Hello All

Newbie here. I am looking for some information on a project that my mechanic is considering. He asked me to look for info on the net so here I am. Before posting my question to you, allow me to state that I have used the search function here and have come up with partial answers to the question I am posting so I have done some homework. I would be greatly appreciative of some further advice.

The potential project is a 1987 Blazer. 2.8 V6 TBI 4x4.

I want to know if a 4.3 TBI from a 1992 4X4 will go into the 1987 Blazer? Basically, I need to address all the issues that I can expect to run into. For example;

Computer compatibilty
Transmission compatibility (I have the tranny from the '92)
Exhaust compatibilty
Any other "hidden" expectations such engine/tranny mounts, ect.

I have done the research on other posts and understand that the transmisson bell housing (on the '87 2.8 V6) is not compatible with the 4.3 TBI from the '92.

I need to report back with a thorough examination of all issues that can be expected so that we can make a decision on whether to proceed or not. ANY advice or help would be appreciated.

Thank you in advance for your input.

 

New motor mounts, use the whole combo, both engine and tranny. May have to improve cooling. If you have access to the other radiator, it would help.

Computer issues are much simpler than many here will tell you. If you intend to use a tbi (throttle body) the wiring and sensors are common through about 91-92. The computer may even work. I cannot vouch for this but am probably right. Would at least be worth trying. The reason I write this is because I have been investigating this very closely. The simple fact that all of these motors are asked by the factory to run to just about the same standard and even use the same sensors and wiring (though some have different part numbers) means to me that input and output information to and from the socalled computer is pretty much the same. The throttle bodies are the same in construction other than having to be sure you use exactly the same KIND of vacuum port and on some 2.8's there is one extra vaccuum port. Injectors are different for each size engine, but both fire at the same time in all even the v8 tbi systems, just a step larger injector is difference. The 2.8 tbi holes are a little smaller; exterior the same. All from 4.3 through the 305 and 350 are the same after that, body wise.

On the other hand, should you be doing something other than a tbi; you would have serious problems. So as long as you drop in the whole system and buy new motor mounts or adaptors (search for JTR,...Jaquars that run. Go to their website) Good place for motor mounts. Yes lots of v8 information, but the v8 and the 4.3 are very much alike.

Issues about transmission and speedo may crop up. Cant tell you about driveshaft problems, but if your other tranny is the same length, you ough to be fine.

I see lots of advice that says this is a lot of trouble, but haynes manuals lumps all v6's under the same diagram to 92. I beleive its less trouble that thought. If it is possible to catch the computer from the 4.3, do it.

Exhaust may need some adaptation, though if you leave yours hanging from the cat, muffler and tailpipe, you ought to be able to adapt it. The exhaust ssytems run the same way and occupies the same space on my 95 / 4.3 as on my 89 / 2.5 , 86 / 2.8. Diameter of inlet for cat is my only serious question. If it isnt then you may place some restriction on the flow by using narrower pipes all the way.

 

If I were you I would consider going to a 350 conversion and get it overwith.As for your changeover your asking about, everything works on the ign side.Personall I would not waste my time.We have lt1s in blazers.You can do anything.If I wre you I would go 350or atleast a 305 as your changeing from stock you might as well spend $200 or $300 more and get a 350 in.

 

Thank you Blazingsadle. I read your posting that you made looking for advice on how do a "4.3 to replace 2.8" Did you ever get the project started? What have you discovered so far? I must take a second to thank "Hanr3" for his feedback in that posting. I personally am doing the same research and have read many postings that are all interelated even if they don't address the actual project we are contemplating. Your posting was the first one tackling the same project as I am proposing.

From all the information I am reading I have found out this;

The PCM on the '87 2.8 L may do well to stay on the vehicle if I bring over the TBI from the '92 with the 4.3 L so that the engine is not starved of fuel. Apparently we feel there is no need to change the PCM. Is that correct "thepurelife"?

The swap is going to involve purchasing or modifying both engine and tranny mounts. BTW, blazingsadle, again I thank you for asking the question in a previous post about mounts. Thank you for asking and thank you Hanr3 for clearing the confusion in my mind as well.

The drive shaft in the '87 2.8 is 34.65" and in the '92 it is 37.30" This leads me to believe there would have to be some cutting somewhere. Anyone have any feedback on this part of the project. This is the one area I have not seen any posting on yet. How about you Hanr3? Does your conversion manual give any info on driveshaft modification requirements? I have the tranny from the '92 so that won't be a problem.

I look forward to your feedback. As well, allow me to thank "livingthepurelife" for his feedback.


km

 

Trannys- specifically to the S10-Trucks and specifically the 700R4/4L60/4L60E auto trannies used in all S10 trucks, regardless of which V6 it is bolted up to. I am not going to elaborate on the 700R4/4L60/4L60E trannies as they relate to fullsize trucks, except to say that all 700R4/4L60/4L60E trannies that bolt up to the 4.3L V6 will also bolt up to the small block chevy V8 engines.

The only difference (for this swap) between the 2.8L V6 700R4/4L60 tranny and the 4.3L V6 700R4/4L60 tranny is the bellhousing. You cannot bolt the 2.8L V6 tranny to the 4.3L V6 engine and vise versa.

The outside dimensions of the 2.8L and 4.3L V6 700R4/4L60 trannies are the same. They are both the same length.

The difference in driveshaft length could be due to a 4wdr tranny verse a 2wdr tranny. A 2wdr tranny has an extension housing and longer output shaft then a 4wdr tranny and will require a longer driveshaft. The 4wdr tranny has a shorter output shaft and no tailhousing. There is an adapter housing to connect the t-case to the tranny, and will have a shorter rear driveshaft. The tranny output shaft can be swapped if needed and it isn't that difficult to do. You do have to take the tranny aprat to do it though.

One other difference between a 2wdr tranny and 4wdr tranny. The location of the VSS (vehicle speed sensor). The 2wdr tranny has the VSS in the tranny tailhousing. While the 4wdr has the VSS in the t-case. Now, in '88 GM stopped putting the VSS behind the dash and put it in the tranny or t-case (2wdr or 4wdr).

Post up any more questions.