Changing my 86 carb to 88 EFI, HELP!!!!!

[jkade]

Here is the deal. I have a 86 K10 4x4 which as you all know has a carb. I am picking up a one owner 88 2wd suburban for free, it has a bad intake gasket. I have a stock gm crate 350 that I took out of my truck, I intend on building that motor and putting the EFI on that motor. My question is what can you do to give these motors a little power. I there anyway to put a set of vortec heads on this setup with the 88 EFI? Can you get a intake to work with the EFI and vortec heads? What would be a good cam to go with? How hard is it going to be to install the components for the EFI on my truck? Any help would be greatly appreciated. ttt

[bloertcher]

Yes,vortec heads can be used with TBI.GMPP makes an intake,but it is pricey.
I have used the Melling MTC-1 cam with great success on TBI engines,BUT,be aware that the stock ECM is VERY limited when it comes to engine mods.You can get pretty crazy and it will run,but poorly.Be prepared to get friendly with a tuner with chip burning facilities if you plan on doing anything more than a mild cam in this thing.

[Russell]

Actually, TBI swap isn't too bad at all. Esspecially if you have a complete parts vehicle

Biggest problem you'll run into is going to be fuel delivery. TBI needs 12 - 15 PSI to operate correctly, and a stock mechanical pump only provides about 4 - 5 PSI. So, you'll need to either replace your saddle tank (s) with the tank from the suburban between the rear frame rails, get yourself an 87 EFI saddle tank (or two), or just install an inline fuel pump. You'll want the pump as close to the saddle tank as possible, as they are built to push fuel, not pull it. If you have dual tanks, you'll want to install it directly after the diverter valve, behind the pump is suction, so no worries about leaking diverter valves etc. Infront of that, you can use your 88's fuel lines to run from the throttle body to the frame, use it's filter etc.

Less the fuel delivery, the only other major challenges you'll face will be how you mount the intake (swap to the 88 heads, or modify your intake's center 4 bolt holes to fit the older heads) and the electrical (again, shouldn't be too tough if you don't cut any more wires than you absolutely have to)

Keep in mind that TBI isn't built for major horsepower, but more for low end grunt. So while Vortec heads may be great for high horsepower applications (and even there they arn't that amazing) they may not be worth the money for a TBI 4x4. If I was to switch heads, I'd look for a set of f-body L98 heads. I can't remember the casting numbers off the top of my head, but they'll be found on any 350 tuned port engine. The Corvettes actually had an aluminum version of them! The heads come in two version -- Center and perimeter bolt valve covers. You'll want the centerbolt covers so your TBI will bolt straight up.

As far as a camshaft goes, all the different cam manufactures sell EFI cams, and I would HIGHLY reccomend putting the extra money down on one. You can get cams for these TBI engines that don't require and chip changes, but will wake your engine up a whole lot. The biggest thing with the EFI cams is their lobe seperation angle. They need to be a numerically higher number (112 - 114 is best, more torwards the 112 mark) or you'll get a very rich idle.

Oh, one more thing, Vehicle speed sensor! Make sure you don't skip this critical component -- Esspecially when they are as easy to install as they are in these trucks!

Just take the yellow wire that goes to your cruise controller from the optical sensor on the back of the speedometer, and feed it into your ECM, problem solved right there! If your truck doesn't have cruise, thats alright, your speedometer head is setup for the VSS anyways. Just give me a shout, and I'll have a VSS in the mail for you for the cost of shipping the next day

[jkade]

Originally Posted by Russell

Actually, TBI swap isn't too bad at all. Esspecially if you have a complete parts vehicle

Biggest problem you'll run into is going to be fuel delivery. TBI needs 12 - 15 PSI to operate correctly, and a stock mechanical pump only provides about 4 - 5 PSI. So, you'll need to either replace your saddle tank (s) with the tank from the suburban between the rear frame rails, get yourself an 87 EFI saddle tank (or two), or just install an inline fuel pump. You'll want the pump as close to the saddle tank as possible, as they are built to push fuel, not pull it. If you have dual tanks, you'll want to install it directly after the diverter valve, behind the pump is suction, so no worries about leaking diverter valves etc. Infront of that, you can use your 88's fuel lines to run from the throttle body to the frame, use it's filter etc.

