Hello all,
I am looking for some help/ reassurance with and engine swap. For a little background, I bought these vehicles from my neighbor that was moving for my son's first vehicle (he has been in love with them for the last couple years) I have a 1998 Bravada engine code w (and it has the l35 in the glove box). It is also a smattrack. I also have a 1996 Blazer with the same w and l35( but it is in a different place on the sticker than the Bravada) that one is push button 4 wheel. They are both 4dr. The Bravada has a good motor and the blazer wraps after it warms up. The Bravada engine chugs a little but I think that is 02 sensors(i ran a full tank of 3 yr old gas through it before it started doing that). Well here comes the questions.
1. Will these direct swap? I am only concerned because the awd vs 4x4 I figure that should all be tranny/transfer case but not sure about any sensor issues.
2.I have noticed a few differences in the engine bay such as the blazer has a row of relays on the firewall that the Bravada doesn't, there is a difference in what I am assuming is an intake sensor on top of the engine and a few other small things is it ok to just use the stuff out of the Bravada and swap plugs if necessary or should I swap over the parts from the blazer engine to the Bravada one?
3. Third and final is will the ignition system be the same. I can pull the setup off the blazer and swap it over. It looks the same but you never know.
Thanks for reading this long winded post, I have done alot of searches in this forum and google but havent gotten clear answers for these questions. I am also open to any tips tricks or links that will help us get this done.

 

Just to be sure. I understand, you're taking an engine from a 1998 Bravada and putting it in a 1996 Blazer.
The engine assembly is a direct swap. Same block, heads, manifolds and even the sensor, ignition and electrical bits are all the same.
The engine and associated harnesses are almost the only thing that are the same between 1995-1997 models and the 1998 + models. Did you notice there's a big fuse block on the 1998 that isn't present in the 1996 (or 1995 -1997 models). The three relays on the firewall in the 1996 are A/C related, not engine related. Ignore them for your swap. Keep the Blazer wiring for everything and you'll be fine.
Everything should be exactly the same. If it's not, there's no reason not to keep the parts from the Blazer and put them on the Bravada engine.

Now for some observations, recommendations and opinions.

Since you have the engine separated from the transmission, you definitely should replace the rear crankshaft seal. If you don't change it now, you'll have to pull the whole thing apart again to replace it when it starts leaking. You've done all the labor except for actually installing the new seal.

The same goes for all the rest of the gaskets and seals. It's so much easier to replace those while you have the engine out, on an engine stand.

I would summarily replace the front cover/front crankshaft seal for the same reason, and unless I have a dated receipt from within the past year for the water pump and fan clutch, I'd replace those as well. Those come off to get to the front cover/seal. Foolish to put the old ones back on IMO.

Inspect closely where the metal lower manifold meets the head. If you see a plastic gasket frame there (often blue or aqua color), I would definitely do all the intake manifold gaskets and plenum gaskets. I'd actually get the FelPro set with the metal framed lower gaskets and that set includes the valve cover gaskets as well.

Here's how I decide about head gaskets. First, if I'm pulling the donor engine from a live donor, or at least a donor with a functional starter, I do a compression check before I even start pulling. If that indicates a problem, I either reject the donor or plan to remove heads and oil pan and address the compression issue.

Assuming a good compression donor, I next pull the valve covers, and I set my torque wrench for the final torque setting for the head bolts. On these engines, it's a torque + angle spec for tightening the head bolts, but I still only go with the final torque, which for this engine is 22 ft. lbs. I then go around all the head bolts, in tightening sequence and put the torque wrench to them. If any head bolt turns before the wrench clicks, on either head, I replace the head gaskets (both heads), and while I have the heads off, I inspect closely.

Generally if the heads come off because of loose head bolts, I check the for flatness, and I have a machine shop pressure test them. I also don't reuse head bolts in "torque to yield" applications (where there's a torque + angle tightening spec).

 

Nice response RacerX. But I think you must have typoed on the 22ft.lb torque on the head bolts. I think a head bolt is just to damn loose and would be a certain problem at 30 ft.lbs.

Les

 

I did a double take on that torque spec as well. But I checked 3 different sources, and 22 ft. lbs. plus angle is the correct specification.

Chevrolet uses a bunch of fairly small head bolts on the Vortec small blocks. Actually, I seem to remember that's the case with the older style small blocks as well. On the 4.3L V6, there are 13 head bolts (not the usual 8 for most other V6 engines), and the torque spec is all bolts to 22 ft. lb. in order:



After that, the short bolts (2, 3, 6, 7, 10 an 11 in the picture, IIRC) go 55 degrees after the 22 ft. lb., the medium bolts ( I think that's 12 and 13 in the picture) go 65 degrees after the 22 ft. lb. initial torque, and the long bolts (1, 4, 5, 8 and 9 in the picture, I think) go 75 degrees after the initial 22 ft. lb. torque. The bolts start to stretch somewhere between 25 and 28 ft. lbs. IIRC. You'll never get them to 30 ft. lbs.

If you don't have a torque-angle meter, 55 degrees is 5 degrees before one point of the nut, 65 degrees is 5 degrees past one point of the nut, and 75 degrees is turning the point to the exact center of the next flat. You can mark things with a paint pen and turn them that way.

 

Yeah I know how you tighten a certain number of degrees with an angle gauge after bringing to a light torque spec - done it many times! In this case 22 ft.lbs + a certain number of degrees. But you were in effect telling him that a head bolt that remains above the magic number of 22 ft. lbs is OK. I disagree with that. SBC head bolts need to be much tighter, and the same on 4.3 V6 engines. I could tighten 22 ft. lbs with a short 1/2" combination wrench. Stretch head bolts go way past 30 ft. lbs. Certainly you are not implying that a stretch head bolt could be broken with 30ft.lbs. Is that where we are disagreeing? SBC head bolts are more like 65 ft lbs. Using an angle gauge and stretch bolts doesn't make them less tight - only more consistently tight - and tightening a certain number of degrees past a light torque setting takes out the friction factor that can make the head bolts looser than the torque wrench indicates. This is why I use moly paste and washers on head bolts heads, and Teflon sealer on the threads on my race car with ARP bolts (definitely non-stretch) - to eliminate the error in torque reading cause by friction. It's just another way of accomplishing the same thing.

 

Zak hasn't logged in since the day of his original and only post. So we are making much ado for nothing I suspect!