engine swap project

[waterpirate]

So after 300,000 plus miles my motor is toast. Truck is the family mascot. Wife and I bought it in 92 and had it ever since.

Truck is a 87 short bed 4x4 with a 5.7 tbi motor

Donor truck motor is a 84 5.7 2 barrel jasper reman with around 25,000 miles on it.

How do I determine if my intake is compatible with donor, or should I use a adapter plate on current intake and simply plumb in the coolant sensor? My current line of thought is to use adapter plate so donor motor stays intact, no muss no fuss.

Any thoughts or suggestions from the group?

Thanx in advance for the help

Eric

 

[1987 GMC Jimmy]

There are differing bolt angles between TBI and carbed intakes for certain bolts. I think it’s four of the holes that would have to be machined on the TBI intake. It’d be nice to switch to a different intake, the Holley performer looks way better than the Edelbrock, but it would add more steps to getting you back running. Rather than adapting the carb intake, it would look cleaner to reuse the original. My concern is how well is the TBI going to run with the factory PROM parameters on heads that it wasn’t designed to use. It might run fine, or the PROM might need to be reburned. @4WDKC

 

[waterpirate]

Thanx for the info, I am open to sending out my old heads and bolting them on the donor engine. That would solve the wrong head and intake issue all in one step. Thoughts on that notion?
Eric

Just left epay and the cost of the tbi to 2 barrel intake is 50.00, mighty attractive to roll the dice, swap the distributor and see what happens. worse case scenario would be burn new chip or swap in heads and intake if easy route fails?
Eric

 

[1987 GMC Jimmy]

Reusing the TBI heads would definitely clear up any issues of what you’d need to do to adapt. Let it be known that TBI heads are notoriously crappy. They’re made well, but that’s about it. If you want to make anything more than meager power, they instantly become throwaways.

You could do that, and plenty of people do. There’s nothing wrong with it; I just like everything to be its simplest version possible so I tend to stay away from adapters when I can. If you found a water neck that was threaded for a coolant temp sensor, that would be all you needed. Like you said, you’d know what to do if it ran kinda weird. The ‘84 heads are definitely better but still a far cry from what was available fifteen years before that, fifteen years after that, or currently with aftermarket heads. It doesn’t sound like this is a very performance oriented build, though, you just need to get the motor back together. While I like cleanliness and simplicity, I couldn’t justify the money to rebuild the TBI heads so this might be the more cost effective route. You should be fine.

 

[waterpirate]

Thanx for the gut check. I spent some serious time this morning on the net learning about all the different sbc heads. I am not so sure now that the PO did not modify it before I got it. I am going to move forward with identifying the heads I have and the heads on the donor and see what I am working with before committing either way.
Will keep this thread updated as I move forward for more help I am sure, and to leave tracks for those who may follow.
Eric

 

[4WDKC]

There are differing bolt angles between TBI and carbed intakes for certain bolts. I think it’s four of the holes that would have to be machined on the TBI intake. It’d be nice to switch to a different intake, the Holley performer looks way better than the Edelbrock, but it would add more steps to getting you back running. Rather than adapting the carb intake, it would look cleaner to reuse the original. My concern is how well is the TBI going to run with the factory PROM parameters on heads that it wasn’t designed to use. It might run fine, or the PROM might need to be reburned. @4WDKC

sorry was busy moving.. you are correct the center bolts on the 87-95 engines are at a different angle than the 55-86 sbc heads. If you drill the 84 heads you risk damaging them, drilling the intake for the 84 heads will make it impossible to remove and install the bolts due to the tbi plentum of the intake. Personally I wouldnt touch the tbi heads, and would look for a set of tpi camaro heads for cheap or used aftermarket with the correct bolt pattern. If you use the tpi heads it should run fine on a stock chip, it may be a little low on fuel but I think the ecm should catch it.

 

[bucket]

If building a bone stock 350 for a TBI truck, the swirl port TBI heads would be my first choice.

Yeah, they suck for high rpm power and don't support many engine mods. But who gives a crap in a truck with a stock engine. Low and mid-range power band is far more important than top end.

 

[waterpirate]

Thanx for the replies. A catastrophic failure at work has consumed all 4 bays in the mechanical shop, so I am on hold for my project. With any luck I can clear the paying work lol, and get on to my personal project in 2 weeks.
Eric

 

[waterpirate]

Well work finally stopped sucking. Pulled the donor motor out yesterday. All went well. The manual 5 speed tranny is a heavy mother trucker! Going to split them today and get the motor on the engine stand for asymbly. I chose to pull dead motor heads and intake and re use instead of rolling the dice. Does it make any diff what fuel pump block off plate I use? Good one bad one all the same?
Eric

 

[dajn37]

I have only done three engine swaps in my life. As far as not being concerned about upgrades, it's always best in my opinion to find the correct complete engine from a reputable junkyard or seller and just drop it in. A guy could find a decent tbi 350 for pretty reasonable I would think. Anyways, goodluck with your project.

 

[waterpirate]

So the donor motor is on the engine stand and the dead motor is hanging on the chain hoist. I am going to pull the intake and heads to send them out this week. Donor was a 1 piece rear main with 5 speed. My 87 was 2 piece and automatic. I need to be buying which flex plate for donor motor? Also harmonic balancer and pulleys up front need to be changed. Any issues just swapping them?
Thanx in advance!
Eric

 

[Jrgunn5150]

So the donor motor is on the engine stand and the dead motor is hanging on the chain hoist. I am going to pull the intake and heads to send them out this week. Donor was a 1 piece rear main with 5 speed. My 87 was 2 piece and automatic. I need to be buying which flex plate for donor motor? Also harmonic balancer and pulleys up front need to be changed. Any issues just swapping them?
Thanx in advance!
Eric

Match the flexplate to the engine, you'll need a 2 piece flexplate to go to your current automatic. Changing the accesories over will not be an issue since you're reusing your original heads anyway.

 

[waterpirate]

Thanx for the reply. Looking things over the 87 has a 3 belt pulley and the 84 has only 2. The bottom pulleys will not swap over balance to balance. Is it OK to pull the 87 and install on the 84?
Thank you all for the help and kid gloves. I am a well driller by trade and only pretending to be a mechanic.
Eric

 

[Jrgunn5150]

Thanx for the reply. Looking things over the 87 has a 3 belt pulley and the 84 has only 2. The bottom pulleys will not swap over balance to balance. Is it OK to pull the 87 and install on the 84?
Thank you all for the help and kid gloves. I am a well driller by trade and only pretending to be a mechanic.
Eric

Yes, swapping the 87 onto the 84 shouldn't be an issue. They are balanced the same.

 

[waterpirate]

Awesome information! Any suggestions on which puller to buy? The pro form model looks rugged as well as the one from summit.
Eric