located father forward that the RWD block. I will also need a Camaro dual pocket bell housing. I need to use a 87' or newer neutral balanced flywheel and the 87' -88' S10 oil pan and timing cover. I will need to flip the intake manifolds 180 too. Thanks for the info on the fuel pump I almost forgot about that. I think that will get the engine into my truck, next comes the Ecm fun. I am not scared of the electronics and wiring but I go really slow with it. Did I read that there is a documented 7730/27 ecm swap out on the web? Does the 7730 use all of the sensors on the 3100?

Thanks, Andy

[2.8-350TBI]

There are documents laying around on other sits, but there are wiring diagrams on the site here too...
Too bad I didnt find them until I decoded them using other sites maps.

Here is the link. http://60degreev6.com/forum/local_links.php?catid=10

Id like to see you get this project done!
Youll probably finish before I get my 3.4/3500 done

[Axelsmancave]

Thanks for the link! I learn something new about these engines everyday and I am blown away at how powerful these things can be. What have you got in your Blazer now?

[2.8-350TBI]

Yup its gonna be your best bet that link is 100% right for my 7730, the diagrams I saw were for the v8 7730 and were off in certain spots.

My blazer has a 2.8 TBI with a 5-speed behind it.
All ive done to it is a throttle body swap and cold air intake, it runs with 4.3 tbi's all day, cuz its lighter than most of em (3400# with full tank of gas, spare tire, a small toolbox, and me) and has 3:73 gears in the rear end. Its the vortec 4.3's I cant touch tho...

[Axelsmancave]

I went to pull the ECM form the blazer and I think I don't have one. I pulled part my dashboard and underneath and didn't find one. I then double checked my carb and it is a non-feedback carb. Am I correct that I do not have an ecm?

[2.8-350TBI]

Yes, you dont have an ecm lol.
You will have to make and add the whole wiring harness for it, or pull one from a tbi blazer and splice it with a 3100 harness to whatever your computer needs.

[Axelsmancave]

Good, I thought I was crazy for not finding it. The funny thing is their is a guy here in NM that is going to buy it from me who told me I had one behind the glove box.

[2.8-350TBI]

if you were injected yes, but thats where it should be once you swap

[geoffinbc]

You cannot use an S-10 oil pan it will not bolt to the 3X00 motors. You will need to modify the aluminum pan to clear the S-10 cross member.

[Axelsmancave]

Hi BTY,

Thanks for the info on oil pan. What kind of mods need to happen to it? As you know its an aluminum casting.

I got started tearing down my motor for the engine pull. Here are some pictures.

[Axelsmancave]

Hi All,

So I started measuring my 3100 motor components and so far the first few bores on the block have measured great at 3.5047" ish. So far so good. I removed the old rings from the pistons clean them up some and began measuring them and they measure all over the place. I am assuming this is a high mileage engine so there is some wear in the pistons. Here is what I measured:

-Thrust sides of piston: at bottom part of skirt = 3.5000" ; at top ring land 3.4800"
-30 deg form thrust side: at bottom of skirt = 3.5020": at top ring land 3.4804"

I suspect this isn't normal. What should a factory, never used piston measure? This piston did have the rod with the spun bearing. Looks like overheating?

[Joseph Upson]

Hi All,
-Thrust sides of piston: at bottom part of skirt = 3.5000" ; at top ring land 3.4800"
-30 deg form thrust side: at bottom of skirt = 3.5020": at top ring land 3.4804"

I suspect this isn't normal. What should a factory, never used piston measure? This piston did have the rod with the spun bearing. Looks like overheating?

Not following your measurements completely I can still say the differences are normal, not sure what the specs are to say the piston is within them. You are measuring the differences in a barrel shaped piston that was tapered that way to allow for expansion to a more uniform shape as it heats up. I measured the same difference in my brand new and used pistons for my recent engine build and also read about it.

If you have a welder and something to cut with I think I'd address the oil pan issue this way; about half way down the page:

http://www.v6z24.com/jbodyforum/also-growing-a-mullet-t112374,start,90.html

[Axelsmancave]

WOW! Thanks for the awesome link. I found a lot of good information on that thread.

I found a good article about pistons and how they are made, so my measurements now make sense to me. I do have three pistons that are worn well under spec. I've been looking for replacement pistons. I see a lot of replacement pistons for earlier 3.1 engines. Is there a major difference between the vin "M" pistons and earlier models? Parts Dinosaur seems to have what I need but I was looking for stuff on ebay too.