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Old 12-21-2011, 05:57 AM
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350 vortec to tbi conversion

im trying to find out can a take a 5.7 vortec out of a 97 tahoe and put it in to my 87 suburban that is still set up for a tbi and what would i have to do ?

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Old 12-21-2011, 10:44 AM
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You can do about anything...just depends on how much work you are up for. The thing with the 97 to 87 is that just about nothing electrical is reuseable. IMO, the best option would be to transplant the engine and transmission with every inch of applicable wiring, ECM, and sensors. I know there is alot of information out there on vortec swaps, but I am not an expert in the matter. However, if you transplant everything I suspect it will be easier than trying to "adapt" the engine only.
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Old 12-21-2011, 10:53 AM
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well the thing about that is that the tranny isnt available to me and also i should have mentioned that my suburban is 2wd. and i keep hearing about the harness and the obd 2 computer.
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Old 12-21-2011, 11:26 AM
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Quote:
Originally Posted by thekcbeast
im trying to find out can a take a 5.7 vortec out of a 97 tahoe and put it in to my 87 suburban that is still set up for a tbi and what would i have to do ?
The easiest way to go about this will be to use a Vortec TBI intake to reuse the TBI unit from the '87 on the Vortec engine. Reuse the sensors from the '87 on the '97 Vortec engine as well.

The spider/poppet EFI set up used on the '97 Vortec isn't a favorite among builders, anyway- even though they work OK for a stock or mild application. You could use a TBI adaptor (others are available, I believe Trans-Dapt are the least expensive) on a Vortec carbed intake instead of the GMPP TBI Vortec intake, this option could be cheaper if you can find a used Vortec carb intake.


(click on image for more info)

Last edited by cobalt327; 12-21-2011 at 11:37 AM.
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Old 12-21-2011, 11:35 AM
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ok i think i would probably go with a carb intake and an adapter,because of the cost. and also what about the computer,and all the extra sensors such as the o2 sensor because my truck already has " true dual" exauhst?
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Old 12-21-2011, 11:48 AM
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Quote:
Originally Posted by thekcbeast
ok i think i would probably go with a carb intake and an adapter,because of the cost. and also what about the computer,and all the extra sensors such as the o2 sensor because my truck already has " true dual" exauhst?
You need to reuse the '87 sensors or replace any that are missing from the '87, including welding on an O2 sensor bung to use an O2 sensor, else the ECM cannot go into closed loop operation.

If the '97 Vortec engine is stock the ECM might work fine as-is. If not, or if you want to run a bigger cam w/less vacuum, you can have a chip burned for it by tbichips.com or others who do this. An injector change to the 7.4L TBI injectors might be needed as well.
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Old 12-21-2011, 03:16 PM
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Quote:
Originally Posted by thekcbeast
im trying to find out can a take a 5.7 vortec out of a 97 tahoe and put it in to my 87 suburban that is still set up for a tbi and what would i have to do ?
You will need the 87 distributor which is alot different from the 97 Vortec. So that just carries over from the 87, it fits into the 97 just fine. If there is an issue it will be with the drive gear where the 87 used a cast iron flat tappet cam the 97 uses a roller. OEM roller cams are a cast steel which may be incompatible with the older distributor. I'm squishy here only because GM tried different solutions at different times but the safest thing to do is get the Melonized gear from GM for the 96 and up Vortec engine or use the one from the Vortec if it isn't worn through the surface hardening.

You will not need the crank position sensor on the front timing cover, it just is left alone, not hooked up.

The intake is the biggest problem, the heads have a different bolt pattern between 87 and 97 so the TBI intake doesn't simply bolt to the 97 heads. Also the Vortec heads do not have an exhaust heat source to warm the intake and supply the EGR. A simple solution would be to rebuild the 87 heads and put them on the 97, that completely gets around the intake fit and EGR exhaust source problems. This combination would continue to use the 97's push rods which are shorter than the 87s to make up for the taller roller lifters in the 97 block.

If you use the 97 heads then you've got to use an aftermarket Vortec to 4 barrel intake with TBI adapter or the GMPP Vortec to TBI which is a damned pricey but a lot simpler solution, especially where the EGR is concerned. If you don't need to pass an emissions test you could get by without the EGR, but that will cause the mixture to be lean in the zones where EGR functions which will cause surging, back firing, and detonation, though because of the detonation sensor you may not be aware of it, but the automatically retarded timing will reduce performance and increase fuel consumption. To regain the proper mixtures at the proper times would require a custom computer chip, this is about as expensive as GMPP's golden manifold. The GMPP intake uses an external exhaust supply to the intake, all of this is over the counter GM parts, consisting of a left side exhaust manifold with an adapter pipe that feeds the intake's hot spot and EGR. Much of this system is on your 97 engine.

Bogie
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Old 12-21-2011, 04:53 PM
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The GM Performance p/n 12496821 that I liked to above has EGR supplied by the factory Vortec exhaust manifolds. Also has hot water provision to heat the TBI. EGR and coolant passages shown below. And no, it ain't cheap.



Use a 1996 exhaust manifold p/n 12557828, EGR supply tube p/n 10220275, and EGR valve p/n 17052693 if yours are missing from the Vortec engine you have.

