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Need advice on engine direction, which way to go?

bassackwards

bassackwards

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I recently picked up a 1989 Blazer with 107k on the clock. It was a stalled project from an old lady. I have not yet gotten it to start and believe the starter is toast. It has the 700r4 with NP241 trans with speedo cable.

I have a set of CUCV axles with 4.56 gears and 35" tires for it already.

Will I be disappointed with the stock engine power? (I loved driving the 6.0 Escalade). Cost, ease of completion, and final power satisfaction are all important in balance.

Should I try bolt ons including head/cam swap? I found an older Edelbrock EFI kit for Vortec heads for my truck.

Or Just go for an LS swap? If I go this route I see 5.3s for $600 and 6.0 for $2k. How much real difference is there performance wise?
 
bassackwards said:
I recently picked up a 1989 Blazer with 107k on the clock. It was a stalled project from an old lady. I have not yet gotten it to start and believe the starter is toast. It has the 700r4 with NP241 trans with speedo cable.

I have a set of CUCV axles with 4.56 gears and 35" tires for it already.

Will I be disappointed with the stock engine power? (I loved driving the 6.0 Escalade). Cost, ease of completion, and final power satisfaction are all important in balance.

Should I try bolt ons including head/cam swap? I found an older Edelbrock EFI kit for Vortec heads for my truck.

Or Just go for an LS swap? If I go this route I see 5.3s for $600 and 6.0 for $2k. How much real difference is there performance wise?
Click to expand...

A 5.3 with a ls6 cam and springs and a good tune will put you just shy of 400hp/tq. Now with the smaller displacement that will be higher up in the rpm range. My 5.3 has no problem bouncing of my 6500 limiter. I have never been left wanting for power in my truck. 5.3/465/205/ 4.56 gears and 37”s. Even with the 4.10s I pulled out. The engine is also stupid easy to keep cool with the small displacement.

Is it a 6.0? No. There is no replacement for the displacement. But at half the cost I can justify the 5.3 all day
 
What all needed to be changed? I just want to stick with my 700r4 and transfer case for cost reasons.

Did you use a donor harness or a new one? How about tuning?

I also have 4.56 gears. Did you run yours with the stock cam first?

It almost seems like scoring a good LS ends up being cheaper than pumping up the original 350. Am I right or wrong here?
 
bassackwards said:
What all needed to be changed? I just want to stick with my 700r4 and transfer case for cost reasons.

Did you use a donor harness or a new one? How about tuning?

I also have 4.56 gears. Did you run yours with the stock cam first?

It almost seems like scoring a good LS ends up being cheaper than pumping up the original 350. Am I right or wrong here?
Click to expand...

I don’t know about auto, for me I just bolted on a flywheel with correct crank spacing for my engine year and was good to go. There were two crank stick outs depending on year. You may or may not need a spacer to get your flex plate in the right place for your trans. Also with a 700r4 you will need to keep the tv cable in mind. I have a drive by wire engine so no way to hook it up. You may want to look into drive by cable engines. You can use advance adapter motor mount plates to bolt the Ls to your stock engine mounts and it will line up with your trans. You will need to clearance the crossmemebr a bit or buy a ORD crossmemebr. Fuel pump can be done with a walbro 255 in a stock TBI sending unit in your tank. Convert he metric fittings to AN, run a corvette filter/reg and plumb it up to the front

The stock harness was trimmed to be stand alone. It’s a 5 wire hook up. 12v constant, 12v ignition, start, tach, and fuel pump. If you mount the battery on the driver side of the engine bay you can use the stock battery cables off of the new engine with no mods. My tuning was done by the engine builder.


I never ran mine with stock cam but I have ridden in a surburban with a stock cam. That guy had no complaints but still wouldn’t mind more power.


I agree with you on it being cheaper. The engine will cost what a cheap set of 350 heads will cost. Everything else will cost what your efi kit would cost. Don’t have to pay for the machine shop or bottom end parts


I have a full install info in my 80 build thread
 
@jkroberts @sreidmx I'm sure can give some advice on this but if you're wanting to stay with the 700r4 then go 5.3. I would say find a 5.3/4l60e combo and just use that..the trans is the same thing and since it's already mated together you will have less problems.

If you're staying with 35s then the 5.3 will be enough but if you plan to go bigger in tires size, add more weight like bumpers and stuff then go 6.0. You'll be that much ahead.
 
i have had a 5.3 with a 4l60e and 4.56 gears and 35's for a while. my 5.3 has the LS6 cam and valve springs. Like mentioned before, it rips up top. the 4.56's help with low end torque. It was my daily driver for many years and ive never had an issue except for my buddy with a cammed 6.0 blowing my doors off. Even then i get him back with my better MPG. ditch the 700r4 if you go LS.
 
Will my xfer case suffice? It has both the vss and the speedo cable I believe. I don't want to get into trying to get the speedo to work after a swap.
 
89s have a mechanical speedo. Will have to convert to electric or Dakota digital sells an adapter.

But the TC itself should bolt up to the 4l60e no problem.
 
the 5.3/4l60e is literally a bolt in. no transmission cross member modification necessary. bolts right to your tcase. you can even use your factory driveshafts. as for your speedo cable, you will need to run a signal generator. its a little device that screws into your speedo cable that generates an electronic signal for the PCM.
 
It looks like I can get an inline vss signal generator that screws into the transfer case in place of the cable then the cable screws into it. That is easy!
 
The only one I see an issue with is the tach. Oil pressure, volts and temp should be OK since they are mechanical.
 
I didn't have a tach factory in mine, so didn't think about that before I replied.
 
whatever 4l60e came behind the 5.3 shold work fine. tach is easy. there is a tach signal out from the PCM you just plug into any tach and itll work.
 
I'm one of the lone nutjobs running a 5.3/700r4 combo. Using the right flexplate, Cable throttle and Bowtie Overdrives TV cable kit for the LS truck engine and it works just fine. Is it as desirable as the 4l60e for tunability? No. But the late 700's and 4l60e's are the same basic transmission except for the fact one is electrically controlled and the other isn't. Yes, later 4l60's got the removeable bellhousing and more fortifications, but it's the same basic design.

Once I did the required modifications for the Bowtie Overdrive kit (a new TV spring comes in it) and got the bracketry set up it was a matter of setting the tension on the cable. Little tip, it needs to be tighter than you think. I thought I had it tight and it would not detent downshift. Made another adjustment and it's downshifting on it's own just fine.

My 5.3 is completely stock except for the minor tune in the ecm. I'm running 35's with 4.10 gearing. It's pretty good, as in it's waaaaay better than a tbi 350 on it's best day. However, in my case with the camper I'm looking for more power. Wind resistance and weight are killing my fun. If I keep it wound up it's fine, but I can find it lacking on long mountain grades on the highway.

I've rationalized about not changing cams as the stock 5.3 cam makes the most torque down low than even the LS6 cam and many others, but I'm coming around to the idea that running a better cam may be the best way to get the power back. I'd be tickled with 400hp with a LS6 cam and a set of springs. I'll have to fool around tuning again, but it wouldn't be a big thing. The only issue is the fact that the torque curve moves up the RPM band, but I'm already spinning the piss out of it already I might as well be making some power with it. The stock cam just runs out of breath with it wound up.
 
If you run a cable throttle maybe not. If you go drive by wire, the ecm or tac module could do control it with inputs from the cruise switch.

I have a factory cruise servo from a 2001 Silverado I'm going to run. It will connect to the throttle body like factory.

Just so you know, the ls swap has been regularly done around here so there is a ton of information in this site to help you along your way. Just got to look for it and ask if you aren't sure what you need.
 
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