Less the fuel delivery, the only other major challenges you'll face will be how you mount the intake (swap to the 88 heads, or modify your intake's center 4 bolt holes to fit the older heads) and the electrical (again, shouldn't be too tough if you don't cut any more wires than you absolutely have to)

Keep in mind that TBI isn't built for major horsepower, but more for low end grunt. So while Vortec heads may be great for high horsepower applications (and even there they arn't that amazing) they may not be worth the money for a TBI 4x4. If I was to switch heads, I'd look for a set of f-body L98 heads. I can't remember the casting numbers off the top of my head, but they'll be found on any 350 tuned port engine. The Corvettes actually had an aluminum version of them! The heads come in two version -- Center and perimeter bolt valve covers. You'll want the centerbolt covers so your TBI will bolt straight up.

As far as a camshaft goes, all the different cam manufactures sell EFI cams, and I would HIGHLY reccomend putting the extra money down on one. You can get cams for these TBI engines that don't require and chip changes, but will wake your engine up a whole lot. The biggest thing with the EFI cams is their lobe seperation angle. They need to be a numerically higher number (112 - 114 is best, more torwards the 112 mark) or you'll get a very rich idle.

Oh, one more thing, Vehicle speed sensor! Make sure you don't skip this critical component -- Esspecially when they are as easy to install as they are in these trucks!

Just take the yellow wire that goes to your cruise controller from the optical sensor on the back of the speedometer, and feed it into your ECM, problem solved right there! If your truck doesn't have cruise, thats alright, your speedometer head is setup for the VSS anyways. Just give me a shout, and I'll have a VSS in the mail for you for the cost of shipping the next day

Sounds like you know your stuff. Will the stock EFI intake work with the L98 heads? There is a couple of sets on ebay right now. I apprecaite you wisdom on this matter. Would I be better off to just get me some heads,cam,intake,and carb for my motor or do the swap? I want a daily driver and I figured the EFI would add to the value of my truck. What do you think. Thanks, Kade

[Russell]

Originally Posted by jkade

Sounds like you know your stuff. Will the stock EFI intake work with the L98 heads? There is a couple of sets on ebay right now. I apprecaite you wisdom on this matter. Would I be better off to just get me some heads,cam,intake,and carb for my motor or do the swap? I want a daily driver and I figured the EFI would add to the value of my truck. What do you think. Thanks, Kade

Hey Kade!

In a nutshell -- I'd most definitely switch to EFI. Esspecially for a DD

There are lots of guys who are very anti EFI, and in high horsepower applications, I totally agree with them. But for a very mild engine, EFI is a great way to get awesome low end torque, very reliable cold weather starts, and overall excellent throttle response.

Anyone who tells you that your EFI will get better milage than a carb is technically incorrect. A good Q-jet can be tuned to get just as good of milage as a TBI vehicle, but where technicality comes in is that as soon as the temperature changes, or you change altitude, or even barometric pressure, the carb will suddenly be out of tune, while the EFI will immediately compensate for that

Now, to answer your questions:

Yes, a stock TBI intake will bolt directly up to a set of centerbolt L98 heads If you do wind up with a perimeter bolt set, you'll need to do some die grinding on the center 4 holes of your TBI intake to get the bolt angles correct. After the die grinding, it will bolt up without any problems.

Oh, BTW, the difference between center bolt and perimeter bolt is simply how the valve cover bolts on. The center bolts have 4 bolts along the top of the valve cover that hold the cover on, while perimeter bolts (like all pre 86 chevy engines) have 4 bolts on the lip of the valve covers. The center bolts, while not having as many options for aftermarket covers, seal way better than the older perimeter bolt covers

And yes, I would get a cam, and heads for your TBI truck. They can be made to perform fairly well with some very simple modifications to the throttle body (still not a 750 demon carb, but it'll get your 350 moving pretty well).