Last edited by cobalt327; 12-21-2011 at 05:05 PM. Reason: Add p/n's.
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Old 12-21-2011, 04:54 PM
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Quote:
ok i think i would probably go with a carb intake and an adapter,because of the cost. and also what about the computer,and all the extra sensors such as the o2 sensor because my truck already has " true dual" exhaust?
NO NO NO NO, the fuel consumption of an non-ECM controlled engine will far outweigh even the cost of a $400 intake.
Get the calculator out and test what I said.. my base for conversions w/mpg concerns is for 100,000 miles, easy math that way.

I expect fuel economy on your "87 Suburban to drop from say 12-14~mpg to 8-10mpg~ AND a serious loss of power.

For a Suburban, You want torque AND economy.
Scrap the duals for a large single system.
A large single tube will meet any pulling needs you have.
Too much exhaust flow lowers back pressure, raising the torque curve and killing mpg.
MORE, back-pressure lowers your peak torque curve and increases fuel economy.

The Vortec to TBI intake looks most promising to me. Vortec TBI Intake at Jegs

A Vortec Long Block topped with a TBI / TBI Distributor and all the original TBI stuff hooked up and you're good.

[[U]The exterior stuff, like the Harmonic Balancer, and its Size, Belt width and depth, and accessory mounting holes, etc I do Not know!!.

Timing marks are NON-Existent on a Vortec, someone Shout about how to get some idea on this issue..

Make sure to replace the knock sensor off your TBI block, it's near the freeze plugs, as well as the O2 sensor EGR, MAP and all others

GM made it pretty easy for this, the last time I did some work on a TBI, I noticed the plugs were different and would not interchange, dunno if this is still the case.

You MAY need to get a flash done on your chip if you encounter spark knock or other oddities.

A benefit to the TBI engine is that you can actually set your timing.
On the OBD-II Vortec engines, the computer will re-set the timing if you jack it up too high.
Timing set too Low on the Vortec gives a rich code setting. Odd huh ?

"True' dual exhausts do not mean you have no fitting for a O2 sensor.
Usually they cut the pipe just before the converter, the o2 sensor is high up, near the flange.

One user said, "on some model years, the Vortec exhaust manifolds are different than TBI",
I don't have a clue on this.


Just make sure to use the TBI O2 sensor however it works out.
The "Y' pipe on the donor vehicle and exhaust manifolds may be necessary, grab the catalytic converter too, while you're at it.

Set up your TV Cable to the trans, do it right the 1st time, reading up on TV cable setup procedure may prolong your trans life as the TV cable controls pressure.


Gluck
DrVette

Last edited by DrVette; 12-21-2011 at 05:00 PM.
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Old 12-21-2011, 05:09 PM
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DrVette, I think you misunderstood the reference to "a carb intake and an adapter"- he meant to use a carb intake w/a TBI adaptor to use the OEM EFI set up.

One difference in the exhaust manifolds between the TBI and Vortec engines is the Vortec manifold has a provision to run exhaust up to the EGR valve. I'm unsure if that's what was being referenced or not, though.
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Old 12-21-2011, 05:09 PM
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the vortec fuel pump puts out 60-66 psi also , it may be ok on the TBI system,but the fuel lines at the back of the motor are also very different, neccessitating a change for those also.
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Old 12-21-2011, 05:10 PM
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Quote:
Originally Posted by cobalt327
DrVette, I think you misunderstood the reference to "a carb intake and an adapter"- he meant to use a carb intake w/a TBI adaptor to use the OEM EFI set up.
I had to read that twice to see it too.
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Old 12-21-2011, 05:14 PM
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Quote:
Originally Posted by latech
the vortec fuel pump puts out 60-66 psi also , it may be ok on the TBI system,but the fuel lines at the back of the motor are also very different, neccessitating a change for those also.
I think the Vortec long block is going to replace a TBI engine in his '87 'Burb, so the fuel pump should be OK, right?
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Old 12-21-2011, 05:21 PM
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Quote:
A simple solution would be to rebuild the 87 heads and put them on the 97, that completely gets around the intake fit
OldBoogie,

Aren't the 5.7L - Vortec Combustion chamber volume 64cc ?

and the 5.7L - 87-95 TBI heads 76cc ?

You are quite correct this would resolve a major hurdle, however it would take a competent machine shop to shave the heads on an "angle-cut" to resolve the major lack of compression.

Sorry, for the lack of understanding the adapter from MPFI to TBI deal

Edit to say:
Thanks guys for the lack of lighting me up with a 55gl trash bag full of acetylene
Interpretation, thanks for not Flaming Me as a N00b here

Last edited by DrVette; 12-21-2011 at 05:28 PM.
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Old 12-21-2011, 05:46 PM
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Notice, the adapters at "Trans-Dapt" are only listed to bolt to carburetor type intakes.

The TBI to manifold adapters listed were Holley, they may have the same bolt pattern I dunno.

I took a quick look at my 5.7L Vortec, the diameter of the hole is near 3" or so.

I'm pretty sure I could make an adapter to put the TBI on it at home..

Only issue is, my "estimates" on labor regarding things of this nature are,,, errr WRONG Every time.

Still, I'm sure a handyman could fabricate one from steel or aluminum if the has a TIG setup in a few hours.

IF someone does this trick, I'd bet 10cents the hood clearance would come into play, time for the old "Mount the air cleaner on the fender-well trick"

Someone said e-bay had some but they were hand made..

Quote:
thekcbeast
Just Hang On a bit, this issue can be sorted out with hopefully a minimal cost to you.

DrVette
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