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Topic Review (Newest First)
11-18-2012 03:33 PM
Pre-Tuner The DRAC up to '91 is inside of the cluster and not a separate unit.

If all of the gauges have issues, then there is probably one problem, not several. Could be the ground. I hate my half-moon gauges too.

The TBI distributors are still considered HEI. If you want more spark, make sure the distributor is in good condition (good cap, rotor, and make sure the pickup coil isn't falling apart), then buy a better coil from one of the aftermarket companies. Also check your timing with the timing connector disconnected.
11-18-2012 03:11 PM
Originally Posted by Hittman View Post
But the deal is my gauges are screwed up and I trying to figure out what to do. My truck has the Half moon stock gauges. I was wondering if i could upgrade or maybe interchange with another chevy truck style gauges. Got to get rid of these gauges i just dont like them. Thanks for yalls help. Iam new to this fuel injection stuff always had older trucks without it.
If you're having gauge problems don't aurttomatically blame the cluster, check to make sure the ground wire is still on the thermostat housing stud, if that goes bad you lose most of your gauges. Next would be the sending units. 1990 and early 1991 Chevy and GMC trucks had needle type gauges and are a direct swap for the '88-'89 cluster and use the same sending units. Late '91 had a factory tach but requires 3 wires to be switched in the harness and you have to run a seperate tach wire, they are getting harder to find too. I put one in my '88 to replace the "moonies" but I went through 4 clusters before I found a good one! Then I had to replace the DRAC module that controls the speedo in the circuit board with DIP switches so I could calibrate the speedometer for different gears and tires and that was a royal PITA! Not so much putting the DIP switches in but finding the right combination. So make sure you get one from a truck with the same gear ratio and tire combo if at all possible. The factory speedo calibration kits for the '88-'93 trucks have been out of production for many years and if you do find one NOS it is EXPENSIVE. The oil pressure sender for your factory gauge is down by the oil filter, the one up top controls the fuel pump.

You can also swap in a '92-'94 cluster but it's a bit more work, you can find the details at Fullsize Chevy, ChevyTalk or The 1947-Present Chevy Truck Board.
11-18-2012 01:43 PM
66GMC Alright, if that's the case, then I suppose the easiest, quickest, and least destructive method would be to mount electric guages in a A-Pillar Pod.

I don't think I've ever seen a speedometer small enough to fit there, though.

If you've got DEEP pockets, Dakota Digital makes a set for your truck
11-18-2012 12:56 PM
Originally Posted by Hittman View Post
Wondering if some of yall could help me out. I have heard that if you have a TBI 350 that you can install a HEI distributor to get more power and make it run better. Need some input on the wireing and what to do. I have a HEI distributor but no sure what needs to be done or if its better. Thanks
The answer here would be no. The modern era of automobiles including pickup trucks starts about 1986 with the introduction of what's called On Board Diagnostics I or (OBD I). This is a Systems Engineering approach to the dual requirements of lower emissions and increasing fuel efficiency. This is unlike the patchwork gadget add-on approach of the late 1960's up to the mid 1980's. OBD I starts down this road of everything under digital management by a computer, this includes your 1989's speedometer which looks for all the world to be an old fashion cable driven mechanical (analog) speedo. It isn't what it appears to be it is in fact a digital unit that uses a Digital to Analog (D to A or D/A) converter to drive the needle. The connection to the transmission is a wire bundle not a rotating cable in a jacket.

The distributor receives its base timing position from the computer, as it does for the advance curve. Unlike the mechanical/vacuum distributor that has one mechanical curve and one vacuum curve built in that is dependent upon RPMs and manifold vacuum thus having no adjustment for what would be the best curve for how hard the engine is working and in which transmission gear. The digital system is reading engine power demand and torque loading on the output shaft to pick an advance setting for the ignition as well as fuel flow for the injectors based upon the power demand. Further the ignition system is listening for detonation or preignition with a sensor that will reduce the timing advance just enough to prevent these events from damaging the engine. In this age of hyper-eutectic pistons and very edgy cooling capacity this is vitally important to prevent costly damage to the engine and transmission.

As time has come forward the Rocket Science of Systems Integration has hugely increased with the advanced system adaption industry wide in 1996 with OBD II and we are now moving beyond this to higher levels of complexity. Going, going, gone are the days of the shade tree mechanic. These modern vehicles require mechanic's with at least a 2 year automotive technology degree and many dealer shops keep a graduate engineer in automotive systems either on staff or on call. These highly integrated systems are how modern cars are delivering 30 miles to the gallon and 300 or more horsepower. Where today's lowly V6 Mustang will have the original "Bullet" 390 FE block Mustang for lunch any day of the week and twice on Sunday.

The news isn't all bad for OBD I truck owners, there's power to mined from a TBI, Swirl Port 350 if you know where to hunt. Setting aside your 350 since 1989 is getting rather old and may need a major overhaul to restore it even to its original power output; there are things that can be done to really wake this motor up. The two big power limiters to this engine are the camshaft and the cylinder heads.

The original camshaft has barely 170 degrees of duration and less than .4 inch lift at the valve. While TBI likes a lot of manifold vacuum which a short cam supplies, this can be pushed a good 20-30 degrees without getting into serious reprogramming of the computer chip. Edlebrock sells a cam part number 3207 made specifically for TBI engines a

The timing and lift on this cam are pretty close to the old Chevy "929" cam of the 300 horse 327. So it's a pretty big wake up call to your OEM 207 hp, 350.