As far as a cam goes, finish all your engine mods, then all Lunati, Comp Cams, or someone similar, and see what they'd suggest. Tell them absolutely everything about what you intend to do with the truck, all of the modifications, what type of pistons, heads, intake / throttle body mods etc, and if you want to do chip changes or not, and they'll tell you exactly what you should run.

PS -- Here are some links for how you can improve on the stock TBI, fairly cheapy These are for camaros, but the TBI setups are basically the same thing:

http://www.thirdgen.org/newdesign/te...imatetbi.shtml

http://www.thirdgen.org/newdesign/te...matetbi2.shtml

[jkade]

Originally Posted by Russell

Hey Kade!

In a nutshell -- I'd most definitely switch to EFI. Esspecially for a DD

There are lots of guys who are very anti EFI, and in high horsepower applications, I totally agree with them. But for a very mild engine, EFI is a great way to get awesome low end torque, very reliable cold weather starts, and overall excellent throttle response.

Anyone who tells you that your EFI will get better milage than a carb is technically incorrect. A good Q-jet can be tuned to get just as good of milage as a TBI vehicle, but where technicality comes in is that as soon as the temperature changes, or you change altitude, or even barometric pressure, the carb will suddenly be out of tune, while the EFI will immediately compensate for that

Now, to answer your questions:

Yes, a stock TBI intake will bolt directly up to a set of centerbolt L98 heads If you do wind up with a perimeter bolt set, you'll need to do some die grinding on the center 4 holes of your TBI intake to get the bolt angles correct. After the die grinding, it will bolt up without any problems.

Oh, BTW, the difference between center bolt and perimeter bolt is simply how the valve cover bolts on. The center bolts have 4 bolts along the top of the valve cover that hold the cover on, while perimeter bolts (like all pre 86 chevy engines) have 4 bolts on the lip of the valve covers. The center bolts, while not having as many options for aftermarket covers, seal way better than the older perimeter bolt covers

And yes, I would get a cam, and heads for your TBI truck. They can be made to perform fairly well with some very simple modifications to the throttle body (still not a 750 demon carb, but it'll get your 350 moving pretty well).

As far as a cam goes, finish all your engine mods, then all Lunati, Comp Cams, or someone similar, and see what they'd suggest. Tell them absolutely everything about what you intend to do with the truck, all of the modifications, what type of pistons, heads, intake / throttle body mods etc, and if you want to do chip changes or not, and they'll tell you exactly what you should run.

PS -- Here are some links for how you can improve on the stock TBI, fairly cheapy These are for camaros, but the TBI setups are basically the same thing:

http://www.thirdgen.org/newdesign/te...imatetbi.shtml

http://www.thirdgen.org/newdesign/te...matetbi2.shtml

I think you have me on the right track and I appreciate all the info. I will Let you know how it turns out when I get it done. Thanks, Kade

[jkade]

[QUOTE=Russell;1588598]Actually, TBI swap isn't too bad at all. Esspecially if you have a complete parts vehicle





If I was to switch heads, I'd look for a set of f-body L98 heads. I can't remember the casting numbers off the top of my head, but they'll be found on any 350 tuned port engine. The Corvettes actually had an aluminum version of them! The heads come in two version -- Center and perimeter bolt valve covers. You'll want the centerbolt covers so your TBI will bolt straight up.

Are the heads off a 305 tpi the same???? Sucks I am just getting serious about doing this but the truck was sold for a year and I have just bought it back and I am going to do the swap if the deal on the 91 suburban works out. I ended up selling the 88 suburban so the 91 is going to be my new candidate. Thanks

[piecesparts]

EFI is a good way to go in these days of fuel crunch, however the basic TBI can be improved upon. There are companies that do make upgrades to the computer programming (Hypertech and Super Chips for example). I have a 91 truck with the TBI in it and I am going to change that out soon to a l-98 corvette TPI motor and intake. However, I definitely improved my TBI throttle response with an "Airaid" throttle body spacer, K&N fiter, and the MSD multi-spark setup, including coil, wires, 6AL unit, cap and rotor, Hypertech chip and a 180 degree T/stat. I realized a better response and better MPG.