Now you’re not going to get 300 hoses out of the TBI 350 because the Swirl Port heads and the fueling capacity of the TBI wound permit that much. The Swirl Port head is a huge limiting factor, the swirl vane adjacent to the valve guide boss limits flow to a peak RPM of about 4500. The solutions vary from porting the vane out of the existing heads or getting a set these passenger car heads you would need part number 10125377 to use your existing intake with the 72 degree bolt angle to the heads. The p/n 10125377 head can be made from castings 14096217 or 14101083 but these also make a head with the pre 1986 bolt angle of 90 degrees (p/n 10159552) to the head these would not fit your intake without a substantial modification to the existing bolt hole angle in the manifold and having to either re-spot face the bolt-head pad or making an angle adapter so the bolt-head lies flush to the surface its clamping. These heads are a cast iron version of the aluminum Corvette L98 head; these should take the engine to 250 with the Edlebrock cam. The L31 Vortec head of 1996 and up really wakes this engine up with a 20-30 hp gain over the L98 style head landing about 270 to 280 hp. This is the outside limit of your TBI to crack 300 horses’ takes a 670 cfm TBI with 88 pound injectors and reprogramming the computer with a new chip.

Installation of the 3207 cam and a set of cast iron L98 heads can be accommodated by installing an adjustable pressure regulator to the TBI you have. This isn't as clean as a new chip and won't get you past an emissions test if that's a requirement, but it'll be pretty good certainly comparable to a carburetor in accuracy.

11-18-2012 11:08 AM
Hittman But the deal is my gauges are screwed up and I trying to figure out what to do. My truck has the Half moon stock gauges. I was wondering if i could upgrade or maybe interchange with another chevy truck style gauges. Got to get rid of these gauges i just dont like them. Thanks for yalls help. Iam new to this fuel injection stuff always had older trucks without it.
11-18-2012 09:50 AM
Originally Posted by LATECH View Post
Leave it be.

I think I recall going through a phase in my late teens where I thought ANYTHING "aftermarket" equated to "better than OEM" ... and that OE engineers were just mindless corporate slaves or something.

Well OK, that thinking might not have changed when it comes to having to spend 1-1/2 hours removing components to "get to" changing an unnessecarily obstructed part.

In the case of an EFI vehicle, that "electric speedometer" probably serves double-duty as a VSS (Vehicle Speed Sensor) which provides information to the PCM.
11-18-2012 09:31 AM
LATECH Leave it be.
11-18-2012 08:30 AM
Hittman K cool that helps a lot. What about the speedomter since its electric how would u do that. It has a 700r4 tranny in it.
11-17-2012 05:23 PM
LATECH Unhooking wont hurt anything, except the Oil pressure sender/switch.
That turns the fuel pump on after oil pressure is established, it also has the circuit for the dash gauge in it.
The sender/switch is at the back of the intake , but you can put the line for the mechanical gauge in a different location. Down on the side of the block next to the oil filter may be a port that you can use, and leave the electric gauge hooked up as well.
Also, the coolant sensor for the TBI is next to the thermostat housing, and you dont want to remove that one.
The temp sender for the temp gauge, should be in the side of the cylinder head, on the drivrs side. Look for the sender and the hole it is in. There may be a hole on the opposite cylinder head that you can use( just remove the plug) for the mechanical gauge and also leave the electric coolant gauge hooked up.
Hope this helps
11-17-2012 04:45 PM
Hittman May u no something about this. My truck is a 1989 chevy truck with TBI 350. Iam wanting to install aftermarket gauges. But i dont no what to go with Mechanical or Electric gauges. The trucks gauges are factory Electric gauges and they run off sensors. All the gauges that i have looked that are Mechanical go in place of the stock temp sensor and oil sensor locatings. Will it hurt to just unplug them and put the new stuff in or do i need to buy Electric gauges.
11-17-2012 04:36 PM
Hittman Thanks i apperciate it i have the stock TBI one it runs i drive it everday just heard it would give more power but thanks for your help.
11-17-2012 03:26 PM
LATECH Use the stock TBI HEI distributor.
There isnt any gain in spending time wiring that old distributor into the sytem. Even if it did work, I cant see where it would change performance any if at all.
If it is all you have, it probably could be wired in, and run. But if you are looking for more horsepower , it isnt there.
11-17-2012 03:18 PM
Hittman It came out of a 1982 chevy C-10 that had a 305 in it. I do no it is a vacum advance. It has a coil on the top and four wire plug on one side and another plug on the other side. I had it on this motor when it was in my 82. But put the motor in my 89 and switched to TBI. Its a gm crate 260 horse.
11-17-2012 02:23 PM
LATECH You need to elaborate on what kind of HEI. Does it have mechanical and vacuum advance? Is it the remote coil type with no advance?
11-17-2012 12:37 PM
1989 chevy truck TBI 350 HEI Install

Wondering if some of yall could help me out. I have heard that if you have a TBI 350 that you can install a HEI distributor to get more power and make it run better. Need some input on the wireing and what to do. I have a HEI distributor but no sure what needs to be done or if its better. Thanks

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