As for adding value to your truck; Value is in the eye of the beholder---The truck will be better for you, but the gas prices and the market for older trucks will definitely hurt your drive for increased value. If you happen onto another avid trucking sole, when you want to sell your truck then you could possibly make out better than with a carb. Be sure you install the new setup in a clean professional way. Nothing hurts a sale more than a lot of scraggly wires and hoses hanging all over.

[Russell]

You can physically bolt 305 heads onto a 350, but they have fairly small combustion chambers which puts your compression ratio through the roof, and usually have smaller valves too, which tends to choke the engine out.

I'd actually tend to suggest you just unbolt the engine from the 92 suburban, and bolt it straight into your 86. That way you don't have to worry about tuning anything but before you can drive the truck normally. Once you have it installed and running, then you'd probally just want to leave it just the way it is for now

If you are a big fan of the TBI, but want more oomph, take your 86's engine, and rebuild it from the ground up, with an EFI roller cam, set of good aftermarket heads etc. Something that'll make 300 horse under 4800 rpm, and swap that in, then take it somewhere to be dyno tuned.

[jkade]

Originally Posted by Russell

You can physically bolt 305 heads onto a 350, but they have fairly small combustion chambers which puts your compression ratio through the roof, and usually have smaller valves too, which tends to choke the engine out.

I'd actually tend to suggest you just unbolt the engine from the 92 suburban, and bolt it straight into your 86. That way you don't have to worry about tuning anything but before you can drive the truck normally. Once you have it installed and running, then you'd probally just want to leave it just the way it is for now

If you are a big fan of the TBI, but want more oomph, take your 86's engine, and rebuild it from the ground up, with an EFI roller cam, set of good aftermarket heads etc. Something that'll make 300 horse under 4800 rpm, and swap that in, then take it somewhere to be dyno tuned.

So I can take a inline pump and make it work with my dual tanks fairly easy with the burb fuel lines? What about the return, I know the carb has a return to the tanks, so can I hook the burb return close to the tanks with there factory line? Does that make sense? What I am asking, will the factory returns work if I attach the new return as close to the tank (tanks) as possible? Will the pump work good since it will always be above the fuel level?
Thanks, Kade

[gchemist]

Here are a few links for you.
http://www.cfm-tech.com/GM_tbi_tuning_tips.htm
Conversion website article: http://users.california.com/~eagle/howell.html

[alemanc]

Originally Posted by jkade

Here is the deal. I have a 86 K10 4x4 which as you all know has a carb. I am picking up a one owner 88 2wd suburban for free, it has a bad intake gasket. I have a stock gm crate 350 that I took out of my truck, I intend on building that motor and putting the EFI on that motor. My question is what can you do to give these motors a little power. I there anyway to put a set of vortec heads on this setup with the 88 EFI? Can you get a intake to work with the EFI and vortec heads? What would be a good cam to go with? How hard is it going to be to install the components for the EFI on my truck? Any help would be greatly appreciated. ttt

When dealing with these issues i like to talk with the techs at summit racing. they're very knowledgeable and have reasonable prices.

[jkade]

If I have the computer harness that goes to the engine out and the computer out, what else will I need to run the tbi? I don't need the whole suburban under dash harness do I? I know I will need a power wire to the computer, what else will I need to make it work beside fuel?

I have the computer and the underhood harness out and no cut wires.

[kevinr1970]

I just pulled the 350TBI and 700r4 tranny out of an '88 GMC Suburban. I don't recall having to diconnect any wires from the computer under the dash.
I believe it is "stand-alone".

[jkade]

Originally Posted by kevinr1970

I just pulled the 350TBI and 700r4 tranny out of an '88 GMC Suburban. I don't recall having to diconnect any wires from the computer under the dash.
I believe it is "stand-alone".

I pulled harness and the computer from the 91, the fuse block and all its wiring is still there. What I am asking what else besides the computer and computer harness that goes out through the firewall will I need.
Thanks

[jkade]

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